Differential expression of beta 1, beta 3, and beta 4 integrin subunits in nonneoplastic neural cells of the peripheral and autonomic nervous system and in tumors derived from these cells

Abstract

Background: Extracellular matrix proteins and their receptors take part in physiologic neural development and organization and also in abnormal neoplastic growth and spread. There is increasing evidence for the implication of integrins in these processes.

Experimental design: Human tissues containing nonneoplastic neural cells of the peripheral and autonomic nervous system and a comprehensive series of neural tumors were examined for the in situ expression of beta 1, beta 3, and beta 4 integrins. Serial frozen sections of each tissue sample were immunostained using an indirect streptavidin/biotin-peroxidase method and monoclonal antibodies against beta 1, alpha 1 to alpha 6, beta 3, alpha v, and beta 4 subunits.

Results: Both small- and large-diameter nerve fibers of normal peripheral nerve trunks were consistently beta 1+, alpha 6+, and beta 4+ in the absence of alpha 3, alpha 4, alpha 5, and beta 3. Small-diameter nerve fibers further expressed alpha 1, alpha 2, and alpha v. Meissner's corpuscles and inner cores of Pacinian corpuscles shared the integrin repertoire of small-diameter nerve fibers with additional expression of alpha 3; outer cores of Pacinian corpuscles were beta 1+, alpha 3+, alpha 6+, and beta 4+. Regenerating nerve fibers paralleled the integrin profile of normal peripheral nerves. By contrast, malignant schwannomas showed considerable changes in integrin expression. These alterations consisted mainly in a neoexpression of alpha 3, alpha 4, and alpha 5 and in an abnormal loss of alpha 6 and beta 4. Expression of alpha 1, alpha 2, and alpha v was variable; absence of beta 3 was generally conserved. In ganglion cells, integrin expression was restricted to beta 1 and alpha 3 subunits, and chromaffine cells of the adrenal medulla even lacked any detectable beta 1, beta 3, and beta 4 integrin subunits. (Ganglio)-neuroblastomas, however, were beta 1+, alpha 1+, and alpha 3+, whereas primitive peripheral neuroectodermal tumors were beta 1+ and alpha 5+.

Conclusions: Nonneoplastic human neural cells exhibit a complex and, at the same time, differential pattern of beta 1, beta 3, and beta 4 integrin subunit expression. Malignant transformation leads to considerable changes in this integrin profile. The observation of neoplasia-associated abnormalities underlines the important role of integrins in the orderly development and maintenance of human neural tissue. Some aspects of the emerging integrin subunit patterns are useful for the differential diagnosis of neural soft-tissue tumors.