Pachymic acid is a natural triterpenoid chemical that can be extracted from the root of various Pinus species, where it is produced by parasitic fungus Wolfiporia extensa (synonym Wolfiporia cocos). The dried sclerotia of the fungus is used as a traditional Chinese medicine, and pachymic acid is one of the major bioactive components of it. Pachymic acid (PA) is a purified triterpene extracted from medicinal fungus Poria cocos. In this paper, we investigated the anticancer effect of PA on human chemotherapy resistant pancreatic cancer. PA triggered apoptosis in gemcitabine-resistant pancreatic cancer cells PANC-1 and MIA PaCa-2. Comparative gene expression array analysis demonstrated that endoplasmic reticulum (ER) stress was induced by PA through activation of heat shock response and unfolded protein response related genes. Induced ER stress was confirmed by increasing expression of XBP-1s, ATF4, Hsp70,
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