The membrane external proteins of human astrocytomas in culture

The cell surface proteins of some human astrocytomas have been investigated. Cell cultures were initiated from the tumours and surface proteins labelled with radioiodine in monolayer cultures. Normal glial and astrocytoma cells were found to possess a common surface protein pattern. In the molecular weight (MW) range of 225,000-75,000 daltons, the protein profile contained 6 well-defined peaks. The 195,000-dalton component (pb) was found liable to resolve into pb and a forerunning component pb'. Component pd (130,000 daltons) similarly showed resolution into subcomponents in 5 out of 9 tumours. The remaining components appeared more homogeneous in electrophoresis. There were also significant quantitative changes in the expression of the various components of the astrocytomas as compared with the normal glial cell line. Component pa was found to be reduced by greater than 70% in 7 out of 9 astrocytomas. The levels of 225,000-dalton proteins were found to be directly proportional to the survival times of the patients. Components pc appeared to be amplified by a factor of 1.6-3.5 in all the astrocytomas as compared with the normal glial line. Increased incorporation of radioiodine was also seen in 7 out of 9 tumours in components with MW of less than 75,000 daltons. The possible significance of the differential expression of the surface components is discussed. It is suggested that some of these changes, especially in component pa, may be associated with the malignant state.