Novel tumor metastasis suppressorgene LASS2/TMSG1 S248A mutant promotes invasion of prostate cancer cells through increasing ATP6V0C expression / 北京大学学报(医学版)

OBJECTIVE@#LASS2/TMSG1 gene is a novel tumor metastasis suppressor gene cloned from human prostate cancer cell line PC-3M in 1999 by Department of Pathology,Peking University of Basic Medical Sciences. It was found out that protein encoded by LASS2/TMSG1 could interact with the c subunit of vacuolar-ATPase (ATP6V0C). In this study, we explored the effect of LASS2/TMSG1 and its mutants on proliferation, migration and invasion of human prostate cancer cells and its molecular mechanism.@*METHODS@#We constructed four LASS2/TMSG1 mutants and stably transfected the variants to human prostate cancer cell line PC-3M-1E8 cell with high metastatic potential. The stable transfectants were identified by qPCR and Western blot through analyzing the expression of LASS2/TMSG1 and ATP6V0C, the cell biology functions of LASS2/TMSG1 and its four mutants were studied using growth curve,MTT assay, soft agar colony formation assay, wound migration assay, Matrigel invasion study and flow cytometry. Furthermore, immunofluorescence was used to analysis the interaction of LASS2/ TMSG1 mutants and ATP6V0C.@*RESULTS@#LASS2/TMSG1 mRNA and protein in LASS2/TMSG1 group and Mut1-Mut4 groups were higher than that in Vector group; Western blot showed that ATP6V0C protein in LASS2/TMSG1 wild group was lower than that in Vector group, but ATP6V0C protein in LASS2/TMSG1 S248A group was obviously higher than that in Vector group. MTT test and growth curve assay showed growth ability in LASS2/TMSG1 S248A group was increasing compared with other groups from day 5. Soft Agar colony formation experiment showed anchor independent growth ability in LASS2/TMSG1 S248A group was higher than those in the other groups (P<0.05), Cell migrations (from 35.3%±3.2% to 70.3%±3%) in LASS2/TMSG1 S248A group was increasing compared with LASS2/TMSG1 wild group (P<0.01), and more cells passed through Matrigel in LASS2/TMSG1 S248A group compared with LASS2/TMSG1 wild group (from 50±3.2 to 203±6.5, P<0.01), the apoptosis rate in LASS2/TMSG1 S248A group was obviously higher than that in LASS2/TMSG1 wild group (from 7% to 15.1%, P<0.05), and the G0/G1 ratio in LASS2/TMSG1 S248A group was obviously higher than that in LASS2/TMSG1 wild group (from 51.0% to 85.4%). Furthermore, double immunofluorescent staining observed the colocalization between ATP6V0C and LASS2/TMSG1 protein and its mutations, the expression of ATP6V0C in LASS2/TMSG1 S248A group increased significantly compared with the other groups.@*CONCLUSION@#LASS2/TMSG1 S248A promotes proliferation, migration and invasion of prostate cancer cells through increasing ATP6V0C expression, suggesting that aa248-250 is an important function site for LASS2/TMSG1 in invasion suppression of prostate cancer cells.

LASS2/TMSG1 gene silencing promotes the invasiveness and metastatic of human prostatic carcinoma cells through increase in vacuolar ATPase activity / 中华病理学杂志

<p><b>OBJECTIVE</b>To explore the effects of LASS2/TMSG1 silencing on the growth, invasion and metastasis of prostate carcinoma cells and to investigate the related molecular mechanisms.</p><p><b>METHODS</b>LASS2/TMSG1 expression of human prostate carcinoma cell line with low metastatic potentiality (PC-3M-2B4 cells) was knocked down using DNA vector-based small interfering RNA (shRNA), followed by evaluations of tumor cell invasion and metastasis.</p><p><b>RESULTS</b>A stable PC-3M-2B4 cell line with expression of LASS2/TMSG1-shRNA was successfully established. MTT assay showed PC-3M-2B4 cells exhibited a strong proliferation after transfection of LASS2/TMSG1-shRNA.LASS2/TMSG1-shRNA transfected clones demonstrated an increased clonogenicity by soft agar colony formation assay and a significant increase of tumor cell invasion by matrigel invasion study.Flow cytometry showed that after LASS2/TMSG1 gene silencing, the apoptotic rate of PC-3M-2B4 cell significantly decreased (P<0.01) without significant cell cycle change (P>0.05).Eight weeks after implantation into subcutaneous tissues in BAL B/c (nu+) mice, the size and weight of sh-LASS2/TMSG1 xenografts were significantly larger than those of the control group (P<0.05).Nuclear proliferation index of the subcutaneous tumor was also higher in the LASS2/TMSG1 shRNA group than those in the control group. Lymph node metastasis was observed in 5 of 6 mice of LASS2/TMSG1 shRNA group and only 1 of 6 of the control group. V-ATPase activity, activities of secreted MMP-2 and MMP-9 and extracellular hydrogen ion concentration were significantly increased in LASS2/TMSG1-shRNA group compared with the control group (P<0.05).</p><p><b>CONCLUSION</b>Silencing of LASS2/TMSG1 promotes the growth, invasion and metastasis of prostate cancer cells through up-regulation of V-ATPase activity, indicating that LASS2/TMSG1 is a tumor metastasis suppressor gene.</p>

