Inhibition of Prostate Tumor Cell Invasiveness by Chemically Modified Tetracyclines with Broad 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 activities of matrix metalloproteinases (MMPs) as well as the serine proteinase human neutrophil elastase, reduces levels of MMPs released by cells in culture, and exhibits selective cytotoxicity towards the human prostate tumor cell line LNCaP but not towards normal prostate stromal cells in culture. In response to photoreactions in patients receiving CMT-3 in Phase I clinical trials at NCI, we have 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 have also 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. The cytotoxicities of the new CMTs have been investigated using multiple criteria including membrane permeability to the DNA-binding dye SYTO 17 and failure to reduce the tetrazolium salt MTS. In addition to LNCaP cells, we use R22 rat smooth muscle cells and normal human epithelial cells as targets. The most promising CMTs display preferential dose-dependent cytotoxicity towards tumor cells, and induce morphologic changes, including rounding, detachment, and loss of confluence which mark a departure from the invasive phenotype. We plan to test the new CMTs with explant cultures of resected prostate tumors for inhibition of proteinase activities and cytotoxicity.