bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2022‒04‒17
28 papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Blood Adv. 2022 Apr 12. pii: bloodadvances.2022006968. [Epub ahead of print]
      In adult acute myeloid leukemia (AML), acquisition of driver somatic mutations may be preceded by a benign state termed clonal hematopoiesis (CH). To develop therapeutic strategies to prevent leukemia development from CH, it is important to understand the mechanisms by which CH-driving and AML-driving mutations cooperate. Here, we use mice with inducible mutant alleles common in human CH (DNMT3AR882; mouse Dnmt3aR878H) and AML (NPM1c; mouse Npm1cA). We find that Dnmt3aR878H/+ hematopoietic stem cells (HSCs), but not multipotent progenitor cell (MPP) subsets, have reduced expression of cytokine and pro-inflammatory transcriptional signatures and a functional competitive advantage over their wild-type counterparts. Dnmt3aR878H/+ HSCs are the most potent cell type transformed by Npm1cA, generating myeloid malignancies in which few additional cooperating somatic mutation events were detected. At a molecular level, Npm1cA in cooperation with Dnmt3aR878H acutely increased accessibility of a distinct set of promoters in HSCs compared to MPP cells. These promoters were enriched for cell cycling, PI3K/AKT/mTOR signaling, stem cell signatures, and targets of transcription factors including NFAT and the chromatin binding factor HMGB1, which have been implicated in human AML. These results demonstrate cooperativity between pre-existing Dnmt3aR878H and Npm1cA at the chromatin level, where specific loci altered in accessibility by Npm1cA are dependent on cell context as well as Dnmt3a mutation status. These findings have implications for biological understanding and therapeutic intervention into transformation from CH to AML.
  2. Leukemia. 2022 Apr 13.
      The identification of characteristic differences between cancer stem cells and their normal counterparts remains a key challenge for cancer treatment. Here, we investigated the role of immunoglobulin superfamily member 8 (Igsf8, also known as EWI-2, PGRL, and CD316) on normal and malignant hematopoietic stem cells, mainly using the conditional knockout model. Deletion of Igsf8 did not affect steady state hematopoiesis, but it led to a significant improvement of survival in mouse myeloid leukemia models. Deletion of Igsf8 significantly depletes leukemia stem cells (LSCs) through enhanced apoptosis and β-catenin degradation. At a molecular level, we found that activation of β-catenin in LSCs depends on Igsf8, which promotes the association of FZD4 with its co-receptor LRP6 in the presence of Igsf8. Similarly, IGSF8 inhibition blocks the colony-forming ability of LSCs and improves the survival of recipients in xenograft models of myeloid leukemia. Collectively, these data indicate strong genetic evidence identifying Igsf8 as a key regulator of myeloid leukemia and the possibility that targeting IGSF8 may serve as a new therapeutic approach against myeloid leukemia.
  3. Blood Adv. 2022 Apr 12. pii: bloodadvances.2021006303. [Epub ahead of print]
      The phase III MIRROS trial (NCT02545283) evaluated the efficacy and safety of the small-molecule MDM2 antagonist idasanutlin plus cytarabine in patients with relapsed/refractory acute myeloid leukemia (R/R AML). Adults (N=447) with R/R AML whose disease relapsed or was refractory after ≤2 prior induction regimens as initial treatment or following salvage chemotherapy regimen, with Eastern Cooperative Oncology Group performance status ≤2 were enrolled regardless of TP53 mutation status and randomly assigned 2:1 to idasanutlin 300 mg or placebo orally twice daily plus cytarabine 1 g/m2 intravenously on days 1 to 5 of 28-day cycles. At primary analysis (cutoff, November 2019), 436 patients were enrolled, including 355 in the TP53 wild-type intention-to-treat (TP53WT-ITT) population. The primary endpoint, overall survival in the TP53WT-ITT population, was not met (median, 8.3 vs 9.1 months with idasanutlin-cytarabine vs placebo-cytarabine; stratified hazard ratio, 1.08; 95% CI, 0.81-1.45; p = .58). The complete remission (CR) rate, a key secondary endpoint, was 20.3% vs 17.1% (odds ratio [OR], 1.23; 95% CI, 0.70-2.18). The overall response rate (ORR) was 38.8% vs 22.0% (OR, 2.25; 95% CI, 1.36-3.72). Common any-grade adverse events (≥10% incidence in any arm) were diarrhea (87.0% vs 32.9%), febrile neutropenia (52.8% vs 49.3%), and nausea (52.5% vs 31.5%). In summary, despite improved ORR, adding idasanutlin to cytarabine did not improve overall survival or CR rates in patients with R/R AML.
