| The last twenty years have witnessed the revolution in our JL understanding of the processes responsible for the carcinogenesis at molecular level, but the problems still exist, or even are growing as the average lifespan in many countries steadily rises. So far, colorectal cancers are usually classified into three subgroups in terms of molecular biology, genetics as well as clinical features: Familial Adenomatous Polyposis (FAP)-associated CRC, Hereditary Non-Polyposis Colon Cancer (HNPCC) and Sporadic Colorectal Cancer (SCRC), each of them has its predominant molecular portrait.Besides surgery, radiotherapy and biological therapy, chemotherapy is proven effective in reducing mortality for advanced CRC patients by killing micrometastases disseminated at surgery or occult metastases already present at surgery. Among various regimens, combination therapies of 5-fluorouracil (5-FU) with some second-line agents have been the mainstay of adjuvant chemotherapy for CRC patients to date, but regardless of regimens, the outcome of CRC patients is far from satisfaction owing to various biochemical or non-biochemical mechanisms. In various tumors, at least five groups of sensitivity-associated factors have been identified, including drug efflux, detoxification, DMA repair, drug target regulations and other factors as apoptosis, length of telomere, etc. In addition, clinical data suggests that, in retrospect, nearly half of the patients with Dukes' C colorectal caner might not require adjuvant chemotherapy and about 35%would die even when treated with systemic chemotherapy. This also highlights the need for informative predictive or prognostic markers that will aid identification of patients best treated with surgery alone, those requiring chemotherapy and those who might benefit from aggressive or experimental therapy.To elucidate the possible biochemical mechanisms of chemosensitivity, and to identify possible factors involved in response to 5-FU-based regimens in CRC, we studied the chemosensitive phenotype to 5-FU, CDDP or their combination therapy, alterations of cell cycle distribution and transcription level of TS in exposure to drugs, expression of several proteins and the microsatellite status in three human colon cancer cell lines. By comparing the phenotype and their genetic background, we look forward to revealing whether these molecular events can be used as convenient predictors for drug-optimization or prognosis-assessment in CRC patients.Part IPhenotype of chemosensitivity to 5-fluorouracil & cisplatin and p53 expression in three human colon cancer cell linesFirstly, we determined the phenotype of chemosensitivity to 5-fluorouracil and cisplatin in LoVo, SW480 and SW1116 cell lines in vitro, using microscopic morphology, MTT assay and Flow cytometry. Considering that big controversies exist in the biological role of p53 in chemosensitivity, we also analyzed its expression in those three cell lines by immunocytochemistry.Results showed that 5-FU and CDDP were cytotoxic to all three cell lines despite different extent. Morpfiofogicalfy compared with the control in which cells grow free from drugs, LoVo cells, 72 hours after 5-FU treatment at 8 n M or 64 u M, become karyopyknostic, round, refrangibile, anddecrease in number. In SW480 cells and SW1116 cells.however, they showed less cytotoxicity than LoVo cells. &ff vialnGty assay in exposure to 5-FU also suggested that 5-FU be cytotoxic to all three cell lines. At 12h, 48h and 120h, LoVo was most sensitive to low concentrations of 5-FU (<4 u mol/L), SW480 was least sensitive, and SW1116 was intermediate. At 120h, the ICso of LoVo (0.8 u mol/L) was significantly lower than those for SW480 and SW1116 (2.2 y mol/L and 1.9 u mol/L, respectively, p=0.000). Time-effect curves indicated that survival rates of the three cell lines all decreased with time. But LoVo is most sensitive and SW480 least at lower concentrations of 5-FU(<4 u mol/L, p<0.05). Analyses of the sensitivity and responsiveness of LoVo, SW480 and SW1116 cells to CDDP and...
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