PROLACTIN RECEPTORS IN HUMAN MENINGIOMAS - CHARACTERIZATION AND BIOLOGICAL ROLE

Sixty cerebral meningioma specimens obtained at surgery from 34 female and 26 male patients were examined for the presence of prolactin (PRL ) receptors. These were compared with normal arachnoid tissue from whi ch these rumours arise. PRL receptors were detected in 61.7% of mening iomas whereas no PRL binding was found in samples of normal arachnoid tissue. No relationship was found when sex or histological findings we re compared with the presence of PRL receptors. Receptor-positive tumo urs had saturable and high-affinity (K-d, 48 +/- 0.5 ng/ml) receptors with hormonal specificity for human PRL, (hPRL) resembling that of oth er target tissues of PRL in man. The biological role of these receptor s was investigated in primary cell cultures derived from meningioma ti ssue characterized for PRL receptor. When human PRL was added to the c ulture medium, in doses ranging from 1 to 200 ng/ml, a dose-dependent stimulation of H-3-thymidine incorporation was observed only in PRL-re ceptor positive rumours. The PRL concentrations required to produce a half-maximal effect ranged from 11 to 20 ng/ml and were quite close to the dissociation constant (K-d) of binding of PRL to its receptors. P RL also caused an increase of cell number compared with control with a significant effect after 3 and 4 days of culture. In conclusion, thes e findings indicate that a large number of human meningiomas express s pecific and functional receptors for PRL which are involved in mediati ng its proliferative effects.