Chromomycin A2 disrupts leukemia cell viability via integrated autophagic and apoptotic programs

Acute leukemias urgently require new therapeutic approaches due to high relapse rates and frequent resistance to standard treatments. Advances in molecular profiling have enabled more selective and less toxic strategies, especially for patients with poor prognosis. Chromomycins have emerged as potential agents because they bind GC-rich DNA regions, alter chromatin architecture, inhibit RNA polymerase, and suppress transcriptional programs essential for leukemic cell survival. Among them, chromomycin A2 remains largely unexplored in hematologic cancers despite reported activity in some solid tumors. We investigated chromomycin A2 in a broad panel of leukemia models. Twenty-two human blood cancer cell lines were analyzed (14 myeloid, 17 lymphoid), including resistant variants to venetoclax (n=2), quizartinib (n=1), and ATRA (n=1). Viability (MTT), apoptosis (annexin V/PI), and autonomous clonal growth in cytokine-free methylcellulose were evaluated. Ex vivo assays used primary AML (n=3) and ALL (n=3) samples. Molecular analyses included PCR arrays covering genes related to autophagy, apoptosis, DNA damage, and cell-cycle control, together with Western blotting. Statistical significance was defined as p <0.05. Chromomycin A2 reduced viability in all models in a dose-dependent manner (IC50: 0.40 - 4.42 nM). Resistant derivatives showed slightly higher IC 50 values but remained sensitive. The compound induced time- and dose-dependent apoptosis and fully suppressed autonomous clonal growth at ≥5 nM. Early responses involved autophagy markers (LC3B-II accumulation, SQSTM1/p62 reduction), compatible with decreased transcriptional output and weakened survival signaling. With longer exposure, apoptotic markers (cleaved PARP1) and DNA damage (gammaH2AX) predominated. Gene expression data indicated a temporal sequence: activation of autophagy and cell-cycle arrest at 6 h, followed by apoptosis-related genes at 12 h. Enrichment analyses highlighted macroautophagy, mitochondrial apoptosis, and G1 DNA damage checkpoint pathways. In ex vivo assays, IC 50 values ranged from 1.6 to 31.8 nM, with 81-92% efficacy in primary AML and ALL cells. Chromomycin A2 displayed strong antileukemic activity across in vitro and ex vivo models, including resistant subtypes. Its sequential induction of autophagy, apoptosis, and DNA damage suggests a multitarget mechanism. The inhibition of clonal growth indicates potential activity against leukemic stem/progenitor cells. These results support further preclinical development. Supported by FAPESP, CAPES, and CNPq.