Characteristics and growth patterns of human peritoneal mesothelial cells: comparison between advanced epithelial ovarian cancer and non-ovarian cancer sources

Abstract

To compare the characteristics and growth patterns of human peritoneal mesothelial cells (HPMCs) from advanced epithelial ovarian cancer (EOC) patients with those from non-EOC patients. Peritoneal and omental biopsies were obtained from treatment-naïve patients. Formalin-fixed biopsies and cytologic touch preparations were studied immunochemically. HPMCs were isolated from tissue biopsies or malignant ascites and cultured with or without growth factors. Cell growth was determined by the MTT assay. Cultured HPMCs were further characterised by flow cytometry analysis (FACS). Peritoneal biopsies showed a continuous flat mesothelial cell layer in non-EOC patients, whereas in advanced EOC, the mesothelium was a discontinuous layer of rounded cells. In all peritoneal biopsies, the mesothelium expressed cytokeratin 8/18, vimentin, and the mesothelioma cell antigen but not E-cadherin. In touch preparations, expression of the putative fibroblast antigen ranged from negative to weakly positive. HPMC from non-EOC cases grew slowly in vitro except when exposed to L-cysteine (L-cys 30 micrograms/mL) during the initial 24 hours of culture. Conversely, cells from EOC sources grew more rapidly, especially when exposed to both epidermal growth factor (EGF 10 ng/mL) and hydrocortisone (HC 400 ng/mL). HPMC coexpressed cytokeratin 8/18 and vimentin in vitro, but the expression of the putative fibroblast antigen increased during primary culture, whereas that of the mesothelioma cell antigen decreased in successive passages. Furthermore, in FACS, cultured HPMC did not express CD14, CD16, or CD34. In peritoneal biopsies from non-EOC and EOC patients, HPMCs showed different morphology but similar immunostaining characteristics, whereas cultured cells from different sources were similar in both morphology and phenotype. L-cysteine enhanced the growth of non-EOC but not of EOC-derived HPMCs, which had a maximal response to EGF and HC. The growth advantage of HPMCs from EOC in vitro suggests these cells are in a primed or activated state.