Abstract C172: A synthetic glycolipid induces macrophage-mediated apoptosis of cancer cells via nitric oxide-dependent downregulation of thoc1 gene.

Abstract

Abstract Activation of Toll-like receptor 4 (TLR4) triggers both innate and adaptive immunity. We previously developed a synthetic TLR4 agonist, CCL-34, which can induce anticancer immunity in vitro and in vivo. The CCL-34-activated macrophages were shown to induce nitric oxide (NO)-dependent apoptosis of cancer cells. In addition, the THO complex 1 (thoc1) gene was suppressed in cancer cells co-cultured with CCL-34-activated macrophages and in tumors of CCL-34-treated mice, suggesting the involvement of Thoc1 in the CCL-34-induced anticancer activity. It has been shown that Thoc1 promoted cell survival and was overexpressed in many cancer cells. However, regulation of thoc1 and its downstream effectors in Thoc1-mediated cell survival remains unknown. In this study, we investigated the role of Thoc1 in the cancer cell apoptosis induced by CCL-34-activated macrophages and the underlying molecular mechanisms. Our data showed that the suppressed Thoc1 in bladder cancer cells (MBT-2) co-cultured with CCL-34-activated macrophages was restored by iNOS inhibitor (L-NMMA), and direct treatment of MBT-2 cells with NO donor repressed Thoc1 expression. Moreover, treatment of either CCL-34 or NO donor resulted in the suppression of thoc1 promoter activity in MBT-2 cells, whereas mutations in certain region of this promoter region abolished such repression. Notably, MBT-2 cells overexpressing thoc1 (MBT/thoc1) exhibit higher resistance to the cytotoxicity induced by treatment of NO donor or CCL-34-activated macrophages than MBT-2 cells, while both treatments suppressed Bcl-2 expression in MBT-2 cells but not in MBT-2/thoc1 cells. Together, our results demonstrate that NO-mediated thoc1 downregulation is a key step in the cancer cell apoptosis induced by CCL-34- treated macrophages. In addition, the decreased expression of thoc1 could lead to downregulation of Bcl-2 and subsequent induction of cancer cell apoptosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C172.