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LASS2 is a novel tumor-suppressor gene and has been characterized as a ceramide synthase, which synthesizes very-long acyl chain ceramides. However, LASS2 function and pathway-related activity in prostate carcinogenesis are still largely unexplored. Here, we firstly report that LASS2 promotes β-catenin degradation through physical interaction with STK38, SCYL2, and ATP6V0C via the ubiquitin-proteasome pathway, phosphorylation of LASS2 is essential for β-catenin degradation, and serine residue 248 of LASS2 is illustrated to be a key phosphorylation site. Furthermore, we find that dephosphorylation of LASS2 at serine residue 248 significantly enhances prostate cancer cell growth and metastasis in vivo, indicating that phosphorylated LASS2 inhibits prostate carcinogenesis through negative regulation of Wnt/β-catenin signaling. Thus, our findings implicate LASS2 as a potential biomarker and therapeutic target of prostate cancer., (© 2021 Wiley Periodicals LLC.)

The tumor metastasis suppressor gene 1 (TMSG1), also designated homo sapiens longevity assurance homologue 2 of yeast LAG1 (LASS2), is a novel tumor metastatic suppressor gene. Although its effects on metastasis have been reported, its biological functions remain unclear. The purpose of this study was to investigate the effects of TMSG1/LASS2 protein on apoptosis and proliferation in human embryonic kidney cell lines HEK293 and 293 T and explore the potential mechanisms. Cell growth, morphology, expressions of apoptotic-related proteins and cell cycle distribution were evaluated in HEK293 and 293 T cells transfected with TMSG1/LASS2 expression plasmids or vector controls. MTT assays showed that overexpression of TMSG1/LASS2 inhibited cell proliferation; and morphological observations and flow cytometric assays with Annexin V/propidium iodide showed TMSG1/LASS2 overexpression increased apoptosis in these cells. Western blot analysis demonstrated that overexpression of TMSG1/LASS2 resulted in the downregulation of Bcl-2, release of cytochrome c from mitochondria, activation of procaspase-9 and procaspase-3, and the cleavage of PARP. Subsequent cell cycle analysis showed that TMSG1/LASS2 overexpression inhibited cell proliferation by mediating the induction of G0/G1 cell cycle arrest. Together, these results confirmed that TMSG1/LASS2 is a potential metastasis suppressor gene, and suggested that the mechanism involved the induction of apoptosis and inhibition of cell proliferation via a caspase-dependent mitochondrial pathway., (© 2015 Wiley Periodicals, Inc.)

Homo sapiens longevity assurance homolog 2 of yeast LAG1 (LASS2), also known as tumor metastasis suppressor gene 1 (TMSG1), was firstly cloned by our laboratory in 1999. However, its antitumor molecular mechanisms are still unclear. LASS2/TMSG-1 could directly interact with the C subunit of Vacuolar H(+) ATPase (V-ATPase), which suggested that LASS2/TMSG1 might inhibit the invasion and metastasis through regulating the function of V-ATPase. In this study, we explored the effect of small hairpin RNA (shRNA) targeting LASS2/TMSG1 on the invasion and metastasis of human prostate carcinoma cell line PC-3M-2B4 with low metastatic potential and its functional interaction with V-ATPase. Silencing of LASS2/TMSG1 gene in PC-3M-2B4 cells increased V-ATPase activity, extracellular hydrogen ion concentration and in turn the activation of secreted MMP-2 and MMP-9, which coincided with enhancing cell proliferation, cell survival, and cell invasion in vitro, as well as acceleration of prostate cancer (PCA) growth and lymph node metastases in vivo. Thus we concluded that silencing of LASS2/TMSG1 enhances invasion and metastasis of PCA cell through increase of V-ATPase activity. These results establish LASS2/TMSG1 as a promising therapeutic target for advanced PCA., (© 2013 Wiley Periodicals, Inc.)

