IN VIVO MOLECULAR EVIDENCE ON CHEMOSENSITIZATION OF PANCREATIC TUMOR BY GENISTEIN

Abstract

Purpose: In our previous communications, we reported the efficacy of genistein in augmenting the effects chemotherapeutic agents such as cisplatin and gemcitabine in pancreatic cancer cells in vitro (S.Banerjee et.al., APA-2004; AACR-2005). Here we report mechanism based evidence for the observed beneficial effect in vivo in SCID mice bearing orthotopically implanted pancreatic cancer cells. Method: Female nude mice (ICR-SCIDS) orthotopically implanted with COLO-357 and L3.6pl tumor cells were randomized into treatment groups comprising (n = 7): (a) Untreated control; (b) Only cisplatin or gemcitabine treatment; (c) Genistein treated (1 mg/mouse/day orally by gavage); and (d) Genistein and cisplatin or gemcitabine following the schedule as for individual treatments. After treatment, tumor samples were analyzed for NF-κB (EMSA) and Western immunoblotting for proapoptotic entities such as, Bcl-xL, and PARP. Results: Analysis of average pancreatic tumor weight in different treatment groups revealed that treatment with genistein and cisplatin/or gemcitabine resulted in a significant reduction in tumor weight relative to tumor weight in control animals. Furthermore, corollary to our previous in vitro findings, we confirmed in our in vivo animal model the potential of genistein to abrogate cisplatin/gemcitabine induced NF-κB activation (which contributes in attenuating chemotherapeutic - drug induced chemo-resistance) resulting in sensitizing tumor cells to undergo apoptotic cell death. Elucidation of downstream targets of NF-κB such as anti-apoptotic BcL-xL was also down regulated alongwith PARP cleavage by genistein treatment thereby augmenting therapeutic efficacy of chemotherapeutic drugs and enhanced apoptosis relative to single agents. Conclusion: Our data provides novel mechanistic insights by which genistein sensitizes in vivo pancreatic tumor cells to chemotherapeutic drugs such as cisplatin and gemcitabine, suggesting that this strategy could be useful clinically in the future.