Abstract 4081: Lung metastasis of ovarian cancer in a transplantable MUC1.Tg mouse model is accompanied by upregulation of MUC1 expression and epithelial to mesenchymal transition
Authors: Zhang Lixin , Ma Tianzhou , Brozick Joan , Babalola Kathlene , Budiu Raluca , Tseng George , Vlad Anda 
Published: August 2015

Introduction: Patients with ovarian cancer are usually diagnosed late, when tumors have already spread to the surrounding tissues. Hematogenous dissemination of ovarian cancer cells can also occur and lung metastasis can be found in 12% of ovarian cancer patients. Human mucin1 (MUC1) is a large transmembrane glycoprotein with roles in cell adhesion and migration. More than 80% of ovarian cancer overexpress MUC1, regardless of histology. MUC1 is a widely used vaccine target for numerous adenocarcinomas, including ovarian tumors.

Approach and results: We have recently described the triple transgenic (Tg) mice with conditional (cre-loxP) mutations in Kras and Pten pathways that progress to human MUC1-expressing endometrioid ovarian tumors. Using orthotopic tumors from these mice we generated here several new murine cell lines. The MKP-L cell line was derived from an ovarian tumor implant attached to the liver surface. Intraperitoneal (IP) injection of MKP-L cells into syngeneic mice triggers IP tumors and multiple lung metastatic masses. Cells isolated from lung metastases (MKP-Lung cell line) triggered peritoneal tumors as well as lung metastases, suggesting that they retain the original homing capacity. Compared to the parental, endometrioid-looking and low-MUC1 expressing MKP-L cells, the metastatic MKP-Lung cells showed morphological changes consistent to epithelial-to-mesenchymal transition (EMT) and are homogeneously high in MUC1. Mouse WG6 microarray analysis of MKP-L and MKP-Lung cells revealed expression changes of several EMT-associated transcription factors as well as their downstream proteins. Western blot confirmed upregulation of ZEB1, vimentin and downregulation of cytokeratins. To dissect the mechanistic roles of Kras and Pten pathways in EMT and MUC1 regulation, we also generated a series of ovarian surface epithelial (OSE)-derived cell lines with conditional (Cre-loxP) oncogenic mutations in Kras (MKOSE), deletion in Pten (MPOSE) or both (MKPOSE). Using these cell lines we recapitulated in vitro the EMT phenotype and MUC1 upregulation acquired by MKP-Lung cells in vivo. Furthermore, small molecule inhibitors of oncogenic Kras (AZD6244) and Pi3K/Pten pathway (BEZ235) demonstrated that MUC1 expression is significantly upregulated in response to Pten deletion and that Pi3K inhibitor (BEZ235) downregulated MUC1. In contrast, Kras activation slightly lowered MUC1 expression while cell exposure to AZD6244 upregulated MUC1.

Conclusions: We report here the first transgenic mouse metastatic ovarian cancer model that expresses human MUC1.Usig this model we identified a gene signature consistent with lung metastasis and EMT and identified mechanisms of MUC1 upregulation during these processes. These findings have important consequences for MUC1 immunobiology in metastatic ovarian tumors with mutations in Kras, Pten/Pi3K or both.

Citation Format: Lixin Zhang, Tianzhou Ma, Joan Brozick, Kathlene Babalola, Raluca Budiu, George Tseng, Anda Vlad. Lung metastasis of ovarian cancer in a transplantable MUC1.Tg mouse model is accompanied by upregulation of MUC1 expression and epithelial to mesenchymal transition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4081. doi:10.1158/1538-7445.AM2015-4081