bims-tucedo Biomed News
on Tumor cell dormancy
Issue of 2020‒06‒28
thirty-five papers selected by
Isabel Puig Borreil
Vall d’Hebron Institute of Oncology

  1. Cancer Discov. 2020 Jun 22. pii: CD-19-1228. [Epub ahead of print]
    Ngo B, Kim E, Osorio-Vasquez V, Doll S, Bustraan S, Liang RJ, Luengo A, Davidson SM, Ali A, Ferraro GB, Fischer GM, Eskandari R, Kang DS, Ni J, Plasger A, Rajasekhar VK, Kastenhuber ER, Bacha S, Sriram RK, Stein BD, Bakhoum SF, Snuderl M, Cotzia P, Healey JH, Mainolfi N, Suri V, Friedman A, Manfredi M, Sabatini DM, Jones DR, Yu M, Zhao JJ, Jain RK, Keshari KR, Davies MA, Vander Heiden MG, Hernando E, Mann M, Cantley LC, Pacold ME.
      A hallmark of metastasis is the adaptation of tumor cells to new environments. Metabolic constraints imposed by the serine and glycine-limited brain environment restrict metastatic tumor growth. How brain metastases overcome these growth-prohibitive conditions is poorly understood. Here, we demonstrate that 3-phosphoglycerate dehydrogenase (PHGDH), which catalyzes the rate-limiting step of glucose-derived serine synthesis, is a major determinant of brain metastasis in multiple human cancer types and preclinical models. Enhanced serine synthesis proved important for nucleotide production and cell proliferation in highly aggressive brain metastatic cells. In vivo, genetic suppression and pharmacological inhibition of PHGDH attenuated brain metastasis, but not extracranial tumor growth, and improved overall survival in mice. These results reveal that extracellular amino acid availability determines serine synthesis pathway dependence, and suggests that PHGDH inhibitors may be useful in the treatment of brain metastasis.
  2. Oncogene. 2020 Jun 21.
    Nollet EA, Cardo-Vila M, Ganguly SS, Tran JD, Schulz VV, Cress A, Corey E, Miranti CK.
      The androgen receptor (AR) is the major driver of prostate cancer growth and survival. However, almost all patients relapse with castration-resistant disease (CRPC) when treated with anti-androgen therapy. In CRPC, AR is often aberrantly activated independent of androgen. Targeting survival pathways downstream of AR could be a viable strategy to overcome CRPC. Surprisingly, little is known about how AR drives prostate cancer survival. Furthermore, CRPC tumors in which Pten is lost are also resistant to eradication by PI3K inhibitors. We sought to identify the mechanism by which AR drives tumor survival in CRPC to identify ways to overcome resistance to PI3K inhibition. We found that integrins α6β1 and Bnip3 are selectively elevated in CRPC downstream of AR. While integrin α6 promotes survival and is a direct transcriptional target of AR, the ability of AR to induce Bnip3 is dependent on adhesion to laminin and integrin α6β1-dependent nuclear translocation of HIF1α. Integrins α6β1 and Bnip3 were found to promote survival of CRPC cells selectively on laminin through the induction of autophagy and mitophagy. Furthermore, blocking Bnip3 or integrin α6β1 restored sensitivity to PI3K inhibitors in Pten-negative CRPC. We identified an AR driven pathway that cooperates with laminin and hypoxia to drive resistance to PI3K inhibitors. These findings can help explain in part why PI3K inhibitors have failed in clinical trials to overcome AR-dependent CRPC.
  3. Cancer Metastasis Rev. 2020 Jun 22.
    Jonkers J, Pai P, Sukumar S.
      Knowledge of the role of HOX proteins in cancer has been steadily accumulating in the last 25 years. They are encoded by 39 HOX genes arranged in 4 distinct clusters, and have unique and redundant function in all types of cancers. Many HOX genes behave as oncogenic transcriptional factors regulating multiple pathways that are critical to malignant progression in a variety of tumors. Some HOX proteins have dual roles that are tumor-site specific, displaying both oncogenic and tumor suppressor function. The focus of this review is on how HOX proteins contribute to growth or suppression of metastasis. The review will cover HOX protein function in the critical aspects of epithelial-mesenchymal transition, in cancer stem cell sustenance and in therapy resistance, manifested as distant metastasis. The emerging role of adiposity in both initiation and progression of metastasis is described. Defining the role of HOX genes in the metastatic process has identified candidates for targeted cancer therapies that may combat the metastatic process. We will discuss potential therapeutic opportunities, particularly in pathways influenced by HOX proteins.
    Keywords:  Cancer; Differentiation; EMT; HOX; Invasion; Metastasis; Migration; Obesity; Stem cells; Therapy; Transcription factor
  4. Biotechnol Bioeng. 2020 Jun 26.
    Lam T, Aguirre-Ghiso JA, Geller MA, Aksan A, Azarin SM.
      Around 20-30% of ovarian cancer patients exhibit chemoresistance, but there are currently no methods to predict whether a patient will respond to chemotherapy. Here, we discovered that chemoresistant ovarian cancer cells exhibit enhanced survival in a quiescent state upon experiencing the stress of physical confinement. When immobilized in stiff silica gels, most ovarian cancer cells die within days, but surviving cells exhibit hallmarks of single cell dormancy. Upon extraction from gels, the cells resume proliferation but demonstrate enhanced viability upon re-immobilization, indicating that initial immobilization selects for cells with a higher propensity to enter dormancy. RNA-seq analysis of the extracted cells shows they have signaling responses similar to cells surviving cisplatin treatment, and in comparison to chemoresistant patient cohorts, they share differentially expressed genes that are associated with platinum-resistance pathways. Furthermore, these extracted cells demonstrate greater resistance to cisplatin and paclitaxel, despite being proliferative. In contrast, serum starvation and hypoxia could not effectively select for chemoresistant cells upon removal of the environmental stress. These findings demonstrate that ovarian cancer chemoresistance and the ability to enter dormancy are linked, and immobilization rapidly distinguishes chemoresistant cells. This platform could be suitable for mechanistic studies, drug development, or as a clinical diagnostic tool. This article is protected by copyright. All rights reserved.
    Keywords:  chemoresistance; immobilization; ovarian cancer; quiescence; silica gel
  5. Cancer Res. 2020 Jun 26. pii: canres.0212.2020. [Epub ahead of print]
    Benjamin DC, Kang JH, Hamza B, King EM, Lamar JM, Manalis SR, Hynes RO.
      The oncogene YAP has been shown previously to promote tumor growth and metastasis. However, how YAP influences the behavior of tumor cells traveling within the circulatory system has not been as well explored. Given that rate-limiting steps of metastasis are known to occur while tumor cells enter, travel through, or exit circulation, we sought to study how YAP influences tumor cell behavior within the circulatory system. Intravital imaging in live zebrafish embryos revealed that YAP influenced the distribution of tumor cells within the animal following intravenous injection. Control cells became lodged in the first capillary bed encountered in the tail, whereas cells over-expressing constitutively active YAP were able to travel through this capillary plexus, re-enter systemic circulation, and seed in the brain. YAP controlled transit through these capillaries by promoting active migration within the vasculature. These results were recapitulated in a mouse model following intravenous injection, where active YAP increased the number of circulating tumor cells over time. Our results suggest a possible mechanism where tumor cells can spread to organs beyond the first capillary bed downstream from the primary tumor. These results also show that a specific gene can affect the distribution of tumor cells within an animal, thereby influencing the global pattern of metastasis in that animal.