Transcriptional activation of TMSG-1 by complex of KLF6 and Sp1 / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate the regulatory mechanism of the transcription of tumor metastasis suppressor gene TMSG-1.</p><p><b>METHODS</b>Luciferase reporter assay and site-directed mutagenesis were used to analyze the regulatory region of TMSG-1. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) were carried out to verify the interaction of KLF6 and Sp1 with the regulatory region of TMSG-1. Co-immunoprecipitation (CoIP) was performed to analyze the interaction between KLF6 and Sp1. TMSG-1 and wt-KLF6 mRNA expressions in cells with different metastatic capacities were quantitated by real-time PCR. Cell invasive capability was determined by Matrigel invasion assay.</p><p><b>RESULTS</b>A 63 bp inducible regulatory region (+59 bp - +123 bp) in exon 1 was identified by luciferase assay using reporter plasmids with a series of TMSG-1 regulatory region deletions. Mutations in KLF6/Sp1 binding sites of this region resulted in a decrease of luciferase activity, while cotransfection with KLF6 or Sp1 expressing plasmids led to a remarkable increase of luciferase activity. EMSA and ChIP demonstrated that KLF6 as well as Sp1 interacted with this region. CoIP also indicated a possible interaction between KLF6 and Sp1 proteins. In the highly metastatic cell sublines, a low level of wild type KLF6 was associated synchronously with a low TMSG-1 level. Prostate carcinoma cells overexpressing KLF6 exhibited a higher TMSG-1 level and a lower invasive capability.</p><p><b>CONCLUSIONS</b>Transcription factor complex of KLF6 and Sp1 may participate in the inducible transcriptional regulation of TMSG-1, and a decreased wild type KLF6 expression is likely associated with a low TMSG-1 level in the highly metastatic cell sublines.</p>

Identification of nucleolar localization signal sequence of tumor metastasis suppressor gene-1 / 中华病理学杂志

<p><b>OBJECTIVE</b>To identify the putative specific localization signal sequence of tumor metastasis suppressor gene-1 (TMSG-1) and to explore the mechanism of subcellular localization of TMSG-1 protein.</p><p><b>METHODS</b>Vectors expressing green fluorescence protein (GFP) tagged different TMSG-1 fragments were generated and transfected into human embryo kidney 293 (HEK293) cells. The expression of those fusion proteins was detected by Western blotting and their subcellular localizations were observed by laser confocal microscope.</p><p><b>RESULTS</b>GFP was fused with the native TMSG-1(aa1-380) or different fragments including T1 (aa1-70), T2 (aa1-128), T3 (aa129-380), T4 (aa71-128), T5 (aa71-179) and T6 (aa71-380). Anti-GFP Western blotting showed that these fusion proteins were successfully expressed. Under laser confocal microscope, GFP fused with fragment T4 (aa71-128) localized mainly in the nucleolus; GFP fused with fragment T6 (aa71-380) localized diffusely in the nucleus; while other fusion proteins with TMSG-1 (aa1-380) or fragment T1 (aa1-70), T2 (aa1-128), T3 (aa129-380) and T5 (aa71-179) localized in the cytoplasm. Fragment T4(Δ119-128) was generated from T4 with deletion of 10 amino acid of the C terminal. GFP fused with fragment T4(Δ119-128) remained in the nucleus, but no longer in the nucleolus.</p><p><b>CONCLUSIONS</b>There is a nucleolar localization signal (aa119-128 RRRRNQDRPS) within TMSG-1. This finding may have laid the foundation for further investigations into subcellular localization and function of TMSG-1.</p>

LASS2 interacts with V-ATPase and inhibits cell growth of hepatocellular carcinoma / 生理学报

