Abstract 1214: TIMP-1 and the TIMP-1 interacting cell surface protein CD63 in cultured astrocytoma derived spheroids: expression and co-expression with stem cell markers

In previous studies we have shown that the immunohistochemical expression of TIMP-1 (tissue inhibitor of metalloproteinases-1) and CD63 increases with tumor grade in astrocytomas grade II-IV. Moreover, we demonstrated that a high TIMP-1 protein expression in glioblastomas was associated with a shorter overall patient survival. Recent studies have suggested that TIMP-1 can prevent chemo-induced apoptosis and in a study, using human breast epithelial cells (MCF10A), it was demonstrated that the interaction of TIMP-1 and CD63 is necessary for the TIMP-1 anti-apoptotic pathway. The aim of the present study was to investigate the expression of TIMP-1 and CD63 in cultured organotypic multicellular spheroids (OMS) and cell line spheroids (CLS) derived from astrocytomas in order to assess spheroid models for future studies involving TIMP-1, CD63 and chemo-resistance. By investigating the spheroids immunohistochemically, we wanted to elucidate if TIMP-1 and CD63 are co-expressed within the spheroids and whether they are expressed by tumor stem like-cells, since these cells are known to be more resistant to chemotherapeutic treatment. In the present study OMS from nine astrocytomas and CLS from three commercial astrocytoma cell lines were included as well as the glioblastoma tumor stem cell line SJ-1 made in our laboratory. In general high levels of CD63 protein was detected in all the original tumors, whereas TIMP-1 was moderately expressed. TIMP-1 and CD63 expression in OMS was similar to the expression in the original tumors. TIMP-1 was expressed at low to moderate levels in CLS, whereas CD63 was expressed by all tumor cells in all spheroids. TIMP-1/CD63 double immunofluorescence staining was performed on selected OMS and CLS showing tumor cells expressing both proteins. Furthermore, double staining was performed with TIMP-1 and the stem cell markers CD133, nestin and Sox2 demonstrating that a population of the tumor stem like-cells expressed TIMP-1. In conclusion, this study shows that spheroid models can be used in future studies investigating the role of TIMP-1 and CD63 in chemo-induced apoptosis. Furthermore, these results indicate that a fraction of the tumor stem like-cells could be protected by TIMP-1/CD63 interaction. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1214.