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Published on: March 14, 2019
Integrated NGS and ddPCR analysis of RAS/RAF mutations in metastatic colorectal cancer among Kazakhstani patients: a
Gulmira Kulmambetova1, Pavel Tarlykov1, Dana Auganova1
1Department of Genomics, National Center for Biotechnology, Astana, Kazakhstan.
Background:
Colorectal cancer (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide, and metastatic colorectal cancer (mCRC) is associated with poor prognosis and limited treatment options. Mutations in the KRAS, BRAF oncogenes are key molecular drivers of colorectal cancer development and promote activation of the MAPK/ERK signaling pathway. The presence of mutations serves as an important prognostic biomarker for response to targeted therapy against EGFR. However, molecular epidemiological data on RAS/RAF mutations in patients with colorectal cancer from Kazakhstan remain limited. Therefore, the aim of this study was to characterize the KRAS, BRAF mutation profile in patients with metastatic colorectal cancer from Kazakhstan using targeted NGS and ddPCR approaches.
Methods:
Formalin-fixed, paraffin-embedded (FFPE) tumor tissue samples from 30 patients with metastatic colorectal cancer (mCRC), including samples from primary tumors and liver metastases, were analyzed. Genomic DNA was isolated and analyzed for mutation hotspots in the KRAS and BRAF genes using droplet digital PCR (ddPCR). Mutation profiles of the KRAS, BRAF genes were also confirmed using targeted next-generation sequencing.
Results:
KRAS mutations were detected in 55.6% of primary tumors and 44.4% of metastatic samples by ddPCR, while BRAF mutations were present in 7.4 and 16.7% of cases, respectively. Targeted sequencing identified KRAS mutations in 65.2% of tumors and 64.3% of metastases, BRAF mutations in 4.4 and 14.3% of samples. The most frequent alterations were observed in codons 12, 13 of the KRAS gene. Comparative analysis of tumor-metastasis pairs revealed both common driver mutations and site-specific variants, indicating potential molecular heterogeneity.
Conclusion:
KRAS mutations are the most common genetic alterations in metastatic colorectal cancer, while BRAF mutations are less common. The combination of targeted next-generation sequencing and droplet digital PCR improves the accuracy of mutation detection in FFPE samples. These data clarify the molecular characteristics of metastatic colorectal cancer in Kazakhstan and support the development of precision oncology approaches in clinical practice.
