Yubin Ge

Children with Down syndrome (DS) frequently develop transient abnormal myelopoiesis that can evolve to the myeloid leukemia of DS (ML-DS). TAM spontaneously resolves in most cases but progresses to ML-DS with additional mutations, most commonly in the cohesin complex. However, the mechanisms by which these alterations promote leukemia are unknown. We leveraged the RAD21-mutant CMY cell line and RAD21-corrected CMY isogenic clones, as well as patient data, to investigate the effect of cohesin mutations during leukemia progression. RNA-sequencing revealed that HLA-class II genes were significantly down-regulated with cohesin mutations. Furthermore, HLA-DR was found to be lower in ML-DS relative to TAM, and these decreased levels were associated with increased risk of leukemia progression. Multi-omic analyses revealed that haploinsufficiency of RAD21 altered chromatin accessibility and impaired the occupancy of GATA1s and CIITA, the master regulator of HLA-class II gene expression. Chromatin binding of CIITA was increased with RAD21 correction, providing a mechanism by which restoration of cohesin improves HLA-class II expression. Finally, decreased levels of RAD21 or STAG2 expression in other subtypes of AML also exhibited reduced expression of HLA-class II genes. Thus, cohesin may contribute to leukemia by altering HLA-class II gene expression.

Background: Acute erythroid leukemia (AEL) or AML-M6 predominantly affects older adults and is rare in childhood. Compared with other AML subtypes, AEL remains relatively understudied because of its rarity. We established LS-CHM, a novel AEL cell line derived from the ascitic fluid of a patient with congenital leukemia. Interestingly, leukemic cells persisted in the ascitic fluid even after successful eradication from the bone marrow and extramedullary sites. Method: Leukemia cells from the ascites fluid exhibited robust proliferation in culture independent of cytokine requirement and were further characterized by flow cytometric immunophenotyping, cytogenetics, cell cycle and doubling time analysis, colony formation, genome and RNA sequencing, myeloid gene next generation sequencing, and cytotoxicity analysis. Results: LS-CHM displayed CD36, partial CD235a, CD31, CD43, and CD71 expression and demonstrated in vitro robust growth and high sensitivity to chemotherapeutic agents. A PDX mouse model showed development of leukemia. Genomic analysis revealed a frameshift BCOR mutation in the absence of additional mutations and downregulated TP53 expression with an exonic non-deleterious mutation. RNA sequencing of LS-CHM cells revealed upregulation of two cohesin complex genes, RAD21 and SMC3, whose high levels are associated with hematopoietic stem cell differentiation into erythroid lineage. Conclusions: LS-CHM represents the first congenital AEL-derived cell line, in contrast to the predominantly adult-origin and often secondary erythroid leukemia cell lines available currently. Thus, LS-CHM provides a unique pediatric and extramedullary AEL model, expanding the existing spectrum of AEL cell lines and offering valuable opportunities for biologic and therapeutic investigations.

Nucleoside analogs remain central to the treatment of hematologic malignancies and solid tumors, yet resistance frequently occurs, contributing to relapse and disease-related mortality. Rather than arising from a single mechanism, effective nucleoside analog activity requires successful navigation of multiple biological barriers, including cellular uptake, intracellular activation, nucleotide pool balance, genome surveillance, and mitochondrial stress responses. This review integrates recent advances describing how alterations at each of these levels contribute to resistance to nucleoside analog therapies. We further highlight emerging therapeutic strategies centered on small-molecule inhibitors that exploit these vulnerabilities to enhance the efficacy of nucleoside analogs. Together, this integrative perspective supports the need for development of small molecule inhibitors and design of combination approaches aimed at restoring apoptotic competence and improving the use of nucleoside analog-based therapies for the treatment of cancer.

Relapsed/refractory (R/R) disease is a major hurdle to long‐term survival of acute myeloid leukemia (AML) patients treated with intensive cytarabine (AraC)‐based chemotherapy. R/R AML salvage treatment with venetoclax (VEN) + azacitidine (AZA) results in overall response rates between 20% and 60%, and responses are not durable, highlighting the need for new therapies. Here, we report elevated mTORC1 signaling in AraC‐resistant AML cell lines, primary AML patient samples, and patient‐derived xenograft (PDX) AML cells derived from patients at relapse postchemotherapy. The CDK9 inhibitor AZD4573 suppresses mTORC1 signaling and downregulates c‐MYC and MCL‐1, inducing AraC‐resistant AML cell death. AZD4573 in combination with VEN + AZA significantly increases AML cell death compared to any of the two‐drug combinations and suppresses AML progenitor cells but spares normal hematopoietic progenitor cells. The efficacy of this triple combination remains even with a 10‐fold reduction of VEN concentration. The roles of MCL‐1 and c‐MYC in the three‐drug combination were confirmed by knockdown. This study demonstrates that AZD4573 enhances the activity of VEN + AZA against AraC‐resistant AML by downregulating c‐MYC and MCL‐1 and to a lesser extent cellular respiration.