  6. Clin Cancer Res. 2020 Jun 22. pii: clincanres.4035.2019. [Epub ahead of print]
    Hafez N, Rugo HS, Tempero MA, Fox E, Reaman GH, Lyerly HK, Walker D, LoRusso PM.
      The 2019 Accelerating Anticancer Agent Development (AAADV) Workshop assembled a panel of experts for an in-depth discussion session to present "Novel Therapeutic Interventions Early in the Disease Trajectory." The panel reviewed the limitations of evaluating investigational cancer therapeutics solely in advanced metastatic and relapsed/refractory disease settings, and recommended strategies for drug evaluation earlier in the disease course, including in the first line in combination with standard chemotherapy and in the maintenance and neoadjuvant disease settings. Advantages of earlier drug evaluation were discussed, including expanding the population of evaluable patients, earlier response assessment via surrogate endpoints, earlier clinical benefit in the disease course, tailoring of therapies based on response, and furthering our understanding of biomarker-driven therapies.
  7. Cancers (Basel). 2020 Jun 18. pii: E1621. [Epub ahead of print]12(6):
    Beauvarlet J, Nath Das R, Alvarez-Valadez K, Martins I, Muller A, Darbo E, Richard E, Soubeyran P, Kroemer G, Guillon J, Mergny JL, Djavaheri-Mergny M.
      Lysosomes play a key role in regulating cell death in response to cancer therapies, yet little is known on the possible role of lysosomes in the therapeutic efficacy of G-quadruplex DNA ligands (G4L) in cancer cells. Here, we investigate the relationship between the modulation of lysosomal membrane damage and the degree to which cancer cells respond to the cytotoxic effects of G-quadruplex ligands belonging to the triarylpyridine family. Our results reveal that the lead compound of this family, 20A promotes the enlargement of the lysosome compartment as well as the induction of lysosome-relevant mRNAs. Interestingly, the combination of 20A and chloroquine (an inhibitor of lysosomal functions) led to a significant induction of lysosomal membrane permeabilization coupled to massive cell death. Similar effects were observed when chloroquine was added to three new triarylpyridine derivatives. Our findings thus uncover the lysosomal effects of triarylpyridines compounds and delineate a rationale for combining these compounds with chloroquine to increase their anticancer effects.
    Keywords:  G-quadruplex ligand; Lysosome; cancer; cell death; lysosomal membrane permeabilization; resistance to therapy; triarylpyridine compounds
  8. Mol Cancer Res. 2020 Jun 26. pii: molcanres.1226.2019. [Epub ahead of print]
    Han J, Jiang Z, Wang C, Chen X, Li R, Sun N, Liu X, Wang H, Hong L, Zheng K, Yang J, Ikezoe T.
      Intratumoral tumor-specific activated CD8+ T cells with functions in antitumor immune surveillance predict metastasis and clinical outcome in human colorectal cancer (CRC). Intratumoral CD8+ T cells also affect treatment with immune checkpoint inhibitors. Interestingly, inhibition of Aurora kinase A (Aurora-A) by its selective inhibitor alisertib obviously induced infiltration of CD8+ T cells. However, the mechanisms by which inhibition of Aurora-A promotes infiltration of intratumoral CD8+ T cells remain unclear. Our recent results demonstrated that conditional deletion of the AURKA gene or blockade of Aurora-A by alisertib slowed tumor growth in association with an increase in the infiltration of intratumoral CD8+ T cells as well as the mRNA levels of their interleukin-10 receptor a (IL-10Ra). The antitumor effects of targeting Aurora-A were attenuated in the absence of CD8+ T cells. Additionally, antibody-mediated blockade of IL-10Ra dramatically decreased the percentage of intratumoral CD8+ T cells. In further experiments, we found that the levels of IL-10 were elevated in the serum of Azoxymethane (AOM)/Dextran Sodium Sulfate (DSS)-treated AURKAflox/+;VillinCre+ mice. Unexpectedly, we found that in addition to Aurora-A's mitotic role, inhibition of Aurora-A elevated IL-10 transcription, which in turn increased the IL-10Ra mRNA levels in CD8+ T cells. Thus, inhibition of Aurora-A could be a useful treatment strategy for recruiting tumor-specific intratumoral CD8+ T cells. Implications: Understanding the mechanisms by which inhibition of Aurora-A promotes CD8+ T cell infiltration and activation, as mediated by the IL-10 pathway, could provide a potential strategy for tumor immunotherapy.
  9. Cancers (Basel). 2020 Jun 21. pii: E1645. [Epub ahead of print]12(6):
    Harrington BS, Ozaki MK, Caminear MW, Hernandez LF, Jordan E, Kalinowski NJ, Goldlust IS, Guha R, Ferrer M, Thomas C, Shetty J, Tran B, Wong N, House CD, Annunziata CM.
      Disease recurrence is the major cause of morbidity and mortality of ovarian cancer (OC). In terms of maintenance therapies after platinum-based chemotherapy, PARP inhibitors significantly improve the overall survival of patients with BRCA mutations but is of little benefit to patients without homologous recombination deficiency (HRD). The stem-like tumor-initiating cell (TIC) population within OC tumors are thought to contribute to disease recurrence and chemoresistance. Therefore, there is a need to identify drugs that target TICs to prevent relapse in OC without HRD. RNA sequencing analysis of OC cells grown in TIC conditions revealed a strong enrichment of genes involved in drug metabolism, oxidative phosphorylation and reactive oxygen species (ROS) pathways. Concurrently, a high-throughput drug screen identified drugs that showed efficacy against OC cells grown as TICs compared to adherent cells. Four drugs were chosen that affected drug metabolism and ROS response: disulfiram, bardoxolone methyl, elesclomol and salinomycin. The drugs were tested in vitro for effects on viability, sphere formation and markers of stemness CD133 and ALDH in TICs compared to adherent cells. The compounds promoted ROS accumulation and oxidative stress and disulfiram, elesclomol and salinomycin increased cell death following carboplatin treatment compared to carboplatin alone. Disulfiram and salinomycin were effective in a post-surgery, post-chemotherapy OC relapse model in vivo, demonstrating that enhancing oxidative stress in TICs can prevent OC recurrence.
    Keywords:  ALDH; HRD; maintenance therapy; ovarian cancer; oxidative stress; recurrence model; relapse prevention; tumor-initiating cells
  10. Cancer Cell. 2020 Jun 09. pii: S1535-6108(20)30268-3. [Epub ahead of print]
    Kudo Y, Sugimoto M, Arias E, Kasashima H, Cordes T, Linares JF, Duran A, Nakanishi Y, Nakanishi N, L'Hermitte A, Campos A, Senni N, Rooslid T, Roberts LR, Cuervo AM, Metallo CM, Karin M, Diaz-Meco MT, Moscat J.
