[DLys6]-luteinizing hormone releasing hormone-curcumin conjugate inhibits pancreatic cancer cell growth in vitro and in vivo

Pancreatic ductal adenocarcinomas are invariably lethal, and developing effective treatments that have minimal side effects is a challenge. Previous studies from our laboratory have shown that conjugates of cell membrane disrupting lytic peptides and luteinizing hormone releasing hormone (LHRH) target and destroy human prostate and breast cancer cells in xenografts in the nude mouse model (Hansel et al., Mol Cell Endocrinol 2007; 260-262: 183-9; Hansel et al., Mol Cell Endocrinol 2007; 269: 2633), which express LHRH receptors. The objectives of our study were to synthesize a bioconjugate of LHRH analog ([DLys(6)]-LHRH) and a dietary microchemical (curcumin) and test the hypothesis that [DLys(6)]-LHRH-curcumin targets and inhibits pancreatic cancer cell growth in vitro and in vivo. In in vitro studies, we determined by confocal microscopy, flow cytometry analysis and reverse transcriptase-polymerase chain reaction that MIAPaCa-2, Panc-1 and BxPC-3 pancreatic cancer cell lines express LHRH receptors. [DLys(6)]-LHRH-curcumin inhibited cell proliferation of pancreatic cancer cell lines and induced apoptotic cell death (p < 0.05). Apoptosis was induced by cleavage of polyadenosine-5'-diphosphate-ribose-polymerase and caspase-3. The activity of [DLys(6)]-LHRH-curcumin was equal to free curcumin at equimolar concentrations in vitro. Unlike curcumin itself, the [DLys(6)]-LHRH-curcumin conjugate is water soluble which allows its intravenous administration. In two in vivo studies, [DLys(6)]-LHRH-curcumin given intravenously caused a significant (p < 0.01) reduction in tumor weights and volumes, and free curcumin given by gavage at an equal dose failed to cause a significant reduction in tumor weights and volumes in the nude mouse pancreatic cancer model. [DLys(6)]-LHRH-curcumin treatment enhanced apoptosis compared to [DLys(6)]-LHRH and vehicle-treated controls in tumor tissue. In conclusion, [DLys(6)]-LHRH-curcumin may be useful in treating pancreatic cancer.