Objective： To investigate the expression of cyclooxygenase-2 （COX-2） mRNA in drug-sensitive cell and drugresistant clones of ovarian cancer cell lines. Methods： RT-PCR and immunocytochemistry were used to investigate the expression of cyclooxygenase-2 in 3 clones drug-sensitive and 5 clones drug-resistant ovarian cancer cell. Results： Strong COX-2 mRNA expressions were detected in 3 clones of drug-sensitive cell and weak expressions were detected in 5 clones of drug-resistant cell. The protein expression of COX-2 in drug-sensitive cell was strongly positive reaction in immunocytochemistry stain and there was a weak positive reaction in 5 clones of drug-resistant cell. Conclusion： The expression of COX-2 mRNA in drug-sensitive cell strains is much higher than that in drugresistant strains of ovarian cancer cell lines, providing a basis of the chemoprevention for ovarian cancer.
Objective： To investigate whether the change of drug resistance degree could be evaluated by apoptotic rate in ovarian cancer cell lines. Methods： Human epithelia ovarian cancer cell line A2780 and its platinum （DDP） resistance cell line AD4 were used. They were divided into 4 groups respectively （A2780-DDP group, A2780-DDP＋VRM group, AD4-DDP group and AD4-DDP＋VRM group）. 3-（4, 5- dimethylthiazol-2-yl）-2, 5-diphenyl-2H-tetrazolium bromide （MTT） was used to measure the multiple of drug resistance. The expression of drug-resistance genes （mdrl, TopoⅡα and GSTπ） was detected by using reverse transcription polymerase chain reaction （RT-PCR）. Semi-quantity assay was proceed by rate the of multidrug resistance genes to G3 PDH gene. Apoptosis was measured by DNA gel electrophoresis and flow cytometry respectively. The advantages and disadvantage of evaluating drug-resistance with these three methods were analyzed. Results： The 50% inhibition concentration （IC50） of A2780 and AD4 was 19.2 μg/mL and 66 μg/mL respectively, and the resistance fold of the AD4 was 3.4. Some drug-resistance genes could be detected by RT-PCR in A2780 and AD4 cell lines. The expression of mdrl was only （0.09±0.03）×10^-2 ： 1 and （0.10±0.02） × 10^-2：1 respectively （rate to G3 PDH gene） with the difference being not significant between them. The expression of TopoⅡα in the A2780 cells was （2.60±0.12）×10^-2：1 and （0.11±0.03）× 10^-2：1 in the AD4 cells respectively with the difference between them being significant. On the contrary, the expression of GSTπ in A2780 cells was lower than in AD4 cells, and the ratio was （0.11±0.03）×10^-2：1 and （3.13±0.14）×10^-2：1 respectively with tile difference being significant between them. There was no significant difference among the genes expression after the drugs were given for 6 h, 12 h and 24 h. couldn＇t reflect the change of drug-resistance timely. DNA gel electrophoresis used to detect apoptosis was only a qu
Objective： To evaluate the expression of p16INK4A gene in ovarian cancer and analyze the relation between this alteration and the promoter methylation of p16INK4A DNA. Methods： Seven ovarian cancer cell lines and eighteen ovarian cancer specimens were selected for the study. Genomic DNA and RNA were extracted from fresh tissues and cell lines, DNA was treated with sodium bisulfite and then analyzed with methylation-specific PCR （MSP） to detect p16INK4A methylation. The expression of p16INK4A mRNA was detected by reverse transcription-polymerase chain reaction （RT-PCR）. In addition, the proliferation of methylated cell lines before and after treatment of demethylating agent 5-Aza-2＇-deoxycytidine （5-ADC） was examined with 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide （MTT） assay in vivo. Results： Compared with the control, the expression of p16INK4A mRNA decreased significantly or absolutely defaulted in 10 of 18 （55.56%） ovarian cancer specimens and 71.4% （5/7） ovarian cancer cell lines （P〈0.05）, and the expression of p16INK4A protein also decreased （P〈0.05）. The decrease of p16INK4A was due, in part, to p16INK4A methylation, which was found in the first exon of three cell lines and six ovarian cancer specimens and the rate was 42.86% and 33.33% in ovarian cancer cell lines and specimens respectively. All the methylated cells and tissues showed expression defect of p16INK4A, but the treatment of 5-ADC reactivated the expression of p16INK4A in methylated cells and decreased the proliferation of tumor cells in vitro and in vivo. Conclusion： The expression defect of p16INK4A gene possibly has an important role in the development of ovarian cancer, and this alteration is due, in part, to the methylation of the first exon in p16INK4A.