      Oxidative stress plays a critical role in liver tissue damage and in hepatocellular carcinoma (HCC) initiation and progression. However, the mechanisms that regulate autophagy and metabolic reprogramming during reactive oxygen species (ROS) generation, and how ROS promote tumorigenesis, still need to be fully understood. We show that protein kinase C (PKC) λ/ι loss in hepatocytes promotes autophagy and oxidative phosphorylation. This results in ROS generation, which through NRF2 drives HCC through cell-autonomous and non-autonomous mechanisms. Although PKCλ/ι promotes tumorigenesis in oncogene-driven cancer models, emerging evidence demonstrate that it is a tumor suppressor in more complex carcinogenic processes. Consistently, PKCλ/ι levels negatively correlate with HCC histological tumor grade, establishing this kinase as a tumor suppressor in liver cancer.
    Keywords:  NRF2; PKCζ; PKCι; PKCλ; atypical PKC; autophagy; hepatocellular carcinoma; metabolic reprogramming; oxidative phosphorylation; reactive oxygen species
  11. Nat Commun. 2020 Jun 22. 11(1): 3157
    Fernandes Neto JM, Nadal E, Bosdriesz E, Ooft SN, Farre L, McLean C, Klarenbeek S, Jurgens A, Hagen H, Wang L, Felip E, Martinez-Marti A, Vidal A, Voest E, Wessels LFA, van Tellingen O, Villanueva A, Bernards R.
      Resistance to targeted cancer drugs is thought to result from selective pressure exerted by a high drug dose. Partial inhibition of multiple components in the same oncogenic signalling pathway may add up to complete pathway inhibition, while decreasing the selective pressure on each component to acquire a resistance mutation. We report here testing of this Multiple Low Dose (MLD) therapy model in EGFR mutant NSCLC. We show that as little as 20% of the individual effective drug doses is sufficient to completely block MAPK signalling and proliferation when used in 3D (RAF + MEK + ERK) or 4D (EGFR + RAF + MEK + ERK) inhibitor combinations. Importantly, EGFR mutant NSCLC cells treated with MLD therapy do not develop resistance. Using several animal models, we find durable responses to MLD therapy without associated toxicity. Our data support the notion that MLD therapy could deliver clinical benefit, even for those having acquired resistance to third generation EGFR inhibitor therapy.
  12. J Clin Invest. 2020 Jun 23. pii: 137660. [Epub ahead of print]
    Dodhiawala PB, Khurana N, Zhang D, Cheng Y, Li L, Wei Q, Seehra K, Jiang H, Grierson PM, Wang-Gillam A, Lim KH.
      NF-kB transcription factors, driven by the IRAK-IKK cascade, confer treatment resistance in pancreatic ductal adenocarcinoma (PDAC), a cancer characterized by near universal KRAS mutation. Through reverse-phase protein array and RNAseq we discovered IRAK4 also contributes substantially to MAPK activation in KRAS-mutant PDAC. IRAK4 ablation completely blocked RAS-induced transformation of human and murine cells. Mechanistically, expression of mutant KRAS stimulated an inflammatory, autocrine IL-1b signaling loop that activated IRAK4 and MAPK pathway. Downstream of IRAK4, we uncovered TPL2/MAP3K8 as the essential kinase that propels both MAPK and NF-kB cascades. Inhibition of TPL2 blocked both MAPK and NF-kB signaling, and suppressed KRAS-mutant cell growth. To counter chemotherapy-induced genotoxic stress, PDAC cells upregulated TLR9, which activated pro-survival IRAK4-TPL2 signaling. Accordingly, TPL2 inhibitor synergized with chemotherapy to curb PDAC growth in vivo. Finally, from TCGA we characterized two MAP3K8 point mutations that hyperactivate MAPK and NF-kB cascades by impeding TPL2 protein degradation. Cancer cell lines naturally harboring these MAP3K8 mutations are strikingly sensitive to TPL2 inhibition, underscoring the need to identify these potentially targetable mutations in patients. Overall, our study establishes TPL2 as a promising therapeutic target in RAS- and MAP3K8-mutant cancers and strongly prompts development of TPL2 inhibitors for pre-clinical and clinical studies.
    Keywords:  Inflammation; NF-kappaB; Oncogenes; Oncology; Protein kinases
  13. Clin Cancer Res. 2020 Jun 22. pii: clincanres.1024.2020. [Epub ahead of print]
    Chu JE, Johnson B, Kugathasan L, Morris VK, Raghav K, Swanson L, Lim H, Renouf DJ, Gill S, Wolber R, Karsan A, Kopetz S, Schaeffer DF, Loree JM.
      PURPOSE BRAFV600E mutations portend poor prognosis in metastatic colorectal cancer (mCRC); however, the true prevalence and prognosis are unknown, as unwell patients may not undergo BRAF sequencing. PATIENTS AND METHODS We reviewed a population-based cohort of 1898 patients with CRC that underwent reflexive immunohistochemistry (IHC) mismatch repair (MMR) & BRAFV600E testing. Outcomes among IHC detected BRAFV600E mCRC (BRAFIHC) were compared to patients with next generation sequencing identified BRAFV600E mutated mCRC from two institutions (BRAFNGS) with patients spanning from 2004-2018. RESULTS All-stage population prevalence of BRAFV600E was 12.5% (238/1898) and did not differ between early and metastatic stages (p=0.094). Prevalence among mCRC was 10.6% (61/575), of whom 51 (83.6%) were referred to oncology and 26 (42.6%) had NGS testing. BRAFIHC had worse median overall survival (mOS) than BRAFNGS (5.5 vs 20.4 months, hazard ratio (HR) 2.90, 95% confidence interval (CI) 1.89-4.45, p<0.0001) which persisted in multivariate analysis (p<0.0001). Across a combined NGS and IHC cohort, BRAFV600E tumors with deficient MMR showed worse mOS compared to MMR proficient tumors (8.9 vs 17.2 months, HR 1.46, 95% CI 0.96-2.27, p=0.043). In this combined cohort, first-line progression free survival was 5.9 months, with minimal differences between regimens. Within the population-based cohort, attrition between treatment lines was high with only 60.7% receiving first-line chemotherapy and 26.2% receiving second-line. CONCLUSION BRAFV600E mutated mCRC has a worse prognosis than previously suggested, potentially arising from referral bias for testing. High attrition between lines of therapy suggests efficacious therapies need to be prioritized early for patients to benefit.
  14. Mol Cancer. 2020 Jun 24. 19(1): 109
    Li Y, Tian Z, Tan Y, Lian G, Chen S, Chen S, Li J, Li X, Huang K, Chen Y.
