CURCUMIN SENSITIZES PANCREATIC CANCER CELLS TO APOG2 INDUCED KILLING

Abstract

Objectives: In Pancreatic cancer, several important survival molecules such as NF-κB, a key transcription factor playing important roles in tumorigenesis, metastasis and inflammation is highly upregulated along with NF-κB downstream proteins like Bcl-2 and Bcl-xL. Thus novel agents that have the capacity of inactivating such crucial target proteins could enhance the antitumor activity. ApoG2, new derivative of natural product gossypol, is a potent small molecule inhibitor of Bcl-2 and Bcl-xL proteins. Curcumin, an active ingredient from the rhizome of the plant, Curcuma longa, has anti oxidant, anti-inflammatory and anti-cancer activities and works by inactivation of NF-κB activity. In this study we have tested our hypothesis whether inactivation of NF-κB by curcumin could enhance anti-tumor activity of ApoG2. Methods: The BxPC-3 human pancreatic cell line was used in this study. For cell viability, apoptosis and NF-κB studies, MTT assay, ELISA and electrophoretic mobility shift assay were used respectively. Western blot assays was done to study Bcl-2 and Bcl-xL. Results: Treatment of human pancreatic cell line BxPC-3 with curcumin sensitized ApoG2 induced cell killing. In the dose escalation study with ApoG2 at 72 hrs, 1μM showed 60% cell viability, while 5μM of curcumin at 72 hrs showed 78 % cell viability. Combination treatment with 1μM of ApoG2 and 5μM of curcumin at 72 hrs showed 45 % cell viability. (P = <0.0001). Apoptosis by Histone/DNA ELISA showed 7-fold induction with ApoG2 and 6-fold induction with curcumin at 72 hrs. However, combination treatment with curcumin and ApoG2 at 72 hrs showed 11-fold induction in apoptosis compared to the control. Bcl-xL and Bcl-2 expression levels were down regulated along with the inactivation of NF-κB in the combination treatment group compared with curcumin and ApoG2 alone. Conclusion: From these results, we conclude that curcumin enhanced ApoG2 induced cell growth inhibition and apoptosis of Pancreatic BxPC-3 cancer cells. This effect is partly due to inactivation of NF-κB activation by curcumin and inhibition of Bcl-2 and Bcl-xL.