  4. Blood. 2022 Apr 14. pii: blood.2021014465. [Epub ahead of print]
      Leukemic transformation (LT) of myeloproliferative neoplasm (MPN) has a dismal prognosis and is largely fatal. Mutational inactivation of TP53 is the most common somatic event in LT, however the mechanisms by which TP53 mutations promote LT remain unresolved. Using an allelic series of mouse models of Jak2/Trp53 mutant MPN, we identify that only biallelic inactivation of Trp53 results in LT (to a pure erythroleukemia (PEL)). This PEL arises from the megakaryocyte erythroid progenitor (MEP) population. Importantly, the BMP2/SMAD pathway is aberrantly activated during LT, and results in abnormal self-renewal of MEPs. Finally, we identify that Jak2/Trp53 mutant PEL is characterized by recurrent copy number alterations and DNA damage. Using a synthetic-lethality strategy, by targeting active DNA-repair pathways, we demonstrate that this PEL is highly sensitive to combination WEE1 and PARP inhibition. These observations yield new mechanistic insights into the process of p53 mutant LT, and offer new, clinically-translatable therapeutic approaches.
  5. Cancer Discov. 2022 Apr 11. pii: candisc.0956.2021. [Epub ahead of print]
      Leukemic blasts are immune cells gone awry. We hypothesized that dysregulation of inflammatory pathways contributes to the maintenance of their leukemic state and can be exploited as a cell-intrinsic, self-directed immunotherapy. To this end, we applied genome-wide screens to discover genetic vulnerabilities in acute myeloid leukemia (AML) cells implicated in inflammatory pathways. We identified the immune modulator interferon regulatory factor 2 binding protein 2 (IRF2BP2) as a selective AML dependency. We validated AML cell dependency on IRF2BP2 with genetic and protein degradation approaches in vitro and genetically in vivo. Chromatin and global gene expression studies demonstrated that IRF2BP2 represses IL-1B/TNFa signaling via NF-κB, and IRF2BP2 perturbation results in an acute inflammatory state leading to AML cell death. These findings elucidate a hitherto unexplored AML dependency, reveal cell-intrinsic inflammatory signaling as a mechanism priming leukemic blasts for regulated cell death, and establish IRF2BP2-mediated transcriptional repression as a mechanism for blast survival.
  6. J Clin Med. 2022 Mar 30. pii: 1923. [Epub ahead of print]11(7):
      Acute myeloid leukemia (AML) in children remains deadly, despite the use of maximally intensive therapy. Because leukemia stem cells (LSCs) significantly contribute to chemoresistance and relapse, therapies that specifically target the LSCs are likely to be more beneficial in improving outcome. LSCs are known to have high telomerase activity and telomerase activity is negatively correlated with survival in pediatric AML. We evaluated the preclinical efficacy of imetelstat, an oligonucleotide inhibitor of telomerase activity in patient-derived xenograft (PDX) lines of pediatric AML. Imetelstat treatment significantly increased apoptosis/death of the LSC population in a dose-dependent manner in six pediatric AML PDX lines ex vivo, while it had limited activity on the stem cell population in normal bone marrow specimens. These results were validated in vivo in two distinct PDX models wherein imetelstat as single agent or in combination with chemotherapy greatly reduced the LSC percentage and prolonged median survival. Imetelstat combination with DNA hypomethylating agent azacitidine was also beneficial in extending survival. Secondary transplantation experiments showed delayed engraftment and improved survival of mice receiving imetelstat-treated cells, confirming the diminished LSC population. Thus, our data suggest that imetelstat represents an effective therapeutic strategy for pediatric AML.
