Somatic mutation analysis of KRAS, BRAF, HER2 and PTEN in EGFR mutation-negative non-small cell lung carcinoma: determination of frequency, distribution pattern and identification of novel deletion in HER2 gene from Indian patients.

Abstract

Somatic mutations of KRAS, BRAF, HER2, PTEN genes are the most important molecular markers after the EGFR gene mutation. The current study evaluated the frequency and distribution pattern of KRAS, BRAF, HER2, PTEN mutation in Indian non-small cell lung carcinoma patients. The frequency of KRAS, BRAF, HER2, PTEN mutations was 6.4% (14/204), 1.5% (3/204), 1.5% (3/204), 0% (0/204), respectively. KRAS, BRAF, HER2 mutations were more prevalent in males than in females. KRAS and HER2 showed a trend of a higher frequency of mutation in the age group of <60years, whereas BRAF mutations were more frequent in the age group of ≥60years. Sequencing analysis of KRAS gene revealed c.34G>T (G12C) (n=8), c.35G>A (G12D) (n=3), c.35G>T (G12V) (n=1) and c.34G>T (G12C)/c.41T>C (V14A) (n=2) mutations. Three different BRAF mutations (L584P: n=1, V600E: n=1, K601E: n=1) were detected. Two cases harboured c.2324_2325ins12 (ATACGTGATGGC duplication) in HER2 gene, and one case was positive for NG_007503.2 (NM_001005862.2):c.2218-4del. It is less certain, but still quite possible that this mutation will affect splicing as the deletion of one C actually brings in one additional purine into the region. In conclusion, the present study demonstrates an instance of diverse nature of KRAS, BRAF, HER2 and PTEN gene in Indian patients and confirms that the frequency of these gene mutations varies globally. To the best of our knowledge, this is the first Indian study to evaluate KRAS, BRAF, HER2 and PTEN gene mutations.