Effects Of RNAi And Nolatrexed On Thymidylate Synthase Expression And Cell Proliferation Of Human Colorectal Carcinoma LoVo Cell

Background and objective:Colorectal cancer is common malignancy tumor in China in recent years,the incidence of the disease tends to increase.The surgical resection is still the most effective treatment method to the colorectal cancer. Chemotherapy is also play an important role as an adjuvant therapy after surgery, but the problems of chemotherapy drug resistance to cancer therapy in the course of chemotherapy have not solved. Nolatrexed is a novel thymidylate synthase (Thymidylate synthase, TS) inhibitor,which is fat-soluble and do not contain glutamic acid side-chain and be easily cellular uptake, thereby increasing the concentration in tumor cells. When nolatrexed was taken into the cells,it can interfere with DNA synthesis and inhibit the proliferation of cells division and play the role of anti-tumor. At present, nolatrexed as a new anti-tumor chemical synthetic drugs in clinical trials has confirmed that its has a good effect on the liver cancer, head and neck cancer and other solid cancer. Studies have shown that TS expression levels are directly related to the efficacy of chemotherapy. RNA interference (RNAi) technology is the most effective mean of suppressing gene expression in the post-transcriptional level, while the incidence of colorectal cancer is due to the oncogene activation and inactivation. The study also showed that higher TS expression levels in tumor cells may lead to worse effect in chemotherapy. The purpose of this paper is to explore the dynamic changes of TS expression and proliferation in LoVo cells after treatment with nolatrexed, chemically synthesized siRNA and two joint, which can provide a theoretical basis to improve the efficacy of chemotherapy drugs.Results:Nolatrexed can inhibit LoVo cells proliferation significantly, the IC50is about6.31μmol/L. It can also promote the cells apoptosis,the apoptosis rate increased with the action time extend.The result of RT-PCR demonstrated that in the mRNA levels,TS/GAPDH ratio continue to rise all along within the time period in LoVo cells, only the ratio of48h and60h have significant difference to the untreatment group.When LoVo cells were treated with the same dose nolatrexed in the different time, the level of TS protein expression also keep rising as time goes on.TS siRNA can significantly reduce the expression of TS gene and protein in LoVo cells, inhibit cell growth.Combined with TS siRNA and nolatrexed can also significantly lower the IC50of LoVo cells and promote cell apoptosis compare with a single group. Conclusions:Nolatrexed can significantly promote cell apoptosis and produce TS-induced phenomenon.TS siRNA can partly suppress the expression of TS gene in LoVo cells, inhibit the cells proliferation, promote cell apoptosis.TS siRNA can enhance the cell sensitivity to apoptosis induced by nolatrexd. Combination of TS siRNA and nolatrexed can inhibit tumor cell growth, promote apoptosis of tumor cells.