    Keywords:  imetelstat; leukemia stem cells; patient-derived xenograft models; pediatric acute myeloid leukemia; telomerase
  7. Blood Cancer Discov. 2022 Apr 11. pii: bloodcandisc.BCD-21-0144-E.2021. [Epub ahead of print]
      Approximately 20% of patients with myeloproliferative neoplasms (MPNs) harbor mutations in the gene calreticulin (CALR), with 80% of those mutations classified as either type 1 or type 2. While type 2 CALR mutant proteins retain many of the Ca2+ binding sites present in the wild type protein, type 1 CALR mutant proteins lose these residues. The functional consequences of this differential loss of Ca2+ binding sites remain yet unexplored. Here, we show that the loss of Ca2+ binding residues in the type 1 mutant CALR protein directly impairs its Ca2+ binding ability, which in turn leads to depleted endoplasmic reticulum (ER) Ca2+ and subsequent activation of the IRE1a/XBP1 pathway of the unfolded protein response. Genetic or pharmacological inhibition of IRE1a/XBP1 signaling induces cell death only in type 1 mutant but not type 2 mutant or wild type CALR-expressing cells, and abrogates type 1 mutant CALR-driven MPN disease progression in vivo.
  8. Mol Cell Oncol. 2021 ;8(6): 2003161
      Tissue-inappropriate expression of FOXC1 (Forkhead Box C1) in acute myeloid leukemia confers a monocyte/macrophage lineage differentiation block. We discovered that FOXC1 interacts with RUNX1 (Runt-Related Transcription Factor 1) to stabilize a RUNX1, HDAC1 (Histone Deacetylase 1) and TLE3 (Transducin-like enhancer protein 3) repressor complex at enhancers controlling myeloid differentiation genes.
    Keywords:  AML; FOXC1; Groucho; RUNX1; TLE3
  9. Clin Lymphoma Myeloma Leuk. 2022 Feb 26. pii: S2152-2650(22)00065-9. [Epub ahead of print]
      Acute myeloid leukemia (AML) treatment landscape had evolved over the last decades with better understanding of the disease genomics and the use of the targeted therapy, despite this treatment evolution, 7 + 3 remains the mainstay treatment for most AML cases. Many attempts had been made to improve the treatment outcome with 7 + 3 like manipulating the doses or the duration, but with no significant change in the outcome. In 2017 FDA approved CPX-351,a liposomal formulation of cytarabine and daunorubicin at a fixed 5:1 molar ratio, for the treatment of adults with newly diagnosed AML with myelodysplasia-related changes and therapy-related AML (t-AML). Since the approval, many trials were conducted or still ongoing in assessing the role of CPX-351 in treating different patient populations, AML subcategories or when combined with different agents. In this review, we will summarize the current role of CPX-351 in treating this largely heterogeneous disease.
    Keywords:  Acute Myeloid Leukemia; CPX -351; Induction Chemotherapy; Myelodysplastic Syndromes
  10. Cancers (Basel). 2022 Mar 28. pii: 1723. [Epub ahead of print]14(7):
      Hematopoietic stem cells (HSCs) are rare, self-renewing cells that perch on top of the hematopoietic tree. The HSCs ensure the constant supply of mature blood cells in a tightly regulated process producing peripheral blood cells. Intense efforts are ongoing to optimize HSC engraftment as therapeutic strategy to treat patients suffering from hematopoietic diseases. Preclinical research paves the way by developing methods to maintain, manipulate and expand HSCs ex vivo to understand their regulation and molecular make-up. The generation of a sufficient number of transplantable HSCs is the Holy Grail for clinical therapy. Leukemia stem cells (LSCs) are characterized by their acquired stem cell characteristics and are responsible for disease initiation, progression, and relapse. We summarize efforts, that have been undertaken to increase the number of long-term (LT)-HSCs and to prevent differentiation towards committed progenitors in ex vivo culture. We provide an overview and compare methods currently available to isolate, maintain and enrich HSC subsets, progenitors and LSCs and discuss their individual advantages and drawbacks.
