Structural and functional alterations associated with transformation in rat ovarian cell model systems

Abstract

In vitro cell model systems derived from rat granuloma cells were developed for the study of multistep ovarian carcinogenesis. Spontaneously immortalized rat granuloma cells (SIGC) were transfected with either the pSV3neo plasmid which contains the SV40 early region genes (SV-SIGC) or the plasmid containing the Her-21neu oncogene (neu-SIGC). Additionally, SIGC were continuously passaged in culture. The three cell model systems were evaluated according to structural and functional alterations associated with the transformed phenotype. SV-SIGC cells were injected into nude mice and the resulting tumors were expanded into an additional cell line (T-SVSIGC). Utilizing indirect immunofluorescence and monoclonal antibodies, the expression of desmosomes and associated cytokeratins in SV-SIGC was lower when compared to SIGC, but T-SV-SIGC showed the most dramatic decrease compared to SIGC. SIGC subject to low calcium medium showed a dramatic reduction of desmoglein staining at cell-cell borders, as well as, single cell migration in the wound healing assay. Additionally, gap junctional intercellular communication (GJIC) was reduced in a step-wise fashion in the SIGC-> SV-SIGC-> T-SV-SIGC system. SIGC transfected with the neu oncogene were anchorage-independent, as shown by soft agar assay. The cytokeratin pattern density was diminished in the neu-SIGC and also showed decreased desmosome expression when compared to SIGC. GJIC was also significantly reduced in the neu-SIGC when compared to the parental line SIGC. GSH was elevated in neu-SIGC compared to SIGC. Late passage SIGC readily formed clones in soft agar and showed a decrease in desmosomal and cytokeratin associated protein organization. They also exhibited a decrease in the rate of GJIC and an increase in glutathione levels compared to low passage (23) SIGC.