COX-2/PGE2Pathway Is Involved In1,25-Dihydroxyvitamin D₃-Induced Downregulation Of Cyp1B1in Breast Cancer Cell Line MCF-7

Objective:To investigate the expressions of COX-2and CYP1B1in human breast cancer tissues and ERa-positive human breast cancer cell line MCF-7,to analyze the correlation between the expression and clinicopathologic characteristic in human breast cancer tissues,and to analyze the covariation between COX-2and CYP1B1expression,and its significance. On this basis,to study the influence of1,25-dihydroxyvitamin D3[1,25(OH)2D3] on proliferation, cell cycle transformation, and CYP1B1protein expression of the ERa-positive human breast cancer cell lines MCF-7and the related mechanisms.Methods:Immunohistochemical detection was applied to examine the expression of COX-2and CYP1B1protein in42cases of breast cancer tissues,and their association was analyzed combined with clinical pathology characteristics. The effects of1,25(OH)2D3on MCF-7cell proliferation was investigated by MTT assay to the optimal concentration of1,25(OH)2D3was determined for the following experiment.The cell cycle was analyzed by flow cytometry and COX-2mRNA expression in MCF-7cells was measured by RT-PCR.PGE2level was detected by ELISAin the cell culture supernatant; The expression of COX-2, p-ERK, p-ERα and CYPIBI protein was determined by Western blotting analysis and the distribution of COX-2, p-ERα and CYP1B1in MCF-7cells was examined by immune cell fluorescence.Results:In human breast cancer tissues, positive expression rates of COX-2and CYP1B1were78.6%and73.8%respectively,COX-2expression was relevance to CYP1B1expression(P<0.05).Expression of COX-2correlated with axillary lymph node metastasis and histologic grade(p<0.05),whereras expression of CYP1B1correlated with histologic grade and estrogen receptor(P<0.05).1,25(OH)2D3inhibited the proliferation of MCF-7cells in a time-and dose-dependent manner (P<0.05).Treatment with100nmol/L1,25(OH)2D3for72h significantly arrested cell cycle in G0/G1phase (P<0.05),decreased the expression of COX-2mRNA in MCF-7cells(P<0.05),decreased the level of PGE2in cell culture supernatant (P<0.01),and down-regulated p-ERK, p-ERα and CYP1B1protein expression(P<0.05).Conclusions:COX-2/PGE2pathway plays a positive role on regulation of the expression of CYP1B1in breast cancer,which exert important influence in human breast tumorigenesis.1,25(OH)2D3may inhibits the growth of MCF-7cells and downregulate CYP1B1through COX-2/PGE2pathway.