The Expression Of PKCs In Malignant Tumor And The Effects Of Amoitone A Against Gastric Cancer Cells

Cancer is a genetic disease. Currently, in the field of life sciences, the researcheson the mechanisms of tumorigenesis and the development of anticancer drugs arehotspot. In this dissertation, using modern biological technologies, the relevancebetween the expressions of protein kinases C (PKCs) in breast cancer and gastriccancer BGC-823 cells and the degrees of differentiation was studied. The inhibitoryeffects of PKCαsiRNA and amoitone A on the growth of gastric cancer BGC-823cells were observed in vitro and in vivo.First, the relevance between PKCs and breast cancer differentiation, andmetastasis was studied. In 48 cases of breast cancer patients, the expressions of PKCisozymes were accessed by immunohistochemical methods which showed nosignificant correlation between the expressions of breast cancer PKCα, PKCβ, andthe degree of tumor cell differentiation. However, the expressions of PKCηand PKCζwas significantly correlated to the degree of breast cancer cell differentiation.Through HE staining, the PKC immunohistochemical results showed that theexpressions of PKCηand PKCζmarkedly increased in the majority of invasiveductal breast cancer cells. In the cytoplasm of breast tumor tissue, the expression ofPKCηand PKCζwas positively correlated with the magnitude of the tumor celldifferentiation, and inversely correlated with the degree of malignancy.Secondly, in 80 cases of gastric cancer samples, the expressions of PKCisozymes, particularly PKCα, were examined with the relevance to the degrees oftumor cell differentiations by immunohistochemical avidin-biotin peroxidase method.The results showed that the positive rates of PKCαwere 67.5% and 19.1% (p＜0.05)in typesⅠ-ⅡandⅢgastric cancer cells, respectively. In the case of gastric cancerwith metastasis, the expression levels of PKCs were generally high, which wassignificantly correlated with the degree of tumor cell metastasis (p＜0.01). In addition,PKCs protein expression levels had no correlations with ages of cancer patients.Thirdly, the effects of PKCαsiRNA on the growth of human gastric cancer cellBGC-823 were studied. The recombinant PKCαsiRNA was constructed andtransferred into BGC-823 cells. PKCαsiRNA suppressed the expression of target geneand the growth of tumor. The expressions of genes c-myc and PCNA, that are correlated with cell proliferation, were founded decrease, showing that knock down ofPKCαmay inhibit the growth of tumor cell, and suppress the expression of tumorgrowth gene. PKCαsiRNA packed by cationic liposome Oligofectamine, applied bytail vein injection, suppressed the tumor growth under nude mice skin. But as timeextended, its inhibition rate decreased gradually compared with the control group,which may be caused by the degradation of siRNA in cells during cell proliferations.This result suggested that to achieve the best results, antisense gene therapy need moredrug delivery or combined with other treatments.Lastly, the natural product namely amoitone A isolated from a marine fungalstrain, was tested for its antitumor activity in BGC-823 cells. The results showed thatamoitone A inhibited the growth of BGC-823 cells with the inhibitory rate ca. 80% at10μg/ml. The apoptosis ratios of BGC-823 increased with increasing amoitone Aconcentrations. Amoitone A inhibited the tumor growth in the experiment of nudemice transplanted with BGC-823 cells treated with amoitone A intraperitoneally, 13mg/kg (twice/week, for four weeks). Further studies showed that amoitone A couldinduce endogenous and exogenous plasma TR3 nuclear translocation, and inducedTR3 expression and nuclear slurry transfer in vivo and in vitro, inhibiting the growthof malignant gastric cancer cells.