      BACKGROUND: We previously reported an inverse relationship between B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) and Raf kinase inhibitory protein (RKIP), which is associated with the prognosis of gastric cancer (GC). In this study, we further explored the microRNA (miRNA) regulatory mechanism between Bmi-1 and RKIP.METHODS: Microarray analysis was first carried out to identify miRNA profiles that were differentially expressed in cells overexpressing Bmi-1. Then, miRNAs that could regulate RKIP were identified. Quantitative real-time PCR (qRT-PCR) and Western blotting were performed to measure the expression of Bmi-1, miR-155, miR-27a and RKIP. RKIP was confirmed as a target of miR-27a and miR-155 through luciferase reporter assays, qRT-PCR and Western blotting. The effects of the Bmi-1/miR-27a/RKIP and Bmi-1/miR-155/RKIP axes on tumor growth, proliferation, migration, invasion, colony-formation ability, metastasis and chemoresistance were investigated both in vitro and in vivo.
    RESULTS: The downregulation of RKIP by Bmi-1 occurred at the protein but not mRNA level. This indicates probable posttranscriptional regulation. miRNA expression profiles of cells with ectopic expression of Bmi-1 were analyzed and compared to those of control cells by microarray analysis. A total of 51 upregulated and 72 downregulated miRNAs were identified. Based on publicly available algorithms, miR-27a and miR-155 were predicted, selected and demonstrated to target RKIP. Bmi-1, miR-27a and miR-155 are elevated in human GC and associated with poor prognosis of GC, while RKIP is expressed at lower levels in GC and correlated with good prognosis. Then, in vitro tests shown that in addition to regulating RKIP expression via miR-27a and miR-155, Bmi-1 was also able to regulate the migration, invasion, proliferation, colony-formation ability and chemosensitivity of GC cells through the same pathway. Finally, the in vivo test showed similar results, whereby the knockdown of the Bmi-1 gene led to the inhibition of tumor growth, metastasis and chemoresistance through miR-27a and miR-155.
    CONCLUSIONS: Bmi-1 was proven to induce the expression of miR-27a and miR-155 and thus promote tumor metastasis and chemoresistance by targeting RKIP in GC. Overall, miR-27a and miR-155 might be promising targets for the screening, diagnosis, prognosis, treatment and disease monitoring of GC.
    Keywords:  Bmi-1; Gastric cancer; RKIP; miR-155; miR-27a
  15. Nat Commun. 2020 Jun 24. 11(1): 3193
    Hadadi E, Taylor W, Li XM, Aslan Y, Villote M, Rivière J, Duvallet G, Auriau C, Dulong S, Raymond-Letron I, Provot S, Bennaceur-Griscelli A, Acloque H.
      Breast cancer is the most common type of cancer worldwide and one of the major causes of cancer death in women. Epidemiological studies have established a link between night-shift work and increased cancer risk, suggesting that circadian disruption may play a role in carcinogenesis. Here, we aim to shed light on the effect of chronic jetlag (JL) on mammary tumour development. To do this, we use a mouse model of spontaneous mammary tumourigenesis and subject it to chronic circadian disruption. We observe that circadian disruption significantly increases cancer-cell dissemination and lung metastasis. It also enhances the stemness and tumour-initiating potential of tumour cells and creates an immunosuppressive shift in the tumour microenvironment. Finally, our results suggest that the use of a CXCR2 inhibitor could correct the effect of JL on cancer-cell dissemination and metastasis. Altogether, our data provide a conceptual framework to better understand and manage the effects of chronic circadian disruption on breast cancer progression.
  16. Cancer Metastasis Rev. 2020 Jun 23.
    Petri BJ, Klinge CM.
      Despite the decline in death rate from breast cancer and recent advances in targeted therapies and combinations for the treatment of metastatic disease, metastatic breast cancer remains the second leading cause of cancer-associated death in U.S. women. The invasion-metastasis cascade involves a number of steps and multitudes of proteins and signaling molecules. The pathways include invasion, intravasation, circulation, extravasation, infiltration into a distant site to form a metastatic niche, and micrometastasis formation in a new environment. Each of these processes is regulated by changes in gene expression. Noncoding RNAs including microRNAs (miRNAs) are involved in breast cancer tumorigenesis, progression, and metastasis by post-transcriptional regulation of target gene expression. miRNAs can stimulate oncogenesis (oncomiRs), inhibit tumor growth (tumor suppressors or miRsupps), and regulate gene targets in metastasis (metastamiRs). The goal of this review is to summarize some of the key miRNAs that regulate genes and pathways involved in metastatic breast cancer with an emphasis on estrogen receptor α (ERα+) breast cancer. We reviewed the identity, regulation, human breast tumor expression, and reported prognostic significance of miRNAs that have been documented to directly target key genes in pathways, including epithelial-to-mesenchymal transition (EMT) contributing to the metastatic cascade. We critically evaluated the evidence for metastamiRs and their targets and miRNA regulation of metastasis suppressor genes in breast cancer progression and metastasis. It is clear that our understanding of miRNA regulation of targets in metastasis is incomplete.
    Keywords:  Breast cancer metastasis; EMT; TGFβ; miRNAs
  17. Cell. 2020 Jun 25. pii: S0092-8674(20)30690-5. [Epub ahead of print]181(7): 1454-1457
    Kloosterman DJ, Akkari L.
      Despite its success in multiple tumor types, immunotherapy remains poorly efficacious in brain malignancies. In this issue of Cell, Friebel et al. and Klemm et al. provide in-depth insights into the versatile nuances of immune cells in primary and metastatic brain tumors, granting the field with a rich framework to explore novel therapeutic avenues.
  18. Nat Commun. 2020 Jun 26. 11(1): 3259
    Parhi L, Alon-Maimon T, Sol A, Nejman D, Shhadeh A, Fainsod-Levi T, Yajuk O, Isaacson B, Abed J, Maalouf N, Nissan A, Sandbank J, Yehuda-Shnaidman E, Ponath F, Vogel J, Mandelboim O, Granot Z, Straussman R, Bachrach G.
      Fusobacterium nucleatum is an oral anaerobe recently found to be prevalent in human colorectal cancer (CRC) where it is associated with poor treatment outcome. In mice, hematogenous F. nucleatum can colonize CRC tissue using its lectin Fap2, which attaches to tumor-displayed Gal-GalNAc. Here, we show that Gal-GalNAc levels increase as human breast cancer progresses, and that occurrence of F. nucleatum gDNA in breast cancer samples correlates with high Gal-GalNAc levels. We demonstrate Fap2-dependent binding of the bacterium to breast cancer samples, which is inhibited by GalNAc. Intravascularly inoculated Fap2-expressing F. nucleatum ATCC 23726 specifically colonize mice mammary tumors, whereas Fap2-deficient bacteria are impaired in tumor colonization. Inoculation with F. nucleatum suppresses accumulation of tumor infiltrating T cells and promotes tumor growth and metastatic progression, the latter two of which can be counteracted by antibiotic treatment. Thus, targeting F. nucleatum or Fap2 might be beneficial during treatment of breast cancer.
