Background: There are several distinct forms of the matrix metalloproteinases (MMP) that degrade collagen in the extracellular matrix. Most involved in the metastatic process are collagenases exhibiting specificity for type IV collagen, the collagen that makes up the backbone of the basement membrane. We chose to examine the expression of one type IV collagenase, MMP-9, in several ovarian cancer cell lines.
Methods: Under the influence of phorbol esters such as TPA, the fibrosarcoma cell line HT1080 is known to express MMP-9. We examined the effect of TPA on MMP-9 expression with Northern analysis, and on MMP-9 collagenase activity with polyacrylamide gel electrophoresis-zymography, in HT1080 cells (positive control) and in six ovarian cancer cell lines: Hey, HeyA8, CAOV3, PA-1, SKOV3, and OVCAR3. Cells were grown to 70% confluence and the growth medium was changed to a serum-free medium for 24 hr. Cells were then treated with 12 ng/mL TPA or its vehicle for an additional 24 hr. Medium was collected for PAGE-zymographic analysis. The cells were lysed and their RNA collected for Northern analysis.
Results: PA-1, a teratocarcinoma, expressed more than 10-fold the amount of RNA for MMP-9 than the other lines following TPA treatment. Both Northern analysis and zymography showed that four of the six ovarian cell lines responded to TPA with increased collagenase expression and activity. The other two cell lines showed no MMP-9 activity either before or after TPA treatment.
Conclusions: These results suggest that ovarian cancer cell lines express collagenase and that this expression may be regulated by phorbol esters which activate the protein kinase C pathway.