    Keywords:  dormancy; ex vivo culture; hematopoietic stem cells; leukemic stem cells; maintenance; self-renewal
  11. Exp Hematol. 2022 Apr 10. pii: S0301-472X(22)00133-3. [Epub ahead of print]
      Acute myeloid leukemia (AML) is an aggressive disease of clonal hematopoiesis with a high rate of relapse and refractory disease despite intensive therapy. Traditionally, relapsed or refractory AML has increased therapeutic resistance and poor long-term survival. In recent years, advancements in the mechanistic understanding of leukemogenesis has allowed for the development of targeted therapies. These therapies offer novel alternatives to intensive chemotherapy and have prolonged survival in relapsed or refractory AML. Unfortunately, a significant portion of patients do not respond to these therapies and relapse occurs in most patients who initially responded. This review will focus on the mechanisms of resistance to targeted therapies in relapsed or refractory AML.
  12. Cancers (Basel). 2022 Mar 29. pii: 1734. [Epub ahead of print]14(7):
      The effectiveness of venetoclax (VEN) in relapsed or refractory acute myeloid leukemia (RR-AML) has not been well established. This retrospective, multicenter, observational database studied the effectiveness of VEN in a cohort of 51 RR-AML patients and evaluated for predictors of response and overall survival (OS). The median age was 68 years, most were at high risk, 61% received ≥2 therapies for AML, 49% had received hypomethylating agents, and ECOG was ≥2 in 52%. Complete remission (CR) rate, including CR with incomplete hematological recovery (CRi), was 12.4%. Additionally, 10.4% experienced partial response (PR). The CR/CRi was higher in combination with azacitidine (AZA; 17.9%) than with decitabine (DEC; 6.7%) and low-dose cytarabine (LDAC; 0%). Mutated NPM1 was associated with increased CR/CRi. Median OS was 104 days (95% CI: 56-151). For the combination with AZA, DEC, and LDAC, median OS was 120 days, 104 days, and 69 days, respectively; p = 0.875. Treatment response and ECOG 0 influenced OS in a multivariate model. A total of 28% of patients required interruption of VEN because of toxicity. Our real-life series describes a marginal probability of CR/CRi and poor OS after VEN-based salvage. Patients included had very poor-risk features and were heavily pretreated. The small percentage of responders did not reach the median OS.
    Keywords:  acute myeloid leukemia; refractory; relapsed; venetoclax
  13. Am J Hematol. 2022 Apr 12.
      Newly diagnosed acute myeloid leukemia is often deemed a medical emergency, requiring urgent treatment. This is in contradiction with the need for accurate cytogenetic and molecular data, which is not immediately available, to select optimal therapy. We hypothesized that cytoreduction with hydroxyurea or cytarabine would enable urgent disease control and provide a bridge to clinical trial enrollment. We analyzed 3 prospective frontline clinical trials that allowed the use of cytoreduction before treatment initiation. Among 274 patients with a median age of 62 (range, 18-89), there was no significant difference in short- and long-term outcome and safety among patients who did (CytoRed) or did not receive (NoCytoRed) cytoreduction. The overall response rate in CytoRed group was 91%, compared to 86% in NoCytoRed group (p=.264). The 30- and 60-day mortality rates were 2% and 7% in CytoRed group, compared to 2% (p= .978) and 6% (p= .652) in NoCytoRed group, respectively. There was no significant difference in overall survival (OS) between in CytoRed group compared to NoCytoRed group (Hazard ratio 0.97, 95% CI 0.70-1.37, p=.879). Results were unchanged after stratification by age (< or ≥ 65 years) or after multivariate analyses for OS. Our data suggests that urgent cytoreduction using hydroxyurea or cytarabine is a feasible and safe approach to facilitate acquisition of complete diagnostic information prior to treatment initiation on a clinical trial. This article is protected by copyright. All rights reserved.
