bims-tucedo Biomed News
on Tumor cell dormancy
Issue of 2020‒05‒10
thirty-five papers selected by
Isabel Puig Borreil
Vall d’Hebron Institute of Oncology


  1. Nat Cell Biol. 2020 May 04.
    Huang Y, Wang H, Hao Y, Lin H, Dong M, Ye J, Song L, Wang Y, Li Q, Shan B, Jiang Y, Li H, Shao Z, Kroemer G, Zhang H, Bai L, Jin T, Wang C, Ma Y, Cai Y, Ding C, Liu S, Pan Y, Jiang W, Zhou R.
      PTEN is a dual-specificity phosphatase that is frequently mutated in human cancer, and its deficiency in cancer has been associated with therapy resistance and poor survival. Although the intrinsic tumour-suppressor function of PTEN has been well established, evidence of its role in the tumour immune microenvironment is lacking. Here, we show that chemotherapy-induced antitumour immune responses and tumour suppression rely on myeloid-cell PTEN, which is essential for chemotherapy-induced activation of the NLRP3 inflammasome and antitumour immunity. PTEN directly interacts with and dephosphorylates NLRP3 to enable NLRP3-ASC interaction, inflammasome assembly and activation. Importantly, supplementation of IL-1β restores chemotherapy sensitivity in mouse myeloid cells with a PTEN deficiency. Clinically, chemotherapy-induced IL-1β production and antitumour immunity in patients with cancer is correlated with PTEN expression in myeloid cells, but not tumour cells. Our results demonstrate that myeloid PTEN can determine chemotherapy responsiveness by promoting NLRP3-dependent antitumour immunity and suggest that myeloid PTEN might be a potential biomarker to predict chemotherapy responses.
    DOI:  https://doi.org/10.1038/s41556-020-0510-3
  2. Cancer Discov. 2020 May 06. pii: CD-19-1242. [Epub ahead of print]
    Leibold J, Ruscetti M, Cao Z, Ho YJ, Baslan T, Zou M, Abida W, Feucht J, Han T, Barriga FM, Tsanov KM, Zamechek L, Kulick A, Amor C, Tian S, Rybczyk K, Salgado NR, Sanchez-Rivera FJ, Watson PA, de Stanchina E, Wilkinson JE, Dow LE, Abate-Shen C, Sawyers CL, Lowe SW.
      To study genetic factors influencing the progression and therapeutic responses of advanced prostate cancer, we developed a fast and flexible system that introduces genetic alterations relevant to human disease directly into the prostate glands of mice using tissue electroporation. These electroporation-based genetically engineered mouse models (EPO-GEMMs) recapitulate features of traditional germline models and, by modeling genetic factors linked to late stage human disease, can produce tumors that are metastatic and castration resistant. A subset of tumors with p53 alterations acquired spontaneous WNT pathway alterations, which are also associated with metastatic prostate cancer in humans. Using the EPO-GEMM approach and an orthogonal organoid based model, we show that WNT pathway activation drives metastatic disease that is sensitive to pharmacological WNT pathway inhibition. Thus, by leveraging EPO-GEMMs, we reveal a functional role for WNT signaling in driving prostate cancer metastasis and validate the WNT pathway as therapeutic target in metastatic prostate cancer.
    DOI:  https://doi.org/10.1158/2159-8290.CD-19-1242
  3. Cancer Discov. 2020 May 08. pii: CD-19-1352. [Epub ahead of print]
    Zhao D, Cai L, Lu X, Liang X, Li J, Chen P, Ittmann M, Shang X, Jiang S, Li H, Meng C, Flores I, Song JH, Horner JW, Lan Z, Wu CJ, Li J, Chang Q, Chen KC, Wang G, Deng P, Spring DJ, Wang YA, DePinho RA.
      Genetic inactivation of PTEN is common in prostate cancer and correlates with poorer prognosis. We previously identified chromodomain-helicase-DNA-binding protein 1 (CHD1) as an essential gene in PTEN-deficient cancer cells. Here, we sought definitive in vivo genetic evidence for, and mechanistic understanding of, the essential role of CHD1 in PTEN-deficient prostate cancer. In Pten and Pten/Smad4 genetically engineered mouse models, prostate specific deletion of Chd1 resulted in markedly delayed tumor progression and prolonged survival. Chd1 deletion was associated with profound tumor microenvironment remodeling characterized by reduced MDSCs and increased CD8+ T cells. Further analysis identified IL-6 as a key transcriptional target of CHD1, which plays a major role in recruitment of immunosuppressive MDSCs. Given the prominent role of MDSCs in suppressing responsiveness to immune checkpoint inhibitors (ICI), our genetic and tumor biological findings support combined testing of anti-IL-6 and ICI therapies, specifically in PTEN-deficient prostate cancer.
    DOI:  https://doi.org/10.1158/2159-8290.CD-19-1352
  4. Mol Cancer. 2020 May 06. 19(1): 83
    Guo X, Zhou Q, Su D, Luo Y, Fu Z, Huang L, Li Z, Jiang D, Kong Y, Li Z, Chen R, Chen C.
      BACKGROUND: Accumulating evidence suggests that circular RNAs (circRNAs) are important participants in cancer progression. However, the biological processes and underlying mechanisms of circRNAs in pancreatic ductal adenocarcinoma (PDAC) are unclear.METHOD: CircRNAs were verified by Sanger sequencing. Colony formation, 5-Ethynyl-2'-deoxyuridine (EdU), and Transwell assays were performed to investigate the effect of circBFAR on the proliferation, invasion, and migration of PDAC cells in vitro. RNA pull-down assays were conducted to verify the binding of circBFAR with microRNA miR-34b-5p.
    RESULTS: In the present study, we identified a novel circRNA (termed as circBFAR, hsa_circ_0009065) that was upregulated in a 208-case cohort of patients with PDAC. The ectopic expression of circBFAR correlated positively with the tumor-node-metastasis (TNM) stage and was related to poorer prognosis of patients with PDAC. Moreover, circBFAR knockdown dramatically inhibited the proliferation and motility of PDAC cells in vitro and their tumor-promoting and metastasis properties in in vivo models. Mechanistically, circBFAR upregulated mesenchymal-epithelial transition factor (MET) expression via sponging miR-34b-5p. Additionally, circBFAR overexpression increased the expression of MET and activated downstream phosphorylation of Akt (Ser 473) and further activated the MET/PI3K/Akt signaling pathway, which ultimately promoted the progression of PDAC cells. Importantly, application of MET inhibitors could significantly attenuate circBFAR-mediated tumorigenesis in vivo.
    CONCLUSIONS: Our findings showed that circBFAR plays an important role in the proliferation and metastasis of PDAC, which might be explored as a potential prognostic marker and therapeutic target for PDAC.
    Keywords:  MET; PI3K/Akt pathway; Pancreatic ductal adenocarcinoma; circBFAR; miR-34b-5p
    DOI:  https://doi.org/10.1186/s12943-020-01196-4
  5. Theranostics. 2020 ;10(12): 5242-5258
    Yang LF, Yang F, Zhang FL, Xie YF, Hu ZX, Huang SL, Shao ZM, Li DQ.
