Vincristine Overcomes Cytarabine Resistance in Acute Myeloid Leukemia By Suppression of ARHGAP18-Mediated Cellular Senescence

Background: Cytarabine is the cornerstone of chemotherapy in patients with acute myeloid leukemia (AML), yet the outcomes remain unsatisfactory because of resistance. Cellular senescence is a novel mode of cytarabine resistance in AML, but its mechanism of action and solution strategy remain unclear.

Methods: We observed the proportion of cellular senescence and the expression level of ARHGAP18 in relapsed and refractory AML patients after treatment with cytarabine. In vitro, we established stable AML cell lines with knockdown and overexpression of ARHGAP18 gene using lentiviral transduction. In vivo, we developed an mouse xenograft model to explore the role of ARHGAP18 gene in the process of cytarabine resistance. Additionally, we used the microtubule inhibitor targeting ARHGAP18 protein to evaluate the potential applicability of overcoming cytarabine resistance in AML.

Results: In this study, we demonstrated that cellular senescence primarily occurred in leukemia cell subsets in AML patients resistant to cytarabine, accompanied by high expression of ARHGAP18 gene and ARHGAP18 protein. Cellular senescence (including cellular senescence specific staining, cell cycle arrest, and cellular senescence related secretory phenotypes) was rare in ARHGAP18 gene wild-type and knockdown leukemia cells but frequent in ARHGAP18 gene overexpressed leukemia cells. Under the stress of cytarabine, both in vitro and in vivo, ARHGAP18 gene knockdown significantly decreased the incidence of cellular senescence and increased chemotherapy sensitivity compared to the wild-type ARHGAP18 gene. Conversely, ARHGAP18 gene overexpression significantly increased the incidence of cellular senescence, chemoresistance, the ability to resume proliferation, and extramedullary invasion, and resulted in shorter survival times. Mechanistically, the p16/Rb and p53/p21 signaling pathways were involved in ARHGAP18-mediated cellular senescence. Importantly, given previous research indicates that the ARHGAP18 is located on microtubules, we found that the microtubule protein inhibitor vincristine significantly disrupted the ARHGAP18 protein, reduced cellular senescence, and increased chemotherapy sensitivity.

Conclusions: ARHGAP18 induces cellular senescence via the p16/Rb and p53/p21 signaling pathways, mediating cytarabine resistance in AML. However, vincristine overcomes cytarabine resistance by suppression of ARHGAP18-mediated cellular senescence.