Fibronectin expression and organization in mesothelial and mesothelioma cells. Ferriola, Patrice C., and Wendy Stewart. Chemical Industry Institute of Toxicology Research Triangle Park, NC 27709
APStracts 3:0126L, 1996.
Mesothelial cells are believed to be the progenitor cells for malignant mesothelioma, a tumor associated with exposure to asbestos and other mineral fibers. Little is known regarding fibronectin (Fn) function in mesothelial and mesothelioma cells. Fn RNA, protein levels and localization were assessed in secondary cultures and later passages of spontaneously immortalized rat pleural mesothelial (NRM) cells as well as in neoplastic cell lines derived from asbestos -induced mesotheliomas. NRM cells expressed similar levels of Fn RNA regardless of passage number or cell density as determined by northern blotting and RNAse protection assays. Western blotting showed that Fn protein was both secreted by NRM cells and associated with cell lysates. Immunofluorescent confocal laser scanning microscopy demonstrated that secondary cultures of NRM cells assembled Fn into abundant, homogeneous fibrillar arrays organized primarily between cells, while later passages of NRM cells displayed abundant, but less homogeneous Fn organization. Fn RNA and protein levels in neoplastic mesothelial cells were slightly less or similar to levels in NRM cells. Organization of Fn in neoplastic cells was heterogeneous compared to secondary cultures of NRM cells, but Fn fibril formation was still apparent. F-actin microfilaments were organized in both NRM and neoplastic cells, however, actin stress fibers were maintained in neoplastic cells, while NRM cells displayed dense actin peripheral bands at high density . The maintenance of organized Fn and actin in mesothelioma cells is surprising, and may contribute to the localized growth and invasive properties of these tumors. 

Received 29 April 1996; accepted in final form 8 July 1996.
APS Manuscript Number L129-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 August 1996