      Rationale: Chromodomain Y-like 2 (CDYL2) is a member of the CDY gene family involved in spermatogenesis, but its role in human cancer has not been reported. Analyses of publicly available databases demonstrate that CDYL2 is abundantly expressed in breast tumors. However, whether CDYL2 is involved in breast cancer progression remains unknown. Methods: Quantitative real-time PCR and immunoblotting assays were used to determine the expression levels of CDYL2 transcript variants in breast cancer cell lines and primary breast tumors. The effect of CDYL2 transcript variants on the malignant phenotypes of breast cancer cells was examined through in vitro and in vivo assays. Immunofluorescent staining, RNA-seq, ATAC-seq, and ChIP-qPCR were used to investigate the underlying mechanisms behind the aforementioned observations. Results: Here we show that CDYL2 generated four transcript variants, named CDYL2a-CDYL2d. CDYL2a and CDYL2b were the predominant variants expressed in breast cancer cell lines and breast tumors and exerted strikingly discrete functions in breast cancer growth and metastasis. CDYL2a was upregulated in the majority of the breast cancer cell lines and tumors, and promoted breast cancer cell proliferation, colony formation in vitro, and tumorigenesis in xenografts. In contrast, CDYL2b was mainly expressed in luminal- and HER2-positive types of breast cancer cell lines and tumors, and suppressed the migratory, invasive, and metastatic potential of breast cancer cells in vitro and in vivo. Mechanistically, CDYL2a partially localized to SC35-positive nuclear speckles and promoted alternative splicing of a subset of target genes, including FIP1L1, NKTR, and ADD3 by exon skipping. Elimination of full-length FIP1L1, NKTR, and ADD3 rescued the impaired cell proliferation through CDYL2a depletion. In contrast, CDYL2b localized to heterochromatin and transcriptionally repressed several metastasis-promoting genes, including HPSE, HLA-F, and SELL. Restoration of HPSE, HLA-F, or SELL expression in CDYL2b-overexpressing cells attenuated the ability of CDYL2b to suppress breast cancer cell migration and invasion. Conclusions: Collectively, these findings establish an isoform-specific function of CDYL2 in breast cancer development and progression and highlight that pharmacological inhibition of the CDYL2a, but not the CDYL2b, isoform may be an effective strategy for breast cancer therapy.
    Keywords:  Breast cancer; CDYL2; alternative splicing; transcript variants; transcriptional repression
    DOI:  https://doi.org/10.7150/thno.43744
  6. Cancer Metastasis Rev. 2020 May 05.
    Jiramongkol Y, Lam EW.
      Forkhead box O (FOXO) transcription factors regulate diverse biological processes, affecting development, metabolism, stem cell maintenance and longevity. They have also been increasingly recognised as tumour suppressors through their ability to regulate genes essential for cell proliferation, cell death, senescence, angiogenesis, cell migration and metastasis. Mechanistically, FOXO proteins serve as key connection points to allow diverse proliferative, nutrient and stress signals to converge and integrate with distinct gene networks to control cell fate, metabolism and cancer development. In consequence, deregulation of FOXO expression and function can promote genetic disorders, metabolic diseases, deregulated ageing and cancer. Metastasis is the process by which cancer cells spread from the primary tumour often via the bloodstream or the lymphatic system and is the major cause of cancer death. The regulation and deregulation of FOXO transcription factors occur predominantly at the post-transcriptional and post-translational levels mediated by regulatory non-coding RNAs, their interactions with other protein partners and co-factors and a combination of post-translational modifications (PTMs), including phosphorylation, acetylation, methylation and ubiquitination. This review discusses the role and regulation of FOXO proteins in tumour initiation and progression, with a particular emphasis on cancer metastasis. An understanding of how signalling networks integrate with the FOXO transcription factors to modulate their developmental, metabolic and tumour-suppressive functions in normal tissues and in cancer will offer a new perspective on tumorigenesis and metastasis, and open up therapeutic opportunities for malignant diseases.
    Keywords:  Cancer metastasis; Forkhead; Post-translational regulation; Protein interactions; Transcription factor; Tumour suppressor
    DOI:  https://doi.org/10.1007/s10555-020-09883-w
  7. Mol Cancer. 2020 May 04. 19(1): 82
    Kong Y, Li Y, Luo Y, Zhu J, Zheng H, Gao B, Guo X, Li Z, Chen R, Chen C.
      BACKGROUND: Patients with lymph node (LN)-positive pancreatic ductal adenocarcinoma (PDAC) have extremely poor survival rates. Circular RNAs (circRNAs), a newly discovered type of endogenous noncoding RNAs, have been proposed to mediate the progression of diverse types of tumors. However, the role and underlying regulatory mechanisms of circRNAs in the LN metastasis of PDAC remain unknown.METHODS: Next-generation sequencing was used to identify differentially expressed circRNAs between PDAC and normal adjacent tissues. In vitro and in vivo experiments were conducted to evaluate the functional role of circNFIB1. RNA pulldown and luciferase assays were performed to examine the binding of circNFIB1 and miR-486-5p.
    RESULTS: In the present study, we identified that a novel circRNA (circNFIB1, hsa_circ_0086375) was downregulated in PDAC and negatively associated with LN metastasis in PDAC patients. Functionally, circNFIB1 knockdown promoted lymphangiogenesis and LN metastasis of PDAC both in vitro and in vivo. Mechanistically, circNFIB1 functioned as a sponge of miR-486-5p, and partially reversed the effect of miR-486-5p. Moreover, circNFIB1 attenuated the oncogenic effect of miR-486-5p and consequently upregulated PIK3R1 expression, which further downregulated VEGF-C expression through inhibition of the PI3K/Akt pathway, and ultimately suppressed lymphangiogenesis and LN metastasis in PDAC.
    CONCLUSIONS: Our findings provide novel insight into the underlying mechanism of circRNA-mediated LN metastasis of PDAC and suggest that circNFIB1 may serve as a potential therapeutic target for LN metastasis in PDAC.
    Keywords:  Lymphatic metastasis; PI3K/Akt signaling pathway; PIK3R1; Pancreatic cancer; circNFIB1
    DOI:  https://doi.org/10.1186/s12943-020-01205-6
  8. Cancer Res. 2020 May 04. pii: canres.3584.2019. [Epub ahead of print]
    Bouchet M, Lainé A, Boyault C, Proponnet-Guerault M, Meugnier E, Bouazza L, Kan CWS, Geraci S, El-Moghrabi S, Hernandez-Vargas H, Benetollo C, Yoshiko Y, Duterque-Coquillaud M, Clézardin P, Marie JC, Bonnelye E.
