Combined effects of cyclooxygenase-1 and cyclooxygenase-2 selective inhibitors on ovarian carcinoma in vivo

Abstract

The present study was designed to investigate the combined effects of cyclooxygenase (COX)-1 and COX-2 selective inhibitors on human ovarian SKOV-3 carcinoma cells xenograft-bearing mice. The animals were treated with 3 mg/kg SC-560 (a COX-1 selective inhibitor) alone, 25 mg/kg celecoxib (a COX-2 selective inhibitor) alone, or SC-560/celecoxib by gavage, twice a day for three weeks. To test the mechanism of inhibition of tumor growth by COX selective inhibitors, the index of proliferating cells in tumor tissues was determined by immunostaining and the index of apoptotic cells by the terminal-deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method. The inhibitory rate on tumor growth in the combination group was 35.54% which is significant statistically compared with that of the control group (P < 0.05). In the combination group, the index of cell proliferation and apoptosis were 12.40% and 51.03% respectively, which are significant statistically compared with those of the control group (22.56%, 19.07%, all P < 0.05). These studies indicate that synergism between two COX inhibitors and inhibitor combination treatment has particular potential for chemoprevention of ovarian cancer growth.

Keywords: apoptosis; cell proliferation; cyclooxygenase selective inhibitor; mice; ovarian carcinoma.

Figure 1

Effects of SC-560 and celecoxib on tumor growth in vivo. The inhibitory of SC-560 and celecoxib on tumor growth were determined in an ovarian cancer model using SKOV-3 cells. After 7 days to allow tumor establishment, mice were treated with SC-560 and celecoxib. Treatment was continued for 21 days. Average tumor volume in SC-560 and celecoxib combination group was significantly different from vehicle-treated mice at day 28. Statistical significance was determined using Student’s t-test. * P < 0.05.

Figure 2

COX protein levels in xenograft tumors of nude mice treated or not treated with combined treatment of SC-560 and celecoxib. COX-1 and COX-2 protein levels were analyzed by Western blotting. Anti-β-actin was used as a control for equal loading. Lanes 1–6: tumor tissues of six mice in control group. Lanes 7–12: tumor tissues of six mice in the combination group.

Figure 3

The ratios of COX-1/actin after autoradiography integrations. Results were expressed in arbitrary units. The COX-1 expression was decreased significantly by 31% in the combination group compared with the control group (* P < 0.01; error bars indicate SE).

Figure 4

Cell proliferation in xenograft tumors of nude mice treated or not treated with SC-560 and/or celecoxib. (A) Immunostaining of cell proliferation (Ki-67) by immunohistochemistry. The combination group of COX selective inhibitor SC-560 and celecoxib attenuates tumor cell proliferation. (B) The index of cell proliferation was determined from the ratio of nuclear Ki-67 protein-positive cells/total nuclei number by immunohistochemical method. * P < 0.05, ** P < 0.01, compared with control; error bars indicate SE.

Figure 5

Cell apoptosis in xenograft tumors of nude mice in either the presence or absence of SC-560 and/or celecoxib. (A) Immunostaining of cell apoptosis in tumors by TUNEL. The combination group of COX selective inhibitor SC-560 and celecoxib accelerates tumor cell apoptosis. (B) The index of cell apoptosis was determined from the ratio of nuclear apoptosis-positive cells/total nuclei number. * P < 0.05, ** P < 0.01, compared with control; error bars indicate SE.