Enhanced cytotoxic T‐cell function and inhibition of tumor progression by Mst1 deficiency

Mammalian ste‐20 like kinase Mst1 plays important roles during apoptosis, proliferation, cell polarity, and migration. Here, we report a novel role of Mst1 for cytotoxic T‐cell responses and tumor suppression. The defect of Mst1 caused decreased levels of FoxO, and promoted cytotoxicity in vitro . Mst1 −/− cytotoxic T cells also exhibited enhanced T‐bet expression that was associated with elevated expression levels of IFN γ and granzyme B. Moreover, Mst1 −/− cytotoxic T cells suppressed tumor growth in vivo . The data suggest that Mst1 inhibits cytotoxicity via T‐bet suppression by FoxO1 and FoxO3a. Thus, Mst1 is a potential therapeutic target for tumor immunotherapy.