EXPRESSION OF TIMP-1, TIMP-2, 72-KDA AND 92-KDA TYPE-IV COLLAGENASE TRANSCRIPTS IN HUMAN ASTROCYTOMA CELL-LINES - CORRELATION WITH ASTROCYTOMA CELL INVASIVENESS

Abstract

Malignant astrocytomas are highly invasive neoplasms which infiltrate diffusely into regions of normal brain. As evidence to support one mechanism by which tumor cells are known to invade, we have previously shown that astrocytoma cell lines secrete a variety of matrix metalloproteinases (MMPs) and metalloproteinase inhibitors (Apodaca et al: Cancer Res 50: 2322-2329, 1990). In the present study we determined the expression of tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, 72-kDa and 92-kDa type IV collagenase transcripts among human astrocytoma cell lines. In addition, we sought to correlate MMP and TIMP transcript levels with astrocytoma invasiveness. RNA from seven well characterized human astrocytoma cell lines was extracted before and after phorbol ester treatment and Northern blot analyses were performed using cDNA probes for the MMPs and TIMPs. All astrocytoma cell lines and normal human leptomeningeal cells were tested for their relative invasive potential using an in vitro invasion assay. There was variable expression of MMP and TIMP transcripts among astrocytoma cell lines. SF-188 was the only cell line to demonstrate a relative abundance of 72- and 92-kDa type IV collagenase transcripts over TIMP-1 and TIMP-2 transcript levels. Interestingly, this cell line was the most highly invasive in the in vitro invasion assay system. U 343 MG-A demonstrated relative abundance of TIMP-1 and -2 transcripts over 72- and 92-kDa type IV collagenase transcripts and was the least invasive cell line. Prior treatment of astrocytoma cell lines with phorbol ester upregulated TIMP-1 and 92-kDa type IV collagenase transcripts, but not TIMP-2 and 72-kDa type IV collagenase transcripts. We conclude that there is only partial correlation between MMP and TIMP transcript levels and in vitro cell invasiveness among the astrocytoma cell lines studied. Our analysis has led to the identification of an astrocytoma cell line, SF-188, which appears to overexpress the 72-kDa and 92-kDa type IV collagenase transcripts relative to low level TIMP-1 and TIMP-2 transcripts. This particular cell line will continue to be of considerable value in dissecting some of the molecular mechanisms involved in astrocytoma cell invasion.