Anacardic acid inhibits pancreatic cancer cell growth, and potentiates chemotherapeutic effect by Chmp1A - ATM - p53 signaling pathway

BACKGROUND: Pancreatic cancer is one of the leading causes of cancer related death and its incidence has risen steadily. Although anticancer drugs have been developed based on the new molecular findings, the drugs have produced unsatisfactory results due to toxicity and resistance. Thus, a complementary therapeutic intervention is urgently needed for pancreatic cancer patients. METHODS: The aim of this study was to assess the potential therapeutic effect of Anacardic acid on pancreatic cancer in vitro and elucidate its underlying mechanisms. Human pancreatic cancer cells were treated with Anacardic acid and assessed for the cytotoxic effect using MTT and spheroid formation assays. Using the same methods, the synergy between Anacardic acid and 5-Fluorouracil or Gemcitabine was determined. To elucidate the underlying molecular mechanisms, Western blot analysis and immunocytochemistry were performed on cancer cells treated with Anacardic acid alone or in combination with 5-Fluorouracil or Gemcitabine. Chromatin Modifying Protein 1A (Chmp1A), Ataxia Telangiectasia Mutated (ATM), and p53 were the primary signaling molecules examined. In addition, Chmp1A was silenced with shRNA to examine the necessity of Chmp1A for the anticancer effect of Anacardic acid, 5-Fluorouracil, or Gemcitabine. RESULTS: Anacardic acid induced an anticancer effect in pancreatic cancer cell lines in a dose dependent manner, and increased the cytotoxicity of 5-Fluorouracil or Gemcitabine in MTT cell viability assays. In spheroid formation assays, spheroids formed were smaller in size and in number upon Anacardic acid treatment compared to control. Mechanistically, Anacardic acid exerted its anticancer activity via the activation of Chmp1A, ATM, and p53. Interestingly, 5-Fluorouracil and Gemcitabine also induced an increase in Chmp1A protein level, suggesting that Chmp1A might mediate the cytotoxic action of chemotherapeutics. Silencing experiments indicate that Chmp1A is required for the action of Anacardic acid, but not for 5-Fluorouracil or Gemcitabine. CONCLUSIONS: Our data suggests that Anacardic Acid might be a promising complementary supplement to slow the initiation or progression of pancreatic cancer.