Proliferation, bcl-2 expression and angiogenesis in pituitary adenomas: relationship to tumour behaviour

The prediction of pituitary tumour behaviour, in terms of response to treat ment from which can be derived optimal management strategies, is a challeng e that has been approached using several different means. Angiogenesis in o ther tumour types has been shown to be correlated with poor response to tre atment and tumour recurrence. The aim of this paper is to assess the role o f measurements of cell proliferation and angiogenesis in predicting pituita ry tumour behaviour. The proliferative capacity of the tumour was assessed using the Ki-67 labelling index (LI) while bcl-2 expression was used to ass ess anti-apoptotic pathways. The microvessel density (MVD) was assessed usi ng antibodies to CD31 and factor VIII-related antigen, and with biotinylate d ulex europaeus agglutinin I. There was no difference between Ki-67 LI and MVD of functionless tumours that recurred and those that did not, but bcl- 2 expression was significantly lower in tumours that subsequently regrew. M acroprolactinomas had significantly higher LI than microprolactinomas and t han all other tumours. Cell proliferation and angiogenesis were not related , showing that both processes are under different control mechanisms in pit uitary tumours. In contrast there was a positive relationship between marke rs of angiogenesis and bcl-2 expression in prolactinomas, GH-secreting tumo urs and non-recurrent functionless tumours with higher levels of bcl-2 expr ession being found in the more vascular tumours. These findings may suggest that angiogenesis is related to the ability of tumour cells to survive rat her than their proliferative activity. (C) 2000 Cancer Research Campaign.