Morphologic Analysis Correlates with Gene Expression Changes in Cultured F344 Rat Mesothelial Cells

Abstract

The gene expression pattern of mesothelial cells in vitro was determined after 4 or 12 h exposure to the rat mesothelial, kidney, and thyroid carcinogen and oxidative stressor potassium bromate (KBrO3). Gene expression changes observed using cDNA arrays indicated oxidative stress, mitotic arrest, and apoptosis in treated immortalized rat peritoneal mesothelial cells. Increases occurred in oxidative stress responsive genes HO-1, QR, HSP70, GADD45, GADD153, p21WAF1/CIP16, GST′s, GAPDH, TPX, and GPX-10; transcriptional regulators c-jun, c-fos, jun B, c-myc, and IκB; protein repair components Rδ, RC10-II, C3, RC-7, HR6B ubiquitin-conjugating enzyme and ubiquitin; DNA repair components PCNA, msh2, and O-6 methylguanine DNA methyltransferase; lipid peroxide excision enzyme PLA2; and apoptogenic components TNFα, iNOS1 and FasL. Decreases occurred in bcl-2 (antiapoptotic), bax α, bad, and bok (proapoptotic) and cell cycle control elements (cyclins). Cyclin G and p14ink4b (which inhibit entry into cell cycle) were increased. Numerous signal transduction, cell membrane transport, membrane-associated receptor, and fatty acid biosynthesis and repair components were altered. Morphologic endpoints examined were number of mitotic figures, number of apoptotic cells, and antibody-specific localization of HO-1 (which demonstrated increased HO-1 protein expression). PCR analysis confirmed HO-1, p21waf1/cip1, HSP70, GPX1, GADD45, QR, mdr1, PGHS, and cyclin D1 changes. A model for KBrO3-induced carcinogenicity in the F344 rat mesothelium is proposed, whereby KBrO3 generates a redox signal that activates p53 and results in transcriptional activation of oxidative stress and repair genes, dysregulation of growth control, and imperfect DNA repair leading to carcinogenesis.