Inhibition of Prostate Tumor Cell Invasiveness by Chemically Modified Tetracyclines With Board Spectrum Antiproteinase Activity

摘要

We have evaluated novel nonantimicrobial chemically modified tetracyclines (CMTs) for management of invasive prostate cancer, based on preliminary results showing that one such CMT (CMT-3) inhibits matrix metalloproteinases (MMPs) as well as the serine proteinase human neutrophil elastase, reduces levels of released MMPs, and is selectively cytotoxic towards the human prostate tumor cell line LNCaP but not towards normal prostate stromal cells in culture. Because patients receiving CMT-3 in Phase I clinical trials at NCI have exhibited photoreactions, we screened all new CMTs with UV-A exposed NIH 3T3 cells to ensure that their phototoxicities in vitro are no greater than that of doxycycline. We evaluated the new CMTs for dose-dependent inhibition of collagenolytic and gelatinolytic activities of MMP-8 and MMP-9, as well as neutrophil elastase activity, and for differential cytotoxicity towards LNCaP cells, based on increased permeability to the dye SYTO 17 and failure to reduce the tetrazolium salt MTS. In addition to directly inhibiting proteolytic activity, the most promising CMTs downregulate expression of several markers of the invasive phenotype, including levels of the serine proteinase Prostate Specific Antigen released by LNCaP cells, MMP-9 released by PC-3 cells in response to TGF-Beta stimulation, and IGFBP-3 released by PC-3 in response to IGF-1 stimulation. These results suggest that the CMTs may be useful agents for management of prostate cancer because of their pleiotropic effects on proteinase activity, cell survival, and expression of multiple markers which correlate with invasiveness in tumors.