DIFFERENTIAL INFLUENCE OF ANTIESTROGENS ON THE IN-VITRO RELEASE OF GELATINASES (TYPE-IV COLLAGENASES) BY INVASIVE AND NONINVASIVE BREAST-CANCER CELLS

Matrix metalloproteinases (MMPs) play an important role in tumor cell invasion and cancer metastasis. Accordingly, a higher level of these e nzymes has been associated with the invasive phenotype, In the present study the effect of the antiestrogens, Analog II (AII), ICI-182,780 ( ICI), and tamoxifen (TAM), on the in vitro release of MMPs, particular ly gelatinases A and B by the MDA-MB-231 (MDA) and MCF-7 (MCF) human b reast cancer cell lines was investigated using a solid-phase radioassa y and substrate gel zymography, Quantitatively, the enzyme activity wa s found to be higher in the incubation medium from estrogen receptor ( ER)-negative and more metastatic MDA cells compared to ER-positive and less metastatic MCF cells. Tissue inhibitor of metalloproteinases-1 ( TIMP-1) reduced the enzyme activity in media from both MDA (56.36%) an d MCF (71.03%) cells, Differential antiestrogen effects on the two cel l lines were observed following 4 days of treatment of cells at a conc entration of 10(-6)M. The enzyme activity from MDA cells was not influ enced by treatment with any of the antiestrogens, whereas, in MCF cell s, ICI produced the greatest enzyme inhibition (47.93%), followed by A II (36.51%) and TAM (24.05%), Concurrent treatment of MCF cells with 1 7-beta-estradiol (10(-9)M) partially reversed the AII- and TAM-induced but did not alter ICI-induced inhibition of enzyme activity, Substrat e gel zymography revealed that among the MMPs, the MDA cells released predominantly progelatinase A (72 kDa) along with minor bands of activ ated forms, 62 kDa and 59 kDa, whereas progelatinase B (92 kDa) was de tected predominantly in the medium from MCF cells, Comparison of the o verall antiestrogen effect indicates that ICI is the most potent inhib itor of enzyme activity in ER-positive MCF cells and that antiestrogen treatment may limit the metastatic potential of ER-positive breast ca ncer.