DIRAS1 Drives Oxaliplatin Resistance in Colorectal Cancer via PHB1-Mediated Mitochondrial Homeostasis.

BACKGROUND: Colorectal cancer (CRC) is a prevalent global malignancy with particularly challenging treatment outcomes in advanced stages. Oxaliplatin (OXA) is a frontline chemotherapeutic agent for CRC. However, 15% to 50% of stage III patients experience recurrence due to drug resistance. Elucidating the molecular mechanisms underlying OXA resistance is, therefore, crucial for improving CRC prognosis. The role of DIRAS1, a RAS superfamily member with reported tumor-suppressive functions in various cancers, remains poorly defined in CRC. METHODS: The effects of DIRAS1 on CRC cell proliferation and migration were evaluated using MTT, wound healing, and colony formation assays. Stable cell lines with knockdown or overexpression of DIRAS1 and PHB1 were established via plasmid and lentiviral systems. Drug sensitivity to OXA was assessed through cytotoxicity assays and IC(50) determination. Clinical relevance was validated through immunohistochemical analysis of CRC tissue samples. Transcriptomic sequencing was performed to explore downstream regulatory mechanisms. RESULTS: DIRAS1 expression was positively correlated with OXA resistance and was significantly upregulated following prolonged chemotherapy exposure. Silencing DIRAS1 reduced the IC(50) of OXA in vitro and increased tumor sensitivity to OXA in vivo. Transcriptome analysis identified PHB1 as a downstream effector of DIRAS1. Functional studies revealed that PHB1 contributes to chemoresistance by maintaining mitochondrial stability. CONCLUSIONS: This study identifies DIRAS1 as a key contributor to OXA resistance in CRC by modulating PHB1 expression and mitochondrial function. Targeting the DIRAS1-PHB1 axis may offer a novel therapeutic strategy to overcome chemoresistance in CRC.