      Bone is the most common metastatic site for breast cancer. Although the estrogen-related receptor alpha (ERRα) has been implicated in breast cancer cell dissemination to the bone from the primary tumor, its role after tumor cell anchorage in the bone microenvironment remains elusive. Here, we reveal that ERRα inhibits the progression of bone metastases of breast cancer cells by increasing the immune activity of the bone microenvironment. Overexpression of ERRα in breast cancer bone metastases induced expression of chemokines CCL17 and CCL20 and repressed production of transforming growth factor beta 3 (TGF-β3). Subsequently, CD8+ T lymphocytes recruited to bone metastases escaped TGF-β signaling control and were endowed with exacerbated cytotoxic features, resulting in significant reduction in metastases. The clinical relevance of our findings in mice was confirmed in over 240 breast cancer patients. Thus, this study reveals that ERRα regulates immune properties in the bone microenvironment that contributes to decreasing metastatic growth.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-3584
  9. Cancer Res. 2020 May 07. pii: canres.3837.2019. [Epub ahead of print]
    Matei D, Nephew KP.
      Ovarian cancer (OC) is an aggressive epithelial tumor that remains a major cause of cancer morbidity and mortality in women. Epigenetic alterations including DNA methylation and histone modifications are being characterized in OC and have been functionally linked to processes involved in tumor initiation, chemotherapy resistance, cancer stem cell survival, and tumor metastasis. The epigenetic traits of cancer cells and of associated tumor microenvironment components have been shown to promote an immunosuppressive tumor milieu. However, DNA methylation and histone modifications are reversible and therapies targeting the epigenome have been implicated in potential reinvigoration of the antitumor immunity. In this review, we provide an overview specifically of DNA methylation and histone modifications as "clothes of the ovarian cancer genome" in relationship to their functional effects and highlight recent developments in the field. We also address the clinical implications of therapeutic strategies to remove or alter specific articles of genomic "clothing" and restore normal cellular function. As the clothes of the genome continue to be deciphered, we envision that the epigenome will become an important therapeutic target for cancer.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-3837
  10. Oncogene. 2020 May 05.
    Huang WJ, Tian XP, Bi SX, Zhang SR, He TS, Song LY, Yun JP, Zhou ZG, Yu RM, Li M.
      Hepatocellular carcinoma (HCC) metastasis is largely responsible for HCC-associated recurrence and mortality. We aimed to identify metastasis-related long non-coding RNAs (lncRNAs) to understand the molecular mechanism of HCC metastasis. We first identified that miR-1258 was downregulated in HCC tissues both in The Cancer Genome Atlas (TCGA) and Sun Yat-sen University Cancer Center (SYSUCC) dataset. MiR-1258 expression negatively correlated with recurrence-free survival and overall survival of HCC patients. MiR-1258 overexpression inhibited migration and invasion of HCC cells both in vitro and in vivo, whereas miR-1258 downregulation promoted cell metastasis. Luciferase assays verified direct binding of miR-1258 to Smad2 and Smad3, thereby attenuating TGF-β/Smad signaling. We further established that lncRNA LINC01278 was a negative regulator of miR-1258. In vivo and in vitro assays demonstrated that LINC01278-mediated HCC metastasis was dependent on miR-1258 expression. Furthermore, miR-1258 downregulation in turn increased LINC01278 expression. We also observed that TCF-4 could bind to the LINC01278 promoter site. In addition, LINC01278 downregulation decreased migration and invasion of HCC cells induced by β-catenin and TGF-β1 both in vitro and in vivo. We uncovered a novel mechanism for β-catenin/TCF-4-LINC01278-miR-1258-Smad2/3 feedback loop activation in HCC metastasis, and the study indicated that LINC01278 could serve as a therapeutic target for HCC metastasis.
    DOI:  https://doi.org/10.1038/s41388-020-1307-3
  11. J Biol Chem. 2020 May 08. 295(19): 6278-6279
    Sweeney C.
      Triple-negative breast cancer (TNBC) is characterized by its aggressive biology, early metastatic spread, and poor survival outcomes. TNBC lacks expression of the targetable receptors found in other breast cancer subtypes, mandating use of cytotoxic chemotherapy. However, resistance to chemotherapy is a significant problem, encountered in about two-thirds of TNBC patients, and new strategies are needed to mitigate resistance. In this issue of the Journal of Biological Chemistry, Geck et al. report that TNBC cells are highly sensitive to inhibition of the de novo polyamine synthesis pathway and that inhibition of this pathway sensitizes cells to TNBC-relevant chemotherapy, uncovering new opportunities for addressing chemoresistance.
    DOI:  https://doi.org/10.1074/jbc.H120.013736
  12. Cancer Res. 2020 May 04. pii: canres.0506.2020. [Epub ahead of print]
    Han L, Long Q, Li S, Xu Q, Zhang B, Dou X, Qian M, Jiramongkol Y, Guo J, Cao L, Chin YE, Lam EW, Jiang J, Sun Y.
      Cellular senescence is a potent tumor-suppressive program that prevents neoplastic events. Paradoxically, senescent cells develop an inflammatory secretome, termed the senescence-associated secretory phenotype (SASP), which is implicated in age-related pathologies including cancer. Here we report that senescent cells actively synthesize and release small extracellular vesicles (sEVs) with a distinctive size distribution. Mechanistically, SIRT1 loss supported accelerated sEV production despite enhanced proteome-wide ubiquitination, a process correlated with ATP6V1A downregulation and defective lysosomal acidification. Once released, senescent stromal sEVs significantly altered the expression profile of recipient cancer cells and enhanced their aggressiveness, specifically drug resistance mediated by expression of ATP binding cassette subfamily B member 4 (ABCB4). Targeting SIRT1 with agonist SRT2104 prevented development of cancer resistance by restraining sEV production by senescent stromal cells. In clinical oncology, sEVs in peripheral blood of posttreatment cancer patients were readily detectable by routine biotechniques, presenting an exploitable biomarker to monitor therapeutic efficacy and predict long-term outcome. Together, this study identifies a distinct mechanism supporting pathological activities of senescent cells and provides a potent avenue to circumvent advanced human malignancies by co-targeting cancer cells and their surrounding microenvironment, which contributes to drug resistance via secretion of sEVs from senescent stromal cells.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-0506
  13. Lancet Oncol. 2020 May;pii: S1470-2045(20)30228-X. [Epub ahead of print]21(5): e233
    Ludmir EB, McCaw ZR, Kim DH, Tian L, Wei LJ.
      
    DOI:  https://doi.org/10.1016/S1470-2045(20)30228-X
  14. Cancer Res. 2020 May 05. pii: canres.2052.2019. [Epub ahead of print]
    Wu F, Zhang C, Zhao C, Wu H, Teng Z, Jiang T, Wang Y.
