FAM3B/PANDER inhibits cell death and increases prostate tumor growth by modulating the expression of Bcl-2 and Bcl-XL cell survival genes

• Grant number: 17/17062-0
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: September 01, 2017
• End date: May 31, 2018
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Humberto Miguel Garay Malpartida
• Grantee: Humberto Miguel Garay Malpartida
• Host Institution: Escola de Artes, Ciências e Humanidades (EACH). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Background: FAM3B/PANDER is a novel cytokine-like protein that induces apoptosis in insulin-secreting b-cells. Since in silico data revealed that FAM3B can be expressed in prostate tumors, we evaluated the putative role of this cytokine in prostate tumor progression.Methods: FAM3B expression was analyzed by quantitative PCR in tumor tissue clinical samples and LnCAP, PC-3, and DU145 prostate tumor cell lines. Culture growth and viability of DU145 cell line were evaluated after treatment with either exogenous FAM3B protein obtained from conditioned media (CM) of 293T cells overexpressing FAM3B or a recombinant FAM3B protein produced in a bacterial host. DU145 cells overexpressing FAM3B protein were produced by lentiviral-mediated transduction of full-length FAM3B cDNA. Cell viability and apoptosis were analyzed in DU145/FAM3B cells after treatment with several cell death inducers, such as TNF-a, staurosporine, etoposide, camptothecin, and serum starvation conditions. Anchorage-independent growth in soft agarose assay was used to evaluate in vitro tumorigenicity. In vivo tumorigenicity and invasiveness were evaluated by tumor xenograft growth in nude mice. Results: We observed an increase in FAM3B expression in prostate tumor samples with high histological grade and poor prognosis when compared to normal tissues. FAM3B was highly expressed by LnCAP cells but much less in PC-3 and DU145 cells. DU145 cell viability and survival increased after exogenous treatment with recombinant FAM3B protein or CM containing FAM3B-secreted protein. Overexpression of FAM3B in DU145 cells promoted inhibition of DNA fragmentation and phosphatidylserine externalization in a time and dose-dependent fashion, upon apoptosis triggered by TNF-a. These events were accompanied by increased gene expression of anti-apoptotic Bcl-2 and Bcl-XL, decreased expression of pro-apoptotic Bax and diminished caspase-3, -8 and -9 proteolytic activities. Furthermore, inhibition of Bcl-2 anti-apoptotic family proteins with small molecules antagonists decreases protective effects of FAM3B in DU145 cells. When compared to the respective controls, cells overexpressing FAM3B displayed a decreased anchorage- independent growth in vitro and increased tumor growth in xenografted nude mice. The immunohistochemistry analysis of tumor xenografts revealed a similar anti-apoptotic phenotype displayed by FAM3B-overexpressing tumor cells. Conclusions: Taken together, by activating pro-survival mechanisms FAM3B overexpression contributes to increased resistance to cell death and tumor growth in nude mice, highlighting a putative role for this cytokine in prostate cancer progression. (AU)