Classification of serrated colorectal tumors

Serrated adenocarcinomas are morphologically different from conventional adenocarcinomas. The serrated pathway has recently been proposed to represent a novel mechanism of colorectal cancer (CRC) formation. However, whether they are biologically different and truly form a distinct subclass of CRC, is not known. This study shows that the gene expression profile of serrated and conventional CRCs differs from each others and that serrated CRCs are not only morphologically novel, but also biologically distinct subclass of CRC. Keywords: molecular classification Total RNA was extracted from fresh frozen tumors with Trizol (GibcoBRL) and purified using RNeasy spin columns (Qiagen). The RNA quality was analyzed using a spectrophotometer and a Agilent 2100 Bioanalyzer (Agilent Technologies). Biotin labeled and fragmented cRNA was prepared from 8 micrograms of total RNA with procedures recommended for the HG-U133 GeneChip expression analysis (Affymetrix). The HG-U133A chips were hybridized, scanned and analyzed with Microarray Suite 5.0 software according to the manufacturer’s instructions (Affymetrix).