      Aberrant activation of the Hedgehog (HH) signaling pathway underlines the initiation and progression of a multitude of cancers. The effectiveness of the leading drugs vismodegib (GDC-0449) and sonidegib (LDE225), both Smoothened (SMO) antagonists, is compromised by acquisition of mutations that alter pathway components, notably secondary mutations in SMO and amplification of GLI2, a transcriptional mediator at the end of the pathway. Pharmacological blockade of GLI2 activity could ultimately overcome these diversified refractory mechanisms, which would also be effective in a broader spectrum of primary tumors than current SMO antagonists. To this end, we conducted a high-content screen directly analyzing the ciliary translocation of GLI2, a key event for GLI2 activation in HH signal transduction. Several prostaglandin compounds were shown to inhibit accumulation of GLI2 within the primary cilium (PC). In particular, prostaglandin E1 (PGE1), an FDA-approved drug, is a potent GLI2 antagonist that overcame resistance mechanisms of both SMO mutagenesis and GLI2 amplification. Consistent with a role in HH pathway regulation, EP4 receptor localized to the PC. Mechanistically, PGE1 inhibited HH signaling through the EP4 receptor, enhancing cAMP-PKA activity, which promoted phosphorylation and degradation of GLI2 via the ubiquitination pathway. PGE1 also effectively inhibited the growth of drug refractory human medulloblastoma (MB) xenografts. Together, these results identify PGE1 and other prostaglandins as potential templates for complementary therapeutic development to circumvent resistance to current generation SMO antagonists in use in the clinic.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-2052
  15. Nature. 2020 May;581(7806): 100-105
    Yamamoto K, Venida A, Yano J, Biancur DE, Kakiuchi M, Gupta S, Sohn ASW, Mukhopadhyay S, Lin EY, Parker SJ, Banh RS, Paulo JA, Wen KW, Debnath J, Kim GE, Mancias JD, Fearon DT, Perera RM, Kimmelman AC.
      Immune evasion is a major obstacle for cancer treatment. Common mechanisms of evasion include impaired antigen presentation caused by mutations or loss of heterozygosity of the major histocompatibility complex class I (MHC-I), which has been implicated in resistance to immune checkpoint blockade (ICB) therapy1-3. However, in pancreatic ductal adenocarcinoma (PDAC), which is resistant to most therapies including ICB4, mutations that cause loss of MHC-I are rarely found5 despite the frequent downregulation of MHC-I expression6-8. Here we show that, in PDAC, MHC-I molecules are selectively targeted for lysosomal degradation by an autophagy-dependent mechanism that involves the autophagy cargo receptor NBR1. PDAC cells display reduced expression of MHC-I at the cell surface and instead demonstrate predominant localization within autophagosomes and lysosomes. Notably, inhibition of autophagy restores surface levels of MHC-I and leads to improved antigen presentation, enhanced anti-tumour T cell responses and reduced tumour growth in syngeneic host mice. Accordingly, the anti-tumour effects of autophagy inhibition are reversed by depleting CD8+ T cells or reducing surface expression of MHC-I. Inhibition of autophagy, either genetically or pharmacologically with chloroquine, synergizes with dual ICB therapy (anti-PD1 and anti-CTLA4 antibodies), and leads to an enhanced anti-tumour immune response. Our findings demonstrate a role for enhanced autophagy or lysosome function in immune evasion by selective targeting of MHC-I molecules for degradation, and provide a rationale for the combination of autophagy inhibition and dual ICB therapy as a therapeutic strategy against PDAC.
    DOI:  https://doi.org/10.1038/s41586-020-2229-5
  16. PLoS One. 2020 ;15(5): e0225290
    Shi S, Huang X, Ma X, Zhu X, Zhang Q.
      PURPOSE: Chemotherapy resistance of esophageal cancer is a key factor affecting the postoperative treatment of esophageal cancer. Among the media that transmit signals between cells, the exosomes secreted by tumor cells mediate information transmission between tumor cells, which can make sensitive cells obtain resistance. Although some cellular exosomes play an important role in tumor's acquired drug resistance, the related action mechanism is still not explored specifically.METHODS: To elucidate this process, we constructed a cisplatin-resistant esophageal cancer cell line, and proved that exosomes conferring cellular resistance in esophageal cancer can promote cisplatin resistance in sensitive cells. Through high-throughput sequencing analysis of the exosome and of cells after stimulation by exosomes, we determined that the miRNA193 in exosomes conferring cellular resistance played a key role in sensitive cells acquiring resistance to cisplatin. In vitro experiments showed that miRNA193 can regulate the cell cycle of esophageal cancer cells and inhibit apoptosis, so that sensitive cells can acquire resistance to cisplatin. An in vivo experiment proved that miRNA193 can promote tumor proliferation through the exosomes, and provide sensitive cells with slight resistance to cisplatin.
    RESULTS: Small RNA sequencing of exosomes showed that exosomes in drug-resistant cells have 189 up-regulated and 304 down-regulated miRNAs; transcriptome results showed that drug-sensitive cells treated with drug-resistant cellular exosomes have 3446 high-expression and 1709 low-expression genes; correlation analysis showed that drug-resistant cellular exosomes mainly affect the drug resistance of sensitive cells through paths such as cytokine-cytokine receptor interaction, and the VEGF and Jak-STAT signaling pathways; miRNA193, one of the high-expression miRNAs in drug-resistant cellular exosomes, can promote drug resistance by removing cisplatin's inhibition of the cell cycle of sensitive cells.
    CONCLUSION: Sensitive cells can become resistant to cisplatin through acquired drug-resistant cellular exosomes, and miRNA193 can make tumor cells acquire cisplatin resistance by regulating the cell cycle.
    DOI:  https://doi.org/10.1371/journal.pone.0225290
  17. PLoS One. 2020 ;15(5): e0231999
    Rinaldi J, Sokol ES, Hartmaier RJ, Trabucco SE, Frampton GM, Goldberg ME, Albacker LA, Daemen A, Manning G.
      BACKGROUND: Metastatic breast cancer is the leading cause of cancer death in women, but the genomics of metastasis in breast cancer are poorly studied.METHODS: We explored a set of 11,616 breast tumors, including 5,034 metastases, which had undergone targeted sequencing during standard clinical care.
    RESULTS: Besides the known hotspot mutations in ESR1, we observed a metastatic enrichment of previously unreported, lower-prevalence mutations in the ligand-binding domain, implying that these mutations may also be functional. Furthermore, individual ESR1 hotspots are significantly enriched in specific metastatic tissues and histologies, suggesting functional differences between these mutations. Other alterations enriched across all metastases include loss of function of the CDK4 regulator CDKN1B, and mutations in the transcription factor CTCF. Mutations enriched at specific metastatic sites generally reflect biology of the target tissue and may be adaptations to growth in the local environment. These include PTEN and ASXL1 alterations in brain metastases and NOTCH1 alterations in skin. We observed an enrichment of KRAS, KEAP1, STK11 and EGFR mutations in lung metastases. However, the patterns of other mutations in these tumors indicate that these are misdiagnosed lung primaries rather than breast metastases.
    CONCLUSIONS: An order-of-magnitude increase in samples relative to previous studies allowed us to detect novel genomic characteristics of metastatic cancer and to expand and clarify previous findings.
