MESSENGER-RNA LEVELS OF MEMBRANE-TYPE-1 MATRIX METALLOPROTEINASE (MT1-MMP), MMP-2, AND MMP-9 AND OF THEIR INHIBITORS TIMP-2 AND TIMP-3 IN NORMAL THYROCYTES AND THYROID-CARCINOMA CELL-LINES

Thyroid cancer can degrade basement membranes and invade tissues. This depends on a cascade of matrix metalloproteinases involving membrane- type 1 matrix metalloproteinase (MT1-MMP), MMP-2, and MMP-9. We analyz ed the expression and role of these MMPs and their specific inhibitors TIMP-2 and TIMP-3 in human highly purified thyroid epithelial, C 643, HTh 74, SW 1736, and 8505 C thyroid carcinoma and thyroid-derived fib roblast cell cultures. The effect of phorbol-myristate acetate (PMA), and of the inflammatory cytokines interleukin-l (IL-1) and tumor necro sis factor-alpha (TNF-alpha) on MMP and TIMP mRNA levels were monitore d by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-DCR) including an internal homologous competitor fragment. The hi ghest MT1-MMP mRNA levels were found in thyroid-derived fibroblasts. T he MT1-MMP mRNA expression was increased up to 10-fold by PMA, while a ll other growth factors tested had only negligible effects. The thyroi d carcinoma cells themselves did not seem to play a crucial role in th e production of MT1-MMP in thyroid tumors. Higher MMP-2 mRNA levels we re found in all cell types investigated. The highest MMP-2 mRNA levels were determined in thyroid-derived fibroblasts and HTh 74 cells. We f ound a lack of MMP-2 response to IL-1, TNF-alpha, and phorbol esters. In unstimulated cells, MMP-9 mRNA was found near the detection limit o r at low levels. In nearly all cell types, treatment with PMA, IL-1, a nd TNF-alpha caused an increase of the MMP-9 mRNA levels. The results of basal and stimulated MMP-2 and MMP-9 mRNA expression were confirmed at the protein level by gelatin zymography. TIMP-2 and TIMP-3 mRNAs w ere expressed at high levels. In contrast to the basal TIMP-3 mRNA lev els, which varied over a great range, there were no striking differenc es the cell types from analyzing TIMP-2 mRNA. There were no or only sl ight stimulatory effects on TIMP-2 and TIMP-3 mRNA expression by IL-1, TNF-alpha, and PMA. Taken together, most enzymes of the MT-MMP/MMP cl ass of proteases facilitating invasion of thyroid tumor cells seem to have been produced by fibroblasts, not by the tumor cells themselves. However, some dedifferentiated thyroid tumor cell lines may be capable of secreting some of these enzymes, as in the case of HTh 74 cells.