Combined analysis of KRAS mutation and p16(INK4a) and p14(ARF) methylation status in locally advanced rectal carcinoma treated with preoperative chemoradiotherapy

Current management of locally advanced rectal carcinoma (LARC) involves preoperative chemoradiotherapy (preCRT) before surgery. Despite improved local control rate, the response to preCRT of individual patients is variable and may reflect heterogeneous biological properties among tumors of the same clinical stage. Identifying novel molecular parameters with predictive and/or prognostic value is of great clinical importance for a personalized therapeutic approach. In this study, KRAS mutation status was analyzed by direct sequencing, while methylation-specific polymerase chain reaction (MSP) was used to examine p16(INK4a) and p14(ARF) gene methylation status in pretreatment tumor biopsies of 60 patients with LARC. The examined molecular changes of KRAS, p16(INK4a) and p14(ARF) genes were mutually independent (p16(INK4a)/KRAS, P=0.272; p14(ARF)/KRAS, P=0.923; p16(INK4a)/p14(ARF), P=0.715). However, the simultaneous presence of p14(ARF) methylation and KRAS mutation was associated with a more frequent appearance of local recurrences and distant metastasis (P=0.027). Moreover, patients with the simultaneous presence of p16(INK4a) and p14(ARF) methylation and KRAS mutation had significantly shorter overall survival (P=0.011). The obtained results strongly suggest that combined analyses of examined genetic and epigenetic molecular alterations could contribute to the identification of LARC patient subgroups with more aggressive tumor behavior and worse disease outcome.