In vivo survivors of transformed mouse ovarian surface epithelial cells display diverse phenotypes for gene expression and tumorigenicity

Ovarian cancer is the fifth most common cause of cancer death in women. Due to a lack of appropriate animal models, studies involving tumorigenicity, tumor progression and immune response at the molecular level are limited. We isolated many clones derived from thesurvivors of a transformed mouse ovarian epithelial cell line IG-10 in immune- competent mice and found that the clones displayed diverse phenotypes. Most clones were deficient in components of the MHC-I antigen presentation pathway. Soft-agarose colony assays showed different growth rates among clones. However, this did not completely correlate with each clone's in vivo tumorigenicity regarding growth, tumor mass and ascites formation, suggesting the possibility that the clones may display contrasting intrinsic gene expression. We therefore performed two types of arrays to evaluate gene expression at transcriptional and translational levels. The results showed differences in expression of COL4α5, NOS-2, and SOCS-1 genes at the transcriptional level, MIP-2 gene at the protein level and CCL5, CXCL-10, IL-1α genes at both transcriptional and protein levels between low and high tumorigenic clones. Thus, our animal cell model together with the identified genes may provide a useful tool to study ovarian cancer immune response, tumorigenicity and tumor-host cell interactions in the tumor microenvironment.