engleski

KRAS mutation analysis in colorectal cancer

Objective: Colorectal cancer is the fourth most common cancer among men and women. The current standard of care for metastatic colorectal cancer (mCRC) is combined of several active cytotoxic chemotherapy and biological agents. The two anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab and panitumumab) were approved for the treatment of advanced CRC, in combination or as a single agent. Although EGFR is overexpressed in approximately 80% of CRC, it failed to predict a therapeutic response. Therefore, candidate predictive biomarkers were sought in downstream signaling. Relevant studies has demonstrated that KRAS gene mutation status detection has become a crucial diagnostic factor for treating mCRC. KRAS mutations occur in 35% to 45% of CRC. Mutations in the KRAS gene lead to abnormal KRAS proteins which is permanently activated resulting in oncogenic activation of the RAS/MAPK signaling pathway, abnormal cell growth and bypassing the EGFR-targeted antibody therapy. Tumors with KRAS mutations in codon 12 and 13 are resistant to anti-EGFR therapy. Methods: 44 patients diagnosed from 2010 to 2013 as CRC were included in our study. Tumour cells collected by biopsy or by tumor extraction, were microdisected from pathohistological slides and DNA was isolated by NucleoSpin Tissue XS kit (Macherey-Nagel). KRAS exon 2, codon 12 and 13 were amplified, cycle-sequenced by Big-Dye Termination method (Applied Biosystems) and sequenced on ABI 310 sequencer using ABI PRISM Sequencing Analysis v5.4 and SeqScape v2.5 softwares for sequence analysis. Results: 44 patients (median age 61, range 32-79, 25 male and 19 female) were included in this study. 14 out of 44 (31.8 %) patients had KRAS mutations. 30 out of 44 CRC patients (68, 2%) had the KRAS wild type. KRAS codon 12 mutations were found in 11/14 (78, 5 %) patients and codon 13 in 3/14 (21, 4%) CRC patients with KRAS mutations. Conclusion: The most frequent mutations in KRAS gene, in codon 12 and 13, accounting for more than 90% of all mutation types, were validated in recent literature as negative predictor of response to anti-EGFR therapy. Therefore, determining the KRAS mutational status of tumor samples has become an essential tool for managing the patients with colorectal cancer.

KRAS mutation; colorectal cancer; sequencing

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