Tumor Necrosis Factor-alpha (TNFα) is a multifunctional pro-inflammatory cytokine implicated in inducing both tumor promotion and tumor inhibition. This paradoxical effect can be partly explained by the fact that TNFα acts as a regulator of both proliferation and apoptosis; however the mechanisms and factors associated with how or whether a tumor cell responds to a microenvironment rich in TNFα have not been fully resolved. Here we provide evidence that the microtubule associate protein Tau inhibits TNFα signaling through its N-terminal domain and implicate it as a novel regulator of the cellular response to this key cytokine. Our findings indicate that over-expression of Tau in the human breast cancer cell lines MCF7, SkBr3 and in the pheochromocytoma cell line PC12 suppresses TNFα-induced apoptosis evident in the control cells. TNFα-induced cell apoptosis in control cells is triggered as early as 6 hrs post-treatment with hallmark features of cell shrinkage, membrane blebbing, disruption of tubulin architecture and caspase-3 activation. While over-expression of wild type full length Tau isoform in these cell lines, completely abrogates all TNFα-associated apoptotic phenotypes. Aside from inhibiting TNFα-induced apoptosis, Tau over-expression also interferes with TNFα-induced NFKB activation. This is evident by a significant decrease in NFKB nuclear translocation in Tau over-expressed cells compared to controls. Suppression of TNFα-signaling by Tau is not associated with its tubulin interaction since a truncated N-terminal projection domain lacking all microtubule binding domains still provides resistance to TNFα-induced apoptosis and NFKB activation. These findings lead us to conclude that the functional domain of Tau that regulates TNFα response lies within its N-terminal region and current studies investigating regions within this domain are ongoing. Our data provide direct evidence that the N-terminal domain of the microtubule associated protein Tau can inhibit TNFα signaling in tumor cells. These findings indicate a novel function for Tau and add to our knowledge of how a tumor cell responds to TNFα-signaling.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-26. doi:1538-7445.AM2012-LB-26

©2012 American Association for Cancer Research
2012