| Objective:Evaluate the association between the genes PIK3CA and PIK3CB expression and the MDR genes in colorectal cancer (CRC) patients and to analyze their correlations. Explore their correlations with the clinic characteristics of human colorectal carcinoma. At the same time, the mechanism of PI3KCA, PI3KCB and MDR were studied in CRC. Explore the effect and mechanism of PIK3CA and PIK3CB in colorectal carcinoma and discuss the correlations between PIK3CA, PIK3CB and MDR and their effects on prognosis of human colorectal carcinoma.Materials and MethodsA total of 316 CRC tissue samples at different stages were collected from the Department of Pathology of Binzhou Medical University Hos-pital between January 2005 and May 2009. All CRC patients were clinically and pathologically proven to have not received preoperative chemotherapy or radiotherapy. Immunohistochemistry was employed to detect the expressions of PIK3CA, PIK3CB, MDR-1, LRP, GST-?, and Topo ? in 316 CRC specimens. Patients were followed-up annually by telephone or at an outpatient clinic.shRNA targeting PIK3CA, PIK3CB was chemically synthesized and was transfected into HCT/FU cell lines in vitro. The stable cell lines was established by infecting the lentivirus particles and the transfection efficiency was examined by RT-PCR and western blot. The cells were divided four groups, including blank control(add the reagent of transfenction), negative control groups(transfeeting nonspecific shRNA)and experimental groups(transfecting PIK3CA-shRNA and PIK3CB-shRNA). The expression of MDR-1 was examined by RT-PCR and western blot. Cell proliferation was examined by CCK-8.ResultsThe expression of MDR-1, Topo ?, LRP, and GST-? was found to be 72.78%, 77.53%,70.89%, and 76.58% in CRC, respectively. Correlation analysis showed that PIK3CA and PIK3CB expression exhibits a positive correlation with MDR-1, LRP, and GST-71 with correlation coefficients of 0.288,0.128, and 0.197, respectively (P<0.05). Kaplan-Meier analysis revealed that the five-year survival rate of patients without lymph node metastasis, positive expression of PIK3CA and PIK3CB, and negative expression of GST-? and MDR-1 was higher than those with these characteristics. Multivariate analysis revealed that the expression of GST-?, MDR-1 and lymph node metastasis could serve as independent predictive factors of overall survival.When silenced PIK3CA and PIK3CB in resistant cells of CRC, the expression of MDR-1 is reduced and the ability of proliferation was reduced. When the genes of PIK3CA and PIK3CB were knocked down, the ability of invasion and clone was suppressed and the cells was more sensitive to gefitinib and 5-FU.Conclusion1. The expression of PIK3CA and PIK3CB were increased in CRC, which revealed that high expression PIK3CA and PIK3CB are closely related to MDR. The multivariate analysis revealed that GST-?, MDR-1 expression and lymph node metastasis could serve as an independent predictive factor of OS, respectively. Our study provides the evidence that not only PIK3CA but PIK3CB may play an important role in CRC carcinoma, drug resistance and prognosis, further suggesting that PIK3CA and PIK3CB may be exploited as potential drug targets for CRC.2. When silenced PIK3CA and PIK3CB in resistant cells of CRC, the ability of proliferation was reduced and the ability of apoptosis was increased. When the genes of PIK3CA and PIK3CB were knocked down, the ability of invasion and clone was suppressed. PIK3CA and PIK3CB may become new targets for the treatment of colorectal cancer.3. Mutations of PIK3CA, PIK3CB in colorectal cancer resistant cells reduce the sensitivity to 5-FU and gefitinib. PIK3CA and PIK3CB may be factors affecting the efficacy of chemotherapy in colorectal cancer.4. Silenced PIK3CA and PIK3CB can improve the sensitivity of colorectal cancer cell lines to gefitinib and 5-FU, suggesting that PIK3CA, PIK3CB can be a reversal of colorectal cancer targeted therapy drug and a new target. |
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