General protease and collagenase (IV) activity in C6 astrocytoma cells, C6 spheroids and implanted C6 spheroids

Abstract

Tumor growth is dependent on the ability of neoplastic cells to induce angiogenesis. Remodelling of blood vessels requires reconstruction of the collagen (type IV) and non-fibrous protein components of basement membrane. This study assessed the general protease and collagenase (IV) activities of C6 astrocytoma cells in monolayer and spheroid culture and C6 astrocytoma spheroids growing in vivo. Extracellular release of non-specific proteases and collagenase IV was maximal during early exponential cell growth. Increased spheroid size resulted in enhanced extracellular activity of both enzyme groups assessed. The size of the implanted spheroid influenced the activity measured in vivo. General proteolytic activity was significantly greater in tumor tissue at all spheroid sizes while only the implantation of 750 microns spheroids resulted in significantly increased collagenase type IV activity. The growth of C6 astrocytoma cells in monolayer and spheroid culture in vitro and in vivo is associated with distinct alterations in intracellular and extracellular activity of the proteolytic enzymes assessed. Increased extracellular release of these enzymes may play important roles in tumor-associated angiogenesis, tumor invasiveness, tumor induced hemorrhage and tumor-associated edema.

Expression of 72 kDa type IV collagenase and invasion activity of human glioma cells

“…Glioma cells have high levels of PAs [29,30] and also of metalloproteinases including type IV collagenase [18,31]. The invasive behavior of gliomas has been studied using various glioma invasion models [12].…”

“…The potential biological significance of PAs in brain tumors has been suggested by others [14][15][16]. Furthermore, type IV collagenase and TIMP-2 are actively expressed in human gliomas [17,18]. In this study, we have asked whether the production of collagenases or PAs is closely correlated with the invasive activity of human glioma cells in culture.…”

Association of increased phosphatidylinositol 3-kinase signaling with increased invasiveness and gelatinase activity in malignant gliomas

“…Increased MMP levels and activity are commonly encountered in GBMs when these tumors are assessed using gel zymography or enzyme-linked immunosorbent type assays. 2,16,41,44,45,57,59 In previous immunohistochemical studies, however, conflicting results were reported in both the presence 45 and absence 41,46 of MMP-2 and MMP-9 in paraffin-embedded clinical specimens. In our study, wherein freshly prepared frozen sections were examined, we found a heterogeneous expression of both MMP-2 and MMP-9.…”

Regulation of angiogenesis by hypoxic stress: from solid tumours to the ovarian follicle

“…As a model of avascular growth saturation, the spheroid provides an interesting system for following the role of metabolic stress in inducing angiogenesis and measuring the impact of angiogenesis on tumour growth. The implanted spheroid model has been employed for following tumour angiogenesis in vivo (Farrell et al 1987;Coomber et al 1988;Vaithilingam et al 1991;Zwi et al 1994;Abramovitch et al 1995;Torres et al 1995) as well as antiangiogenic therapy . When implanted subcutaneously in nude mice, C6 glioma spheroids induce, within about 4 days, growth of vessels that approach the spheroid radially.…”