Inhibition Of Inducible Nuclear Factor-kappa B Activity Reduces Chemoresistance To Adriamycin In Human Stomach Cancer Cell Line

BackgroundStomach cancer is one of the most common malignant tumor. As most of patients suffer from progressive cancer, chemical therapy plays an important role in combined therapy.Chemoresistance is still a major clinical problem.Several investigators studied the metabolic and genetic mechanisms of such resistance ,but only a few studies have examined the molecular mechanisms of chemoresistance based on its apoptotic properties.Disovered in 1986 as a DNA-binding activity that recognized the immunoglobulin light-chain intronic enhancer,nuclear factor-kappaB(NF-B) has been studied intensively for its role in the control of expression of genes involved in immune and inflammatory functions.Recently,the role of NF-B in the regulation of apoptosis of normal and cancer cell has also been studied.NF-KB is avtivatied in several types of cancer cells and constitutive activation of NF-KB protects these cells against apoptosis. Furthmore, transient inhibition of NF-KB using an inhibitor of NF-icB or proteasome inhibitors can reduce the chemoresistance against CPT-11 in some cancer cell lins.These facts suggest that NF-B could participate in resistance to cancer treatment. The aim of the present study was to abolish chemoresistance to adriamycin in human stomach cancer cell line by inhibiting NF-KB activity.Objective1. To investigate the relationship between activation of NF-B and chemoresistance in human stomach cancer cell line2. To search for a new target point of reversing chemoresistanc in stomach cancer.Methods1. A human stomach cancer cell line resistant to adriamycin(SGC7901/ADM) was acquired by repeating 3-month exposures to stepwise-increasing concentrations of adriamycin in vitro.The cytotoxicity of ADM on SGC7901/ADM and SGC7901 stomach cancer cell line was determined by MTT assay.The variety of apoptosis rate of SGC7901/ADM and SGC7901 stomach cancer cell line were measured by flow cytometric analysis.2. The level of nuclear factor-kappaB activity for SGC7901/ADM and SGC7901 stomach cancer cell line was measured by immunohistochemical staining.The expression of nuclear factor-kappaB protein for SGC7901 /ADM and SGC7901 stomach cancer cell line was detected by Western blot.3. The effects of the inhibition of inducible nuclear factor-kappaB activation on chemoresistance against ADM by PDTC were intermined by MTT assay and flow cyotometric analysis.Results1. The SGC7901/ADM stomach cell line was 8.9 times more resistant to adriamycin than the SGC7901 stomach cell line. The apoptosis rate of SGC7901/ADM stomach cell line induced by adriamycin was much lower than SGC7901 stomach cell line ( P < 0.01).2. The level of nuclear factor-kappaB in SGC7901/ADM stomach cell line was significantly higher than SGC7901 stomach cell line (P<0.01).The expression of nuclear factor-kappaB in SGC7901/ADM stomach cell line was increased.3. After Inhibiting inducible NF-KB activity by pyrrolidine dithioearbamate(PDTC), the cytotoxicity of ADM on SGC7901/ADM stomach cancer cell line was increased significantly (p<0.01).Conclusion1. The change of apoptosis rate induced by NF-B activity maybe play an important role in chemoresistance2. Inhibiting NF-KB activity can reduce chemoresistance to adriamycin in human stomach cancer cell line .NF-B could be a new target point of reversing chemoresistanc in stomach cancer.