Abstract 3572: Antitumoral activity of nemorosone on pancreatic cancer cells

Abstract

Abstract Despite substantial and growing knowledge about its biology, pancreatic cancer is constantly evading new treatment strategies due to its chemoresistant nature. Thus, the aim of many oncologists is to identify and evaluate drugs with novel mechanisms of action to overcome resistance. Nemorosone, a polyisoprenylated benzophenone isolated from the flower resin of Clusia rosea, showed extraordinary cytotoxic and antitumoral activity on a panel of cancer cell lines. To assess its potential in more detail for the treatment of pancreatic cancer, the effects of nemorosone on three pancreatic cancer cell lines known to be very chemoresistant were analyzed by cytotoxicity/apoptosis assays as well as gene expression profiling. cDNA microarray data of 3500 genes were analyzed to identify pathways and molecular networks affected by treatment with nemorosone in order to shed light on its molecular mechanism of action. Results were validated using quantitative RT-PCR, RNAi-mediated gene silencing and immunofluorescence. After 72 h of incubation, nemorosone showed a remarkable IC50 of 5 µM on all pancreatic cancer cell lines in comparison to 40 µM on normal fibroblasts. Nemorosone induced cell cycle arrest and apoptosis in a dose- and time-dependent manner. Interestingly, apoptosis rate was dependent on the degree of differentiation of the cell line, with MIA-PaCa-2 (undifferentiated cell line) exhibiting the highest rate of apoptosis and almost no signs of apoptosis in normal fibroblasts. Gene expression analysis after treatment revealed a strong induction of the cell cycle regulator p21 and, consequently, massive down-regulation of many genes associated with the cell cycle and DNA synthesis. The induction of the stress-response protein GADD153 as well as anti-oxidative proteins and many down-stream targets of ATF4 suggests the involvement of the endoplasmic reticulum stress response. It is concluded that these events trigger the intrinsic pathway of apoptosis which results in the fast loss of mitochondrial membrane potential as measured by voltage-dependent staining with JC-1. RNAi-mediated knock-down of GADD153 resulted in a significant reduction of apoptosis rate in MIA-PaCa-2 cells. Furthermore, it is hypothesized that the rapid depolarization of the mitochondrial membrane in cancer cells is also due to ion fluxes from the endoplasmic reticulum to mitochondria, leading to the disturbance of ER homeostasis and, finally, apoptosis. Thus, considering its high efficacy on undifferentiated cells and lower cytotoxicity on normal cells, nemorosone is a potential drug candidate for the treatment of advanced pancreatic cancer which is the fifth most common cancer-related cause of death in the western world. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3572.