  19. Cancer Res. 2020 Jun 25. pii: canres.3533.2019. [Epub ahead of print]
    Zhang Y, Cedervall J, Hamidi A, Herre M, Viitaniemi K, D'Amico G, Miao Z, Valsala Madhavan Unnithan R, Vaccaro A, van Hooren L, Georganaki M, Thulin Å, Qiao Q, Andrae J, Siegbahn A, Heldin CH, Alitalo K, Betsholtz C, Dimberg A, Olsson AK.
      Platelet-derived growth factor B (PDGFB) plays a crucial role in recruitment of PDGF receptor beta (PDGFRbeta)-positive pericytes to blood vessels. The endothelium is an essential source of PDGFB in this process. Platelets constitute a major reservoir of PDGFB and are continuously activated in the tumor microenvironment, exposing tumors to the plethora of growth factors contained in platelet granules. Here we show that tumor vascular function as well as pericyte coverage is significantly impaired in mice with conditional knockout of PDGFB in platelets. A lack of PDGFB in platelets led to enhanced hypoxia and EMT in the primary tumors, elevated levels of circulating tumor cells, and increased spontaneous metastasis to the liver or lungs in two mouse models. These findings establish a previously unknown role for platelet-derived PDGFB whereby it promotes and maintains vascular integrity in the tumor microenvironment by contributing to the recruitment of pericytes.
  20. J Biol Chem. 2020 Jun 23. pii: jbc.RA120.014018. [Epub ahead of print]
    Seachrist DD, Hannigan MM, Ingles NN, Webb BM, Weber-Bonk KL, Yu P, Bebek G, Singh S, Sizemore ST, Varadan V, Licatalosi DD, Keri RA.
      The phenotypes of each breast cancer subtype are defined by their transcriptomes. However, the transcription factors that regulate differential patterns of gene expression that contribute to specific disease outcomes are not well understood. Herein, using gene silencing and overexpression approaches, RNA-Seq, and splicing analysis, we report that the transcription factor B-cell leukemia/lymphoma 11A (BCL11A), is highly expressed in triple-negative breast cancer (TNBC) and drives metastatic disease. Moreover, BCL11A promoted cancer cell invasion by suppressing the expression of muscleblind-like splicing regulator 1 (MBNL1), encoding a splicing regulator that suppresses metastasis. This ultimately increased the levels of an alternatively spliced isoform of integrin-α6 (ITGA6) that is associated with worse patient outcomes. These results suggest that BCL11A sustains TNBC cell invasion and metastatic growth by repressing MBNL1-directed splicing of ITGA6. Our findings also indicate that BCL11A lies at the interface of transcription and splicing and promotes aggressive TNBC phenotypes.
    Keywords:  B-cell leukemia/lymphoma 11A (BCL11A); alternative splicing; breast cancer; gene regulation; gene transcription; integrin-alpha6 (ITGA6); invasion; metastasis; muscleblind-like splicing regulator 1 (MBNL1)
  21. Cancer Res. 2020 Jun 25. pii: canres.2910.2019. [Epub ahead of print]
    Saxena M, Kalathur RKR, Rubinstein N, Vettiger A, Sugiyama N, Neutzner M, Coto-Llerena M, Kancherla V, Ercan C, Piscuoglio S, Fischer J, Fagiani E, Cantù C, Basler K, Christofori G.
      Pygopus 2 (Pygo2) is a co-activator of Wnt/β-catenin signaling that can bind bi- or trimethylated lysine 4 of histone-3 (H3K4me2/3) and participate in chromatin reading and writing. It remains unknown whether the Pygo2- H3K4me2/3 association has a functional relevance in breast cancer progression in vivo. To investigate the functional relevance of histone binding activity of Pygo2 in malignant progression of breast cancer, we generated a knock-in mouse model where binding of Pygo2 to H3K4me2/3 was rendered ineffective. Loss of Pygo2-histone interaction resulted in smaller, differentiated, and less metastatic tumors, due in part to decreased canonical Wnt/β-catenin signaling. RNA and ATAC sequencing analyses of tumor-derived cell lines revealed downregulation of TGFβ signaling and upregulation of differentiation pathways such as PDGFR signaling. Increased differentiation correlated with a luminal cell fate which could be reversed by inhibition of PDGFR activity. Mechanistically, the Pygo2-histone interaction potentiated Wnt/ β-catenin signaling in part by repressing the expression of Wnt signaling antagonists. Furthermore, Pygo2 and β-catenin regulated the expression of miR-29 family members which in turn repressed PDGFR expression to promote de- differentiation of wildtype Pygo2 mammary epithelial tumor cells. Collectively, these results demonstrate that the histone binding function of Pygo2 is important for driving de-differentiation and malignancy of breast tumors, and loss of this binding activates various differentiation pathways which attenuate primary tumor growth and metastasis formation. Interfering with the Pygo2- H3K4me2/3 interaction may therefore serve as an attractive therapeutic target for metastatic breast cancer.
  22. Oncogene. 2020 Jun 25.
    Suo D, Wang Z, Li L, Chen Q, Zeng T, Liu R, Yun J, Guan XY, Li Y.
      Esophageal squamous cell carcinoma (ESCC) is a malignant disease and is a common cause of death in China. By performing an integrative study investigating public databases and clinical samples collected by our group, we found that HOXC10 (homeobox C10) is upregulated in ESCC tumor tissues compared with nontumor tissues and that the upregulation of HOXC10 is correlated with the poor prognosis of patients with ESCC. The enforced expression of HOXC10 promoted ESCC cell proliferation in vitro and in vivo. Our study revealed that HOXC10 could bind the promoter region of human Erb-b2 receptor tyrosine kinase 3 (ERBB3/HER3) and activate the PI3K/AKT pathway. In addition, by immunoprecipitation and mass spectrometry analysis, we found that HOXC10 could bind X-ray repair cross complementing 6 (Ku70) and accelerate the DNA repair mechanism via the nonhomologous end-joining (NHEJ) pathway. We further evaluated HOXC10 expression in ESCC patients receiving adjuvant radiotherapy or platinum-based chemotherapy. The results demonstrate that HOXC10 upregulation predicts the poor prognosis of ESCC patients receiving adjuvant radiotherapy or chemotherapy. Our study reveals that HOXC10 upregulation reflects the poor prognosis of ESCC patients and directs the selection of postoperative therapy regimens.
  23. Cancers (Basel). 2020 Jun 19. pii: E1626. [Epub ahead of print]12(6):
    Boral D, Liu HN, Kenney SR, Marchetti D.
      Despite widespread knowledge that bone marrow-resident breast cancer cells (BMRCs) affect tumor progression, signaling mechanisms of BMRCs implicated in maintaining long-term dormancy have not been characterized. To overcome these hurdles, we developed a new experimental model of clinical dormancy employing patient-isolated Circulating Tumor Cells (de novo CTCs) and their injection in xenografts with subsequent tumor monitoring and CTC characterization (ex vivo CTCs). We hypothesized that significant distinctions exist between signaling pathways of bone marrow-homing vs metastasis-competent CTCs upon transplantation in xenografts. Comparative transcriptomic analyses of ex vivo vs de novo CTCs identified increased mTOR signaling-a critical pathway frequently dysregulated in breast cancer and implicated in cell survival and dormancy-with contrasting actions by its two complementary arms (mTORC2/mTORC1). Heightened mTORC2 downstream targets augmented quiescent CTCs (Ki67-/RBL2+ cells) in paired breast cancer tissues, along with high mTORC2 activity in solitary BMRCs and tissue-resident CTCs. Further, shRNA mediated the knockdown of RICTOR, an essential component of mTORC2, and augmented Ki67/PCNA biomarker expression and proliferation. Collectively, these findings suggest that the balance between mTORC1 vs mTORC2 signaling regulates CTC-associated mitotic and/or dormancy characteristics.