    DOI:  https://doi.org/10.1371/journal.pone.0231999
  18. Cancers (Basel). 2020 Apr 30. pii: E1123. [Epub ahead of print]12(5):
    Bhatia S, Blick T, Pinto C, Waltham M, Monkman J, Ivanova E, Pollock PM, Nagaraj SH, Wiegmans AP, Haviv I, Simpson KJ, Thompson EW.
      BACKGROUND: Breast cancer (BC) is a heterogeneous disease for which the commonly used chemotherapeutic agents primarily include the anthracyclines (doxorubicin, epirubicin), microtubule inhibitors (paclitaxel, docetaxel, eribulin), and alkylating agents (cyclophosphamide). While these drugs can be highly effective, metastatic tumours are frequently refractory to treatment or become resistant upon tumour relapse.METHODS: We undertook a cell polarity/epithelial mesenchymal plasticity (EMP)-enriched short hairpin RNA (shRNA) screen in MDA-MB-468 breast cancer cells to identify factors underpinning heterogeneous responses to three chemotherapeutic agents used clinically in breast cancer: Doxorubicin, docetaxel, and eribulin. shRNA-transduced cells were treated for 6 weeks with the EC10 of each drug, and shRNA representation assessed by deep sequencing. We first identified candidate genes with depleted shRNA, implying that their silencing could promote a response. Using the Broad Institute's Connectivity Map (CMap), we identified partner inhibitors targeting the identified gene families that may induce cell death in combination with doxorubicin, and tested them with all three drug treatments.
    RESULTS: In total, 259 shRNAs were depleted with doxorubicin treatment (at p < 0.01), 66 with docetaxel, and 25 with eribulin. Twenty-four depleted hairpins overlapped between doxorubicin and docetaxel, and shRNAs for TGFB2, RUNX1, CCDC80, and HYOU1 were depleted across all the three drug treatments. Inhibitors of MDM/TP53, TGFBR, and FGFR were identified by CMap as the top pharmaceutical perturbagens and we validated the combinatorial benefits of the TGFBR inhibitor (SB525334) and MDM inhibitor (RITA) with doxorubicin treatment, and also observed synergy between the inhibitor SB525334 and eribulin in MDA-MB-468 cells.
    CONCLUSIONS: Taken together, a cell polarity/EMP-enriched shRNA library screen identified relevant gene products that could be targeted alongside current chemotherapeutic agents for the treatment of invasive BC.
    Keywords:  FGFR; MDM; TGFBR; TP53; chemotherapy resistance; combination chemotherapy; docetaxel; doxorubicin; eribulin; shRNA library screening
    DOI:  https://doi.org/10.3390/cancers12051123
  19. Oncogene. 2020 May 04.
    Yoneda A, Minomi K, Tamura Y.
      Breast cancer (BC) is an aggressive cancer that is a leading cause of cancer-associated death in women worldwide. Although increased expression of heat shock protein 47 (HSP47), a collagen-specific chaperone, is associated with the high malignancy of BC, its role in BC remains largely unclear. Here we show that a small population of high-invasive BC cells expresses HSP47 and that HSP47-positive high-invasive BC cells have a high metastatic potential that is completely abolished by disruption of HSP47. HSP47 interacts with non-muscle myosin IIA (NMIIA) via the unfolded protein response transducer IRE1α, resulting in enhancement of the metastatic potential of high-invasive BC cells by augmenting the contractile force of actin filaments. Ablation of NMIIA abrogates the metastatic potential of HSP47-positive high-invasive BC cells. We further show that forced expression of NMIIA confers a high metastatic potential on low-invasive BC cells in which HSP47 but not NMIIA is expressed. Overall, our study indicates that HSP47 acts as a stimulator for metastasis of BC cells and suggest that HSP47 may be a candidate for a therapeutic target against BC.
    DOI:  https://doi.org/10.1038/s41388-020-1311-7
  20. Nat Commun. 2020 May 08. 11(1): 2264
    Orlando BJ, Liao M.
      ABCG2 is an ABC transporter that extrudes a variety of compounds from cells, and presents an obstacle in treating chemotherapy-resistant cancers. Despite recent structural insights, no anticancer drug bound to ABCG2 has been resolved, and the mechanisms of multidrug transport remain obscure. Such a gap of knowledge limits the development of novel compounds that block or evade this critical molecular pump. Here we present single-particle cryo-EM studies of ABCG2 in the apo state, and bound to the three structurally distinct chemotherapeutics. Without the binding of conformation-selective antibody fragments or inhibitors, the resting ABCG2 adopts a closed conformation. Our cryo-EM, biochemical, and functional analyses reveal the binding mode of three chemotherapeutic compounds, demonstrate how these molecules open the closed conformation of the transporter, and establish that imatinib is particularly effective in stabilizing the inward facing conformation of ABCG2. Together these studies reveal the previously unrecognized conformational cycle of ABCG2.
    DOI:  https://doi.org/10.1038/s41467-020-16155-2
  21. Cancer Res. 2020 May 01. 80(9): 1799-1800
    Hayward SW.
      Carcinoma-associated fibroblasts (CAF) are a potential therapeutic target for both direct and indirect regulation of cancer progression and therapy response. In this issue of Cancer Research, Ford and colleagues investigate the influence of CAF on the immune environment of tumors, specifically focusing on the regulation of CD8+ T cells, required for immune therapy response. Their work suggests a role for stromally expressed NADPH oxidase 4 (NOX4) as a modulator of reactive oxygen species that in turn can reduce the number of CD8+ T cells locally. Inhibition of NOX4 increased CD8+ T cells and restored responsiveness to immune therapy, suggesting an indirect stromally targeted avenue for therapy resensitization.See related article by Ford et al., p. 1846.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-0590
  22. Cancer Discov. 2020 May 05. pii: CD-19-1416. [Epub ahead of print]
    Gstalder C, Liu D, Miao D, Lutterbach B, DeVine AL, Lin C, Shettigar M, Pancholi P, Buchbinder EI, Carter SL, Manos MP, Rojas-Rudilla V, Brennick R, Gjini E, Chen PH, Lako A, Rodig S, Yoon CH, Freeman GJ, Barbie DA, Hodi FS, Miles W, Van Allen EM, Haq R.
      The molecular mechanisms leading to resistance to PD-1 blockade are largely unknown. Here, we characterize tumor biopsies from a melanoma patient who displayed heterogeneous responses to anti-PD-1 therapy. We observe that a resistant tumor exhibited a loss-of-function mutation in the tumor suppressor gene FBXW7, while a sensitive tumor from the same patient did not. Consistent with a functional role in immunotherapy response, inactivation of Fbxw7 in murine tumor cell lines caused resistance to anti-PD-1 in immunocompetent animals. Loss of Fbxw7 was associated with altered immune microenvironment, decreased tumor-intrinsic expression of the dsRNA sensors Mda5 and Rig-I, diminished induction of type I interferon and MHC-I expression. In contrast, restoration of dsRNA sensing in Fbxw7-deficient cells was sufficient sensitize them to anti-PD-1. Our results thus establish a new role for the commonly inactivated tumor suppressor FBXW7 in viral sensing and sensitivity to immunotherapy.
