Publication Date:
2012-04-16
Description:
Our previous study showed that gossypol (GOS) exhibits potent cytotoxic effects via apoptosis induction against human colorectal carcinoma cells; however the role of cyclooxygenase (COX)-2/prostaglandin (PG)E 2 on GOS-induced apoptosis is still unknown. In the present study, 12-O-tetradecanoylphorbol-13-acetate (TPA) addition significantly inhibited GOS-induced apoptosis in human colorectal carcinoma HT-29 cells in accordance with inducing COX-2 protein/PGE 2 production. TPA inhibition of GOS-induced apoptosis was blocked by adding protein kinase (PK)C inhibitors including staurosporine (ST), GF109203X (GF), and H7, characterized by the occurrence of cleaved caspase 3 proteins and a decrease in COX-2 protein/PGE 2 production in HT-29 cells. The addition of COX activity inhibitors, including NS398, aspirin (AS), diclofenac (DI), and indomethacin (IN), suppressed TPA protection of GOS-induced apoptosis with decreased PGE 2 production in HT-29 cells. Application of PGE 2 , but not it analogues PGD 2 , PGJ 2 , or PGF 2α , protected HT-29 cells from GOS-induced DNA ladders, and the EP 1 receptor agonist, 17PT-PGE 2 , mimicked the protection induced by PGE 2 , whereas the selective EP 2 receptor agonist, butaprostol (BUT), the EP 3 receptor agonist, sulprostol (SUL), and the EP 4 receptor agonist, PGE 1 alcohol (PGE 1 ), showed no significant effects on GOS-induced apoptosis in HT-29 cells. PGE 2 's protection against GOS-induced apoptosis was reversed by adding the selective EP 1 receptor antagonist, SC-19220. Furthermore, GOS had an effective apoptotic effect on COLO205 colorectal carcinoma cells which expressed undetectable level of endogenous COX-2 protein than HT-29 cells, and the decreased COX-2 protein level via COX-2 siRNA or addition of COX-2 activity inhibitor NS398 significantly elevated GOS-induced cell death in HT-29 cells. COLO205-T cells were established through sustained TPA incubation of COLO205 cells, and COLO205-T cells showed a lower sensitivity to GOS-induced cell death with increased COX-2 (not Bcl-2 and Mcl-1) protein than parental COLO-205 cells. A decrease in COX-2 protein expression in COLO205-T cells by COX-2 siRNA transfection or enhanced GOS-induced cell death according to an MTT assay and DNA integrity assay. The notion of COX-2/PGE 2 activation against GOS-induced apoptosis in colon carcinoma cells was demonstrated, and the combination of GOS and COX-2 inhibitors to treat colon carcinoma possesses clinical potential worthy of further investigation. J. Cell. Physiol. © 2011 Wiley Periodicals, Inc.
Electronic ISSN:
1097-4652
Topics:
Biology
,
Medicine
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