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

## TL;DR

This study shows that DIRAS1 helps colorectal cancer cells resist the drug oxaliplatin by supporting mitochondrial health through PHB1, suggesting a new way to treat resistant cancers.

## Contribution

The study identifies DIRAS1 as a novel driver of oxaliplatin resistance in colorectal cancer via its regulation of PHB1 and mitochondrial homeostasis.

## Key findings

- DIRAS1 expression increases with chemotherapy exposure and correlates with oxaliplatin resistance in colorectal cancer.
- Silencing DIRAS1 reduces oxaliplatin resistance in vitro and in vivo by downregulating PHB1.
- PHB1 stabilizes mitochondrial function, contributing to chemoresistance in colorectal cancer cells.

## Abstract

Oxaliplatin (OXA) resistance remains a major challenge in colorectal cancer (CRC) chemotherapy, with approximately 15 to 50% of stage III patients developing resistance to this frontline drug. This study explores the role of DIRAS1, a RAS family protein with previously undefined relevance in CRC, in mediating OXA resistance mechanisms. Through a combination of in vitro assays (MTT, wound healing, colony formation), transcriptomic profiling, and in vivo mouse models, we demonstrate that DIRAS1 expression is elevated following prolonged chemotherapy and is positively correlated with OXA resistance. Silencing DIRAS1 reduced OXA IC50 and enhanced tumor sensitivity both in vitro and in vivo. Mechanistically, DIRAS1 promotes chemoresistance by upregulating PHB1, which stabilizes mitochondrial function. Clinical specimen analysis further validated the clinical relevance of the DIRAS1–PHB1 pathway. These findings suggest that targeting the DIRAS1–PHB1 axis may represent a promising strategy to overcome OXA resistance, reduce recurrence, and improve outcomes for CRC patients.

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 IC50 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 IC50 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.