Study On The Effect Of Celecoxib On The Growth And Angiogenesis Of Orthotopic Transplantation Tumor Of Experimental Human Colorectal Cancer

Part One Study on the effect of celecoxib on the growth of orthotopic transplantation tumor of experimental colorectal cancerObjective: To investigate the effect of celecoxib, a selective inhibitor, on the growth of orthotopic transplantation tumor of experimental colorectal cancer. Methods: The cell line HT-29 in log phase of human colorectal cancer was implanted subcutaneously in nude mice to develop implant-tumor, and subcutaneously implanted tumor formed 4 weeks later. Then tumor tissue was collected and orthotopically implanted in the cecum subserosa of 24 nude mice. Postoperatively these nude mice were randomly allocated into four groups: control (C)group and high (H) middle (M)n low (L) dose group of celecoxib. Pure water and the water containing 1500,1000,or 500ppm celecoxib were respectively provided to these nude mice. All mice were sacrificed 42 days later and the changes of weight of all nude mice were observed. The volume and weight of colorectal tumor in situ were measured and the rates of tumor inhibition were evaluated. Simultaneously the method of RIA was used to estimate the content of PGE2 in tumor tissue homogenate, the cyclooxygenase-2 expression of tumor tissue was calculated by immunohistochemistry and the apoptosis of tumor cell was detected by TUNEL to determine apoptotic index (AI).Results: None of the nude mice died and all nude mice formed in situ mass of colorectal tumor. The weights of the experimented mice had never changes significantly, while the statistical differences of the volume and the weight of in situ tumor were significant(respectively P<0.05 P<0.01). With the increasing of celecoxib concentration, the volume and the weight of in situ tumor decreased. The respective rates of the tumor inhibition of L group, M group and H group were 25.30%, 38.80%, 76.92%, and the differences compared with control group (0%)were significant(P<0.05). Furthermore the rates of the tumor inhibition were dose-dependent. With the increasing of celecoxib concentration the content of the PGE2 in tumor tissue homogenate of treated groups decreased gradually and was significantly lower than that in control (P<0.05). The content of the PGE2 was in significant correlation with the weight of tumor(r=0.8814 P<0.05). Except between L and M group the differences of the cyclooxygenase-2 expression of tumor tissue among the other groups were significant(P<0.05) and the expression decreased gradually with the increasing of celecoxib. The content of the PGE2 in tumor tissue homogenate was closely related to the cyclooxygenase-2 expression of tumor tissue(r=0.8249, P<0.05). Compared with control group the apoptosis of tumor cell in treated groups obviously raised and the statistical differences of the apoptotic index (AI) among groups were significant(P<0.01). Conclusions: By inhibiting the cyclooxygenase-2 and the synthesis of PGE₂ of the tumor tissue celecoxib can obviously enhance the apoptosis of tumor cell and inhibit the growth of orthotopic transplantation tumor of colorectal cancer.Part Two Study on the effect of celecoxib on angiogenesis of orthotopic transplantation tumor of experimental colorectal cancerObjects: To investigate the effect of celecoxib, a selective inhibitor, on angiogenesis of orthotopic transplantation tumor of experimental colorectal cancer. Methods: The CD34 expressions of tumor tissue collected from the experiment Part One were detected by immunohistochemistry and the microvessel density (MVD) oftumor tissue was evaluated. Simultaneously the expressions of vascular endothelial growth factor (VEGF) mRNA and Matrix Metalloproteinases-2 (MMP-2) mRNA extracted from the tumor tissue were analyzed by reverse transcriptase polymerase chain reaction(RT-PCR).Results: The positive CD34 expressions of celecoxib-treated groups were obviously lower than that of the control group. Except between group H and M the differences of the MVD among the other groups were significant(P<0.05). The expression lever of VEGFmRNA and MMP-2 mRNA of treated groups decreased obviously compared with the control group. Except between group L and M the differences of the expression lever of VEGFmRNA and MMP-2 mRNA among the other groups were significant(P<0.05). The content of the PGE2 in tumor tissue homogenate, MVD and the expression lever of VEGFmRNA and MMP-2 mRNA in tumor tissue decreased gradually with the increasing of celecoxib concentration. The MVD of tumor tissue was closely related to the content of the PGE2, the expression lever of VEGFmRNA and MMP-2mRNA in tumor tissue(r= 0.9006, r=0.8573, r=0.6427, PO.05).Conclusions: Celecoxib can obviously inhibit angiogenesis of orthotopic transplantation tumor of colorectal cancer by inhibiting the synthesis of PGE2 and the expression of VEGFmRNA and MMP-2 mRNA of tumor tissue.