TRANSFECTION OF AN INVASIVE HUMAN ASTROCYTOMA CELL-LINE WITH A TIMP-1CDNA - MODULATION OF ASTROCYTOMA INVASIVE POTENTIAL

Malignant astrocytomas are highly invasive tumors which infiltrate dif fusely into regions of normal brain. The degradation of the extracellu lar matrix (ECM) by matrix metalloproteinases is thought to be one of the most important steps in the process of tumor invasion. However, th e activity of most matrix metalloproteinases (MMPs) can be modulated b y simultaneously secreted inhibitors (tissue inhibitors of metalloprot einases, TIMPs). We have previously shown that an imbalance between th e levels of MMPs and TIMPs may be essential in the determination of th e invasiveness of certain human malignant astrocytoma cell lines. To d etermine if the up-regulation of TIMP genes and gene products could mo dulate the invasiveness of human malignant astrocytoma cells, in the p resent study we have transfected a highly invasive astrocytoma cell li ne, SF-188, with an expression vector carrying a full-length TIMP-1 cD NA. The parental SF-188 astrocytoma cell line overexpresses the 72-kDa and 92-kDa type IV collagenases with little expression of TIMPs-1 and -2. Following transfection with TIMP-1, SF-188 astrocytoma clones exp ressed the 0.9 kb TIMP-1 message by northern analysis, and produced a 21 kDa metalloproteinase inhibitor by reverse zymography. The stable T IMP-1 SF-188 transformants demonstrated morphological changes and dimi nished growth rates in soft agar when compared to controls. The invasi on of successfully TIMP-1 transfected astrocytoma cells across matrige l-coated filters was significantly decreased over controls. These resu lts suggest that upregulation of TIMP-1 expression in SF-188 astrocyto ma cells has decreased their in vitro invasive potential.