Osteopontin splice variants expression is involved on docetaxel resistance in PC3 prostate cancer cells

Osteopontin (OPN) is a phosphoprotein that activates several aspects of tumor progression. Alternative splicing of the OPN primary transcript generates three splicing isoforms, OPNa, OPNb and OPNc. In this report, we investigated some cellular mechanisms by which OPN splice variants could mediate PC3 prostate cancer (PCa) cell survival and growth in response to docetaxel (DXT)-induced cell death. Cell survival before and after DXT treatment was analyzed by phase-contrast microscopy and crystal-violet staining assays. Quantitative real-time PCR and immunocytochemical staining assays were used to evaluate the putative involvement of epithelial-mesenchymal transition (EMT) and OPN isoforms on mediating PC3 cell survival. Upon DXT treatment, PC3 cells overexpressing OPNb or OPNc isoforms showed higher cell densities, compared to cells overexpressing OPNa and controls. Notably, cells overexpressing OPNb or OPNc isoforms showed a downregulated pattern of EMT epithelial cell markers, while mesenchymal markers were mostly upregulated in these experimental conditions. We concluded that OPNc or OPNb overexpression in PC3 cells can mediate resistance and cell survival features in response to DXT-induced cell death. Our data also provide evidence the EMT program could be one of the molecular mechanisms mediating survival in OPNb- or OPNc-overexpressing cells in response to DXT treatment. These data could further contribute to a better understanding of the mechanisms by which PCa cells acquire resistance to DXT treatment.

Abstract B78: Osteopontin-c splicing isoform is a key molecule in ovarian cancer progression

Introduction: Osteopontin (OPN) is a glyphosphoprotein overexpressed in ovarian carcinoma (OC) and is involved in tumorigenesis and metastasis. Alternative splicing of OPN primary transcript generates 3 isoforms, named as OPNa, OPNb, and OPNc. Objective: This study aimed to characterize the expression profile and functional role of each OPN splicing isoform (OPN-SI) in OC. Methodology: The expression patterns of OPN-SI and a series of genes involved in key cancer pathways were analyzed by real-time PCR. In vitro and in vivo functional assays were performed using the ovarian cancer cell line OvCar-3, stably overexpressing the three OPN-SI and conditoned medium secreted by these cells. Results: OPNc, but not OPNa and OPNb, was specifically expressed on OC samples. OPNc splice variant significantly activated OvCar-3 cell proliferation, migration, invasion and anchorage independent cells growth, besides inducing tumor formation in nude mice. We also found that these features are mainly mediated by PI3K/Akt signaling pathway. By using a real time PCR Cancer Gene Array, we found that OvCar-3 OPNc-overexpressing cells are also able to modulate the expression of 34 genes involved in key cancer pathways. Notably, tumors formed by OPNc-overexpressing cells present high expression levels of typical angiogenic markers, such as VEGF-A, VEGFR-2 and CD34. Based on these data, we also investigated the molecular mechanisms by which OPNc stimulates angiogenic processes. Our data showed that OPNc overexpression activates VEGF-A expression and secretion, besides upregulating the expression of c-Fos, c-Jun and phospho-c-Jun. OPNc role on activating the phosphorylation of c-Jun is mediated by the integrin receptor (αvβ3), in an RGD-dependent manner. In addition, OPNc-conditioned medium is able to induce HUVEC endothelial cell proliferation, migration and adhesion. Conclusion: In summary, our data demonstrate that OPNc is able to activate sereral aspects of OC progression, including angiogenesis, mainly by the PI3K/Akt pathway, indicating that this splice variant could be a putative target for further studies aiming to investigate this molecule for new therapeutic approaches for OC.

Citation Format: Tatiana M. Tilli, Kivvi D. Mello, Vanessa Franco, Bruno Robbs, João Luiz Wanderley, Fabrício Rass, João P B Viola, Georg Weber, Vincent Castronovo, Akeila Bellahcène, Etel R P Gimba, Etel Gimba. Osteopontin-c splicing isoform is a key molecule in ovarian cancer progression. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B78.

The magnitude of CD4(+) T-cell activation rather than TCR diversity determines the outcome of Leishmania infection in mice

CD4(+) T cells play a critical role in determining the disease outcome in murine cutaneous leishmaniasis, and selective usage of T-cell receptor (TCR) is implied in promoting Leishmania major infection. However, little information is available on TCR usage in Leishmania-specific, IFN-γ-producing CD4(+) T cells. In this study, we investigated the TCR diversity and activation of CD4(+) T cells in a nonhealing model associated with L. amazonensis (La) infection and a self-healing model associated with L. braziliensis (Lb) infection. While marked expansion in the absolute number of several subsets was observed in Lb-infected mice, the percentages of TCR Vβ(+) CD4(+) -cell subsets were comparable in draining LN- and lesion-derived T cells in two infection models. We found that multiple TCR Vβ CD4(+) T cells contributed collectively and comparably to IFN-γ production and that the overall levels of IFN-γ production positively correlated with the control of Lb infection. Moreover, pre-infection with Lb parasites provided cross-protection against secondary La infection, owing to an enhanced magnitude of T-cell activation and IFN-γ production. Collectively, this study suggests that the magnitude of CD4(+) T-cell activation, rather than the TCR diversity, is the major determining factor for the outcome of Leishmania infection.