Homo sapiens longevity assurance homologue 2 (LASS2) is a novel gene isolated from a human liver cDNA library by our laboratory, and it is a human homologue of the yeast longevity assurance gene LAG1 (Saccharomyces cerevisiae longevity assurance gene). According to our previous results, LASS2 could interact with subunit c of vacuolar type H(+)-ATPase (V-ATPase), and the overexpression of LASS2 could inhibit the cell growth of a human hepatocellular carcinoma (HCC) cell line, SMMC-7721. In order to understand the role of the interaction between LASS2 and V-ATPase in HCC cell growth, we transiently transfected plasmid pCMV-HA2-LASS2 into HCCLM3, a HCC cell line without the significant expression of endogenous LASS2. The pH-sensitive fluorescence probes, BCECF and BCECF-AM, were used to measure the intracellular and extracellular H(+) concentrations of HCCLM3 cells respectively. The effect of LASS2 gene on apoptosis was evaluated with Annexin-V/FITC and propidium iodide (PI) by flow cytometry. Western blot was used to detect cytochrome c (Cyt c) in the cytosol and mitochondria, as well as pro-caspase-3 in cytosol. The results showed that the cell growth of LASS2-transfected HCCLM3 cells was significantly inhibited compared with that of the mock control. LASS2 transfection increased intracellular H(+) concentration of HCCLM3 cells, while decreased extracellular H(+) concentration. Moreover, LASS2 transfection significantly enhanced the apoptosis of HCCLM3 cells. In LASS2-transfected cells, the amounts of Cyt c increased in the cytosol, while decreased in the mitochondria. Meanwhile, the expression of pro-caspase-3 in the cytosolic extracts was decreased. These results implicate that LASS2 gene might increase intracellular H(+) of HCC cells via the interaction with V-ATPase, thereby inducing cell apoptosis through mitochondrial pathway.

TMSG-1 and its roles in tumor biology / 癌症

TMSG-1 is a newly discovered tumor metastasis suppressor gene, which plays important roles in promoting apoptosis and inhibiting invasion and metastasis of tumor cells. The inhibitory function of TMSG-1 in tumor cells may be related to vacuolar H+-ATPase and ceramide, but the underlying mechanism remains unknown. Studies on TMSG-1 are limited worldwide, and only a research group in Shanghai and our group have recently studied on it. As a new research field, the function of TMSG-1 remains to be explored. This review discusses the discovery of TMSG-1, structure of its encoded protein, its roles and possible mechanism in inhibiting tumor invasion and metastasis.

Overexpression of human tumor metastasis-related gene TMSG-1 suppresses cell proliferation and invasion of a highly metastatic prostate cancer cell line PC-3M-1E8 in vitro / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the effects of tumor metastasis-related gene TMSG-1 overexpression on the proliferation and invasion of a highly metastatic prostate cancer cell line in vitro.</p><p><b>METHODS</b>The eukaryotic expression plasmids containing full-length TMSG-1 cDNAs were stably transfected into the highly metastatic prostate cancer cell line PC-3M-1E8. Clones highly expressing TMSG-1 were identified by RT-PCR and Western Blot analysis after G418 screening. The cell proliferation was detected by cell growth curve, MTT assay and soft agar colony formation assay. The invasive potential of tumor cells in vitro was tested by Matrigel invasion assay.</p><p><b>RESULTS</b>Three TMSG-1 overexpression clones were selected. Cell growth curve and MTT assay showed that TMSG-1 overexpression clones exhibited a strong inhibition of proliferation compared with that of the parental cells or those transfected with vector alone from the third day of culture (P <0.05). In vitro analysis also showed that the TMSG-1 transfected clones exhibited a decreased clonogenicity in soft agar compared with that of the parental cells or those transfected with vector only (P < 0.05). TMSG-1 expression significantly suppressed cell invasion in vitro of TMSG-1-transfected PC-3M-IE8 cells (P < 0.05).</p><p><b>CONCLUSION</b>The TMSG-1 protein may serve as a tumor metastasis suppressor due to inhibiting cell proliferation and invasion of the highly metastatic prostate cancer cell line PC-3M-1E8.</p>

