Abstract 5168: Interaction of sonic hedgehog and TP53/TP63 networks in lymphoma cells

Abstract

Abstract Cellular homeostasis requires a delicate balance between proliferation, apoptosis and differentiation be maintained. These processes are regulated by a number of tumor suppressors and proto-oncogenes that are frequently deregulated during tumor progression. Amongst these are the TP53/TP63 family of tumor suppressors and the sonic hedgehog (SHH) pathway. The SHH network associated with proliferative stem cell niches of many organs has been shown to affect disease progression and metastasis in diverse cancers. We investigated the possibility of interactions between the SHH and the TP53 networks in cancer cells. Using a Ponasterone A inducible TP53 H1299 cell line as a model system we were, able to show alterations in RNA and protein levels of SHH signaling intermediates on TP53 activation suggesting a regulation at the transcriptional level. A preliminary screening of a number of hematological cancer cell lines showed a majority of cell lines having aberrant SHH activation. A panel of diffuse large B-cell lymphoma (DLBCL) cell lines that included activated B-cell (ABC) like DLBCL and germinal center B-cell (GCB) like DLBCL subgroups were selected for further study. These cell lines also varied from p53-deficient to wild type p53. Treatment of these cell lines with nutlin, an HDM2 antagonist showed alterations in the SHH pathway at the protein and transcript levels. In silico analysis of the promoters of genes in the SHH network reveal multiple potential TP53/TP63 binding sites. Luciferase promoter constructs of SHH pathway genes were generated including SHH-luciferase and SUFU-luciferase promoter constructs and confirmed that these promoters were regulated by both TP63 and TP53. Further validation was provided using in vivo chromatin immunoprecipitation (ChIP) studies and site-directed mutational analysis. These findings suggest that there are multiple interacting nodes between the components of the SHH network and TP53/TP63 family of transcription networks. Additionally, a therapeutic strategy involving specific and simultaneous targeting of these networks in DLBCL cells would be expected to result in a more robust therapeutic response. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5168.