A Novel Inhibitor that Targets both p53‐Dependent Apoptotic and Autophagy Pathways as a Pancreatic Cancer Therapeutic

Abstract

In the United States, by 2030, pancreatic cancer (PC) is predicted to be the second most common cause of mortality from cancer. Today, the 5‐year survival rate of pancreatic ductal adenocarcinoma (PDAC, comprising >90% of all pancreatic cancers) remains <5% due to lack of early detection and poor treatment prognosis. The transcription factor (i.e., tumor suppressor gene p53) has been well‐characterized for its susceptibility to genetic or epigenetic modifications. About 75% of PC patients with poor clinical prognosis have intragenic p53 mutations that makes PC cells resistant to chemotherapeutic regimens. A majority of PC patients rely on combination treatment for better outcomes (i.e., gemcitabine with nab‐paclitaxel) in addition to surgery. A drug that potently inhibits PC growth, restores tumor suppressor function, sensitizes and powerfully drives PC cells towards cell death is urgently needed. Compound 1 potently modulated cell death checkpoints and was highly efficacious against both WT and mutant p53‐bearing PDAC cells (i.e., HPAC, MIA PaCa‐2, AsPC‐1). 1 also showed synergistic potency in combination with gemcitabine and/or paclitaxel. In an invasive PDAC tumor model (LM‐P, developed by Dr. Andy Lowy), 1 (20 mg/kg/day, 28 days, i.p.) inhibited tumor growth 65% compared to vehicle‐treated mice without any apparent acute or chronic toxicity. Herein, we report the mechanism of action of 1. 1 potently inhibited PDAC via dual signaling pathways based on the results of in vitro molecular target and mechanism validation (i.e., qPCR, subcellular fractionation, immunoblot, immunoprecipitation, etc.). Treatment of PDAC cells with 1 activated mitotic stress signaling including ATM/ATR‐kinase to induce activation of DNA damage checkpoints. 1 further activated cytosolic p53/Bax by inhibiting the antagonizing effect of Bcl‐2/Bcl‐xL (anti‐apoptotic proteins) towards p53/Bax. This caused activation of pro‐apoptotic markers (i.e., Bak, Bax) and the accumulation of those markers in mitochondria, induced the release of mitochondrial cytochrome c into cytosol and activated caspase and PARP cleavage, and triggered cell apoptosis. 1 also enhanced the interaction between Beclin‐1 (Beclin‐1 plays a critical role in the regulation of autophagy) and Bcl‐2/Bcl‐xL and increased both LC3‐II and p62 to impair lysosomal function. This repressed late‐stage autophagy to induce cell death when apoptotic pathway activation was deficient (i.e., under starvation conditions, late‐stage of treatment, in null p53 cells). 1 is unique and innovative because it is the only known compound that kills PDAC cells via differentially modulating apoptotic and autophagic cell death pathways. 1 also has dual properties to induce crosstalk between apoptotic and autophagic cell death of PC that contributes to potent anti‐PC potency of 1.Support or Funding InformationThis work was supported by 1R41CA176931‐01A1 (KJO) and 1RO1CA155620‐01 (AML) from National Institutes of Health and by funds from the Human BioMolecular Research Institute.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.