    Keywords:  Bone Marrow-Resident Breast Cancer Cells (BMRCs); CTC-associated dormancy; CTC-derived xenograft (CDX); Circulating Tumor Cells (CTCs); RICTOR; bone marrow (BM); mTOR pathway; mTORC1/mTORC2 signaling
  24. Cancers (Basel). 2020 Jun 23. pii: E1663. [Epub ahead of print]12(6):
    Marin JJG, Macias RIR, Monte MJ, Romero MR, Asensio M, Sanchez-Martin A, Cives-Losada C, Temprano AG, Espinosa-Escudero R, Reviejo M, Bohorquez LH, Briz O.
      The poor outcome of patients with non-surgically removable advanced hepatocellular carcinoma (HCC), the most frequent type of primary liver cancer, is mainly due to the high refractoriness of this aggressive tumor to classical chemotherapy. Novel pharmacological approaches based on the use of inhibitors of tyrosine kinases (TKIs), mainly sorafenib and regorafenib, have provided only a modest prolongation of the overall survival in these HCC patients. The present review is an update of the available information regarding our understanding of the molecular bases of mechanisms of chemoresistance (MOC) with a significant impact on the response of HCC to existing pharmacological tools, which include classical chemotherapeutic agents, TKIs and novel immune-sensitizing strategies. Many of the more than one hundred genes involved in seven MOC have been identified as potential biomarkers to predict the failure of treatment, as well as druggable targets to develop novel strategies aimed at increasing the sensitivity of HCC to pharmacological treatments.
    Keywords:  DNA repair; apoptosis; cancer stem cell; epithelial-mesenchymal transition; liver cancer; metabolism; multidrug resistance; refractoriness; transport; tumor environment
  25. Clin Cancer Res. 2020 Jun 22. pii: clincanres.0638.2020. [Epub ahead of print]
    Vidula N, Dubash TD, Lawrence MS, Simoneau A, Niemierko A, Blouch EL, Nagy RJ, Roh W, Chirn B, Reeves B, Malvarosa G, Lennerz JK, Isakoff SJ, Juric D, Micalizzi DS, Wander SA, Spring LM, Moy B, Shannon KM, Younger J, Lanman RB, Toner M, Iafrate AJ, Getz G, Zou L, Ellisen LW, Maheswaran S, Haber DA, Bardia A.
      PURPOSE: Plasma genotyping may identify mutations in potentially "actionable" cancer genes, such as BRCA1/2, but their clinical significance is not well defined. We evaluated the characteristics of somatically acquired BRCA1/2 mutations in patients with MBC.METHODS: Patients with MBC undergoing routine cell-free DNA (cfDNA) next generation sequencing (73 gene panel) before starting a new therapy were included. Somatic BRCA1/2 mutations were classified as known germline-pathogenic mutations or novel variants, and linked to clinicopathological characteristics. The effect of the PARP inhibitor olaparib was assessed in vitro, using cultured circulating tumor cells (CTCs) from a patient with a somatically acquired BRCA1 mutation and a second patient with an acquired BRCA2 mutation.
    RESULTS: Among 215 MBC patients, 29 (13.5%) had somatic cfDNA BRCA1/2 mutations (nine (4%) known germline-pathogenic and rest (9%) novel variants). Known germline-pathogenic BRCA1/2 mutations were common in younger patients (p=0.008), those with triple-negative disease (p=0.022), and they were more likely to be protein-truncating alterations and be associated with TP53 mutations. Functional analysis of a CTC culture harboring a somatic BRCA1-mutation demonstrated high sensitivity to PARP inhibition, while another CTC culture harboring a somatic BRCA2 mutation showed no differential sensitivity. Across the entire cohort, APOBEC mutational signatures (COSMIC Signatures 2 and 13) and the "BRCA" mutational signature (COSMIC Signature 3) were present in BRCA1/2 mutant and wild-type cases, demonstrating the high mutational burden associated with advanced MBC.
    CONCLUSION: Somatic BRCA1/2 mutations are readily detectable in MBC by cfDNA analysis, and may be present as both known germline-pathogenic and novel variants.
  26. Nat Commun. 2020 Jun 24. 11(1): 3191
    Huang W, Sundquist J, Sundquist K, Ji J.
      Phosphodiesterase-5 (PDE5) inhibitors are suggested to have anti-tumor effects and to inhibit surgery-induced immunosuppression. We aimed to explore whether post-diagnostic use of PDE5 inhibitors was associated with a better prognosis among male patients with colorectal cancer (CRC) and the role of open surgery in the association. Here we show that post-diagnostic use of PDE5 inhibitors is associated with a decreased risk of CRC-specific mortality (adjusted HR = 0.82, 95% CI 0.67-0.99) as well as a decreased risk of metastasis (adjusted HR = 0.85, 95% CI 0.74-0.98). Specifically, post-operative use of PDE5 inhibitors has a strong anti-cancer effect. The reduced risk of metastasis is mainly due to distant metastasis but not regional lymphatic metastasis. PDE5 inhibitors have the potential to be an adjuvant drug for patients with CRC to improve prognosis, especially those who have undergone open surgery.
  27. Cancers (Basel). 2020 Jun 19. pii: E1632. [Epub ahead of print]12(6):
    Genna A, Vanwynsberghe AM, Villard AV, Pottier C, Ancel J, Polette M, Gilles C.
      Epithelial-mesenchymal transitions (EMTs) generate hybrid phenotypes with an enhanced ability to adapt to diverse microenvironments encountered during the metastatic spread. Accordingly, EMTs play a crucial role in the biology of circulating tumor cells (CTCs) and contribute to their heterogeneity. Here, we review major EMT-driven properties that may help hybrid Epithelial/Mesenchymal CTCs to survive in the bloodstream and accomplish early phases of metastatic colonization. We then discuss how interrogating EMT in CTCs as a companion biomarker could help refine cancer patient management, further supporting the relevance of CTCs in personalized medicine.
    Keywords:  CTC; EMT; coagulation; early metastasis; heterogeneity
  28. J Biol Chem. 2020 Jun 22. pii: jbc.RA120.014464. [Epub ahead of print]
    Kozlov G, Funato Y, Chen YS, Zhang Z, Illes K, Miki H, Gehring K.