    DOI:  https://doi.org/10.1158/2159-8290.CD-19-1416
  23. Cancer Res. 2020 May 06. pii: canres.1523.2019. [Epub ahead of print]
    Huang W, Navarro-Serer B, Jeong YJ, Chianchiano P, Xia L, Luchini C, Veronese N, Dowiak C, Ng T, Trujillo MA, Huang B, Pflüger MJ, Macgregor-Das AM, Lionheart G, Jones D, Fujikura K, Nguyen-Ngoc KV, Neumann NM, Groot VP, Hasanain A, van Oosten AF, Fischer SE, Gallinger S, Singhi AD, Zureikat AH, Brand RE, Gaida MM, Heinrich S, Burkhart RA, He J, Wolfgang CL, Goggins MG, Thompson ED, Roberts NJ, Ewald AJ, Wood LD.
      Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy characterized by extensive local invasion and systemic spread. In this study, we employed a three-dimensional organoid model of human pancreatic cancer to characterize the molecular alterations critical for invasion. Time lapse microscopy was used to observe invasion in organoids from 25 surgically resected human PDAC samples in collagen I. Subsequent lentiviral modification and small molecule inhibitors were used to investigate the molecular programs underlying invasion in PDAC organoids. When cultured in collagen I, PDAC organoids exhibited two distinct, morphologically defined invasive phenotypes, mesenchymal and collective. Each individual PDAC gave rise to organoids with a predominant phenotype, and PDAC that generated organoids with predominantly mesenchymal invasion showed a worse prognosis. Collective invasion predominated in organoids from cancers with somatic mutations in the driver gene SMAD4 (or its signaling partner TGFBR2). Re-expression of SMAD4 abrogated the collective invasion phenotype in SMAD4-mutant PDAC organoids, indicating that SMAD4 loss is required for collective invasion in PDAC organoids. Surprisingly, invasion in passaged SMAD4-mutant PDAC organoids required exogenous TGFβ, suggesting that invasion in SMAD4-mutant organoids is mediated through non-canonical TGFβ signaling. The Rho-like GTPases RAC1 and CDC42 acted as potential mediators of TGFβ-stimulated invasion in SMAD4-mutant PDAC organoids, as inhibition of these GTPases suppressed collective invasion in our model. These data suggest that PDAC utilizes different invasion programs depending on SMAD4 status, with collective invasion uniquely present in PDAC with SMAD4 loss.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-1523
  24. Mol Cancer. 2020 May 08. 19(1): 85
    Liang Y, Song X, Li Y, Chen B, Zhao W, Wang L, Zhang H, Liu Y, Han D, Zhang N, Ma T, Wang Y, Ye F, Luo D, Li X, Yang Q.
      BACKGROUND: Long noncoding RNAs (lncRNAs) play crucial roles in tumor progression and are aberrantly expressed in various cancers. However, the functional roles of lncRNAs in breast cancer remain largely unknown.METHODS: Based on public databases and integrating bioinformatics analyses, the overexpression of lncRNA BCRT1 in breast cancer tissues was detected and further validated in a cohort of breast cancer tissues. The effects of lncRNA BCRT1 on proliferation, migration, invasion and macrophage polarization were determined by in vitro and in vivo experiments. Luciferase reporter assay and RNA immunoprecipitation (RIP) were carried out to reveal the interaction between lncRNA BCRT1, miR-1303, and PTBP3. Chromatin immunoprecipitation (ChIP) and RT-PCR were used to evaluate the regulatory effect of hypoxia-inducible factor-1α (HIF-1α) on lncRNA BCRT1.
    RESULTS: LncRNA BCRT1 was significantly upregulated in breast cancer tissues, which was correlated with poor prognosis in breast cancer patients. LncRNA BCRT1 knockdown remarkably suppressed tumor growth and metastasis in vitro and in vivo. Mechanistically, lncRNA BCRT1 could competitively bind with miR-1303 to prevent the degradation of its target gene PTBP3, which acts as a tumor-promoter in breast cancer. LncRNA BCRT1 overexpression could promote M2 polarization of macrophages, mediated by exosomes, which further accelerated breast cancer progression. Furthermore, lncRNA BCRT1 was upregulated in response to hypoxia, which was attributed to the binding of HIF-1α to HREs in the lncRNA BCRT1 promoter.
    CONCLUSIONS: Collectively, these results reveal a novel HIF-1α/lncRNA BCRT1/miR-1303/PTBP3 pathway for breast cancer progression and suggest that lncRNA BCRT1 might be a potential biomarker and therapeutic target for breast cancer.
    Keywords:  Breast cancer; LncRNA BCRT1; PTBP3; Progression; miR-1303
    DOI:  https://doi.org/10.1186/s12943-020-01206-5
  25. Lancet Oncol. 2020 May;pii: S1470-2045(20)30227-8. [Epub ahead of print]21(5): e226
    Colloca GA, Venturino A.
      
    DOI:  https://doi.org/10.1016/S1470-2045(20)30227-8
  26. Cancer Metastasis Rev. 2020 May 08.
    Zhong Z, Yu J, Virshup DM, Madan B.
      Since the discovery of the first mammalian Wnt proto-oncogene in virus-induced mouse mammary tumors almost four decades ago, Wnt signaling pathway and its involvement in cancers have been extensively investigated. Activation of this evolutionarily conserved pathway promotes cancer development via diverse mechanisms. Cancer is a complex disease and one outstanding conceptual framework for understanding its biology is the "Hallmarks of Cancer". In this review, we focus on the involvement of Wnt signaling in the ten hallmarks of human cancer. These widespread roles of Wnt signaling in human cancers highlight the importance and feasibility of targeting this signaling pathway for cancer treatment.
    Keywords:  Angiogenesis; Cancer; Genome instability; Immune evasion; Inflammation; Metabolism; Metastasis; TERT; Telomeres; Wnt signaling
    DOI:  https://doi.org/10.1007/s10555-020-09887-6
  27. PLoS One. 2020 ;15(5): e0232754
    Kang JK, Heo S, Kim HP, Song SH, Yun H, Han SW, Kang GH, Bang D, Kim TY.
      Analyzing cell-free DNA (cfDNA) as a source of circulating tumor DNA is useful for diagnosing or monitoring patients with cancer. However, the concordance between cfDNA within liquid biopsy and genomic DNA (gDNA) within tumor tissue biopsy is still under debate. To evaluate the concordance in a clinical setting, we enrolled 54 patients with metastatic colorectal cancer and analyzed their plasma cfDNA, gDNA from peripheral blood mononuclear cells (PBMC), and gDNA from available matched tumor tissues using ultra-deep sequencing targeting 10 genes (38-kb size) recurrently mutated in colorectal cancer. We first established a highly reliable cut-off value using reference material. The sensitivity of detecting KRAS hotspot mutations in plasma was calculated as 100%, according to digital droplet PCR. We could selectively detect clinically important somatic alterations with a variant allele frequency as low as 0.18%. We next compared somatic mutations of the 10 genes between cfDNA and genomic DNA from tumor tissues and observed an overall 93% concordance rate between the two types of samples. Additionally, the concordance rate of patients with the time interval between liquid biopsy and tumor tissue biopsy within 6 months and no prior exposure to chemotherapy was much higher than those without. The patients with KRAS mutant fragments in plasma had poor prognosis than those without the mutant fragments (33 months vs. 63 months; p<0.05). Consequently, the profiling with our method could achieve highly concordant results and may facilitate the surveillance of the tumor status with liquid biopsy in CRC patients.
