Abstract 1143: Pro-proliferative function of SIRT3 in a human melanoma xenograft mouse model

Abstract Melanoma is one of the most aggressive forms of skin cancer and is often lethal, if not treated early. Therefore, it is necessary to try to develop novel target-based strategies to combat this neoplasm. SIRT3 is a nicotinamide adenine dinucleotide (NAD+) -dependent mitochondrial protein deacetylase involved in metabolism- and aging- related disorders, including certain cancers. Interestingly, studies have suggested both tumor suppressor as well as tumor promoter roles of SIRT3 in cancer. However, its role in melanoma is not well-established. Previously, we have shown that SIRT3 was upregulated in human melanoma cells and its lentiviral knockdown resulted in anti-proliferative effects in human melanoma cells. We also found that SIRT3 knockdown resulted in the G1-phase arrest of the cell cycle, induction of senescence, and decrease in cell migration. This study was designed to determine the relevance of our in vitro findings to the in vivo situation, in human melanoma xenograft models. Employing immunodeficient mice (Crl:NU-Foxn1nu, homozygous; Strain 088), we first determined the effect of SIRT3-knockdown on melanoma tumorigenesis. The mice were subcutaneously implanted with shNS-SK-MEL-2 (control) and shSIRT3-SK-MEL-2 (SIRT3-knockdown) melanoma cells, followed by assessing tumorigenesis of melanoma cells. We found that compared to shNS-SK-MEL-2 cells, shSIRT3-SK-MEL-2 cells showed a significantly decreased tumorigenic potential in these mice, in terms of average tumor volume (measured weekly) and average tumor weight (measured at termination of the study). Further, the Kaplan-Meier analysis showed that SIRT3 knockdown resulted in a significant survival advantage, in terms of reaching the cutoff tumor size (2.0 cm in one dimension). In an additional strategy, we determined the tumorigenicity of SIRT3 overexpressing melanoma cells (Hs294T-SIRT3) in NU/NU mice. Our data demonstrated that compared to control Hs294T-pcDNA cells, the SIRT3 overexpressing Hs294T-SIRT3 cells demonstrated a significantly enhanced tumorigenic potential (average tumor volume and tumor weight) in NU/NU mice. Overall, our study provides evidence supporting a pro-proliferative role of SIRT3 in melanoma and suggests that SIRT3 needs to be further evaluated as a potential druggable therapeutic target for melanoma management. However, detailed mechanistic and in vivo studies in relevant melanoma models are needed to further validate our findings. Citation Format: Jasmine George, Minakshi Nihal, Mary A. Ndiaye, Nihal Ahmad. Pro-proliferative function of SIRT3 in a human melanoma xenograft mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1143.