Targeting MCL1-driven anti-apoptotic pathways to overcome hypomethylating agent resistance in RAS -mutated chronic myelomonocytic leukemia.

RAS pathway mutations, which are present in 30% of patients with chronic myelomonocytic leukemia (CMML) at diagnosis, confer a high risk of resistance to and progression after hypomethylating agent (HMA) therapy, the current standard of care for the disease. Using single-cell, multi-omics technologies, we sought to dissect the biological mechanisms underlying the initiation and progression of RAS pathway-mutated CMML. We found that RAS pathway mutations induced the transcriptional reprogramming of hematopoietic stem and progenitor cells (HSPCs), which underwent proliferation and monocytic differentiation in response to cell-intrinsic and -extrinsic inflammatory signaling that also impaired immune cells' functions. HSPCs expanded at disease progression and relied on the NF- K B pathway effector MCL1 to maintain their survival, which explains why patients with RAS pathway- mutated CMML do not benefit from BCL2 inhibitors such as venetoclax. Our study has implications for developing therapies to improve the survival of patients with RAS pathway- mutated CMML.

Cytotoxic effects induced by combination of heliantriol B2 and dequalinium against human leukemic cell lines.

Natural occurring compounds are considered an important source of antitumoral agents. In the present study, the cytotoxic potential of three pentacyclic triterpenes isolated from Chuquiraga erinacea (Asteraceae), against the human leukemic cell lines NB4 and K562 was assessed. Heliantriol B2 (HB2) showed the highest cytotoxic activity after 24 h treatment showing IC(50) values of 1.98 ± 0.12 µm and 3.52 ± 0.14 µm for NB4 and K562 cells, respectively. This activity was higher than that of the reference compound dequalinium (DQA). Apoptosis and necrosis induced by HB2 in both NB4 and K562 cell lines were analysed by Annexin V/PI labeling. Mitochondrial alterations including reactive oxygen species (ROS) production and mitochondrial transmembrane potential (ΔΨm) were also tested. The results demonstrated that HB2 induced cell death by apoptosis and necrosis and showed enhanced cytotoxic effects in combination with DQA. Besides, HB2 induced ROS overproduction in NB4 cells and a slight decrease of ΔΨm. Consequently, our findings prompt further studies on the HB2 mechanism of action and its selectivity to tumor cells in order to assess the potential of HB2 as an agent for cancer treatment.