Abstract 1402: Molecular basis for soy isoflavone genistein in the prevention of posttreatment recurrence of neuroblastoma

Abstract

Abstract Clinical and laboratory evidence suggests that neuroblastoma contain populations of rapidly proliferating clonogens that survive chemoradiation or conventional radiotherapy leading to radioresistance. To that note, radioresistance could be associated with survival advantage resulting in clonal selection and tumor re-growth. Recently, we demonstrated that IR activates NFκB that enhances cell survival by switching on genes that attenuate apoptosis. Coherently, studies have demonstrated Genistein (GEN) inhibits NFκB and radiosensitizes cancer cells. In this study, we investigated the functional mechanistic regulation of NFκB mediated survival advantage and, delineated the efficacy of GEN in this setting. Human SH-SY5Y, IMR-32 and SK-N-MC cells exposed to 2Gy (IR) with or without GEN (100μM) were examined after 15min through 72h. EMSA analysis showed a robust and persistent activation of NFκB at least up to 72h in IR exposed cells. Consistently, IR induced a sustained transactivation (QPCR) and intercellular (ELISA) TNFα in these cells. Forced inhibition of NFκB (SN50, RelA siRNA) or TNFα (TNFR1-Ab) completely and persistently inhibited IR-induced NFκB and/or TNFα demonstrating the IR-induced initiation of NFκB→TNFα→NFκB feed back mechanism (PFC). Consistently, IR simulation experiments with NFκB (SNP, p50/p65 transfection) or TNFα (rH-TNFα) over expression, persistently activated NFκB and/or TNFα exhibiting the occurrence of PFC. Furthermore, IR profoundly induced both mRNA (QPCR) and cellular localization (immunoblotting) of IAP1, IAP2 and Survivin. NFκB knock-out experiments portrait a NFκB dependent activation of IAP1, IAP2 and Survivin in these cells. Conversely, GEN treatment completely and persistently inhibited IR-induced NFκB and, both TNFα transactivation and intercellular levels. Moreover, NFκB and/or TNFα over expression studies with GEN demonstrate the disruption of PFC. In addition, GEN markedly, inhibited IR-induced NFκB dependent IAP1, IAP2 and Survivin and greatly conferred IR-induced inhibition of cell survival. Taken together these results suggests that the surviving neuroblastoma cells may result in the development of survival advantage mediated by persistent activation of NFκB through NFκB→TNFα→NFκB PFC. More importantly, disrupting IR-initiated PFC with GEN may significantly inhibit NFκB dependent survival advantage and, may serve as a potential deliverable in mitigating neuroblastoma relapse and progression after radiotherapy. Funding Support: ACS- IRG-05-066-01; Presbyterian Health Foundation 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 1402.