The Bcsc-1 Gene In Nasopharyngeal Carcinoma Tumor Suppressor Role

We previously observed that inhibition of Man2c1 gene expression by means of antisense technique resulted in a profound reduction of malignant activities of the human nasopharyngeal carcinoma cell CNE-2L2.To explore the molecular mechanisms,mRNA differential display was performed to find the effects of Man2c1 suppression on gene expression of the cell.Compared to control,23 genes were up-regulated and 45 genes were down-regulated in the cell with Man2c1 suppression(AS cell).BCSC-1(i.e.LOH11CR2A) was the gene up-regulated highest in AS cell.Martin et.al proposed that BCSC-1 was a candidate tumour suppressor gene.Therefore, suppressive effects of BCSC-1 expression on the malignant activities of CNE-2L2 cell were studied in this laboratory.The former Ph.D.student SL Cheng and I observed that ectopic BCSC-1 resulted in suppression of growth in culture,colony formation and in vivo tumorigenicity of the cell.However,only ectopic BCSC-1 experiments are not enough to confirm that BCSC-1 is a tumour suppressor gene,since the gene ectopically expressed was exogenous instead of endogenous.Thus,the purpose of my thesis was to examine if inhibition of endogenous BCSC-1 in AS cell exhibited reversed effects on the malignant behaviours of the cell.The data obtained in my experiments showed that BCSC-1 suppression by siRNA did promote cell growth in culture,colony formation and in vivo tumorigenicity of AS cell.Furthermore,we observed that introduction of BCSC-1 cDNA into the tumor grown from W cells implanted in nude mice mediated by adeno virus inhibited growth of the tumor.Therefore,I together with Chen SL confirmed that BCSC-1 is a tumor suppressor gene in CNE-2L2 cell.In order to examine BCSC-1 expression in human nasopharyngeal carcinomas,I prepared a monoclonal antibody anti-BCSC-1,which can be used in immunohistochemistry.Taken the mAb as a probe,BCSC-1 expression on protein level was examined in the biopsy specimens of 3 normal nasopharyngeal tissues and 9 nasopharyngeal carcinomas.BCSC-1 expression in the epithelial cells was observed to be quite strong in all 3 normal tissues tested and weak in the cancer cells in 4/9(44.4%) carcinomas.The possible molecular mechanisms for the suppressive effect on malignant activities of CNE-2L2 cell were explored from 3 aspects.1) Global gene profiling was performed to examine the effect of BCSC-1 on gene expression of the cell.91 genes were up-regulated and 97 genes were down-regulated in the cell with ectopic BCSC-1 compard to control.Go term analysis and pathway analysis were carried out based on the differential displayed genes.2) Effect of BCSC-1 on microRNA expression was examined.3) Effect of BCSC-1 suppression on the expressin of the WNT family members was assayed by real-time RT-PCR.The data implicates that BCSC-1 is a tumor suppressor gene in human nasopharyngeal carcinoma and its inhibited expression might play a part in the development of nasopharyngeal carcinoma in some individuals.