Research Of The Sensitivity Of Human Colorectal Cancer Cell Line LS-174-T To As₂O₃ Used Alone And In Combination With HCPT, And With Regard To Its Possibile Mechanism

Objectives:To investigate the Sensivity of Human Colorectal Cancer Cell Line LS-174-T to As2O3 used alone and in combination with HCPT, and evaluate the value of As2O3 in the clinical treatment of colorectal cancer.Methods: The anti-cancer effects of As2O3 and HCPT used alone and in combination were investigated by MTT assay and and evaluated by the median-effect principle. Flow cytometry(FCM)was used to analyse cell cycle distribution and determine the apotosis index. The ultrastructural changes of cancer cells were observed with transmission electron microscope. Immunocytochemical staining technique was used to detect the changes of expressions of nm23,E-cadherin,HSP70,VEGF.Results: (1) After treated for 24 hours, the anti-cancer effect of As2O3 were very significant even at the lowest concentration(2.5umol/L) (P<0.01). The effects were enhanced as concentration of As2O3 increased. (2) As2O3 was antagonistic with HCPT at low concentration(CI >1),but synergetic action were appeared while the concentrations of both drugsincreased to high level(CI<1). (3) FCM study indicated that not only 1.5umol/L but also 3.0 umol/L As2O3 could hardly change cell cyle distribution of LS-174-T cells. A sub-G1 peak was detected under the treatment of 3.0 umol/L As2O3 but not under 1.5 umol/L As2O3. (4) The ultrastructural changes of the cells were as follows: Treated with 1.5 umol/L of As2O3 for 72 hours, the number of microvilli on the surface of plasm membrane decreased and the nucleolar margination was frequent in nucleus. Vacuolations and swelling mitochondria were seen in cytoplasm. (5)As2O3 could upgrade the expression levels of nm23,E-cadherin and downgrade the expression levels of HSP70,VEGF in LS-174-T cells. Conclusion: (1)According to the results of MTT assay, we can expect a exciting therapic effect with only a low dosage of As2O3 and relatively short time to treat colorectal carcinoma in human, because its anti-cancer effect is largely in dosage dependent pattern; (2) Combinated with HCPT , high dosage As2O3 is reasonable;(3) As2O3 can hardly change the distribution of cell cyle;(4) As2O3 can induce apoptosis in concentration-dependent pattern;(5) As2O3 may inhibits the metastasis of colorectal carcinoma cell through upgrade the expression levels of nm23,E-cadherin;(6) As2O3 may inhibits angiogenesis in colorectal carcinoma by reducingthe expression level of VEGFï¼›(7)By Decreasing the expression level of HSP70, As2O3 may have the action of reverse chemoresistance of colorectal carcinoma.