免疫球蛋白G在膀胱癌细胞中的表达及其抗体诱导肿瘤细胞凋亡的研究

目的： 研究免疫球蛋白G在膀胱癌细胞中的表达以及其抗体诱导肿瘤细胞凋亡的效应。方法： 免疫组织化学法检测56例临床膀胱癌组织和11例正常膀胱黏膜中以及T24和BIU-87细胞中IgG蛋白表达；对体外培养的膀胱癌细胞系T24和BIU-87采用Western blotting、ELISA法和流式细胞术（FCM）检测IgG蛋白的表达，原位杂交法和RT-PCR检测IgG1 mRNA的表达，MTT法检测羊抗人IgG抗体对肿瘤细胞的生长抑制的影响，FCM检测羊抗人IgG抗体诱导肿瘤细胞凋亡效应。结果： 免疫组化显示临床膀胱癌组织中IgG表达率为91.1％（51/56），正常膀胱移行上皮细胞IgG的表达为45.4％（5/11）；T24和BIU-87细胞浆中IgG明显阳性表达。RT-PCR和原位杂交显示IgG mRNA在T24和BIU-87细胞中明显表达。Western blotting显示T24和BIU-87细胞中均有IgG表达。FCM则表明IgG蛋白主要在细胞质内表达，细胞膜上则小部分表达。ELISA法未能在T24和BIU-87细胞培养液的上清液中检测到IgG。MTT显示羊IgG和羊抗人IgG抗体在25 mg/L时对T24和BIU-87细胞的生长抑制率分别为(4.73±3.73)%、（24.98±3.81）% 和（5.36±1.53）%、（22.70±3.72）%，(P<0.05)。FCM 显示羊IgG和羊抗人IgG抗体在25 mg/L时对T24和BIU-87细胞的凋亡率分别为2.3%、20.7％和1.3%、15.3％。结论:膀胱癌细胞能够表达IgG，但其为非分泌型IgG。IgG的抗体体外对膀胱肿瘤细胞的生长具有一定抑制作用，且具有促进肿瘤细胞凋亡的效应，这可能对膀胱肿瘤的治疗提供一个新的靶点。

Expression of IgG in bladder carcinoma and the effect of the antibody against human IgG on tumor cell apoptosis

AIM: To investigate the expression of immunoglobulin G (IgG) in bladder transitional carcinoma cells (BTCC) and the effect of the antibody against human IgG on tumor cell apoptosis.METHODS: The expression of IgG of BTCC was detected by immunohistochemistry, Western blotting, enzyme linked immunosorbent assay (ELISA) and flow cytometry (FCM). The expression of IgG mRNA was tested by hybridization in situ method and RT-PCR in vitro. Antiproliferation effects of the antibody of antihuman IgG on T24 and BIU-87 cell lines were measured by MTT assay. Cell apoptosis was assessed by FCM.RESULTS: The expression of IgG was 91.1％ (51/56) in clinical cases, and 45.4％ (5/11) in normal controls. Immunohistochemistry and Western blotting showed that the IgG was significantly expressed in T24 and BIU-87. FCM indicated the IgG was mainly expressed in cytoplasma. No IgG was detected by ELISA in supernatant of cell culture medium. RT-PCR and hybridization in situ demonstrated IgG mRNA was significantly expressed in two cell lines. Under the treatment of 25 mg/L of goat nonspecific IgG and the antibody of antihuman IgG, the inhibition ratio of cell growth in T24 and BIU-87 were (4.73±3.73)% vs (24.98±3.81)% and (5.36±1.53)% vs (22.70±3.72)%, respectively (P<0.05). The percentages of apoptotic cells in T24 and BIU-87 were 2.3% vs 20.7% and 1.3% vs 15.3%, respectively.CONCLUSION: IgG is significantly expressed in bladder transitional carcinoma cell. The antibody of antihuman IgG inhibits cancer cell growth and induces tumor cell apoptosis.