Expression of focal adhesion kinase (p125 FAK) and proline-rich tyrosine kinase 2 (PYK2/CAKb) in cerebral metastases, correlation with VEGF-R-, ecNOSIII-labelling and morphometric data

Background: Cerebral metastasis occurs in about 20% of all neurosurgical pa tients. Cerebral metastases have a typical spherical morphology with a comm on central necrosis and perifocal oedema. It has been proposed that oedema extension, tumour volumes and infiltrative behaviour are partially mediated by vascular endothelial growth factor (VEGF) and nitric oxide (NO). In sev eral systemic tumour entities NO is suggested as a factor which influences the metastatic potential VEGF has recently been reported to influence the m atrix related migratory activity by interaction with focal adhesion kinase (p125FAK) and proline-rich tyrosine kinase beta (PYK2/CAK beta). Nitric oxi de, which is produced in metastases by three different NOS isozymes is capa ble of antagonizing the binding of FAK to matrix integrins. NO, VEGF; and F AK/PYK 2 are therefore considered to be important mediators of the cerebral metastatic incidence, growth, infiltration and oedema extension. The aim o f our present study was to investigate the expression of p125FAK and the co expression with PYK2/CAK beta, VEGF-receptor FLT-1, NOS isozymes NOS I-III, capillary density and the histology in 130 specimens of resected cerebral metastatic tumours. A further analysis was performed to morphometrically ev aluate tumour and oedema volumes and to correlate the immunohistochemical d ata. in a subgroup of 40 patients. Materials and methods: Cryosections (N = 130) of metastatic resections were investigated immunohistologically using a 4-step scoring evaluation for the expression of NOS I-III, VEGF-receptor FLT-1, and capillary vessel presence by endothelial Von-Willebrand-Factor (VWF) staining. Tumour and oedema extension was measured in preoperative MR I (N = 40) scans by an imageo processing device (Kontron(R)) and the ratios of oedema volumes to total tumour volumes were calculated The data were an alysed statistically (Spearman rank order con elation and Kruskal-Wallis AN OVA) and con-elated with the clinical data. Results: FAK immunoexpression w as observed in 50% of the specimens (31.2% gradings 2 and 3). We observed a significant coexpression (p = 0.0001) with PYK 2 labelling which occurred frequently in 74% of the specimens (42% gradings 2 and 3). The VEGF recepto r FLT-1 could be detected in 70% of them, 24% at higher expression values 2 and 3. The expression of NO synthase was frequently observed. NOS I was de tected in 83.6% of the specimens, values 2 and 3 in 40.5%. NOS III, the end othelial isoform, was observed in 39.4% of the specimens (gradings 2 and 3) and inducible NOS II in 29.4% (grading 2 and 3) of them. Coexpressions wer e statistically significant for FAK and NOS III (Spearman p = 0.008) and FA K and VEGF-R (p = 0.03). The morphometric evaluation resulted in tumour vol umes between 2.0 and 83 cm(3) (mean 22.5 +/- 19.2 SD) with oedema ratios be tween 0 and 100% (mean 62.2 +/- 22.5 SD). FAK expression correlated signifi cantly (p = 0.06) with tumour. volumes and histology. Conclusion: The frequ ent histotypic occurence of FAK and PYK2 in metastases could be an importan t factor in the modulation of metastatic capacity and infiltrative behaviou r and might influence the disease course. Judging from its frequent express ion PYK2 may generate the more relevant signals. A further aspect is the po ssible interaction with endothelial NOS III and VEGF receptor; which could be important for the infiltrative behaviour in a Intent hypoxic scenery and environment.