  14. Nat Commun. 2022 Apr 11. 13(1): 1981
      T cell large granular lymphocytic leukemia (T-LGLL) is a rare lymphoproliferative disorder of mature, clonally expanded T cells, where somatic-activating STAT3 mutations are common. Although T-LGLL has been described as a chronic T cell response to an antigen, the function of the non-leukemic immune system in this response is largely uncharacterized. Here, by utilizing single-cell RNA and T cell receptor profiling (scRNA+TCRαβ-seq), we show that irrespective of STAT3 mutation status, T-LGLL clonotypes are more cytotoxic and exhausted than healthy reactive clonotypes. In addition, T-LGLL clonotypes show more active cell communication than reactive clones with non-leukemic immune cells via costimulatory cell-cell interactions, monocyte-secreted proinflammatory cytokines, and T-LGLL-clone-secreted IFNγ. Besides the leukemic repertoire, the non-leukemic T cell repertoire in T-LGLL is also more mature, cytotoxic, and clonally restricted than in other cancers and autoimmune disorders. Finally, 72% of the leukemic T-LGLL clonotypes share T cell receptor similarities with their non-leukemic repertoire, linking the leukemic and non-leukemic repertoires together via possible common target antigens. Our results provide a rationale to prioritize therapies that target the entire immune repertoire and not only the T-LGLL clonotype.
  15. Proc Natl Acad Sci U S A. 2022 Apr 19. 119(16): e2112482119
      SignificanceWe report on a deregulatory activity on microRNA (miRNA) biogenesis by the FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD) in acute myeloid leukemia. FLT3-ITD provides a divergent signal for concurrent and aberrant miR-155 up-regulation and miR-126 down-regulation via a series of miRNA-protein regulatory loops interconnected through SH2-containing inositol phosphatase 1 (SHIP1)/phosphor-protein kinase B (AKT)/Sprouty related EVH1 domain containing 1 (SPRED1) signaling. This divergent input signal eventually converges and amplifies an output signal for leukemic growth.
    Keywords:  AKT; FLT3-ITD; acute myeloid leukemia; miR-126; miR-155
  16. Blood Adv. 2022 Apr 14. pii: bloodadvances.2021006872. [Epub ahead of print]
      Geriatric assessment (GA) predicts survival among older adults with acute myeloid leukemia (AML) treated intensively. We evaluated the predictive utility of GA among older adults treated with low intensity therapy on a multi-site trial. We conducted a companion study (CALGB 361101) to a randomized phase 2 trial (CALGB 11002) of adults >=60 years considered "unfit" for intensive therapy, testing the efficacy of adding bortezomib to decitabine therapy. On 361101, GA and quality of life (QOL) assessment was administered prior to treatment and every other subsequent cycle. Relationships between baseline GA and QOL measures with survival were evaluated using Kaplan Meier estimation and Cox Proportional Hazards models. One-hundred sixty-five patients enrolled on CALGB 11002 and 96 (52%) of them also enrolled on 361101 (median age, 73.9 years). Among participants, 85.4% completed ≥1 baseline assessment. In multivariate analyses, greater comorbidity (Hematopoietic Cell Transplantation-specific Comorbidity Index >3), worse cognition (Blessed Orientation Memory Concentration score > 4), and lower European Organization for Research and Treatment of Cancer global QOL scores at baseline were significantly associated with shorter overall survival (OS) (p<0.05 each) after adjustment for Karnofsky Performance Status, age and treatment arm. Dependence in Instrumental Activities of Daily Living and cognitive impairment were associated with 6 month mortality (HR 3.5, CI 1.2-10.4, and HR 3.1 CI 1.1-8.6 respectively). GA measures evaluating comorbidity, cognition, and self-reported function were associated with survival and represent candidate measures for screening older adults planned to receive lower intensity AML therapies.