      Phosphatases of regenerating liver (PRLs) are markers of cancer and promote tumor growth. They have been implicated in a variety of biochemical pathways but the physiologically relevant target of phosphatase activity has eluded 20 years of investigation. Here, we show that PRL3 catalytic activity is not required in a mouse model of metastasis. PRL3 binds and inhibits CNNM4, a membrane protein associated with magnesium transport. Analysis of PRL3 mutants specifically defective in either CNNM-binding or phosphatase activity demonstrate that CNNM-binding is necessary and sufficient to promote tumor metastasis. As PRLs do have phosphatase activity, they are in fact pseudo-pseudophosphatases. Phosphatase activity leads to formation of phosphocysteine, which blocks CNNM-binding and may play a regulatory role. We show levels of PRL cysteine phosphorylation vary in response to culture conditions and in different tissues. Examination of related protein phosphatases shows the stability of phosphocysteine is a unique and evolutionarily conserved property of PRLs. The demonstration that PRL3 functions as a pseudophosphatase has important ramifications for the design of PRL inhibitors for cancer.
    Keywords:  autophosphorylation; cancer; cysteine phosphorylation; dual-specificity phosphoprotein phosphatase; magnesium; metastasis; phosphocysteine; protein phosphatase; pseudoenzyme; pseudophosphatase
  29. Blood. 2020 Jun 24. pii: blood.2020005795. [Epub ahead of print]
    Wang Q, Zhao D, Xian M, Wang Z, Bi E, Su P, Qian J, Ma X, Yang M, Liu L, Zu Y, Pingali SR, Chen K, Cai Z, Yi Q.
      Multiple myeloma (MM) remains largely incurable despite significant advances in bio- and chemotherapy. The major problem in MM management is development of drug resistance. Macrophage migration inhibitory factor (MIF) expression was significantly higher in purified MM cells from relapsed patients than those with sustained response, and high MIF MM patients had significantly shorter progression-free survival (PFS) and overall survival (OS). MM cell lines also express high levels of MIF, and knocking out MIF made them more sensitive to proteasome inhibitor (PI) induced apoptosis not observed with other chemotherapy drugs. Mechanistic studies showed that MIF protects MM cells from PI-induced apoptosis by maintaining mitochondrial function via suppression of superoxide production in response to PIs. Specifically, MIF, in the form of a homotrimer, acts as a chaperone for superoxide dismutase 1 (SOD1) to suppress PI-induced SOD1 misfolding and maintain SOD1 activity. MIF inhibitor 4-IPP and homotrimer disrupter ebselen, which do not kill MM cells, enhanced PI-induced SOD1 misfolding and loss of function, resulting in significantly more cell death in both cell lines and primary MM cells. More importantly, inhibiting MIF activity in vivo displayed synergistic antitumor activity with PIs and re-sensitized PI-resistant MM cells to treatment. In support of these findings, gene-profiling data showed a significantly negative correlation between MIF and SOD1 expression and response to PI treatment in MM patients. Hence, this study reveals that MIF plays a crucial role in MM sensitivity to PIs, and suggests that targeting MIF may be a promising strategy to (re)sensitize MM to the treatment.
  30. Dev Cell. 2020 Jun 12. pii: S1534-5807(20)30420-2. [Epub ahead of print]
    Fattet L, Jung HY, Matsumoto MW, Aubol BE, Kumar A, Adams JA, Chen AC, Sah RL, Engler AJ, Pasquale EB, Yang J.
      Mechanical cues from the extracellular matrix (ECM) regulate various cellular processes via distinct mechanotransduction pathways. In breast cancer, increased ECM stiffness promotes epithelial-to-mesenchymal transition (EMT), cell invasion, and metastasis. Here, we identify a mechanosensitive EPHA2/LYN protein complex regulating EMT and metastasis in response to increasing ECM stiffness during tumor progression. High ECM stiffness leads to ligand-independent phosphorylation of ephrin receptor EPHA2, which recruits and activates the LYN kinase. LYN phosphorylates the EMT transcription factor TWIST1 to release TWIST1 from its cytoplasmic anchor G3BP2 to enter the nucleus, thus triggering EMT and invasion. Genetic and pharmacological inhibition of this pathway prevents breast tumor invasion and metastasis in vivo. In human breast cancer samples, activation of this pathway correlates with collagen fiber alignment, a marker of increasing ECM stiffness. Our findings reveal an EPHA2/LYN/TWIST1 mechanotransduction pathway that responds to mechanical signals from the tumor microenvironment to drive EMT, invasion, and metastasis.
    Keywords:  ECM stiffness and breast cancer; EMT; EPHA2; LYN; TWIST1; epithelial-mesenchymal transition; matrix stiffness; mechanotransduction; metastasis
  31. Mol Cancer Res. 2020 Jun 22. pii: molcanres.0108.2020. [Epub ahead of print]
    Tian Y, Liu Q, Yu S, Chu Q, Chen Y, Wu K, Wang L.
      Constitutive NRF2 activation by disrupted KEAP1-NRF2 interaction has been reported in a variety of human cancers. However, studies focusing on NRF2-driven KEAP1 expression under human cancer contexts are still uncommon. We examined mRNA expression correlation between NRF2 and KEAP1 in multiple human cancers. We measured KEAP1 mRNA and protein alterations in response to the activation or silencing of NRF2. We queried ChIP-seq datasets to identify NRF2 binding to KEAP1 promoters in human cells. We used reporter assay and CRISPR editing to assess KEAP1 promoter activity and mRNA abundance change. To determine specimen implication of the feedback pattern, we used gene expression ratio to predict NRF2 signal disruption as well as patients' prognosis. Correlation analysis showed KEAP1 mRNA expression was in positive association with NRF2 in multiple squamous cell cancers. The positive correlations were consistent across all squamous cell lung cancer cohorts, but not in adenocarcinomas. In human lung cells, NRF2 interventions significantly altered KEAP1 mRNA and protein expressions. ChIP-qPCR and sequencing data demonstrated consistent NRF2 occupancy to KEAP1 promoter. Deleting NRF2 binding site significantly reduced baseline and inducible KEAP1 promoter activity and KEAP1 mRNA expression. By incorporating tumor tissue KEAP1 mRNA expressions in estimating NRF2 signaling disruptions, we found increased TXN/KEAP1 mRNA ratio in cases with NRF2 gain or KEAP1 loss and decreased NRF2/KEAP1 mRNA ratio in cases with NRF2-KEAP1 somatic mutations. In TCGA PanCancer datasets, we also identified that cases with loss-of-function mutations in NRF2 pathway recurrently appeared above the NRF2-KEAP1 mRNA expression regression lines. Moreover, compared with previous NRF2 signatures, the ratio-based strategy showed better predictive performance in survival analysis with multiple SQC cohort validations. Implications: NRF2-driven KEAP1 transcription is a crucial component of NRF2 signaling modulation. This hidden circuit will provide in-depth insight into novel cancer prevention and therapeutic strategies.
  32. Cancers (Basel). 2020 Jun 21. pii: E1640. [Epub ahead of print]12(6):
    Becco P, Gallo S, Poletto S, Frascione MPM, Crotto L, Zaccagna A, Paruzzo L, Caravelli D, Carnevale-Schianca F, Aglietta M.
