Pancreatic ductal adenocarcinoma (PC) represents one of the most lethal and aggressive human malignancies and the fourth most common cause of cancer-related deaths in the US with 15% survival when the disease is organ confined, and only 4% when presenting with metastatic disease. In ~90% of PC, the K-ras oncogene is mutated. An obstacle to understanding the pathogenesis of this neoplasm has been the lack of suitable murine models that recapitulate the human condition. This impediment has now been diminished by the development of murine models that utilize a combination of targeted KrasG12D expression in the pancreas and Ink4a/Arf deficiency to develop pancreatic intraepithelial neoplasias (PanINs), which mimic the human disease, progressing rapidly to highly invasive and metastatic cancers. This model is ideally suited for designing and testing novel therapeutic/preventive approaches for this universally fatal human malignancy. We previously cloned melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), a novel member of the IL-10-related cytokine gene family with unique cancer-specific apoptosis-inducing properties. Recent Phase I/II clinical trials confirm its safety and efficacy in humans with advanced carcinomas and melanomas. Unexpectedly, ectopic expression of mda-7/IL-24 in PC cells is ineffective in inducing apoptosis because of a 'translational block'induced by K- ras that delimits association of mda-7/IL-24 mRNA with polysomes. When K-ras expression or its downstream MEK1/MEK2 pathway is inhibited or a reactive oxygen species (ROS) inducer is applied, mda-7/IL-24 mRNA is converted into protein and apoptosis is induced. Recent intriguing preliminary studies show that a dietary monoterpene, perillyl alcohol (POH), facilitates the apoptosis-promoting effects of mda- 7/IL-24 in PC cells. This study provides a first example of a synergistic interaction between a dietary agent and gene therapy in controlling the growth of an aggressive and currently untreatable cancer, such as PC. We currently plan to: i. Analyze the combinatorial effects of Ad.mda-7 and POH on the invasiveness and metastasis of a series of mutant and wild type K-ras PC cells;ii. Elucidate the molecular mechanisms of apoptosis-induction by Ad.mda-7 and POH;iii study the efficacy of mda-7/IL-24 and POH in inhibiting PC development and progression in transgenic PC animal models. We also are developing a compound transgenic mouse overexpressing mda-7/IL-24 in the pancreas to directly confirm that in situ generated mda-7/IL-24 will cooperate with POH in preventing PC development. The studies we propose will provide important information of direct relevance for future efforts designed to translate into patients an effective combination of dietary compounds with a novel cancer-specific apoptosis- inducing cytokine for the chemoprevention and potentially therapy of PC.
Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a pleotrophic tumor suppressor molecule that exhibits the unique property of inducing apoptosis only in cancer cells. Dietary monoterpenes, such as perillyl alcohol (POH) also exhibit anti- tumor properties. The present proposal describes a combinatorial approach of a dietary agent (POH) and adenovirus-based gene therapy, expressing mda-7/IL-24, as chemopreventive and therapeutic regimens for one of the deadliest neoplasms, pancreatic cancer.
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