Abstract 5485: The combined effects of polyamine and GSH inhibition on the viability of human cancer cell lines

Polyamines play essential roles in DNA stability and cell proliferation, making polyamine metabolism a potential target for cancer therapeutics. The spermine analog N1,N11- Diethylnorspermine (DenSpm) reduces levels of ODC, the enzyme responsible for polyamine biosynthesis, and also induces the enzyme SSAT, responsible for the catabolism of polyamines. Polyamines have been shown to inactivate reactive oxygen species (ROS), including peroxides, protecting mammalian cells from oxidative damage to nucleic acids. The catabolism of polyamines by SSAT, in contrast, leads to the production of ROS, which results in cellular death and limits the progression of cancer. Buthionine sulfoximine (BSO) selectively depletes stores of intracellular glutathione GSH, an antioxidant that neutralizes ROS. We hypothesized that treating cancer cell lines with both DenSpm and BSO will have a synergistic cytotoxic effect on the cells, due to the depletion of ROS-scavenging polyamines, the generation of ROS caused by DenSpm and the absence of GSH. Treatment of the four cell lines, MCF-7, MDA-MD-231, Caco-2 and PANC-1, with DenSpm resulted in moderate reductions in cell viability as measured using the Cell Titer Blue assay (Promega, Inc.). As has been widely reported in other mammalian systems, DenSpm (10 µM) reduced intracellular polyamine concentrations (HPLC of benzoylated polyamine derivatives) and induced SSAT (Western Blots). Treatment of cells with BSO (500 µM) caused a significant decrease in intracellular GSH levels. Similar findings have been reported in previous studies with human neuroblastoma lines (Anderson, et al. 1999). The combination of BSO and DenSpm had effects markedly greater than either compound alone. Pretreatment of cells with BSO (500 µM) for 24 hours with subsequent removal of BSO before DenSpm (10, 100, 1000 µM) addition resulted in significantly reduced viability in all cell lines. DenSpm was found to be most effective in the continued presence of BSO as compared to a 24-hour BSO pretreatment. The compounds used in combination also enhanced ROS production, further demonstrating their synergistic effects. Citation Format: John Grady, Davey Holzer, Kaci Keleher, Emma Meetz, Russ Feirer. The combined effects of polyamine and GSH inhibition on the viability of human cancer cell lines [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 Sup