Clinical and functional characterization of atypical KRAS/NRAS mutations in metastatic colorectal cancer

Jonathan M. Loree, Yucai Wang, Muddassir A. Syed, Alexey V. Sorokin, Oluwadara Coker, Joanne Xiu, Benjamin A. Weinberg, Ari M. Vanderwalde, Anteneh Tesfaye, Victoria M. Raymond, Benjamin Miron, Gabi Tarcic, Ori Zelichov, Russell R. Broaddus, Patrick Kwok Shing Ng, Kang Jin Jeong, Yiu Huen Tsang, Gordon B. Mills, Michael J. Overman, Axel GrotheyJohn L. Marshall, Scott Kopetz

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Purpose: Mutations in KRAS/NRAS (RAS) predict lack of anti-EGFR efficacy in metastatic colorectal cancer (mCRC). However, it is unclear if all RAS mutations have similar impact, and atypical mutations beyond those in standard guidelines exist. Experimental Design: We reviewed 7 tissue and 1 cell-free DNA cohorts of 9,485 patients to characterize atypical RAS variants. Using an in vitro cell-based assay (functional annotation for cancer treatment), Ba/F3 transformation, and in vivo xenograft models of transduced isogenic clones, we assessed signaling changes across mutations. Results: KRAS exon 2, extended RAS, and atypical RAS mutations were noted in 37.8%, 9.5%, and 1.2% of patients, respectively. Among atypical variants, KRAS L19F, Q22K, and D33E occurred at prevalence ≥0.1%, whereas no NRAS codon 117/146 and only one NRAS codon 59 mutation was noted. Atypical RAS mutations had worse overall survival than RAS/BRAF wild-type mCRC (HR, 2.90; 95% confidence interval, 1.24-6.80; P = 0.014). We functionally characterized 114 variants with the FACT assay. All KRAS exon 2 and extended RAS mutations appeared activating. Of 57 atypical RAS variants characterized, 18 (31.6%) had signaling below wild-type, 23 (40.4%) had signaling between wild-type and activating control, and 16 (28.1%) were hyperactive beyond the activating control. Ba/F3 transformation (17/18 variants) and xenograft model (7/8 variants) validation was highly concordant with FACT results, and activating atypical variants were those that occurred at highest prevalence in clinical cohorts. Conclusions: We provide best available evidence to guide treatment when atypical RAS variants are identified. KRAS L19F, Q22K, D33E, and T50I are more prevalent than many guideline-included RAS variants and functionally relevant.

Original languageEnglish (US)
Pages (from-to)4587-4598
Number of pages12
JournalClinical Cancer Research
Issue number16
StatePublished - Aug 15 2021

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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