KLF4 p.A472D mutation: An acquired resistant mutation to cetuximab in colorectal cancer

e15077 Background: With the increase of treatment course, acquired resistance of epidermal growth factor receptor (EGFR) blockade is inevitable in patients with metastatic colorectal cancer (mCRC). KRAS mutations have been considered to be primary drivers of this acquired resistance; however, the potential function of other genes has not been extensively investigated. Methods: This study included 17 mCRC patients with acquired cetuximab resistance, and mutations in circulating tumor DNA (ctDNA) from plasma samples were identified using target-capture deep sequencing. Analysis of mutational prevalence in ctDNA, three CRC tissue-based datasets and one ctDNA dataset was performed. Mutation predicted with significant effect on acquired resistance was selected and the functional analysis was validated in CRC cells. Results: The prevalence of mutations identified in ctDNA was consistent with CRC tissue-based and ctDNA datasets. Clonal analysis revealed that 41.2% of patients were positive for at least one subclonal. Multiply resistance mechanisms of cetuximab were co-existed in individual patient, with one of them even harbored nine distinct mutations. In particularly, function analysis of Krüppel-like factor 4 (KLF4) mutation p.A472D revealed increased cetuximab resistance in CRC cells, which was associated with the increased phosphorylation of downstream EGFR signaling proteins. Conclusions: The KLF4 mutation p.A472D contributes to acquired cetuximab resistance in patients with mCRC and it may serve as a new biomarker useful in clinical application. Monitoring somatic mutations related to acquired cetuximab resistance in mCRC patients through ctDNA is an appropriate means of providing real-time insights useful for clinical reference and treatment planning.