Elastase expression by infiltrating neutrophils in gliomas

Polymorphonuclear neutrophil elastase is a neutral protease released by activated polymorphonuclear neutrophils and plays a crucial role in maintaining host defense. However, under certain conditions, this enzyme damages normal tissue and facilitates infiltration of tumor cells. In this study, surgical specimens were obtained from the tumor core and infiltrating margin of the glioma of 12 patients with astrocytoma of varying degrees of malignancy, and the specimens were tested for the presence of elastase by immunohistochemical analysis. Polymorphonuclear neutrophil elastase was not present in the tumor core of any of the 12 cases. Elastase was expressed in areas of tumor infiltration of the brain in all four glioblastoma cases, three of the four anaplastic astrocytoma cases, and none of the four low-grade astrocytoma cases. There was a higher percentage of elastase-positive polymorphonuclear neutrophils in the infiltrating margin of tumors with greater degree of malignancy. Polymorphonuclear neutrophils are recruited to malignant gliomas, and the elastase released by these cells aids in the infiltration of gliomas.