Reduced succinate dehydrogenase B expression is associated with growth and de-differentiation of colorectal cancer cells.

Succinate dehydrogenases (SDH), including SDHA, SDHB, SDHC, and SDHD, form the respiratory complex II in the mitochondria and play an important role in cell growth and homeostasis. In order to evaluate the expression and functional significance of SDH in colorectal cancer, the expression of four SDH subunits was analyzed, and SDHB protein was found to be significantly lower in colorectal cancer tissues. In vitro experiments including cell growth assay, colony formation assay, cell cycle analysis, and nude mouse xenograft of SDHB-transfected colorectal cancer cell line SW620 were performed. Notably, reduced SDHB expression in tumor tissues was associated with tumor de-differentiation, and restoration of SDHB could inhibit the growth of cancer cells both in vitro and in vivo. Furthermore, cDNA microarray of SDHB-transfected cell line showed that most of the differentially expressed genes are related to cell cycle control and cell proliferation. Thus, we conclude that SDHB expression is significantly decreased in human colorectal cancer tissues, and reconstitution of SDHB in colorectal cancer may be a potential therapeutic approach to inhibit aggressiveness of colorectal cancer.