The identification of predictive biomarkers is crucial for optimizing targeted therapy in hematologic malignancies (HMs). This study demonstrates that downregulation of c-Myc expression serves as a robust and reliable indicator of sensitivity to checkpoint kinase 1 inhibitors (CHK1i), particularly in the context of the novel compound PY34. Through comprehensive analysis of both public databases and primary patient samples, a consistent and significant correlation was established between c-Myc suppression and enhanced anti-tumor response.
Initial screening using the GDSC and DepMap datasets revealed that HMs exhibit greater dependency on CHK1 compared to solid tumors, suggesting intrinsic vulnerability to CHK1 inhibition. Subsequent validation with PY34 confirmed potent single-agent activity in multiple HM cell lines, including those derived from acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and multiple myeloma. Notably, this efficacy was not observed in non-responsive solid tumor lines, reinforcing the selective nature of the response in blood cancers.
Transcriptomic profiling of sensitive HM cells treated with PY34 uncovered a shared molecular signature: widespread downregulation of genes regulated by the oncogenic transcription factor c-Myc. This effect was confirmed at both mRNA and protein levels through qPCR and Western blot analyses.KAP1 Antibody In Vivo The reduction in c-Myc was independent of protein degradation, as evidenced by unchanged half-life under cycloheximide treatment and lack of rescue upon proteasome inhibition.LC3B Antibody Autophagy Instead, the data support transcriptional repression as the dominant mechanism driving c-Myc decline.PMID:34847748
Functional experiments further validated the causal role of c-Myc in drug response. Overexpression of c-Myc in MV411 cells significantly attenuated PY34-induced growth arrest and G1 phase blockage. Similarly, in FLT3-ITD and FLT3-D835V mutant models, exogenous cytokines such as IL-3 or GM-CSF restored c-Myc levels and conferred resistance to PY34, directly linking c-Myc restoration to therapeutic escape.
Critically, the clinical relevance of this finding was confirmed in primary patient-derived cells. Among 39 AML and other HM samples tested, 20 were classified as sensitive (IC50 < 1 μM). In these cases, the extent of c-Myc downregulation induced by PY34 strongly correlated with the degree of proliferation inhibition—greater suppression led to stronger anti-cancer effects. No such correlation was observed in resistant samples, where c-Myc levels remained stable. These results establish c-Myc downregulation as a highly specific and predictive biomarker for CHK1i efficacy in HMs. Unlike general markers such as pS345-CHK1 phosphorylation—which reflect target engagement but not functional outcome—c-Myc modulation reflects a downstream biological consequence linked directly to therapeutic response. Its ability to distinguish sensitive from resistant tumors across diverse genetic backgrounds underscores its potential utility in guiding patient selection for future clinical trials. In summary, this work identifies c-Myc suppression as a key determinant of CHK1 inhibitor sensitivity in hematologic malignancies. By providing a measurable, mechanistically grounded biomarker, it enables more precise patient stratification and supports the development of personalized treatment strategies targeting the DNA damage response pathway in blood cancers.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