  17. Blood Cancer J. 2022 Apr 14. 12(4): 64
      RAS mutations prevalent in high-risk leukemia have been linked to relapse and chemotherapy resistance. Efforts to directly target RAS proteins have been largely unsuccessful. However, since RAS-mediated transformation is dependent on signaling through the RAS-related C3 botulinum toxin substrate (RAC) small GTPase, we hypothesized that targeting RAC may be an effective therapeutic approach in RAS mutated tumors. Here we describe multiple small molecules capable of inhibiting RAC activation in acute lymphoblastic leukemia cell lines. One of these, DW0254, also demonstrates promising anti-leukemic activity in RAS-mutated cells. Using chemical proteomics and biophysical methods, we identified the hydrophobic pocket of phosphodiester 6 subunit delta (PDE6D), a known RAS chaperone, as a target for this compound. Inhibition of RAS localization to the plasma membrane upon DW0254 treatment is associated with RAC inhibition through a phosphatidylinositol-3-kinase/AKT-dependent mechanism. Our findings provide new insights into the importance of PDE6D-mediated transport for RAS-dependent RAC activation and leukemic cell survival.
  18. Cell Death Dis. 2022 Apr 12. 13(4): 337
      Patient-derived xenografted (PDX) models were generated through the transplantation of primary acute lymphoblastic leukemia (ALL) cells into immunodeficient NSG mice. We observed that ALL cells from mouse bone marrow (BM) produced extracellular vesicles (EVs) with specific expression of inducible heat shock protein HSP70, which is commonly activated in cancer cells. Taking advantage of this specific expression, we designed a strategy to generate fluorescent HSP70-labeled ALL EVs and monitor the impact of these EVs on endogenous murine BM cells ex vivo and in vivo. We discovered that hematopoietic stem and progenitor cells (HSPC) were mainly targeted by ALL EVs, affecting their quiescence and maintenance in the murine BM environment. Investigations revealed that ALL EVs were enriched in cholesterol and other metabolites that contribute to promote the mitochondrial function in targeted HSPC. Furthermore, using CD34+ cells isolated from cord blood, we confirmed that ALL EVs can modify quiescence of human HSPC. In conclusion, we have discovered a new oncogenic mechanism illustrating how EVs produced by proliferative ALL cells can target and compromise a healthy hematopoiesis system during leukemia development.
  19. Blood. 2022 Apr 15. pii: blood.2021012882. [Epub ahead of print]
      Target identification for CAR T cell therapies remains challenging due to the limited repertoire of tumor-specific surface proteins. Intracellular proteins presented in the context of cell surface HLA provide a wide pool of potential antigens targetable through TCR mimic antibodies. Mass spectrometry (MS) of HLA ligands from eight hematological and non-hematological cancer cell lines identified a shared, non-immunogenic, HLA-A*02 restricted ligand (ALNEQIARL) derived from the kinetochore-associated NDC80 gene. CAR T cells directed against the ALNEQIARL:HLA-A*02 complex demonstrated high sensitivity and specificity for recognition and killing of multiple cancer types, especially those of hematological origin and were efficacious in mouse models against a human leukemia and a solid tumor. In contrast, no toxicities towards resting or activated healthy leukocytes as well as hematopoietic stem cells were observed. This demonstrates how MS can inform the design of broadly reactive therapeutic TCR mimic CAR T cell therapies that can target multiple cancer types currently not druggable by small molecules, conventional CAR T cells, T cells or antibodies.
  20. Br J Cancer. 2022 Apr 14.
      INTRODUCTION: Splice modulators have been assessed clinically in treating haematologic malignancies exhibiting splice factor mutations and acute myeloid leukaemia. However, the mechanisms by which such modulators repress leukaemia remain to be elucidated.OBJECTIVES: The primary goal of this assessment was to assess the molecular mechanism by which the natural splice modulator GEX1A kills leukaemic cells in vitro and within in vivo mouse models.
    METHODS: Using human leukaemic cell lines, we assessed the overall sensitivity these cells have to GEX1A via EC50 analysis. We subsequently analysed its effects using in vivo xenograft mouse models and examined whether cell sensitivities were correlated to genetic characteristics or protein expression levels. We also utilised RT-PCR and RNAseq analyses to determine splice change and RNA expression level differences between sensitive and resistant leukaemic cell lines.
