Abstract 3426: Curcumin is effective in killing gemcitabine resistant pancreatic cancer cells: Studies of the cell cycle, and apoptosis.

Abstract

Abstract Background Gemcitabine resistance is a major challenge in pancreatic cancer where the drug is considered a “gold standard” treatment. Although many studies have attempted to address mechanisms of gemcitabine resistance, these are not yet clear. The complete elimination of these resistant cells will be a major breakthrough in treatment. In many cancers, curcumin is of interest due to its inherently low toxicity to patients even at high doses: The drug can inhibit pancreatic cancer cell growth, and also acts in synergy with gemcitabine reducing viability of several established cancer cell lines. Identifying curcumins efficacy after transition from gemcitabine sensitive to resistant disease is therefore a key question for progress toward treatment. We have created a novel cell line from a parental MIA-PaCa-2 pancreatic adenocarcinoma which is 286 times more resistant to gemcitabine exposure than the parent line. Here we investigated the cell cycling properties of this cell line and its ability to be killed by curcumin. Methods The gemcitabine resistant MIA-PaCa-2 cell line was created by continuous gemcitabine dosing which increased its EC50 for the drug to 286-fold greater than that of the parent line. The extent of resistance was confirmed by MTT for viability and BrdU ELISA for proliferation. The sensitive and resistant Mia-PaCa-2 cells were then incubated in the absence, or presence of varying doses of curcumin (0.01-150μM). Cells were analysed with respect to their cell cycling profiles by staining initially with EdU over a time course, followed by 7-AAD DNA staining of permeabilised cells with subsequent flow cytometric analysis. Early apoptotic, late apoptotic and necrotic fractions of these cells were determined by staining with annexin-V and propidium iodide. Results: Curcumin inhibited growth of both gemcitabine sensitive and resistant cell lines to a similar extent (IC50s =13.7 μM and 16.6 μM for sensitive and resistant lines respectively). Whereas gemcitabine was incapable of causing apoptosis in the resistant strain, curcumin induced similar levels of apoptosis in both lines at doses between 1 and 56μM. With respect to the cell cycle, gemcitabine caused complete S-phase arrest in the sensitive strain and had no effect on the resistant strain, whereas curcumin caused G2/M phase arrest (no increase in G1 and 100% loss of second cycle S-phase) in both cell lines. Conclusions Curcumin is effective as a chemotherapeutic drug against gemcitabine resistant cells due to its ability to inhibit the cell cycle at the G2/M boundary after gemcitabine fails to activate the restriction point. The ability of curcumin to avoid cross resistance after gemcitabine is rendered ineffective should be studied as this could provide mechanisms for the creation of new drugs or highlight the possibilities of curcumin analogues as a second-line therapeutic for the placation of pancreatic adenocarcinoma. Citation Format: Alan Levett, Rachel Allen, Christine Galustian, Angus George Dalgleish. Curcumin is effective in killing gemcitabine resistant pancreatic cancer cells: Studies of the cell cycle, and apoptosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3426. doi:10.1158/1538-7445.AM2013-3426