Fam3b/Pander Inhibits Cell Death And Increases Tumor Growth By Modulating The Expression Of Bcl-2 And Bcl-Xl Cell Survival Genes

FAM3B/PANDER is a novel cytokine-like protein that induces apoptosis in insulin-secreting beta-cells. Since in silico data revealed that FAM3B can be expressed by prostate and breast tumors, we evaluated the putative role of this cytokine in prostate and breast tumor progression. The FAM3B expression was compared by quantitative PCR in LnCAP, PC-3 and DU145 prostate tumor cell lines and MCF-7, ZR-75 and MDA-MB-231 breast tumor cell lines. After treatment with either recombinant FAM3B protein or secreted FAM3B obtained from conditioned media (CM) derived from FAM3B-overexpressing 293T cells , the cell death and viability of DU145 and MDA-MB-231 cell lines were evaluated. DU145 and MDA-MB-231 cells overexpressing FAM3B protein were produced by lentiviral-mediated transduction of full-length FAM3B cDNA. Cell viability and apoptosis were analyzed in DU145-FAM3B and MDA-231-FAM3B cells after treatment with several cell death inducers. Anchorage-independent growth and scratch wound assays were used to evaluate in vitro tumorigenicity and cell migration, respectively. In vivo tumorigenicity and invasiveness were evaluated by tumor xenograft growth in nude mice. We observed that FAM3B was highly expressed by hormone responsive cells (LnCAP and MCF-7) and low expressed in unresponsive hormone cells (PC-3, DU145 and MDA-MB-231). Cell viability and survival of DU145 and MDA-MB-231 cells increased after exogenous treatment with recombinant FAM3B protein or CM containing FAM3B-secreted protein. Overexpression of FAM3B in DU145 and MDA-MB-231 cells promoted an inhibition of apoptosis triggered by TNF-alpha, staurosporine and serum-deprived conditions. Cell death inhibition was accompanied by increased gene expression of the anti-apoptotic Bcl-2 and Bcl-xL genes, and by slight decrease in expression of pro-apoptotic gene Bax and diminished caspases-3, -8 and -9 proteolytic activities. When compared to control, cells overexpressing FAM3B displayed a decreased anchorage independent growth and increased motility in vitro, as well as an increased tumor growth in xenografted nude mice. The immunohistochemistry analysis from tumor xenografts revealed similar anti-apoptotic phenotype displayed by FAM3B-overexpressing tumor cells. Taken together, by activating pro-survival mechanisms, FAM3B overexpression contribute to increased cell death resistance and tumor growth in nude mice, highlighting a putative role for this cytokine in prostate and breast cancer progression. Note: This abstract was not presented at the meeting. Citation Format: Izabela Caldeira, Paula Maciel-Silva, Flavia Ramos Siqueira, Anna Carla Goldberg, Viviane Abreu Nunes, Jose Ernesto Belizario, Humberto Miguel Garay-Malpartida. FAM3B/PANDER inhibits cell death and increases tumor growth by modulating the expression of Bcl-2 and Bcl-XL cell survival genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2331. doi:10.1158/1538-7445.AM2017-2331