Prediction of sensitivity of rectal cancer cells in response to preoperative chemoradiotherapy by DNA microarray analysis of gene expression profiles.

Samples were prospectively collected during colonoscopic examination from 46 rectal cancer patients before starting preoperative chemoradiotherapy. The expression profiles were determined using Affymetrix Human Genome U133 Plus 2.0 arrays. Comparison between the sample groups allow to identify a set of discriminating genes that can be used for prediction of the response to radiotherapy in rectal cancer. Specimens from 46 rectal cancer patients who approved to receive preoperative chemoradiotherapy were studied. We prospectively collected biopsy specimens during colonoscopic examination from rectal cancer before starting preoperative chemoradiotherapy. Specimens from tumors were snap-frozen in liquid nitrogen and stored at -80 C until use. Paralleled tumor specimens were formalin fixed and paraffin embedded for histologic examination and other specimens were used for RNA extraction. RNA was extracted from tumor tissue using frozen samples. The patients provided written, informed consent to the collection of specimens, and the local Ethics Committee approved the study protocol. All patients received a total dose of 50.4 Gy of radiation, UFT(300-500mg/day) and LV (75mg/day) and underwent standardized curative resection, following an interval of 4 weeks after chemoradiotherapy.