ABSTRACT
Background:The tumor suppressor,X-linked inhibitor of apoptosis(XIAP)-associated factor 1(XAF1)is a XIAP-binding protein that antagonizes the anti-caspase activity of XIAP,thereby enhancing apoptosis. Transcriptional variants of XAF1 have been detected in various tumor cells,however,the expression profile of these transcriptional variants in colorectal neoplasms remains unclear. Aims:To investigate the expressions of XAF1 and its transcriptional variants in different colorectal tissues and their roles in tumorigenesis and development of colorectal neoplasms. Methods:Samples of colorectal cancer and paired adjacent tissue,hyperplastic polyp,adenomatous polyp,and normal colorectal mucosa were collected from surgical operation or endoscopic biopsies. XAF1 protein expression was detected by immunohistochemistry and Western blotting,and the transcriptional variants of XAF1 were detected by RT-PCR. Results:Compared with normal colorectal mucosa,the expression level of XAF1 protein in nucleus was significantly reduced( P 0. 05)in hyperplastic polyp,adenomatous polyp,and cancerous tissue,and the overall expression level of XAF1 protein was decreased(P <0. 05). XAF1A protein expression in cancerous tissue was significantly reduced when compared with the paired adjacent tissue(P < 0. 05). mRNA expressions of three transcriptional variants of XAF1,XAF1A,XAF1B and XAF1C were all significantly lower in neoplastic tissues than in normal mucosa(P < 0. 05). Conclusions:XAF1 and its transcriptional variants are differentially expressed in colorectal neoplasms and normal colorectal mucosa. These changes occurred initially in adenomatous polyp accompanied by a redistribution of XAF1 from nucleus to cytoplasm. Post-transcriptional modification may affect XAF1 gene function.
ABSTRACT
Objective To investigate the inhibitory effect of X-linked inhibitor of apoptosis associated factor-1(XAF1) on xenograft growth in nude mice with hepatocellular carcinoma. Methods The models of xenografted nude mice with human hepatocellular carcinoma cell line SMMC7721 were established. Intratumor injection was performed on three tumor sites in each group of mice (n=5) with recombinant adenovirus Ad5/F35-XAF1, control virus Ad5/F35-Null at the same infective titre or PBS of the same volume every two days for two weeks. The volumes of xenografts in all nude mice were measured every three days, and the differences between Ad5/F35-XAF1 group and the other two groups were compared. The apoptosis of tumor cells was determined by in situ end-labeling TUNEL method, the expression of XAF1 protein and microvessel density (MVD) were detected by immunohistochemistry. Results Intratumoral injection of Ad5/F35-XAF1 significantly inhibited the growth of tumor xenografts with smaller tumor size, less tumor weight and lower MVD compared with those injected with control virus Ad5/F35-Null and PBS (P<0.05 or P<0.01). However, the apoptosis index and expression of XAF1 protein in Ad5/F35-XAF1 group were significantly increased compared with the other two groups (P<0.01). Conclusion Ad5/F35-XAF1 significantly inhibits xenograft growth in nude mice with hepatocellular carcinoma, which is probably associated with the effects of XAF1 inducing hepatocellular carcinoma cell apoptosis and suppressing tumor angiogenesis.