Oedema extension in cerebral metastasis and correlation with the expression of nitric oxide synthase isozymes (NOS I-III)

Background: The development of a peritumoral oedema is a common radiologica l sign in preoperative CT- and MRI scans of patients with cerebral metastas is. Large tumours can be accompanied by a marginally extended oedema and vi ce versa. Several cytokines (VEGF) have been identified as mediators of vas cular induction and permeability. Transmitters such as nitric oxide (NO) ha ve been identified as specific mediator of vascular dilation and tumour blo od flow in primary brain tumours in which different NOS isozymes (NOS I and III) are induced as a result of the latent hypoxic metabolic scenery Other authors have considered NO as an endothelial stabilising metabolite. Induc ible NOS II is expressed by microglia and macrophages invading during tumou r growth. At present, no data exist on NO synthesising enzymes in cerebral metastasis. Materials and Patients: Cryosections (N = 96) of metastatic res ections were investigated immunohistologically using a 4-step grading evalu ation for the expression of NOS I-III VEGF-receptor FLT-1, a pan-macrophage marker Ki-M1P, and capillary vessel presence by endothelial Ki-Willebrand- Factor staining. The tumour and oedema extension was measured in pre MRI sc ans by an image processing device (Kontron(R)) and calculated for the ratio s of oedema volumes to total tumour volumes. The data were analysed statist ically (Pearson Chi(2) and Kruskal-Wallis analysis of variances) and correl ated with the clinical data. Inducible NOS II was further investigated by i n situ hybridization with a (4x30 mer) DNA oligoprobe cocktail Results: Bet ween 1987 and 1996 289 patients in our department suffered from a metastati c disease in the brain or spinal cord In 96 cases resected tumour material was processed for the immunohistological investigation. The age distributio n ranged from 14 to 85 years with a median age of 58 years. The mean durati on of symptoms before diagnosis was estimated as 53 days. The expression of NO synthase was frequently observed NOS I was detected in 83.6%, gradings 2 and 3 in 40.5% of them. NOS III, the endothelial isoform, was observed in 39.4% (gradings 2 and 3), inducible NOS II in 29.4% (grading 2 and 3) of t he specimens. The VEGF receptor FLT-I could be detected in 70% of them, 24% in higher expression 2 and 3. The pan macrophage marker Ki-MIP was observe d in 72% of all cases. Fifty seven percent of the specimens exhibited stron g labelling with antibodies against VWF. Coexpressions were statistically s ignificant for the VEGF receptor and NOS I-III (p < 0.01), Ki-M1P and NOS I and II (p < 0.05). A negative correlation was detected for the oedema inde x (oedema volume/total volume) and the labelling data for NOS III (r =- 0.4 4, p = 0.13) and VEGF-R (r = -0.42, p = 0.022). No correlation existed for Ki-MIP, VWF and NOS I. Conclusions: The objective of the study was to inves tigate oedema morphometry, expression of NOS I-III and VEGF-R, presence of capillary vessels and macrophages in cerebral metastasis. A further aim was to investigate a putative oedema induction by NO producing isozymes. Nitri c oxide synthase expression was statistically significantly correlated with the expression of the VEGF receptor and the presence of macrophages and mi croglia. There was a negative correlation between oedema extension and the presence of NOS III and VEGF-R. The results seem to indicate a specific oed ema modulating role of NO in cerebral metastasis.