The Role Of DUTPase In The Development Of Colorectal Tumor

BACKGROUNDThe dUTPase is an important enzyme for the viability of the cells that catalyzes the hydrolysis of dUTP to dUMP and pyrophosphate. It serves a dual function by keeping the intracellular levels of dUTP low to avoid the undesired incorporation of uracil into DNA. Secondly, the hydrolysis of dUTP generates the precursor dUMP which is used in a "salvage" pathway for the synthesis of dTTP. Human dUTPase gene is composed of four exons, which encode for nuclear (DUT-N) and mitochondrial (DUT-M) isoforms generated by alternative splicing. DUT-M is expressed constitutively in non-dividing cells, while DUT-N's expression is cell cycle dependent. Conversely, the loss of the dUTPase appears to be associated with apoptotic process. So far, the enzymatic activity of a colorectal tumor cell, SW620 has been showed to be 3.4 folders higher than that of HT29, and the latter decrease the responses to the cytotoxic drugs once it is transfected to express the E.coli dUTPase. In contrast, the suppression of dUTPase with time and dose-dependent relationship in SW620 by SiRNA results in a significant decline in clonogenic survival and decreased cell proliferation. The colorectal carcinoma patients with lower level of nuclear dUTPase expression are discovered to have better response to 5-FU-based chmothrapy, greater overall survival. Primary colorectal carcinoma patients without lymphnode metastases are found to express lower levels of dUTPase than patients with lymphnode metastases at the time of surgery. Combined with our early discovery that the expression level of dUTPase in different metastatic potential cells: LoVo, SW480, LST-R1 reduce in order, we hypothesis that the dUTPase may play an important role in the development and progression of colorectal tumor, and maybe is a negative marker for the treatment and prognosis of colorectal tumor. In this experiment, four colorectal tumor cells of different pathological source and biological feature: LoVo, SW620, SW480å’ŒPSW1116 are chosen to identify their...