The Study Of Doxycycline Anti-tumor Effect On Epithelial Ovarian Cancer And The Mechanisms Involved

Backgrouds:Ovarian cancer represents the most common cause of death among women withgynecologic malignancies, and the overall5-year survival rate is about30%.70%ovarian cancer is often diagnosed in advanced stage, because of a lack of measurableearly symptoms and ineffective screening techniques making difficult to remove thetumor totally. At present, standard treatment for ovarian cancer involves tumor debulkingand platinum-based chemotherapy administered intravenously or intraperitoneally. Theresponse to this regime is at least60-80%of cases, however, the majority of firstresponders will relapse with a platinum-resistant disease. Most platinum-resisitantovarian cancer cannot be cured and the median survival time for patients after recurrenceis only approximately two years. Now there is no consensus of treatment forplatinum-resisitant ovarian cancer, so detecting a new effective and hypotoxic anticancerdrug for it is an emerging new strategy. Doxycycline (DC) is a kind of second-generationtetracyclines, and is commonly used to treat a variety of infections. Current studies havedemonstrated that it also has antitumor effect. However, the effect of doxycycline onepithelial ovarian cancer cells and the underlying mechanisms remain unknown.Methods:Here, MTT cytotoxicity and cell invasion assay, flow cytometry was used to test theeffect of doxycycline on cisplatin-sensitive (SKOV3) and-insensitive (SKOV3/DDP)epithelial ovarian cancer cells proliferation, apoptosis and invasion. Western-blot analysisand ELISA was used to explore the underlying mechanisms. Nude mice were used toinvestigate the possible effects of doxycycline on the growth of ovarian cancer xenograft.Results:Our experiments demonstrated that doxycycline inhibited the proliferation andinvasion of both SKOV3and SKOV3/DDP cells, and induced a moderate apoptosis inSKOV3/DDP but not in SKOV3cells. In cisplatin-sensitive epithelial ovarian cancercells, the secretion of SDF-1, the expression of CXCR4, MMP-2and MMP-9wasdownregulated significantly when treated with doxycycline. Akt and EKRphosphorylation were activated by SDF-1, which were then inhibited by doxycycline.While in cisplatin-resistant epithelial ovarian cancer cells, we detected almost no SDF-1secretion and MMP-2/MMP-9expression, the inhibitory effect of doxycycline onCXCR4in SKOV3/DDP is not obviously than that in SKOV3. Only EKR phosphorylation were activated by SDF-1, but can not be inhibited by doxycycline.SDF-1had no effect on Akt phosphorylation. Then we compared the expression ofCXCR4, ERK, Akt and caspase-3in two cell lines, we found that caspase-3expressionwas significantly higher in SKOV3cells than that in SKOV3/DDP cells and wasupregulated when treated with doxycycline. In vivo, seven consecutive days injection ofdoxycycline inhibited tumor xenograft and reduced malignant ascites.Conclusion:The overall results indicate that doxycycline has an inhibitory effect on epithelialovarian cancer. SDF-1α/CXCR4-regulated ERK and Akt activations are probablyinvolved in the antitumor effect of doxycycline on SKOV3cells, while upregulation ofcaspase-3may be the main mechanism involved in SKOV3/DDP cells. Thus, clinical useof doxycycline may offer a promising new approach in the effective treatment of humanepithelial ovarian cancer.