LASS2/TMSG1 was a novel tumor metastasis suppressor gene, which was first cloned by our laboratory from non-metastatic and metastatic cancer cell variants of human prostate carcinoma PC-3M using mRNA differential display in 1999. LASS2/TMSG1 could interact with the C subunit of vacuolar ATPase (V-ATPase, ATP6V0C) and regulate V-ATPase activity. In an attempt to provide molecular mechanism of the interaction between LASS2/TMSG1 and V-ATPase, we constructed four variant transfectants containing different functional domain of LASS2/TMSG1 and stably transfected the variants to human prostate cancer cell line PC-3M-1E8 cell with high metastatic potential. Results showed that there were no obvious differences of V-ATPase expression among different transfected cells and the control. However, V-ATPase activity and intracellular pH was significantly higher in the variant transfectants with Homeodomain of LASS2/TMSG1 than that in the control using the pH-dependent fluorescence probe BECEF/AM. Immunoprecipitation, immunofluorescence and immuno-electron microscope alone or in combination demonstrated the direct interaction of Homeodomain of LASS2/TMSG1 and ATP6V0C. Loss of Homeodomain markedly enhanced the proliferation ability but weakened the apoptotic effect of LASS2/TMSG1 in PC-3M-1E8 cells. These lines of results for the first time contribute to the conclusion that LASS2/TMSG1 could regulate V-ATPase activity and intracellular pH through the direct interaction of its Homeodomain and the C subunit of V-ATPase. Their interaction could play important roles in the apoptosis of tumor cells., (Copyright © 2012 Wiley Periodicals, Inc.)

Homo sapiens longevity assurance homologue 2 of yeast LAG1 (LASS2), also known as tumor metastasis suppressor gene 1 (TMSG1), is a newly found tumor metastasis suppressor gene in 1999. Preliminary studies showed that it not only suppressed tumor growth but also closely related to tumor metastasis, however, its molecular mechanisms is still unclear. There have been reported that protein encoded by LASS2/TMSG-1 could directly interact with the C subunit of Vacuolar ATPase (V-ATPase), which suggested that LASS2/TMSG1 might inhibit the invasion and metastasis through regulating the function of V-ATPase. Thus, in this study, we explored the effect of small interference RNA (siRNA) targeting LASS2/TMSG1 on the invasion of human prostate carcinoma cell line PC-3M-2B4 and its molecular mechanisms associated with the V-ATPase. Real-time fluorogentic quantitative PCR (RFQ-PCR) and Western blot revealed dramatic reduction of 84.5% and 60% in the levels of LASS2/TMSG1 mRNA and protein after transfection of siRNA in PC-3M-2B4 cells. The V-ATPase activity and extracellular hydrogen ion concentration were significantly increased in 2B4 cells transfected with the LASS2/TMSG1-siRNA compared with the controls. The activity of secreted MMP-2 was up-regulated in LASS2/TMSG1-siRNA treated cells compared with the controls; and the capacity for migration and invasion in LASS2/TMSG1-siRNA treated cells was significantly higher than the controls. Thus, we concluded that silencing of LASS2/TMSG1 may promote invasion of prostate cancer cell in vitro through increase of V-ATPase activity and extracellular hydrogen ion concentration and in turn the activation of secreted MMP-2., (Copyright © 2012 Wiley Periodicals, Inc.)

The tumor metastasis suppressor gene-1 (tmsg-1) was first cloned as a new tumor suppressor gene in our laboratory several years ago. Since then, however, despite the substantial progression that has been made in investigation of the biologic roles played by this gene, the manner in which it exerts its regulatory influence is still unknown. With transfection of various deletion or mutation constructs, we identified a potential enhancer and three potential silencers in the 5'-flanking region. However, it was particularly interesting to find that a region (+59 to +123 bp) of exon 1 exhibited a strong role in initiation of tmsg-1 gene transcription. Deletion of this region led to essentially complete loss of driving activity of exon-1 sequence on luciferase. Further analysis showed that transcription factors KLF6 and Sp1 are able to interact with each other and bind to their elements in this region. Co-transfection of pGL3-114/+123 with KLF6- and/or Sp1-expressing plasmids resulted in an elevation of luciferase activity and transcription level of tmsg-1, which was abolished by knockdown of KLF6 or Sp1. Analysis of metastatic capacity showed that cells with high metastatic capability exhibited a lower level of KLF6/TMSG-1 proteins with higher invasive capability and vice versa. Thus, we concluded that interaction of KLF6 and Sp1, together with their binding of elements in exon 1 are critical events in initiation of transcription of the tmsg-1 gene. These results reveal a hitherto unreported mechanism for initiation of transcription of the tmsg-1 gene., (Copyright © 2011 Wiley Periodicals, Inc.)