Overexpression of tumor metastasis suppressor gene 1 suppresses proliferation and invasion, but enhances apoptosis of human breast cancer cells MDA-MB-231 cells / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate the effects of tumor metastasis suppressor gene 1 (TMSG-1) overexpression on the proliferation, invasion and apoptosis of breast cancer cells and to determine possible correlations of TMSG-1 and metastasis of breast cancer.</p><p><b>METHODS</b>Full-length human TMSG-1 coding sequences were cloned into plasmid pcDNA3.0-FLAG. The recombinant plasmids constructs were transfeced into MDA-MB-231, a highly malignant breast cancer cell line. Parental, vector-only stable transfectant and TMSG-1 stable transfectant clones were tested by MTT, soft agar colony formation and Boyden chamber assays. At twenty-four hours and forty-eight hours post transient transfection, double staining with Annexin-V-FITC and PI were employed to distinguish apoptotic cells from living cells by flow cytometry analysis.</p><p><b>RESULTS</b>Three TMSG-1 overexpression clones were selected. Compared with the control cells, TMSG-1 overexpression MDA-MB-231 cells showed strong inhibition of proliferation and decreased clonogenicity in soft agar (P<0.05). Transfection of TMSG-1 into MDA-MB-231 cells significantly suppressed the cell invasion ability in vitro (decreased numbers of cells trespassing the matrigel in three experiments: 72.3+/-8.1, 85.0+/-4.2, and 73.5+/-7.8) in comparison with nave cells without transfection (187.5+/-2.1) and cells transfected with the control vector (162.3+/-6.8) (P<0.01). Transient transfection of TMSG-1 into MDA-MB-231 cells could promote cell apoptosis at 24 and 48 hours after transfection (P<0.05).</p><p><b>CONCLUSIONS</b>TMSG-1 protein may have multiple functions in the regulation of proliferation, invasion and apoptosis of metastatic breast cancer cells, likely as a metastasis suppressor gene.</p>

Monoclonal antibodies against human tumor metastasis suppressor gene-1 TMSG-1: preparation, characterization and application / 中华病理学杂志

<p><b>OBJECTIVE</b>In order to clarify the exact molecular weight of tumor metastasis suppressor gene-1 (TMSG-1) protein and its cellular localization, a monoclonal antibody against TMSG-1 was prepared, characterized and applied to evaluate the metastatic potential of human tumors.</p><p><b>METHODS</b>A dominant epitope-TMSG-1(15)-derived from TMSG-1 was synthesized based on Fmoc method, and the hapten was conjugated to Imject Maleimide activated mcKLH as a carrier protein. The antigen preparation was used to immunize BAL B/C mice. Hybridomas were generated and screened by ELISA for specific monoclonal antibodies, which were further characterized by western blotting and immunohistochemical staining.</p><p><b>RESULTS</b>One hybridoma cell line secreting anti-TMSG-1 antibody, designated as C8, was eventually established after primary ELISA screening, followed by rapid limited dilution procedure. It was confirmed that C8 was of IgM isotype. Result of competitive inhibition assay showed that the antibody was TMSG-1 specific. Using this antibody, an expected protein band of about 45,000 (relative molecular mass) was detected in the non-metastatic variants PC(3)-2B4 and PG-LH7 cells by Western blotting, but not in the isogenetic metastatic variants of PC3-1E8 and PG-BE1 cells. Immunohistochemistry using C8 showed a positive staining of cell membrane and cytoplasm of 2B4 and LH7 cells, whereas 1E8 and BE1 cells were non-reactive. Immunostaining using C8 of paraffin sections of 52 breast carcinomas and 41 colon cancers demonstrated a strong positivity in non-metastatic tumors, but none to weakly reactive in metastatic tumors (P < 0.05).</p><p><b>CONCLUSION</b>C8 monoclonal antibody against the synthetic peptide is TMSG-1 specific and is effective for Western blot and immunohistochemistry assays to detect TMSG-1 expression in cancer cells. TMSG-1 protein is about 45 000 (relative molecular mass) at cell membrane and cytoplasm of tumor cells. Expression of TMSG-1 protein correlates well, inversely with the tumor metastatic potential.</p>

Study of the expression membrane protein LASS2 / 生物工程学报

A human membrane protein LASS2 (Homo sapiens longevity assurance homologue 2 of yeast LAG1), which has important physiologic functions, was expressed in three different expression systems. Only the LASS2 protein carboxyl terminal hydrophilic fragment could be expressed in the prokaryote expression system and its polyclonal antibody was produced. The full length of LASS2 protein could be expressed successfully in both eukaryotic in vitro translation system and Bacuvirus expression system: Bac-to-Bac system. SDS-PAGE analysis revealed that the molecular weight of expressed product of LASS2 was about 28 kD. The product was also proved by Western blot. This recombinant LASS2 protein was purified by metal affinity resin and the purity is above 90%.