    RESULTS: We found that, in vitro, GEX1A induced an MCL-1 isoform shift to pro-apoptotic MCL-1S in all leukaemic cell types, though sensitivity to GEX1A-induced apoptosis was negatively associated with BCL-xL expression. In BCL-2-expressing leukaemic cells, GEX1A induced BCL-2-dependent apoptosis by converting pro-survival BCL-2 into a cell killer. Thus, GEX1A + selective BCL-xL inhibition induced synergism in killing leukaemic cells, while GEX1A + BCL-2 inhibition showed antagonism in BCL-2-expressing leukaemic cells. In addition, GEX1A sensitised FLT3-ITD+ leukaemic cells to apoptosis by inducing aberrant splicing and repressing the expression of FLT3-ITD. Consistently, in in vivo xenografts, GEX1A killed the bulk of leukaemic cells via apoptosis when combined with BCL-xL inhibition. Furthermore, GEX1A repressed leukaemia development by targeting leukaemia stem cells through inhibiting FASTK mitochondrial isoform expression across sensitive and non-sensitive leukaemia types.
    CONCLUSION: Our study suggests that GEX1A is a potent anti-leukaemic agent in combination with BCL-xL inhibitors, which targets leukaemic blasts and leukaemia stem cells through distinct mechanisms.
  21. Blood. 2022 Apr 14. pii: blood.2021013750. [Epub ahead of print]
      Mutations in the TINF2 gene, encoding the shelterin protein TIN2, cause telomere shortening and the inherited bone marrow failure syndrome dyskeratosis congenita (DC). A lack of suitable model systems limits the mechanistic understanding of telomere shortening in the stem cells and thus hinders the development of treatment options for bone marrow failure. Here, we endogenously introduced TIN2-DC mutations in human embryonic stem cells (hESCs) and human hematopoietic stem and progenitor cells (HSPCs) to dissect the disease mechanism and identified a gene editing strategy that rescued the disease phenotypes. The hESCs with the T284R disease mutation exhibited the short telomere phenotype observed in DC patients. Yet, telomeres in mutant hESCs did not trigger DNA damage responses at telomeres or show exacerbated telomere shortening when differentiated into telomerase-negative cells. Disruption of the mutant TINF2 allele by introducing a frameshift mutation in exon 2 restored telomere length in stem cells and the replicative potential of differentiated cells. Similarly, we introduced TIN2-DC disease variants in human HSPCs to assess the changes in telomere length and proliferative capacity. Lastly, we showed that editing at exon 2 of TINF2 that restored telomere length in hESCs could be generated in TINF2-DC patient HSPCs. Our study demonstrates a simple genetic intervention that rescues the TIN2-DC disease phenotype in stem cells and provides a versatile platform to assess the efficacy of potential therapeutic approaches in vivo.
  22. Cancer Discov. 2022 Apr 10. pii: candisc.0521.2021. [Epub ahead of print]
      Missense mutations in the polymerase epsilon (POLE) gene have been reported to generate proofreading defects resulting in an ultramutated genome and sensitize tumors to checkpoint blockade immunotherapy. However, many POLE mutated tumors do not respond to such treatment. To better understand the link between POLE mutation variants and response to immunotherapy, we. prospectively assessed the efficacy of nivolumab in a multicenter clinical trial in patients bearing advanced mismatch repair proficient POLE-mutated solid tumors. We found that only tumors harboring selective POLE pathogenic mutations in the DNA binding or catalytic site of the exonuclease domain presented high mutational burden with specific single base substitution signature, high T-cell infiltrates, and high response rate to anti-PD1 monotherapy. This study illustrates how specific DNA repair defects can sensitize to immunotherapy, POLE proofreading deficiency representing a novel tumor agnostic biomarker for response to PD-1 checkpoint blockade therapy.
