Clinicopathological Associations of K-RAS and N-RAS Mutations in Indonesian Colorectal Cancer Cohort
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K-RAS and recently N-RAS gene mutation testing are mandatory requirements prior to anti-epidermal growth factor receptor (EGFR) monoclonal antibody treatment of metastatic CRC. Mutation prevalence and distribution in Indonesian colorectal cancer (CRC) are not known.
Combined methods of PCR high-resolution melt (HRM), restriction fragment length polymorphism (RFLP), and direct DNA sequencing were used to genotype exons 2, 3, and 4 of both K-RAS and N-RAS genes for routine clinical testing of CRC patients. Descriptive analytical review of 595 consecutive CRC patients (years 2013 to 2016) was performed to find associations between gene mutations and clinicopathologic features.
This retrospective study revealed overall K-RAS gene mutation in exon 2 (codon 12 and 13) rates being 34.9%. Women (42.5%), stages I and II (43.4%), and well and moderate differentiations (37.7%) had higher frequency of K-RAS exon 2 mutations than men (29%, p = 0.006), stages (III and IV 31.9%, p = 0.05), and poor differentiation (11.8%, p = 0.002), respectively. At later period (2015–2016), 121 of 595 patients were genotyped for the remaining exons 3 and 4 of K-RAS as well as exons 2, 3, and 4 of N-RAS mutations resulting in overall RAS mutation prevalence of 41%. Mucinous histology had highest frequency of N-RAS mutation.
Combination of PCR HRM with either RFLP or direct DNA sequencing was useful to detect K-RAS exon 2 and extended RAS mutations, respectively. Frequency of all RAS mutations in stage IV Indonesian (41%) was similar among Asians (41–49%), which tend to be lower than western (55%) CRC.
KeywordsK-RAS N-RAS Colorectal cancer mutation Indonesia High-resolution melting Asian
This research effort was funded by an internal grant for PT Kalbe Farma Tbk. We thanked Fitria Yunida, Dewi Nawangwulan, and Siska Yogiwanti for excellent technical assistance.
Compliance with Ethical Standards
This study was determined to be exempt by the Institutional Review Board and performed in accordance to 1964 Helsinki Declaration and its later amendments. This retrospective study was approved by Institutional Review Board (IRB) of Stem-cell and Cancer Institute (SCI).
Conflict of interest
ML, GP, FS, and AU are employees of PT Kalbe Farma; GW and WG are senior pathologists receiving honoraria from PT Bifarma Adiluhung, Kalbe Farma; and all other authors have declared no conflicts of interests.
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