[Proteomic expression analysis of human colorectal cancer: of soluble overexpressed proteins]

Colon cancer is one of the leading causes of cancer deaths in developed countries due to the absence of tumor specific markers for early diagnosis of the disease, providing adequate sensitivity. Search for diagnostic markers of various types of cancer by proteomic approaches has been limited by large differences in protein centration. We used preliminary extraction of major cellular proteins by 0.2 M sodium chloride in presence of nonionic detergent NP-40 in order to raise the sensitivity of the 2D PAGE detection of low-abundant soluble proteins, some of which may penetrate in blood circulation during carcinogenesis. Application of this procedure prior to 2D comparative analysis of proteomes of normal tissues and matched colon cancer specimens led to selection of ten proteins, which are frequently overexpressed in colon adenocarcinomas. Mass-spectrometric identification of selected proteins led to discovery of two novel protein markers of colon tumors--TAF9 and CISH. Low level of CISH expression in various tissues suggests that it is a novel prospective marker for diagnosis of colon cancer.