The Inhibition of HSP70 Induces Apoptosis in Pancreatic Cancer Cells

University Of Miami School Of Medicine, Coral Gables FL

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Abstract

DESCRIPTION (provided by applicant): Pancreatic cancer is a devastating disease with a poor prognosis. The severity of this malignancy can be appreciated from the fact that in 2012 over 44,000 new cases of pancreatic cancer are expected, with almost the same number succumbing to this disease. Studies in our laboratory have shown that triptolide, a natural compound, induces cell death in pancreatic cancer cells and is very effective in reducing tumor growth and loco-regional spread in an orthotopic model of pancreatic cancer. To expedite the clinical application of this compound we have synthesized a water soluble analog of triptolide named Minnelide. Minnelide also is very effective against pancreatic cancer in multiple animal models and will soon be evaluated against pancreatic cancer in phase I clinical trials. The overall goal of the current grant proposal is to elucidate the mechanism by which triptolide induces cell death in pancreatic cancer cells. We believe that defining this mechanism will lead to novel insights into the pathogenesis of cancer and reveal novel approaches to tackle the resistance of pancreatic cancer cells to cell death. We have previously demonstrated that one of the mechanisms by which triptolide induces cell death is by downregulating the pro-survival protein HSP70. However, we believe that triptolide modulates multiple pro-survival pathways and elucidating these pathways would lead to development of novel drug targets. Intriguingly, our preliminary data suggest that triptolide induces ER stress and inhibits NFkB by downregulating Specificity protein1 (Sp1). Our preliminary data also provide novel insight into the mechanism by which triptolide induced ER stress causes cell death by inducing lysosomal membrane permeabilization (LMP) and NFkB inhibition results in inhibition of HSP70, leading to cell death. In the current grant proposal, we will build on these preliminary findings. Aim 1 of th current grant proposal is geared towards evaluating the mechanism by which triptolide downregulates Sp1. Aim 2 and 3 are focused on the evaluation of the role of triptolide induced Sp1 downregulation in induction of ER stress and NFkB inhibition. The experiments proposed in the current proposal will elucidate novel mechanisms by which Sp1 can modulate ER stress and NFkB and by which ER stress and NFkB inhibition can lead to cell death by inducing lysosomal membrane permeabilization and HSP70 downregulation respectively. These mechanisms have not been studied in any cell system till date. We believe that successful completion of these studies will not only elucidate the mechanism of action of triptolide but also will lead to the discovery of novel drug targets eventually leading to development of novel therapies against pancreatic cancer.