    DOI:  https://doi.org/10.1371/journal.pone.0232754
  28. Cancers (Basel). 2020 May 05. pii: E1161. [Epub ahead of print]12(5):
    Zhao X, Wangmo D, Robertson M, Subramanian S.
      Immune checkpoint blockade therapy (ICBT) has revolutionized the treatment and management of numerous cancers, yet a substantial proportion of patients who initially respond to ICBT subsequently develop resistance. Comprehensive genomic analysis of samples from recent clinical trials and pre-clinical investigation in mouse models of cancer provide insight into how tumors evade ICBT after an initial response to treatment. Here, we summarize our current knowledge on the development of acquired ICBT resistance, by examining the mechanisms related to tumor-intrinsic properties, T-cell function, and tumor-immune cell interactions. We discuss current and future management of ICBT resistance, and consider crucial questions remaining in this field of acquired resistance to immune checkpoint blockade therapies.
    Keywords:  CTLA-4; PD-1; T cells; acquired resistance; immune checkpoint blockade; immune response; tumor immunology
    DOI:  https://doi.org/10.3390/cancers12051161
  29. JCI Insight. 2020 May 05. pii: 133929. [Epub ahead of print]
    Alaluf E, Vokaer B, Detavernier A, Azouz A, Splittgerber M, Carrette A, Boon L, Libert F, Soares MP, Le Moine A, Goriely S.
      Tumor-Associated Macrophages (TAMs) contribute to the maintenance of a strong immunosuppressive environment, supporting tumor progression and resistance to treatment. To date, the mechanisms that drive acquisition of these immunosuppressive features are still poorly defined. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme that catabolizes free heme. It displays important cytoprotective, anti-inflammatory and antioxidant properties. A growing body of evidence suggests that HO-1 may also promote tumor development. Herein, we show that HO-1 is highly expressed in monocytic cells in the tumor microenvironment (TME) once they differentiate into TAMs. Deletion of HO-1 in the myeloid compartment enhances the beneficial effects of a therapeutic antitumor vaccine by restoring CD8 T-cell proliferation and cytotoxicity. We further show that induction of HO-1 plays a major role on monocyte education by tumor cells by modulating their transcriptional and epigenetic programs. These results identify HO-1 as a valuable therapeutic target to reprogram the TME and synergize with current cancer therapies to facilitate antitumoral response.
    Keywords:  Cancer immunotherapy; Immunology; Innate immunity; Macrophages; Oncology
    DOI:  https://doi.org/10.1172/jci.insight.133929
  30. Nat Commun. 2020 May 04. 11(1): 2189
    Loveday C, Litchfield K, Proszek PZ, Cornish AJ, Santo F, Levy M, Macintyre G, Holryod A, Broderick P, Dudakia D, Benton B, Bakir MA, Hiley C, Grist E, Swanton C, Huddart R, Powles T, Chowdhury S, Shipley J, O'Connor S, Brenton JD, Reid A, de Castro DG, Houlston RS, Turnbull C.
      While most testicular germ cell tumours (TGCTs) exhibit exquisite sensitivity to platinum chemotherapy, ~10% are platinum resistant. To gain insight into the underlying mechanisms, we undertake whole exome sequencing and copy number analysis in 40 tumours from 26 cases with platinum-resistant TGCT, and combine this with published genomic data on an additional 624 TGCTs. We integrate analyses for driver mutations, mutational burden, global, arm-level and focal copy number (CN) events, and SNV and CN signatures. Albeit preliminary and observational in nature, these analyses provide support for a possible mechanistic link between early driver mutations in RAS and KIT and the widespread copy number events by which TGCT is characterised.
    DOI:  https://doi.org/10.1038/s41467-020-15768-x
  31. Nat Commun. 2020 May 08. 11(1): 2285
    Kim N, Kim HK, Lee K, Hong Y, Cho JH, Choi JW, Lee JI, Suh YL, Ku BM, Eum HH, Choi S, Choi YL, Joung JG, Park WY, Jung HA, Sun JM, Lee SH, Ahn JS, Park K, Ahn MJ, Lee HO.
      Advanced metastatic cancer poses utmost clinical challenges and may present molecular and cellular features distinct from an early-stage cancer. Herein, we present single-cell transcriptome profiling of metastatic lung adenocarcinoma, the most prevalent histological lung cancer type diagnosed at stage IV in over 40% of all cases. From 208,506 cells populating the normal tissues or early to metastatic stage cancer in 44 patients, we identify a cancer cell subtype deviating from the normal differentiation trajectory and dominating the metastatic stage. In all stages, the stromal and immune cell dynamics reveal ontological and functional changes that create a pro-tumoral and immunosuppressive microenvironment. Normal resident myeloid cell populations are gradually replaced with monocyte-derived macrophages and dendritic cells, along with T-cell exhaustion. This extensive single-cell analysis enhances our understanding of molecular and cellular dynamics in metastatic lung cancer and reveals potential diagnostic and therapeutic targets in cancer-microenvironment interactions.
    DOI:  https://doi.org/10.1038/s41467-020-16164-1
  32. Theranostics. 2020 ;10(12): 5209-5224
    Liao Y, Wang C, Yang Z, Liu W, Yuan Y, Li K, Zhang Y, Wang Y, Shi Y, Qiu Y, Zuo D, He W, Qiu J, Guan X, Yuan Y, Li B.
      Angiogenesis, one of the hallmarks of cancer, is essential for both tumor growth and metastasis. However, its molecular mechanisms in hepatocellular carcinoma (HCC) are largely unknown. Here, we report the role of HOXA5 in tumor angiogenesis of HCC. Methods: The expression of miR-130b-3p and HOXA5 was determined by qRT-PCR and immunohistochemistry, respectively. Capillary tube formation assay, chicken chorioallantoic membrane assay, and subcutaneous xenograft experiments were performed to investigate the role of miR-130-3p and HOXA5. Luciferase reporter assay and chromatin immunoprecipitation assay were performed to evaluate the interaction between Sp1, miR-130b-3p and HOXA5. Results: miR-130b-3p was found up-regulated in HCC and correlated with a poor prognosis. miR-130b-3p promoted HCC angiogenesis both in vitro and in vivo. Mechanistically, HOXA5 was validated as a direct target of miR-130b-3p. Furthermore, we demonstrated that HOXA5 was down-regulated in HCC and its down-regulation was associated with larger tumor size, shorter overall survival, and higher recurrence probability. Moreover, HOXA5 was significantly associated with angiogenesis biomarkers such as CD31 and CD34. Functional studies revealed that the knockdown of HOXA5 also significantly promoted HCC angiogenesis both in vitro and in vivo. Knocking-down HOXA5 significantly provoked HCC cells to induce the capillary tube formation, migration and proliferation of endothelial cells. In xenograft animal models, we found that a decrease of HOXA5 effectively enhanced tumor growth and increased microvessel densities. We further demonstrated that miR-130b-3p could be directly transcriptionally regulated by Sp1. Conclusions: This study showed that a dysregulation in the Sp1/miR-130b-3p/HOXA5 axis contributed to HCC progression and angiogenesis, and that HOXA5 can be considered as a promising therapeutic target for treating HCC.
