The GAS2–KLF4 axis regulates mitochondrial apoptosis and therapeutic responsiveness in colorectal cancer

Impaired intrinsic apoptosis contributes to colorectal cancer (CRC) progression, yet the upstream regulators governing mitochondrial integrity remain incompletely defined. Growth arrest-specific protein 2 (GAS2) has been implicated in CRC malignancy, whereas Krüppel-like factor 4 (KLF4) functions as a tumor suppressor; however, their functional relationship in apoptotic regulation is unclear. Here, we demonstrate that GAS2 expression is elevated while KLF4 is reduced in advanced CRC tissues, metastatic CRC cell lines, and The Cancer Genome Atlas datasets, exhibiting a significant inverse correlation. Genetic suppression of GAS2 restored KLF4 expression and induced mitochondrial fragmentation, membrane depolarization, and apoptotic cell death in CRC cells. Silencing KLF4 attenuated mitochondrial depolarization following butyrate treatment, indicating that KLF4 is required for mitochondrial apoptotic responses downstream of GAS2 suppression. Ultrastructural analyses revealed that butyrate induces mitochondrial remodeling and reduces lysosomal density, changes that are consistent with activation of intrinsic apoptotic pathways. In vivo, administration of the butyrate-producing bacterium Butyricicoccus pullicaecorum mitigated tumor progression in a chemically induced CRC model and partially reversed the GAS2–KLF4 imbalance. Furthermore, GAS2 knockdown or idarubicin treatment independently reduced tumor burden and metabolic activity in xenograft models. Collectively, these findings identify the GAS2–KLF4 axis as a regulator of mitochondrial apoptosis in CRC and suggest that targeting GAS2 may restore apoptotic vulnerability and enhance therapeutic responsiveness.