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Siva1 suppresses epithelial-mesenchymal transition and metastasis of tumor cells by inhibiting stathmin and stabilizing microtubules.

ABSTRACT: Epithelial-mesenchymal transition (EMT) enables epithelial cells to acquire motility and invasiveness that are characteristic of mesenchymal cells. It plays an important role in development and tumor cell metastasis. However, the mechanisms of EMT and their dysfunction in cancer cells are still not well understood. Here we report that Siva1 interacts with stathmin, a microtubule destabilizer. Siva1 inhibits stathmin's activity directly as well as indirectly through Ca(2+)/calmodulin-dependent protein kinase II-mediated phosphorylation of stathmin at Ser16. Via the inhibition of stathmin, Siva1 enhances the formation of microtubules and impedes focal adhesion assembly, cell migration, and EMT. Low levels of Siva1 and Ser16-phosphorylated stathmin correlate with high metastatic states of human breast cancer cells. In mouse models, knockdown of Siva1 promotes cancer dissemination, whereas overexpression of Siva1 inhibits it. These results suggest that microtubule dynamics are critical for EMT. Furthermore, they reveal an important role for Siva1 in suppressing cell migration and EMT and indicate that down-regulation of Siva1 may contribute to tumor cell metastasis.

SUBMITTER: Li N

PROVIDER: S-EPMC3150944 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe investigation of underlying mechanism and the exploitation of novel therapies for metastatic prostate cancer (PCa) are still urgently needed. miR-199b-5p has been suggested to function as tumour suppressor in various human cancers. However, the clinical significance and role of miR-199b-5p in PCa remain unclear.MethodsThe current study sought to investigate the expression status of miR-199b-5p in PCa and the involved molecular mechanisms in PCa metastasis by using bioinformatics analyses, loss-and gain-of-functions and rescue experiments in vitro and in vivo.ResultsWe demonstrated that miR-199b-5p was significantly downregulated in metastatic PCa tissues and cells when compared with the normal prostate tissue, the localised disease, the weakly metastatic and androgen-dependent PCa cell and the normal prostate epithelial cell. We also found that miR-199b-5p drastically suppressed PCa cell proliferation, migration and invasion in vitro and inhibited xenografts tumour growth and metastasis in vivo. Mechanistically, our results showed that miR-199b-5p could inhibit discoidin domain receptor tyrosine kinase 1 (DDR1) expression by directly targeting its 3'-UTR, thereby hindering epithelial-mesenchymal transition (EMT)-associated traits, which were induced by DDR1 activating ERK signalling pathway. Moreover, PCa patients with low miR-199b-5p expression level had a remarkably shorter overall survival than those with high miR-199b-5p level, indicating an association of miR-199b-5p loss with poor prognosis in patients with PCa. Furthermore, DDR1 was upregulated in PCa, and significantly correlated with high Gleason score, advanced pathological stage, tumour metastasis and shorter overall survival.ConclusionsOur study, for the first time, provide evidence of a tumour-suppressive function of miR-199b-5p in the invasion and metastasis of PCa, supporting the translational exploitation of miR-199b-5p-based therapeutic approaches for PCa metastases. Also, the miR-199b-5p-DDR1-ERK signalling axis identified in this study represents a novel mechanism of regulating EMT in PCa metastases.

Project description:Deguelin is known to suppress the growth of cancer cells; however, its anti-metastatic effects have not been studied so far in any cancer model. In the present study, we aimed to evaluate the anti-metastatic potential of deguelin in vivo and in tumor growth factor-?1 (TGF?1)-stimulated cells. Our results demonstrate that tumor growth, peritoneal dissemination and liver/lung metastasis of orthotopically implanted PanC-1-luc cells were significantly reduced in deguelin-treated mice along with the induction of apoptosis. Furthermore, deguelin-treated tumors showed increased epithelial signature such as increased expression of E-Cadherin and cytokeratin-18 and decreased expression of Snail. Similar observations were made when PanC-1, COLO-357 and L3.6pl cells were treated in vitro with deguelin. Moreover, E-cadherin was transcriptionally upregulated and accumulated in the membrane fraction of deguelin-treated cells, as indicated by increased interaction of E-Cadherin with ?-catenin. TGF?1-induced downregulation of E-Cadherin and upregulation of Snail were abrogated by deguelin treatment. In addition, deguelin inhibited TGF?1-induced Smad3 phosphorylation and Smad4 nuclear translocation in PanC-1 cells. Furthermore, when TGF?1-induced nuclear factor kappa B (NF?B) activation was inhibited, TGF?1-induced Snail upregulation or E-Cadherin downregulation was blocked. Deguelin also significantly downregulated the constitutive phosphorylation and DNA binding of NF?B in a dose-dependent manner. Interestingly, overexpression of either NF?B or Snail completely abrogated deguelin-mediated epithelial-to-mesenchymal transition (EMT) inhibition, whereas overexpression of NF?B but not Snail rescued cells from deguelin-induced apoptosis. Hence, deguelin targets NF?B to induce reversal of EMT and apoptosis but downstream effectors might be different for both processes. Taken together, our results suggest that deguelin suppresses both pancreatic tumor growth and metastasis by inducing apoptosis and inhibiting EMT.

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Siva1 suppresses epithelial-mesenchymal transition and metastasis of tumor cells by inhibiting stathmin and stabilizing microtubules.

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