Investigating the Pathogenicity of Uncommon KRAS Mutations and Their Association with Clinicopathologic Characteristics in Patients with Colorectal Cancer

Kirsten rat sarcoma viral oncogene homolog (KRAS) somatic mutations occur in 30% to 40% of patients with colorectal cancer (CRC). These were thought to equally affect prognosis and resistance to anti-epidermal growth factor receptor agents; however, recent data show the activity of KRAS-G12C and pan-RAS inhibitors. The effects of uncommon KRAS (uKRAS) variants are largely unexplored. The distribution and pathogenicity of uKRAS mutations and their relationship with patients' clinicopathologic features were assessed. A total of 2427 CRCs were profiled for KRAS using next-generation sequencing (NGS). The study and control groups included patients with uKRAS (<1% frequency in CRC data sets on cBioPortal) and canonical KRAS mutations, respectively. In silico protein structure modifications and prediction analyses were performed by using PyMOL, trRosetta, and PolyPhen-2. uKRAS mutations affected 35 cases (1.5%), with G13C (28.6%), G12R (20%), and V14I (8.6%) being most common. Missense mutations (D33E, G12W, G12F, Q22H, Q61L, and L19F) occurred in nine cases (25.7%). Duplications (G10dup and L52_G60dup) affected two cases. Pathogenicity analyses showed that G12W, Q22R, L56V, and A130I mutations are probably damaging, with scores between 0.928 and 1.000. No differences were seen in clinicopathologic features. uKRAS mutants had lower event-free survival but no difference in overall survival compared with controls. Although these data are hypothesis generating and need further confirmation, they highlight the importance of NGS-based profiling to identify CRC patients with uKRAS mutations as candidates for personalized therapy.