Hypoxia-inducible factor 1alpha/vascular endothelial growth factor axis in astrocytomas. Associations with microvessel morphometry, proliferation and prognosis.

Hypoxia-inducible factor (HIF)-1alpha is a transcription factor that promotes ischaemia-driven angiogenesis. The aim of this study was to determine the relation of HIF-1alpha to vascular endothelial growth factor (VEGF; an important angiogenic molecule in brain tumours), p53 expression, angiogenesis, proliferative potential and clinical outcome in a large series of diffuse astrocytomas. Expression of HIF-1alpha, VEGF, Ki-67 (a proliferation-associated marker) and p53 was determined immunohistochemically in 83 adult patients with supratentorial diffuse astrocytomas. Microvessels, highlighted by means of anti-CD34 immunohistochemistry, were enumerated with computer-assisted image analysis. Although HIF-1alpha and VEGF were expressed in the majority of cases, their levels increased significantly with increasing grade and proliferative potential. HIF-1alpha positively correlated with microvessel counts and VEGF with total vascular area and the presence of rounder vessel sections. There was a positive correlation of VEGF with p53 expression in astrocytomas and anaplastic astrocytomas. In univariate analysis, both VEGF and HIF-1alpha were associated with shortened survival in the entire cohort, but lost significance when grades II/III and grade IV were analysed separately. Multivariate analysis revealed that the combination of HIF-1alpha with grade was a significant prognostic indicator. HIF-1alpha expression may be used to refine the prognostic information provided by grade in patients with diffuse astrocytomas. Its adverse prognostic effect is most likely mediated by hypoxia, the driving force for HIF-1alpha accumulation.

Prognostic implications of microvessel morphometry in diffuse astrocytic neoplasms.

Astrocytic brain tumours, particularly malignant astrocytomas, are recognized to be highly vascular neoplasms with potent angiogenic activity. Recent research has shown that quantification of microvessel density (MVD), as a measure of the degree of angiogenesis, constitutes a strong prognostic indicator in patients with astrocytomas. However, the significance of other morphometric aspects of microvessel network has not been tested so far. In this report, histological sections from 70 astrocytomas (grades II to IV), immunostained for CD34, were evaluated by image analysis for the quantification of MVD, total vascular area (TVA), and microvascular branching, as well as several morphometric parameters related to vessel size or shape. Minor axis length increased with grade (P = 0.045) but MVD and TVA presented a peak in grade III (P = 0.033 and P < 0.001, respectively). Size and shape related parameters affected survival in univariate analysis of grade IV and grades II/III, respectively. In multivariate analysis, only branching counts, along with age and grade, were the independent predictors of survival. Although MVD, TVA and branching counts were adversely related to disease-free survival in grades II and III (univariate analysis), only TVA remained statistically significant in multivariate analysis. It is concluded that TVA and branching counts are prognostically more informative than MVD for patients with diffuse astrocytic tumours.

Mitosin and DNA topoisomerase IIalpha: two novel proliferation markers in the prognostication of diffuse astrocytoma patient survival.

The expression of two novel proliferation-associated markers, mitosin and topoisomerase IIalpha (Topo IIalpha), was evaluated immunohistochemically in consecutive paraffin sections from 60 diffuse astrocytomas (grades 2 to 4) in relation to clinicopathologic parameters, proliferating cell nuclear antigen (PCNA) and Ki-67 (MIB-1) expression and survival. The percentage of mitosin and Topo IIalpha-positive cells (LI) increased with grade and Ki-67 LI, but could not discriminate between grade 3 on the one hand and grades 2 or 4 on the other hand. In 51% of cases, Ki-67 LI exceeded Topo IIalpha LI, especially within grade 4. Topo IIalpha and mitosin expression was adversely related to overall and disease-free survival in the entire cohort and in grades 2/3. However, only Topo IIalpha LI affected disease-free survival in grade 4 tumors. Multivariate analysis selected only mitosin LI along with the age of the patient, as the independent parameters predicting overall survival, whereas Topo IIalpha emerged as the single independent predictor of disease-free survival. It is concluded that the proliferative potential of astrocytomas, as measured by mitosin and Topo IIalpha immunostaining, conveys useful prognostic information, in addition to that obtained by standard clinicopathologic parameters.