Preclinical Testing of PI3K/AKT/mTOR Signaling Inhibitors in a Mouse Model of Ovarian Endometrioid Adenocarcinoma

Genetically engineered mouse (GEM) models of ovarian cancer that closely recapitulate their human tumor counterparts may be invaluable tools for preclinical testing of novel therapeutics. We studied murine ovarian endometrioid adenocarcinomas (OEA) arising from conditional dysregulation of canonical WNT and PI3K/AKT/mTOR pathway signaling to investigate their response to conventional chemotherapeutic drugs and mTOR or AKT inhibitors. OEAs were induced by injection of adenovirus expressing Cre recombinase (AdCre) into the ovarian bursae of Apc(flox/flox); Pten(flox/flox) mice. Tumor-bearing mice or murine OEA-derived cell lines were treated with cisplatin and paclitaxel, mTOR inhibitor rapamycin, or AKT inhibitors API-2 or perifosine. Treatment effects were monitored in vivo by tumor volume and bioluminescence imaging, in vitro by WST-1 proliferation assays, and in OEA tissues and cells by immunoblotting and immunostaining for levels and phosphorylation status of PI3K/AKT/mTOR signaling pathway components. Murine OEAs developed within 3 weeks of AdCre injection and were not preceded by endometriosis. OEAs responded to cisplatin + paclitaxel, rapamycin, and AKT inhibitors in vivo. In vitro studies showed that response to mTOR and AKT inhibitors, but not conventional cytotoxic drugs, was dependent on the status of PI3K/AKT/mTOR signaling. AKT inhibition in APC(-)/Pten(-) tumor cells resulted in compensatory upregulation of ERK signaling. The studies show the utility of this GEM model of ovarian cancer for preclinical testing of novel PI3K/AKT/mTOR signaling inhibitors and provide evidence for compensatory signaling, suggesting that multiple rather than single agent targeted therapy will be more efficacious for treating ovarian cancers with activated PI3K/AKT/mTOR signaling.