      Malignant melanoma is the third most common type of tumor that causes brain metastases. Patients with cerebral involvement have a dismal prognosis and their treatment is an unmet medical need. Brain involvement is a multistep process involving several signaling pathways such as Janus kinase/signal Transducer and Activator of Transcription (JAK/STAT), Phosphoinositide 3-kinase/Protein Kinase B (PI3K/AKT), Vascular Endothelial Growth Factor and Phosphatase and Tensin Homolog (PTEN). Recently therapy that targets the MAPK signaling (BRAF/MEK inhibitors) and immunotherapy (anti-CTLA4 and anti-PD1 agents) have changed the therapeutic approaches to stage IV melanoma. In contrast, there are no solid data about patients with brain metastases, who are usually excluded from clinical trials. Retrospective data showed that BRAF-inhibitors, alone or in combination with MEK-inhibitors have interesting clinical activity in this setting. Prospective data about the combinations of BRAF/MEK inhibitors have been recently published, showing an improved overall response rate. Short intracranial disease control is still a challenge. Several attempts have been made in order to improve it with combinations between local and systemic therapies. Immunotherapy approaches seem to retain promising activity in the treatment of melanoma brain metastasis as showed by the results of clinical trials investigating the combination of anti-CTL4 (Ipilimumab) and anti-PD1(Nivolumab). Studies about the combination or the sequential approach of target therapy and immunotherapy are ongoing, with immature results. Several clinical trials are ongoing trying to explore new approaches in order to overcome tumor resistance. At this moment the correct therapeutic choices for melanoma with intracranial involvement is still a challenge and new strategies are needed.
    Keywords:  brain metastases; metastatic melanoma; target therapy
  33. Mol Cancer. 2020 Jun 20. 19(1): 107
    Li H, Liu ZY, Wu N, Chen YC, Cheng Q, Wang J.
      Due to the DNA repair defect, BRCA1/2 deficient tumor cells are more sensitive to PARP inhibitors (PARPi) through the mechanism of synthetic lethality. At present, several PAPRi targeting poly (ADP-ribose) polymerase (PARP) have been approved for ovarian cancer and breast cancer indications. However, PARPi resistance is ubiquitous in clinic. More than 40% BRCA1/2-deficient patients fail to respond to PARPi. In addition, lots of patients acquire PARPi resistance with prolonged oral administration of PARPi. Homologous recombination repair deficient (HRD), as an essential prerequisite of synthetic lethality, plays a vital role in killing tumor cells. Therefore, Homologous recombination repair restoration (HRR) becomes the predominant reason of PARPi resistance. Recently, it was reported that DNA replication fork protection also contributed to PARPi resistance in BRCA1/2-deficient cells and patients. Moreover, various factors, such as reversion mutations, epigenetic modification, restoration of ADP-ribosylation (PARylation) and pharmacological alteration lead to PARPi resistance as well. In this review, we reviewed the underlying mechanisms of PARP inhibitor resistance in detail and summarized the potential strategies to overcome PARPi resistance and increase PARPi sensitivity.
    Keywords:  Homologous recombination; PARPi; Resistance; Synthetic lethality
  34. J Clin Invest. 2020 Jun 23. pii: 130323. [Epub ahead of print]
    Garcia-Recio S, Thennavan A, East MP, Parker JS, Cejalvo JM, Garay JP, Hollern DP, He X, Mott KR, Galván P, Fan C, Selitsky SR, Coffey AR, Marron D, Brasó-Maristany F, Burgues O, Albanell J, Rojo F, Lluch A, Martinez de Dueñas E, Rosen JM, Johnson GL, Carey LA, Prat A, Perou CM.
      Mechanisms driving tumor progression from less aggressive subtypes to more aggressive states represent key targets for therapy. We identified a subset of Luminal A primary breast tumors to give rise to HER2-enriched (HER2E) subtype metastases, but remain clinically HER2 negative (cHER2-). By testing the unique genetic and transcriptomic features of these cases, we developed the hypothesis FGFR4 likely participates in this subtype switching. To evaluate this, we developed two FGFR4 genomic signatures using a PDX model treated with a FGFR4 inhibitor, which inhibited PDX growth in vivo. Bulk tumor gene expression analysis and single cell RNAseq demonstrated that the inhibition of FGFR4 signaling caused molecular switching. In the METABRIC breast cancer cohort,FGFR4-induced and FGFR4-repressed signatures each predicted overall survival. Additionally, FGFR4-induced signature was also an independent prognostic factor beyond subtype and stage. Supervised analysis of 77 primary tumors with paired metastasis revealed that the FGFR4-induced signature was significantly higher in luminal/ER+ tumor metastases compared with their primaries. Finally, multivariate analysis demonstrated that the FGFR4-induced signature also predicted site-specific metastasis for lung, liver and brain, but not for bone or lymph nodes. These data identify a link between FGFR4-regulated genes and metastasis, suggesting treatment options for FGFR4-positive patients, whose high expression is not caused by mutation or amplification.
    Keywords:  Breast cancer; Genetics; Oncology
  35. Cancer Res. 2020 Jun 26. pii: canres.2232.2019. [Epub ahead of print]
    Yamauchi Y, Kodama Y, Shiokawa M, Kakiuchi N, Marui S, Kuwada T, Sogabe Y, Tomono T, Mima A, Morita T, Matsumori T, Ueda T, Tsuda M, Nishikawa Y, Kuriyama K, Sakuma Y, Ota Y, Maruno T, Uza N, Masuda A, Tatsuoka H, Yabe D, Minamiguchi S, Masui T, Inagaki N, Uemoto S, Chiba T, Seno H.
      Pancreatic neuroendocrine tumors (PanNET) were classified into grades (G) 1-3 by the World Health Organization in 2017, but the precise mechanisms of PanNET initiation and progression have remained unclear. In this study, we used a genetically engineered mouse model to investigate the mechanisms of PanNET formation. Although pancreas-specific deletion of the Rb gene (Pdx1-Cre;Rbf/f) in mice did not affect pancreatic exocrine cells, the α-cell/β-cell ratio of islet cells was decreased at 8 months of age. During long-term observation (18-20 months), mice formed well-differentiated PanNET with a Ki67-labeling index of 2.7%. In contrast, pancreas-specific induction of a p53 mutation (Pdx1-Cre;Trp53R172H) had no effect on pancreatic exocrine and endocrine tissues, but simultaneous induction of a p53 mutation with Rb gene deletion (Pdx1-Cre;Trp53R172H;Rb f/f) resulted in the formation of aggressive PanNET with a Ki67-labeling index of 24.7% over the short-term (4 months). In Pdx1-Cre;Trp53R172H;Rb f/f mice, mRNA expression of Pten and Tsc2, negative regulators of the mTOR pathway, significantly decreased in the islet cells, and activation of the mTOR pathway was confirmed in subsequently formed PanNET. Thus, by manipulating Rb and p53 genes, we established a multistep progression model from dysplastic islets to indolent PanNET and aggressive metastatic PanNET in mice. These observations suggest that Rb and p53 have distinct roles in the development of PanNET.