    Keywords:  Angiogenesis; HOXA5; Hepatocellular carcinoma; miR-130b-3p
    DOI:  https://doi.org/10.7150/thno.43640
  33. Oncogene. 2020 May 04.
    Zhang C, Huang S, Zhuang H, Ruan S, Zhou Z, Huang K, Ji F, Ma Z, Hou B, He X.
      N6-methyladenosine (m6A) RNA methylation contributes to the cancer stem cell (CSC) phenotype through regulating gene expression. YTHDF2, an m6A reader, was shown to be associated with hepatocellular carcinoma (HCC) patient prognosis. However, the effect of YTHDF2 on liver CSC and cancer metastasis and the molecular mechanism of this effect have not been documented. Here, we show that YTHDF2 expression is negatively correlated with HCC patient survival in both data from the Cancer Genome Atlas (TCGA) database and clinical data from our center. By detecting CD133+ cells and carrying out sphere culture assays, we found that knockdown of YTHDF2 led to impaired stemness in Hep3B and Huh7 cells. In contrast, overexpression of YTHDF2 increased the CSC phenotype. Mechanistically, the knockdown and overexpression of YTHDF2 in liver cancer cells resulted in decreased and increased m6A levels in the 5'-untranslated region (UTR) of OCT4 mRNA, respectively, leading to decreased and increased OCT4 protein expression, respectively. A luciferase activity assay showed that mutation of the corresponding m6A methylation sequence in the 5'-UTR of OCT4 mRNA caused significantly decreased gene expression, suggesting a role for YTHDF2-dependent m6A methylation in protein translation. Polysome profiling results also indicated the knockdown and overexpression of YTHDF2 could decrease and increase OCT4 translation, respectively. In particular, overexpression of OCT4 rescued the impaired stemness caused by YTHDF2 depletion, which confirmed the effect of YTHDF2 on CSC phenotype is dependent on OCT4. In vivo, the loss of YTHDF2 reduced tumor burden and inhibited lung metastasis following orthotopic transplantation in nude mice. Last, we demonstrated that YTHDF2 expression is positively correlated with OCT4 expression and m6A levels in the 5'-UTR of OCT4 mRNA in clinical HCC specimens. In conclusion, YTHDF2 promotes the CSC liver phenotype and cancer metastasis by modulating the m6A methylation of OCT4 mRNA.
    DOI:  https://doi.org/10.1038/s41388-020-1303-7
  34. EMBO J. 2020 May 05. e103181
    Lin Z, Niu Y, Wan A, Chen D, Liang H, Chen X, Sun L, Zhan S, Chen L, Cheng C, Zhang X, Bu X, He W, Wan G.
      N6-methyladenosine (m6 A) is an abundant nucleotide modification in mRNA, known to regulate mRNA stability, splicing, and translation, but it is unclear whether it is also has a physiological role in the intratumoral microenvironment and cancer drug resistance. Here, we find that METTL3, a primary m6 A methyltransferase, is significantly down-regulated in human sorafenib-resistant hepatocellular carcinoma (HCC). Depletion of METTL3 under hypoxia promotes sorafenib resistance and expression of angiogenesis genes in cultured HCC cells and activates autophagy-associated pathways. Mechanistically, we have identified FOXO3 as a key downstream target of METTL3, with m6 A modification of the FOXO3 mRNA 3'-untranslated region increasing its stability through a YTHDF1-dependent mechanism. Analysis of clinical samples furthermore showed that METTL3 and FOXO3 levels are tightly correlated in HCC patients. In mouse xenograft models, METTL3 depletion significantly enhances sorafenib resistance of HCC by abolishing the identified METTL3-mediated FOXO3 mRNA stabilization, and overexpression of FOXO3 restores m6 A-dependent sorafenib sensitivity. Collectively, our work reveals a critical function for METTL3-mediated m6 A modification in the hypoxic tumor microenvironment and identifies FOXO3 as an important target of m6 A modification in the resistance of HCC to sorafenib therapy.
    Keywords:  FOXO3; METTL3; N6-methyladenosine; autophagy; hypoxia
    DOI:  https://doi.org/10.15252/embj.2019103181
  35. Clin Cancer Res. 2020 May 04. pii: clincanres.3402.2019. [Epub ahead of print]
    Posadas EM, Chi KN, de Wit R, de Jonge MJA, Attard G, Friedlander TW, Yu MK, Hellemans P, Chien C, Abrams C, Jiao JJ, Saad F.
      INTRODUCTION: Apalutamide is a next-generation androgen receptor (AR) inhibitor approved for patients with nonmetastatic castration-resistant prostate cancer (CRPC) and metastatic castration-sensitive prostate cancer. We evaluated the pharmacokinetics, safety, and antitumor activity of apalutamide combined with abiraterone acetate plus prednisone (AA-P) in patients with metastatic CRPC (mCRPC).MATERIALS AND METHODS: Multicenter, open-label, phase Ib drug-drug interaction study conducted in 57 mCRPC patients treated with 1,000-mg AA plus 10-mg P daily beginning on cycle 1 day 1 (C1D1) and 240-mg apalutamide daily starting on C1D8 in 28-day cycles. Serial blood samples for pharmacokinetic analysis were collected on C1D7 and C2D8.
    RESULTS: Systemic exposure to abiraterone, prednisone, and prednisolone decreased 14%, 61%, and 42%, respectively, when apalutamide was coadministered with AA-P. No increase in mineralocorticoid excess-related adverse events was observed. Patients without prior exposure to AR signaling inhibitors had longer median treatment duration and greater mean decrease in prostate-specific antigen (PSA) from baseline compared with those who had received prior therapy. Confirmed PSA reductions of ≥50% from baseline at any time were observed in 80% (12/15) of AR signaling inhibitor-naïve patients and 14% (6/42) of AR signaling inhibitor-treated patients.
    CONCLUSION: Treatment with apalutamide plus AA-P was well tolerated and showed evidence of antitumor activity in patients with mCRPC, including those with disease progression on AR signaling inhibitors. No clinically significant pharmacokinetic interaction was observed between abiraterone and apalutamide; however, apalutamide decreased exposure to P. These data support development of 1,000-mg AA plus 10-mg P daily with 240-mg apalutamide daily in patients with mCRPC.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-19-3402