Function Analysis Of The Protein Biomarker In Colorectal Cancer

Colorectal cancer is one of the most common malignancies in the world. It is important to identify genes that related to the development and progression of colorectal cancer. In our previous studies, we found that7p,8q and18q were the chromosomal regions frequently detected in colorectal cancer by using comparative genomic hybridization (CGH).Based on the CGH results, we analyzed the expression of150proteins in500cases of colorectal cancer by the technique of immunohistochemistry. In comparing with adjacent tissues, the expression of15proteins remarkably increased in tumor tissues, in which six were for the first time observed with elevated expression in colorectal cancer. The sensitivity for the detection of colorectal cancer was86.3%in an optimal combination of several overexpression proteins.The patients with DNAJB1, DNAJB6or KIAA1522over-expression had poor prognosis compared to those with low expression. We further analyzed the relationship between the three proteins and clinico-pathological parameters. DNAJB6, DNAJB1and KIAA1522presented strong expression in53.3%(112/210),50.7%(118/197) and50.7%(58/126) of tumors, respectively. The tumor-free survival time of patients with strong expression of DNAJB6, DNAJB1or KIAA1522was significantly shorter than those with low or negative expression. Multivariate analysis showed that both DNAJB6and KIAA1522were independent prognostic factors.In order to explore the molecular mechanisms of DNAJB6in the carcinogenesis and develpment of colorectal cancer, we examined DNAJB6expression in multiple colorectal cancer cell lines. We knocked down DNAJB6in high DNAJB6-expressed cell lines HCT-116and DLD-1by using the siRNA transfection assay. The results showed that DNAJb6down-regulation did not influence cell proliferation, cell cycle progression and apoptosis, whereas DNAJB6RNAi decreased the invasion and increased the adhesion of colorectal cancer cells. The expression of active S6K and S6protein was decreased after the DNAJB6knockdown. Immunohistochemistry assay revealed a significantly positive correlation between the high expression of DNAJB6and phospho-S6in colorectal cancer tissues. These data indicated that DNAJB6may play a role in the process of colorectal tumorigenesis through impacting on mTOR-S6K-S6signaling pathway. Also, we found that the expression of active ERK protein was inhibited after the DNAJB6was koncked down, suggesting that DNAJB6may function in MEK-ERK signaling pathway in colorectal tumors.In summary, the combination of overexpression proteins had higher sensitivity for the detection of colorectal cancer. The patients with overexpression of DNAJB1, DNAJB6or KIAA1522had poor prognosis compared to those with down-expression. Both DNAJB6and KIAA1522were independent prognostic factors. DNAJB6may play a role in colorectal tumorigenesis through impacting on mTOR-S6K-S6and MEK-ERK signaling pathways.