| Prostate cancer is a common malignant tumor in male genitourinary system, its morbidity is increasing in recent years, and the most common reason leads people to death is the metastasis. Lymph node, bone and lung are the liable organs for prostate cancer metastasis and in this process Matrix Metalloproteinase shows a major role. ECM (extracellular matrix) is a complicated reticular structure, which is composed of fibrous protein and proteoglucan. It is essential in many physiological processes, such as development, growth, and repair of tissues. Degradation of ECM around tumor is one of the key steps in tumor invasion and metastasis. MMPs are a family composed of at least 24 zinc-dependent endopeptidases, capable of degrading all ECM components. MMP-2 is a member of the families. Studies show that MMPs not only facilitate tumor invasion by degradation of ECM, but also play an important role in tumor growth and angiogenesis. Expression of MMPs is strongly associated with poor outcome of malignant tumor. Anti-cancer therapy aiming directly at MMPs receives attention increasingly. Doxycycline, a kind of antibiotic belonging to tetracyclines, can inhibit activity of MMPs and decrease the invasion as well as metastasis of tumor. By using prostate cancer cell line PC-3, we carried out some experiments to study the role of MMP-2 on invasion of prostate cancer and to clarify the effects of Doxycycline on proliferation of prostatecancer.the results are listed below:1. Morphological study: Morphological changes were observed by invert microscope. After different concentrations of DOXY were added to PC-3 cells culture medium and took effects, the cells shrinked and appeared irregular shapes, and were easier to detach. The morphological changes were positively associated to the time of culturing and the concentration of Doxy.2. Effects of DOXY on cell proliferation: Inhibition of cell proliferation by DOXY was time and dose dependent.3. Effects of DOXY on cell adhensiveness: Doxy could inhibt the ability of PC-3 adhension to matrigel.4. Effects of DOXY on expression of MMP-2: Immunohistochemical staining showed after treated PC-3 with DOXY, the expression of MMP-2 in PC-3 cells was decreased.5. TEM showed that DOXY selectively acted on mitochondrion of PC-3 cells, caused mitochondrion swollen and blocked energy metabolism. DOXY may inhibit the proliferation of PC-3 cells by this way.6. Effects of DOXY on cell cycle: The result of FCM showed that cell cycle was blocked at GI stage and the proportion of S stage decreased obviously and closely related with time and dosage. Apoptosis peak was not observed. This result also indicated that DOXY was not through inducing apoptosis to inhibit the proliferation of PC-3 cells.7. Effects of DOXY on secretion and activity of MMP-2: SDS-polyactylamide gels only detected secrete and activity of MMP-2. The activity of MMP-2 protease was inhibited by both 5 y g/ml and 10 u g/ml Doxy.8. Effects of DOXY on invasive behavior of PC-3: The cells moved through the membrane was(82.04?.62)/field in control group, with the cell numbers decreased to (26.1 ?.56)/field,(7.17?.21)/field and (3.25 ? 0.74)/field in 5 mg ? L'',10 mg ? L'1 and 20 mg ?l/'Doxycycline-treated PC-3 cell respectively ,and the difference was significant.(P<0.01).Conclusions: MMP-2 is highly expressed in PC-3 cells. DOXY not only depress the proliferation of PC-3 cells, but also depress the expression and secretion of MMP-2 in PC-3 cells, and decrease the invasion and metastasis of PC-3 with time and dosage dependence. Thus it may have therapeutic potential to decrease recurrence and metastasis after surgery of7patients with prostate cancer.
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