  23. Cancer Discov. 2022 Apr 11. pii: candisc.0158.2022. [Epub ahead of print]
      Covalent inhibitors of KRASG12C have shown antitumor activity against advanced/metastatic KRAS G12C-mutated cancers, though resistance emerges and additional strategies are needed to improve outcomes. JDQ443 is a structurally unique, covalent inhibitor of GDP-bound KRASG12C that forms novel interactions with the switch II pocket. JDQ443 potently inhibits KRASG12C-driven cellular signaling and demonstrates selective antiproliferative activity in KRAS G12C-mutated cell lines, including those with G12C/H95 double mutations. In vivo, JDQ443 induces AUC exposure-driven antitumor efficacy in KRAS G12C-mutated cell-derived (CDX) and patient-derived (PDX) tumor xenografts. In PDX models, single-agent JDQ443 activity is enhanced by combination with SHP2, MEK or CDK4/6 inhibitors. Notably, the benefit of JDQ443 plus the SHP2 inhibitor TNO155 is maintained at reduced doses of either agent in CDX models, consistent with mechanistic synergy. JDQ443 is in clinical development as monotherapy and in combination with TNO155, with both strategies showing antitumor activity in patients with KRAS G12C-mutated tumors.
  24. Nature. 2022 Apr 13.
      Chimeric antigen receptor (CAR) therapy has had a transformative effect on the treatment of haematologic malignancies1-6, but it has shown limited efficacy against solid tumours. Solid tumours may have cell-intrinsic resistance mechanisms to CAR T cell cytotoxicity. Here, to systematically identify potential resistance pathways in an unbiased manner, we conducted a genome-wide CRISPR knockout screen in glioblastoma, a disease in which CAR T cells have had limited efficacy7,8. We found that the loss of genes in the interferon-γ receptor (IFNγR) signalling pathway (IFNGR1, JAK1 or JAK2) rendered glioblastoma and other solid tumours more resistant to killing by CAR T cells both in vitro and in vivo. However, loss of this pathway did not render leukaemia or lymphoma cell lines insensitive to CAR T cells. Using transcriptional profiling, we determined that glioblastoma cells lacking IFNγR1 had lower upregulation of cell-adhesion pathways after exposure to CAR T cells. We found that loss of IFNγR1 in glioblastoma cells reduced overall CAR T cell binding duration and avidity. The critical role of IFNγR signalling in susceptibility of solid tumours to CAR T cells is surprising, given that CAR T cells do not require traditional antigen-presentation pathways. Instead, in glioblastoma tumours, IFNγR signalling was required for sufficient adhesion of CAR T cells to mediate productive cytotoxicity. Our work demonstrates that liquid and solid tumours differ in their interactions with CAR T cells and suggests that enhancing binding interactions between T cells and tumour cells may yield improved responses in solid tumours.
  25. Blood. 2022 Apr 11. pii: blood.2021015129. [Epub ahead of print]
      Advances in conditioning, graft-versus-disease (GVHD) prophylaxis, and anti-microbial prophylaxis have improved the safety of allogeneic hematopoietic cell transplantation (HCT), leading to a substantial increase in the number of patients transplanted each year. This influx of patients along with progress in remission-inducing and post-transplant maintenance strategies for hematologic malignancies has led to new GVHD risk factors and high-risk groups: HLA-mismatched related (haplo) and unrelated (MMUD) donors; older recipient age; post-transplant maintenance; prior checkpoint inhibitor and autologous HCT exposure; and patients with benign hematologic disorders. Along with the changing transplant population, the field of HCT has dramatically shifted in the last decade due to the widespread adoption of post-transplantation cyclophosphamide (PTCy), which has increased the use of HLA-mismatched related donors to levels comparable to HLA-matched related donors. Its success has led investigators to explore PTCy's utility for HLA-matched HCT, where we predict it will be embraced as well. Additionally, combinations of promising new agents for GVHD prophylaxis such as abatacept and JAK inhibitors with PTCy inspire hope for an even safer transplant platform. Using three illustrative cases, we review our current approach to transplantation of patients at high risk of GVHD using our modern armamentarium.