Celecoxib inhibits proliferation and induces apoptosis via prostaglandin E2 pathway in human cholangiocarcinoma cell lines.

AIM: To evaluate the roles and mechanisms of celecoxib in inducing proliferation inhibition and apoptosis of human cholangiocarcinoma cell lines.
METHODS: Cyclooxygenase-2-overexpressing human cholangiocarcinoma cell line QBC939 and cyclooxygenase-2-deficient human cholangiocarcinoma cell line SK-CHA-1 were used in the present study. The anti-proliferative effect was measured by methabenzthiazuron (MTT) assay; apoptosis was determined by transferase-mediated dUTP nick end labeling (TUNEL) detection and transmission electron microscopy (TEM). Cell cycle was analyzed by flow cytometry (FCM). The PGE(2) levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).
RESULTS: Celecoxib suppressed the production of PGE(2) and inhibited the growth of QBC939 cells. Celecoxib at 10, 20, and 40 micromol/L inhibited PGE(2) production by 26 %, 58 %, and 74 % in QBC939 cells. The PGE(2) level was much lower constitutively in SK-CHA-1 cells (18.6+/-3.2) compared with that in QBC939 (121.9+/-5.6) cells (P<0.01) and celecoxib had no significant influence on PGE(2) level in the SK-CHA-1 cells. The PGE(2) concentration in SK-CHA-1 cells also reduced but not significantly after treatment with celecoxib. The PGE(2) concentration in SK-CHA-1 cells was (16.5+/-2.9) ng/well, (14.8+/-3.4) ng/well, (13.2+/-2.0) ng/well and (12.6+/-3.1) ng/well respectively, when pre-treated with 1 micromol/L, 10 micromol/L, 20 micromol/L and 40 micromol/L of celecoxib for 48 h (P>0.05, vs control). The anti-proliferation effect of celecoxib (20 micromol/L) on QBC939 cells was time-dependent, it was noticeable on day 2 (OD490=0.23+/-0.04) and became obvious on day 3 (OD490=0.31+/-0.07) to day 4 (OD490= 0.25+/-0.06), and the OD490 in the control group (day 1) was 0.12+/-0.03 (P<0.01, vs control). The anti-proliferation effect of celecoxib could be abolished by the addition of 200 pg/mL PGE(2). The proliferation of SK-CHA-1 cells was inhibited slightly by celecoxib, the cell density OD490 in the presence of celecoxib and in control group was 0.31+/-0.04 and 0.42+/-0.03 respectively on day 2 (P>0.05), 0.58+/-0.07 and 0.67+/-0.09 respectively on day 3 (P>0.05), and 0.71+/-0.08 and 0.78+/-0.06 respectively on day 4 (P>0.05). Celecoxib induced proliferation inhibition and apoptosis by G(1)-S cell cycle arrest: the percentage of QBC939 cells in G(0)-G(1) phase after treatment with 40 micromol/L (74.66+/-6.21) and 20 micromol/L (68.63+/-4.36) celecoxib increased significantly compared with control cells (54.41+/-5.12, P<0.01). The percentage of SK-CHA-1 cells in G(0)-G(1) phase after treatment with various concentrations of celecoxib didn't change significantly compared with control cells. The TUNEL index was much higher in QBC939 cells treated with 20 micromol/L celecoxib for 2 d (0.063+/-0.018) and for 4 d (0.102+/-0.037) compared with control cells (0.017+/-0.004, P<0.01).
CONCLUSION: The current in vitro study indicates that inhibition of proliferation and induction of apoptosis in human cholangiocarcinoma cells by cyclooxygenase-2 specific inhibitor celecoxib may involve in COX-dependent mechanisms and PGE(2) pathway. Celecoxib as a chemopreventive and chemotherapeutic agent might be effective primarily on COX-2-expressing cholangiocarcinoma.