Human brain tumor cyst fluid is mitogenic for primary astrocytes in culture

Tumor cyst fluid from five patients with malignant glial neoplasms was assayed for mitogenic activity by measuring [3H]thymidine uptake by rat astrocyte cultures in serum-free defined media. Cyst fluid from all patients stimulated [3H]thymidine uptake three- to fourfold in astrocyte cultures in comparison with untreated controls. Mitogenic activity was found to be soluble and resistant to freezing, but inactivated by heat and trypsin. The activity was retained by ultrafiltration through a 100-kd molecular weight filter. It appears from these results that mitogenic factor(s) for nonneoplastic astrocytes are present in human brain tumor cyst fluid and that such factors appear to be protein in nature and associated with a complex of molecular weight greater than 100,000.