Predictive and prognostic role of p1 Ink a, p1 arf and kraS genes in humnan rectal carcinoma

Karcinom rektuma (KR) čini oko 30% svih slučajeva kolorektalnih karcinoma (KRK), koji se u zadnje vreme proučava kao zaseban klinički entitet. Aktuelan terapijski pristup u lečenju lokalno uznapredovalih stadijuma KR podrazumeva primenu preoperativne hemioradioterapije (HRT), nakon koje sledi hirurško uklanjanje tumora. Iako se ovim tretmanom postiže bolja lokalna kontrola bolesti, individualni odgovor na primenjenu terapiju je varijabilan i ukazuje na značajnu biološku heterogenost tumora u okviru istog kliničkog stadijuma. Stoga je u cilju kreiranja i primene personalizovane terapije neophodno definisati prediktivne i prognostičke molekularne parametre. Primenom PCR metode specifične za metilaciju (MSP), ispitivan je metilacioni status gena p16INK4a i p14ARF, dok je automatskim sekvenciranjem analiziran mutacioni status gena KRAS u pre-tretmanskim biopsijama tumorskog tkiva obolelih od KR u lokalno uznapredovalom stadijumu, kao bi se utvrdio njihov potencijalni prediktivni i prognostički značaj. Rezultati ove studije su pokazali da ispitivane promene u genima p16INK4a, p14ARF i KRAS pojedinačno gledano, nisu značajni prediktivni i prognostički faktori kod obolelih od KR, mada je istovremeno prisustvo metilacije gena p14ARF i mutacije gena KRAS povezano sa agresivnijim ponašanjem tumora, dok je istovremeno prisustvo izmena u sva tri ispitivana gena povezano sa kraćim ukupnim preživljavanjem. Međutim, kombinovane analize genetičkih, epigenetičkih i imunohistohemijskih parametara (EGFR, VEGF, Bcl-2 i Ki-67), mogu imati klinički značaj u identifikaciji podgrupa obolelih, koje se međusobno razlikuju kako prema odgovoru na HRT, tako i prema toku i ishodu bolesti.Rectal carcinoma (RC) represents approximately 30% cases of colorectal carcinomas (CRC), which is nowadays studing as a distinct clinical entity. The current management of locally advanced rectal carcinoma involves neoadjuvant chemoradiotherapy (CRT) prior to surgery. Despite improved local control rate, individual patient response to CRT is variable and may reflect heterogeneous biological properties among tumors of the same clinical stage. So, there is utility to define predictive and prognostic molecular parameters of response and to personalize therapeutic approach. Methylation-specific polymerase chain reaction (MSP) was used to examine p16INK4a and p14ARFmethylation status, while KRASmutation status was analyzed by direct sequencing in pretreatment tumor biopsies of patients with locally advanced RC, in order to evaluate its potential predictive and/or prognostic role. According to the results of this study, examined molecular changes of p16INK4a, p14ARF and KRAS genes, considering separately, were not proven to be significant predictive and prognostic factors in RC patients, although simultaneous presence of p14ARFmethylation and KRAS mutation was associated with more aggressive tumor behavior, while concurrent presence of genetic/epigenetic alteration in all three examined genes was correlated with shorter overall survival. However, combined analyses of genetic, epigenetic and immunohistochemical parameters (EGFR, VEGF, Bcl- 2 and Ki-67), could have important clinical relevance in identification of RC patients subgroups, with distinct pattern of response to CRT and disease outcome