Culture condition-dependent cytotoxicity of bendamustine in mouse embryonic stem cells, independent of STAT3 and p53 pathways

Abstract

Bendamustine, an alkylating agent with STAT3-inhibitory activity in cancer cells, was investigated using mouse embryonic stem (ES) cells as a model. ES cells are valuable for understanding drug studies owing to their self-renewal and pluripotency under defined culture conditions. This study uncovered novel, STAT3-and p53-independent cytotoxic mechanisms of bendamustine using mouse ES cells as a model system. Although it acts primarily through STAT3 inhibition in cancer cells, bendamustine induced potent cytotoxicity in ES cells without affecting STAT3 signaling, demonstrated by maintained STAT3 phosphorylation, transcriptional activity, and target gene expression. Bendamustine's cytotoxicity depended heavily on culture conditions. ES cells in 2i medium exhibited approximately 90 % reduced cell viability, whereas those in LIF-containing medium showed 50 % reduction. STAT3-knockout ES cells in 2i medium and p53-knockout ES cells in LIF medium responded similarly to wild-type cells. Although bendamustine activated the p53-p21 pathway in wild-type cells, these results indicate that its cytotoxic effects operate independently of both STAT3 and p53 pathways. These findings reveal new actions of bendamustine and highlight ES cells as a valuable tool for discovering previously uncharacterized properties of known drugs.

Keywords: Bendamustine; Embryonic stem cells; STAT3 signaling; p53-independent cell death.