Enzyme immunoassay of glioma cell tenascin secretion and augmentation by tumor necrosis factor-α

Abstract

Expression of tenascin, an extracellular matrix glycoprotein, was measured in glioma cell lines using a newly established enzyme immunoassay. Secreted tenascin was found at concentrations greater than 800 ng/ml in eight of 14 glioma, three small cell lung carcinoma, two melanoma, and one sarcoma cell lines. The remaining six glioma and other carcinoma cell lines, and cell lines originating from normal tissues demonstrated low levels or no secretion into the supernatant. The glioma cell line, U-251-MG nu/nu, which had almost 100% transplantability in nude mice, had the highest expression level of tenascin among the glioma cell lines examined. Even low secretor glioma cell lines released high concentrations of tenascin, detectable by assaying the NP-40 solubilized cell lysates. Flow cytometric analysis revealed that tenascin was located on both the cell surface and primarily in the cytoplasm of glioma cells. When the glioma cell lines were exposed to tumor necrosis factor-α (TNF-α), levels of secreted tenascin increased between 36% and 380%, whereas transforming growth factor-β induced only minimal changes. These results suggest that glioma cell lines may be classified according to the degree of tenascin secretion/expression: high secretor type, low secretor type, and non-expressing type. The increase in tenascin secretion by TNF-α suggests that the expression of tenascin in glioma growth and development may be mediated through a cytokine network.