Endoplasmic reticulum stress and IRE-1 signaling cause apoptosis in colon cancer cells in response to andrographolide treatment
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Aditi Banerjee1, Hafiz Ahmed2, Peixin Yang3, Steven J. Czinn1, Thomas G. Blanchard1
1Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland, U.S.A.
2GlycoMantra Inc, Baltimore, Maryland, U.S.A.
3Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland, U.S.A.
Aditi Banerjee, email: firstname.lastname@example.org
Keywords: endoplasmic reticulum stress, unfolded protein response, apoptosis, chemotherapy, andrographolide
Received: December 11, 2015 Accepted: April 23, 2016 Published: May 05, 2016
The plant metabolite andrographolide induces cell cycle arrest and apoptosis in cancer cells. The mechanism(s) by which andrographolide induces apoptosis however, have not been elucidated. The present study was performed to determine the molecular events that promote apoptosis in andrographolide treated cells using T84, HCT116 and COLO 205 colon cancer cell lines. Andrographolide was determined to limit colony formation and Ki67 expression, alter nuclear morphology, increase cytoplasmic histone-associated-DNA-fragments, and increase cleaved caspase-3 levels. Andrographolide also induced significantly higher expression of endoplasmic reticulum (ER) stress proteins GRP-78 and IRE-1 by 48 h but not PERK or ATF6. Apoptosis signaling molecules BAX, spliced XBP-1 and CHOP were also significantly increased. Moreover, chemical inhibition of ER stress or IRE-1 depletion with siRNA in andrographolide treated cells significantly limited expression of IRE-1 and CHOP as determined by immunofluorescence staining, real time PCR, or immunobloting. This was accompanied by a decreased BAX/Bcl-2 ratio. Andrographolide significantly promotes cancer cell death compared to normal cells. These data demonstrate that andrographolide associated ER stress contributes to apoptosis through the activation of a pro-apoptotic GRP-78/IRE-1/XBP-1/CHOP signaling pathway.
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