The effects of Wnt inhibition on tumor progression and the tumor microenvironment in a syngeneic mouse model of ovarian cancer

e17078 Background: Alterations in the Wnt/β-catenin pathway have been associated with tumor progression in multiple cancers. Gene expression profiling in ovarian cancer has correlated Wnt upregulation to patterns of immune evasion in the tumor microenvironment (TME). We investigated effects of in vitro Wnt inhibition in a murine ovarian cancer cell line with p53 knocked out as a model to mimic human ovarian carcinoma. Methods: We used a small molecule inhibitor, CGX-1321, in C57Bl6 mice, an immunocompetent mouse model, injected intraperitoneally with either ID8 cells, a murine ovarian cancer cell line, or ID8-p53-/- cells. Mouse omentums were collected and weighed for evaluation of tumor growth. Representative histology slides were stained for H&E. Western blots for β-catenin baseline levels were performed on the cell lines. TopFlash Assays with WNT3A stimulation were used for analysis of cell line nuclear β-catenin levels. Flow cytometry was performed on mouse omentums for TME evaluation. Results: Treatment with CGX-1321 decreased tumor size via omentum weight with both cell lines, p = 0.0098 with ID8 cells and p = 0.0855 with ID8-p53-/- cells. H&E slides revealed a decreased tumor progression. Western blots confirmed a difference in baseline β-catenin levels between these two cell lines. However, TopFlash assays showed a response to stimulation. Changes in the TME between treated samples with ID8-p53-/- cells did now show significant differences via flow cytometry. Conclusions: In the syngeneic mouse model with a murine ovarian cancer cell line, with p53 knocked out, tumor size and proliferation were decreased with treatment with Wnt inhibition. Surprisingly, the TME changes were inconclusive via flow cytometry. Perhaps these cells do not rely upon the Wnt/ β-catenin pathway as heavily, as seen in changes to baseline β-catenin levels, or perhaps tumors progress quicker and the critical time point of TME change is being overlooked. More investigation needs to be performed to further elucidate these differences.