Abstract 256: Analysis of combined drug effects on hENT1 and hENT4 in pancreatic cancer cells

Abstract

Abstract Pancreatic cancer is the 4th leading cause of cancer death and diagnosis usually occurs at late stages due to the lack of symptoms and early detection, making surgical intervention almost unfeasible due to low survival rates. Pancreatic cancer patients have one of the worst prognoses among all cancer types with a 5 year survival rate of less than 5%. Despite significant improvement in understanding molecular and epigenetic changes of this disease, the prognosis and management remained unchanged. Gemcitabine, a deoxycytidine nucleoside analog, is the golden standard of advanced pancreatic cancer treatment for patients with locally advanced or metastatic cancer of the pancreas. Patients treated with gemcitabine can, however, eventually develop resistance to this drug. Previously published data from our laboratory demonstrated enhanced efficacy of gemcitabine with the dietary agent, indole-3-carbinol (I3C) though up-regulation of the human equilibrative nucleoside transporter 1 (hENT1). hENT1 (SLC29A1) is the major drug transporter for gemcitabine. One of the drugs currently being investigated for treatment of pancreatic cancer is metformin. Metformin is most commonly used for the treatment of type 2 diabetes mellitus and has exhibited both chemopreventive and chemotherapeutic activities in preclinical human pancreatic cancer cells and animal models. Metformin has been found to be transported by another member of the equilibrative nucleoside transporter (ENT) family named hENT4 (SLC29A4). The current study examined the combined drug effects of gemcitabine, metformin and I3C on hENT1 and hENT4 in pancreatic cancer cells. Several pancreatic cell lines were examined for cell viability, drug synergy and modulation of hENT1 and hENT4 expression when treated with either gemcitabine, metformin, I3C or in combination for 24h and 72h. The results varied for each of the cell lines. After 24h and 72h treatment there was a significant decrease in cell viability when pancreatic cancer cells were treated with metformin or gemcitabine or 500μM I3C alone or in combination. The decrease in cell viability for these treatment conditions was also time dependent, where pancreatic cancer cells treated for 72h exhibited lower cell viability compared to 24h treatment. Pancreatic cancer cells treated with 250μM I3C alone or in combination did not decrease cell viability after 24h; however after 72h the cell viability varies based on the cell line. In most cases the drug activity exhibited antagonistic effect in combination therapy treatment. hENT1 and hENT4 expression levels varied between cell lines, where gemcitabine resistant cell lines exhibited lower hENT levels. Our initial findings showed that gemcitabine may also modulate hENT4 expression in gemcitabine sensitive cell lines and I3C modulations hENT4 expression levels. Citation Format: Stancy J. Joseph, Beverly Word, Beverly Lyn-Cook. Analysis of combined drug effects on hENT1 and hENT4 in pancreatic cancer cells. [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 256.