Apoptosis Of Gastric Carcinoma SGC7901 Cells Would Be Induced By Small Interfering RNA-Mediated Nuclear Factor-κB P65 Suppression Associated With 5-Fu

Objective The nuclear factorκB has been widely studied for the past few years as a transcriptional control factor in eukaryocyte.It can enhance the transcription and expression of the related genes when it binded specificly with the promotor and the enhancer in several cytogenes. The data have indicated that NF-κB is one of the key factors in the tumorigenesis and growth of the gastric carcinoma. p65,the activation subunit of NF-κB, may trans-activate many genes,including cyclinD1 ,VEGF, matrix metalloproteinases (MMP), intercellular adhension molecule (ICAM-1), multidrug resistance genes (MDR), so as to modulate the proliferation of tumor cells, apoptosis resistance, angiopoiesis, invasion, metastasis and drug resistance[1-2]. Hence we chose p65 as the target, which was inhibited by small interference RNA aiming at NF-κB p65. The gene expression and the effect on the proliferation, apoptosis, and the drug–resistance to 5-Fu in gastric tumor cell were observed when siRNA was administered with or without chemotherapeutic 5-Fu. Methods①Cultured SGC7901 cells were randomly allocated into five groups: the blank with untreated, the group with liposome, the group with 5-Fu, the group with siRNA and the group with both 5-Fu and siRNA.②Small interfering RNA(siRNA) synthesized against human NF-κB P65 was transfected via cation liposome (LipofeetamineTM2000) into gastric carcinoma strain SGC7901. The effect of siRNA on cell proliferation was evaluated by MTT at five individual concentrations(50,75,100,150,200mg/L).The expression of NF-κB p65 was detected by Western blotting and the apoptosis by Annexin V- PI bioassay.③The growth of SGC7901 after transfection with five different concentrations(50,75,100,150,200mg/L)was assessed by MTT assay.Results①The protein NF-κB p65 was highly expressed in the group with untreated and the group with liposome, and low expressed in other three groups. Comparing with the blank, its expression was suppressed obviously in SGC7901 cells of other three groups, with an inhibition ratio of 41.91%, 50.68%, 71.28%, respectively.②The inhibition ratio of the apoptosis was 1.4±0.20 %, 2.36±0.58%, 6.68±0.34 %, 6.60±0.64% and 21.62±1.12 %, respectively. 5-Fu and siRNA may induce apoptosis markedly and the most powerful induction was achieved when treated with both. The number of apoptotic cells in the other three groups increased 5, 4 and 16 times, respectively.③The viability of SGC7901 cells transfected with siRNA was significantly decreased in the MTT assay, worsening with increasing of the concentrations and extending of the exposure time.Conclusion The siRNA may suppress the expression of NF-κB p65, thus inhibit the proliferation of SGC7901 cells, promote the apoptosis, augment the sensitivity to chemotherapeutics in tumor cells. It was suggested that blockage of NF-κB signaling pathway might function in gene therapy.