Abstract 1935: Potent anti-tumor effects of TIC10 require Foxo3a and TRAIL gene upregulation

Abstract

Abstract TNF-related apoptosis-inducing ligand (TRAIL; Apo2L) is an endogenous protein that induces tumor-selective apoptosis and is currently being tested in clinical trials as an anti-tumor agent. Despite promising preclinical activity, recombinant human TRAIL suffers from efficacy-limiting properties such as short serum half-life, stability, cost, and limitations in delivery, e.g. to the central nervous system. We hypothesized that induction of the human TRAIL gene by small molecules may overcome these limitations of TRAIL-based protein therapy. A cell-based luciferase reporter screen using the human TRAIL promoter identified TIC10 as a p53-independent small molecule inducer of the TRAIL gene. TIC10 induces TRAIL on the surface of normal and tumor cells, in sera of non-tumor-bearing mice, and throughout the tumor microenvironment. Co-culture experiments suggest that TRAIL upregulation by normal cells can contribute to the anti-tumor response of TIC10 through a TRAIL-mediated bystander effect. TIC10-induced TRAIL causes tumor-specific and TRAIL-mediated cell death as indicated by inhibition of cytotoxic effects following TRAIL gene knockdown in vitro and in vivo. Expression profiling of TIC10-induced transcriptional changes revealed altered expression levels of Foxo3a target genes, including DR5. We found that TIC10 causes the nuclear translocation of Foxo3a, but not Foxo1, to upregulate TRAIL gene transcription as determined by chromatin-immunoprecipitation assays. Western blot analysis indicated that TIC10 potently inhibits the phosphorylation of Foxo3a at Ser253 and Ser294 that normally docks the transcription factor to 14-3-3 proteins in the cytosol. Dual inhibition of Akt and ERK by TIC10, by other individual small molecule kinase inhibitors in combination or targeted siRNA inhibited the phosphorylation of these critical serine residues and synergistically induced Foxo3a-dependent TRAIL and TRAIL-mediated cell death. TIC10 is a promising first-in-class anti-tumor agent with a broad range of anti-tumor effects in preclinical animal models including othrotopic GBM, immunocompetent lymphoma, xenografted colon, lung, or breast cancers, and exhibits synergy with taxanes as well as bevacizumab among other agents. TIC10 appears to have no measurable toxic effects in mice including evaluation of serum chemistries, liver function studies, LDH, tissue histology, weight of the animals or behavioral changes. We are pursuing the clinical translation of these important findings that indicate a favorable and wide therapeutic index for a novel anti-tumor agent. 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 1935. doi:1538-7445.AM2012-1935