Abstract 1522: Targeted gene therapy · c-MYC and hTERT in the scope

Abstract

Abstract In the past decade immunotherapy and kinase inhibitors have revolutionized the approach for cancer therapy, particularly for melanoma which has benefit from this new therapy in the last 5 years. Although, new treatment increase patient survival, there is no cure and treatments are often limited to a subtype of patients. Therefore there is still an urgent need for efficient therapy for melanoma. Among potential targets for cancer therapy, c-MYC and hTERT which are overexpressed in up-to 85% of all cancers are the most promising. The overexpression of hTERT provides indefinite division to cancer cells. Deregulation of c-MYC affect a large array of genes involved in cell cycle, proliferation/differentiation and apoptosis. Notably, both c-MYC and hTERT genes have in their promoter area a G-rich sequence that form secondary structure called G-quadruplex. These G-quadruplex structures are part of the silencers and are required for the repression of c-MYC or hTERT transcription. Mutations in the G-rich sequences of hTERT promoter destabilize the G-quadruplex and are associated with incidence of melanoma. We have shown that oligonucleotides encoding for the G-quadruples sequences of these genes promoter downregulate their respective gene expression and inhibit cell growth in different cell lines. We investigated the effect of targeting c-MYC or hTERT gene expression in melanoma cell lines using oligonucleotides targeted to the silencer G-quadruplex sequence. Four cell lines where investigated (SK-Mel-2, SK-Mel-3, SK-Mel-28 and A375) for the effect of Pu27 (targeting c-MYC) and Tert-FL (targeting hTERT) on cell proliferation using MTT assay. The treatment for 6 days resulted in 60% growth inhibition in the presence of Pu27 and 50% in the presence of Tert-FL for SK-Mel-2, SK-Mel-3, SK-Mel-28 while A375 was less sensitive. Gene expression evaluated by QRT-PCR showed down-regulation of c-MYC and hTERT in cell exposed to Pu27 and hTERT in cells exposed to Tert-FL. hTERT expression is regulated by c-MYC and in our experiment the down-regulation of c-MYC correlate with down-regulation of hTERT suggesting a cascade effect. In addition, SOX2 gene expression was also down-regulated by Pu27 suggesting an effect on the cancer stem cells (CSC). Our data demonstrate that oligonucleotides targeted to c-MYC and hTERT down-regulate gene expression associated with melanoma cell growth inhibition and possibly on metastasis. Citation Format: Francine Rezzoug, Shelia D. Thomas, Segen Tella, Donald M. Miller. Targeted gene therapy · c-MYC and hTERT in the scope [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1522. doi:10.1158/1538-7445.AM2017-1522