7052

TGM2

Tissue transglutaminase (TG2), an enzyme involved in cell proliferation, differentiation and apoptosis is overexpressed in ovarian carcinomas, where it modulates epithelial-to-mesenchymal transition (EMT) and promotes metastasis. Its regulation in ovarian cancer (OC) remains unexplored. Here, we show that transforming growth factor (TGF)-beta, a cytokine involved in tumor dissemination is abundantly secreted in the OC microenvironment and induces TG2 expression and enzymatic activity. This is mediated at transcriptional level by SMADs and by TGF-beta-activated kinase 1-mediated activation of the nuclear factor-kappaB complex. TGF-beta-stimulated OC cells aggregate as spheroids, which enable peritoneal dissemination. We show that TGF-beta-induced TG2 regulates EMT, formation of spheroids and OC metastasis. TG2 knock-down in OC cells decreases the number of cells harboring a cancer stem cell phenotype (CD44+/CD117+). Furthermore, CD44+/CD117+ cells isolated from human ovarian tumors express high levels of TG2. In summary, TGF-beta-induced TG2 enhances ovarian tumor metastasis by inducing EMT and a cancer stem cell phenotype.

Several members of the Poly(ADP-ribose) polymerase (PARP) family are essential regulators of genome integrity, actively prospected as drug targets for cancer therapy. Among them, PARP3 is well characterized for its functions in double-strand break repair and mitotis. Here we report that PARP3 also plays an integral role in TGFbeta and reactive oxygen species (ROS) dependent epithelial-to-mesenchymal transition (EMT) and stem-like cell properties in human mammary epithelial and breast cancer cells. PARP3 expression is higher in breast cancer cells of the mesenchymal phenotype and correlates with the expression of the mesenchymal marker Vimentin while being in inverse correlation with the epithelial marker E-cadherin. Furthermore, PARP3 expression is significantly upregulated during TGFbeta-induced EMT in various human epithelial cells. In line with this observation, PARP3 depletion alters TGFbeta-dependent EMT of mammary epithelial cells by preventing the induction of the Snail-E-cadherin axis, the dissolution of cell junctions, the acquisition of cell motility and chemoresistance. PARP3 responds to TGFbeta-induced ROS to promote a TG2-Snail-E-cadherin axis during EMT. Considering the link between EMT and cancer stem cells, we show that PARP3 promotes stem-like cell properties in mammary epithelial and breast cancer cells by inducing the expression of the stem cell markers SOX2 and OCT4, by increasing the proportion of tumor initiating CD44high/CD24low population and the formation of tumor spheroid bodies, and by promoting stem cell self-renewal. These findings point to a novel role of PARP3 in the control of TGFbeta-induced EMT and acquisition of stem-like cell features and further motivate efforts to identify PARP3 specific inhibitors.

The mechanism of early recurrence of hepato-cellular carcinoma (HCC) is not well understood. To examine whether early intrahepatic metastasis of HCC can be determined by the reliable molecular characteristics of the primary HCC, we focused on early-stage tumors of primary and solitary HCC cases. Proteomic differences were investigated between two groups, 11 early (recurrence within 12 months) and 10 late (no recurrence within 48 months) HCC cases, using two-dimensional fluorescence difference gel electrophoresis. Overall, 10 upregulated and 9 downregulated proteins were identified from a total of 1623 protein spots detected in early recurrent HCC. Cluster analysis using the 19 proteins successfully divided the 21 HCC samples exactly into the two above groups. A multifunctional protein, transglutaminase 2 (TGM2), was upregulated in the early recurrence group. Immunohistochemistry revealed the frequent observation of TGM2-positive HCC cells in the early group, with a tendency of TGM2-positive staining in HCC cells adjacent to fibrous stroma. To examine whether two major TGM2-associated pathways, epithelial-mesenchymal transition (EMT) and integrin signaling, were activated in the early recurrence group of HCC, downstream molecules of TGM2 were measured. The mRNA level of EMT-related genes was highly positively correlated with TGM2 mRNA. However, E-cadherin (CDH1) mRNA and protein were not downregulated in correlation with TGM2 expression. The phosphorylation of FAK and Akt and the downregulation of PTEN were not associated with the quantity of TGM2. Therefore, TGM2 might contribute to early HCC recurrence through signaling pathways not related to EMT and integrin signaling. The proteomics of strictly classified HCCs would be useful for characterizing pro-metastatic HCC and for developing a new therapeutic target for treatment of metastasis.

BACKGROUND/AIM: The aim of this study was to investigate the role of transglutaminase 2 (TGM2) in colorectal cancer stem cells (CCSCs). MATERIALS AND METHODS: We used the TU12 cell line possessing CD133-expressing CCSCs. After isolating CD133 (-) and CD133 (+) CCSCs, we overexpressed and knocked-down TGM2 to investigate its role in human CCSCs. RESULTS: The expression level of TGM2 was 25-fold higher in tumorigenic cells than non-tumorigenic cells. We found that knockdown of TGM2 by specific RNA interference markedly inhibited cell growth and caused down-regulation of the stemness markers, CD133, SOX2, and beta-catenin. We further demonstrated that knockdown of TGM2 inhibited cell metastatic abilities by down-regulating N-cadherin and vimentin and up-regulating E-cadherin. These findings revealed that TGM2 expression is markedly increased in human colorectal cancer and that down-regulation of TGM2 in tumors may serve as a treatment for colorectal cancer patients. Therefore, this study indicate that TGM2 affects the metastatic potential and stemness of CCSCs by regulating EMT- and stemness-related proteins. CONCLUSION: The metastatic potential of CSCs arises from highly expressed TGM2.CI - Copyright(c) 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.