Overexpression of TIMP-1 and Sensitivity to Topoisomerase Inhibitors in Glioblastoma Cell Lines

The multifunctional protein - tissue inhibitor of metalloproteinases-1 (TIMP-1) - has been associated with a poor prognosis in several types of cancers including glioblastomas. In addition, TIMP-1 has been associated with decreased response to chemotherapy, and especially the efficacy of the family of topoisomerase (TOP) inhibitors has been related to TIMP-1. As a second line treatment of glioblastomas, the vascular endothelial growth factor (VEGF) antibody bevacizumab is administered in combination with the TOP1 inhibitor irinotecan and glioblastoma cell levels of TIMP-1 could therefore potentially influence the efficacy of such treatment. In the present study, we aimed to investigate whether a high TIMP-1 expression in glioblastoma cell lines would affect the sensitivity to TOP inhibitors, and whether TIMP-1 overexpressing cells would have alterered growth and invasion. We established TIMP-1 overexpressing subclones from two human glioblastoma cell lines. TIMP-1 overexpressing U87MG cells were significantly more resistant than low TIMP-1 expressing clones and parental cells when exposed to SN-38 (TOP1 inhibitor) or epirubicin (TOP2 inhibitor). No significant differences were observed for the TIMP-1 transfected A172 cells. Implantation of both U87MG and A172 spheroids into organotypic brain slice cultures revealed a reduced growth of TIMP-1 overexpressing U87MG spheroids, however, no significant differences in invasion were observed. The present study suggests that TIMP-1 overexpression reduces the effect of TOP inhibitors in glioblastoma. TIMP-1 also appeared to reduce spheroid growth, but did not influence invasion. Whether TIMP-1 plays a role in irinotecan resistance and has a predictive potential in glioblastoma patients remains to be elucidated.