Functional Research Of LASS2 Gene

The hepatocarcinogenesis and development of hepatocellular carcinoma (HCC)is a multistep process associated with changes in host gene expression, some ofwhich correlate with the appearance and progression of tumor. Tumor progression ischaracterized by LOH involving tumor suppressor genes on many chromosomes andby gene amplification of selected oncogenes. An understanding of the molecularpathogenesis of HCC may provide new markers for tumor staging, for assessment ofthe relative risk of tumor formation, and open new opportunities for therapeuticintervention. A method based on the growth of cells was established to select cancer relatedgenes in Oncogenes and Relative Genes National Laboratory of Shanghai CancerInstitute. LASS2 gene was also isolated by this method from a human liver cDNAlibrary. LASS2 is a homologue of LAG1 (Saccharomyces cerevisiae longevityassurance gene). Over expression of LASS2 can inhibit the growth of HCCSMMC-7721 cells. The results about bioinformatics analysis dedicate that LASS2 contains twodomains: HOX and TLC , and has an identical segment : TMSG-1. It is interestingthese two domains associate with ceramide synthesis. Ceramide, a bioactive lipidarising from the hydrolysis of sphingomyelin or from de novo formation, has beenproposed to play important roles in growth arrest, differentiation, and apoptosis. Wefind TMSG-1( Homo sapiens tumor metastasis-suppressor)is only a segment ofLASS2 .Expression lever of TMSG-1 is lower in prostate cancer cell PC-3M subline1E8 of high metastatic potential than in PC-3M subline 2B4 of non-metastaticpotential . Through RT-PCR and northern blot assay, we found that the expression level ofLASS2 is higher in tumor cell lines of high metastatic potential SCI-375 andHCCLM3 than in tumor cell lines of low metastatic potential A-375 and MHCC97-L. 广西医科大学肿瘤专业 硕士研究生论文 5人源性长寿保障基因 LASS2 的功能研究The expression level of LASS2 is higher in normal liver tissue than in all four tumorcell lines A-375, MHCC97-L, SCI-375 and HCCLM3.Based on this result, weinvestigated function of LASS2. Over expression of LASS2 can inhibit the growth of A-375 and HCCLM3 cellsin vitro. The same result we can get from animal assay. Herein, we show that LASS2can arrest tumor cells in G0/G1. Maybe, the mechanism of LASS2 inhibiting tumorcell proliferation associates with the level of ceramide in cells. Over expression of LASS2 can also suppress SCI-375 cells and HCCLM3 cellsmetastasize to the lung in vivo. Through RT-PCR and northern blot assay, we foundthat the expression level of VPL is lower in tumor cell lines of high metastaticpotential SCI-375 and HCCLM3 than in tumor cell lines of low metastatic potentialA-375 and MHCC97-L. The results that LASS2 and VPL can interact with each otherin vivo in former experiments, and LASS2 can inhibit cell-mediated extracellularacidification (data not shown), indicate that there is a possible mechanism that LASS2suppress tumor metastasis through inhibiting V-ATPase function.