Opposite effect of stable transfection of bioactive transforming growth factor-β1 (TGFβ1) versus exogenous TGFβ1 treatment on expression of 92-kDa type iv collagenase in mouse skin squamous cell carcinoma CH72 cells
✍ Scribed by Joyce E. Rundhaug; Jeanie Park; Amy Pavone; Ghislain Opdenakker; Susan M. Fischer
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 262 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0899-1987
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✦ Synopsis
We have previously shown that transforming growth factor-β1 (TGFβ1) mRNA is consistently overexpressed in squamous cell carcinomas relative to normal mouse skin. Here we show that 92-kDa type IV collagenase (matrix metalloproteinase) (MMP-9) mRNA was likewise progressively overexpressed during mouse skin carcinogenesis. To determine if overexpression of MMP-9 and TGFβ1 are linked, we stably transfected a bioactive TGFβ1 into a mouse skin squamous cell carcinoma cell line (CH72), which resulted in about twofold to threefold higher levels of secreted active TGFβ1. Active TGFβ1-transfected cells grew only slightly, but not significantly, more slowly in vitro and in vivo than vector-only transfectants. Two clones overexpressing active TGFβ1 secreted much reduced levels of MMP-9 activity, as determined by zymogram analyses. However, treatment of these clones with 40 pM exogenous TGFβ1 for 48 h enhanced secretion of MMP-9 activity. Constitutive mRNA expression of MMP-9 was reduced twofold to 70-fold in five untreated active TGFβ1-transfected clones relative to the other transfectants. In contrast, treatment with 40 pM exogenous TGFβ1 induced MMP-9 mRNA expression in a time-dependent fashion, from twofold to fourfold after 4 h to a maximum of 12-to 19-fold after 24-48 h. Induction of MMP-9 mRNA was dose dependent at TGFβ1 concentrations of 4-400 pM. Thus, stable transfection of bioactive TGFβ1 downregulated whereas exogenous TGFβ1 treatment upregulated MMP-9 activity and expression. Treatment of transfectants with a neutralizing TGFβ1 antibody slightly downregulated constitutive MMP-9 mRNA (20-30%) but completely blocked induction by exogenous TGFβ1. Thus, the effect of TGFβ1 transfection was not due to secreted TGFβ1 but may have been a secondary effect.