Identification and prognostic analysis of the cetuximab resistance-related gene REV1 in RAS wild-type metastatic colorectal cancer.

The survival of patients with RAS wild-type metastatic colorectal cancer (mCRC) has improved markedly since the introduction of cetuximab, which is an anti-epidermal growth factor receptor monoclonal antibody. However, not all RAS wild-type patients respond to cetuximab treatment. Although some genetic alterations associated with cetuximab resistance have been identified, they cannot fully explain all cases of cetuximab resistance. Thus, in this research, we aimed to identify new genetic alterations associated with resistance to this treatment. The study retrospectively analyzed 70 patients diagnosed with RAS wild-type mCRC at our hospital between November 2009 and July 2018. First, five progression-free survival (PFS)-longest and 5 PFS-shortest tumor deoxyribonucleic acid were analyzed by whole-exome sequencing (WES) to identify differentially mutated genes. Then, PFS analysis of the 70 patients was used to verify the correlation between the candidate gene and cetuximab sensitivity. Finally, data from public databases were used to further verify the relationship between the mRNA expression level of the candidate gene and cetuximab responsiveness. The WES results indicated REV1: c.2108G > A was a candidate gene mutation related to the effectiveness of cetuximab. Survival analysis suggested REV1: c.2108G > A was associated with rapid disease progression (median PFS time, REV1 mutant vs. REV1 wild-type: 4.4 months vs. 8.7 months, P = 0.034). Data from the Genomics of Drug Sensitivity in Cancer and the Gene Expression Omnibus databases suggested low REV1 mRNA levels might be related to the poor response of CRC cells and reduced cetuximab efficacy among mCRC patients. In conclusion, REV1 expression levels and the REV1: c.2108G > A mutation may be related to cetuximab resistance in RAS wild-type mCRC.