Acute myeloid leukaemia (AML) remains a challenging haematological malignancy, with most patients developing resistance to standard-of-care (SOC) treatments. This resistance is often attributed to the overexpression of anti-apoptotic BCL-2 family proteins, which regulate the intrinsic apoptotic pathway by inhibiting pro-apoptotic effector proteins such as BAX and BAK. AML cells exploit this imbalance to evade apoptosis and sustain survival, necessitating the development of novel therapeutic strategies. BH3 mimetics are small-molecule inhibitors targeting the pro-survival BCL-2 family proteins and have emerged as promising agents in patients with AML who are unable to receive high-intensity induction chemotherapy. Co-treatment with the BCL-2-specific inhibitor venetoclax and various SOC therapies has been proven effective, with several combinations now approved by the US Food and Drug Administration for adults with AML who are ≥75 years of age and/or are ineligible for intensive induction chemotherapy, on the basis of improved response rates and survival outcomes compared with the previous SOC. In this Review, we highlight the transformative potential of BH3 mimetics in AML therapy, including ongoing studies investigating novel combination regimens and efforts to further refine treatment strategies, with the ultimate goal of improving outcomes for patients with AML.

Cancer management has traditionally depended on chemotherapy as the mainstay of treatment; however, recent advancements in targeted therapies and immunotherapies have offered new options. Ubiquitin-specific proteases (USPs) have emerged as promising therapeutic targets in cancer treatment due to their crucial roles in regulating protein homeostasis and various essential cellular processes. This review covers the following: (1) the structural and functional characteristics of USPs, highlighting their involvement in key cancer-related pathways, and (2) the discovery, chemical structures, mechanisms of action, and potential clinical implications of USP inhibitors in cancer therapy. Particular attention is given to the role of USP inhibitors in enhancing cancer immunotherapy, e.g., modulation of the tumor microenvironment, effect on regulatory T cell function, and influence on immune checkpoint pathways. Furthermore, this review summarizes the current progress and challenges of clinical trials involving USP inhibitors as cancer therapy. We also discuss the complexities of achieving target selectivity, the ongoing efforts to develop more specific and potent USP inhibitors, and the potential of USP inhibitors to overcome drug resistance and synergize with existing cancer treatments. We finally provide a perspective on future directions in targeting USPs, including the potential for personalized medicine based on specific gene mutations, underscoring their significant potential for enhancing cancer treatment. By elucidating their mechanisms of action, clinical progress, and potential future applications, we hope that this review could serve as a useful resource for both basic scientists and clinicians in the field of cancer therapeutics.

Background: Venetoclax + azacitidine is a frontline treatment for older adult acute myeloid leukemia (AML) patients and a salvage therapy for relapsed/refractory patients who have been treated with intensive chemotherapy. While this is an important treatment option, many patients fail to achieve complete remission and of those that do, majority relapse. Leukemia stem cells (LSCs) are believed to be responsible for AML relapse and can be targeted through oxidative phosphorylation reduction. We previously reported that ONC213 disrupts oxidative phosphorylation and decreases Mcl-1 protein, which play a key role in venetoclax resistance. Here we investigated the antileukemic activity and underlying molecular mechanism of the combination of ONC213 + venetoclax against AML cells. Methods: Flow cytometry was used to determine drug-induced apoptosis. Protein level changes were determined by western blot. An AML cell line-derived xenograft mouse model was used to determine the effects of ONC213 + venetoclax on survival. A patient-derived xenograft (PDX) mouse model was used to determine drug effects on CD45+/CD34+/CD38-/CD123 + cells. Colony formation assays were used to assess drug effects on AML progenitor cells. Mcl-1 and Bax/Bak knockdown and Mcl-1 overexpression were used to confirm their role in the mechanism of action. The effect of ONC213 + venetoclax on mitochondrial respiration was determined using a Seahorse bioanalyzer. Results: ONC213 + venetoclax synergistically kills AML cells, including those resistant to venetoclax alone as well as venetoclax + azacitidine. The combination significantly reduced colony formation capacity of primary AML progenitors compared to the control and either treatment alone. Further, the combination prolonged survival in an AML cell line-derived xenograft model and significantly decreased LSCs in an AML PDX model. Conclusions: ONC213 can resensitize VEN + AZA-resistant AML cells to venetoclax therapy and target LSCs ex vivo and in vivo.