Abstract B66: Novel ovarian cancer transplantable models generated from MUC1KrasPten tumors show different in vitro and in vivo biological behaviors
Authors: Zhang Lixin , Budiu Raluca , Brozick Joan , Vlad Anda 
Published: August 2014

Introduction: Sustained improvement in the development of new therapeutic approaches in ovarian cancer depends in part on the availability of adequate preclinical models for in vivo testing of treatment efficacy. We recently developed triple transgenic (MUC1KrasPten.Tg) mice expressing human MUC1 oncoprotein as self and carrying the conditional K-rasG12D oncoallele (loxP-Stop-loxP-K-rasG12D/+) and the floxed Pten gene (PtenloxP/loxP). The MUC1KrasPten.Tg mice develop MUC1-expressing endometrioid ovarian tumors that closely mirror the human disease and respond to human MUC1-based immune therapy. Compared to the KrasPten mice, tumors from MUC1KrasPten.Tg mice had a higher potential for loco-regional spread, suggesting active MUC1 involvement in local and distant tumor spread.

Approach: In order to study in vitro and in vivo MUC1 roles in tumor growth and metastasis and interactions between MUC1 signaling and Kras and Pten pathways, we generated several new murine ovarian cancer cell lines. These cell lines express human MUC1 as self, while simultaneously carrying constitutively active oncogenic Kras and defective Pten tumor suppressor. The originating cells were derived from either the MUC1KrasPten primary ovarian tumor or the liver implant via trypsinization into single cell suspension. Cells were cultured in vitro for at least 20 passages to generate the stable MKP-T (from primary tumor) and MKP-L (from liver metastasis) ovarian cancer cell lines. Clonal populations were obtained via limiting dilution assays.

Results: Although derived from the same host, the MKP-T and MKP-L cells showed different K-ras status reflective of tumor heterogeneity in vivo. Unlike the MKP-L cells, the MKP-T cells display loss of K-ras heterozygosity. MKP-T and MKP-L showed variable expression pattern of MUC1, EpCAM, folate receptor, ALDH, cytokeratin and vimentin, demonstrating how the anatomical location of each originating tumor influences the cell line's in vitro phenotype. Furthermore, although both cell lines can grow IP tumors in syngeneic triple transgenic MUC1KrasPten.Tg, single transgenic MUC1.Tg as well as wild-type C57BL/6J-bgJ mice, they carry distinct in vivo phenotypes. MKP-L cells grow slower in vitro (doubling time 27.5 hours) and in vivo and trigger distant metastases to the lungs. MKP-T cells multiply at higher rate in vitro (doubling time 13.2 hours) and in vivo and generate larger loco- regional tumors. Two sub-lines (MKP-T-2F8-Asc and MKP-L-Lng) derived from MKP-T ascites and MKP-L lung metastasis, respectively, by in vivo clonal selection, showed stable and high MUC1 expression, further demonstrating its in vivo roles for both loco-regional as well as distant spread. In line with their Kras status, MEK 1/2 inhibitor AZD6244 (currently tested in several Phase II clinical trials) showed more inhibition on MKP-T cells than on MKP-L cells in vitro, providing support for its use in this preclinical models.

Conclusions: We have generated several novel murine cancer cell lines and characterized the first immune competent transplantable ovarian cancer model expressing human MUC1 as a transgene. The cell lines show various levels of MUC1 and display different metastatic behaviors in vitro and in vivo. MKP-L cells metastasize to the lungs and represent the first in vivo model for distant metastasis in ovarian cancer. Our novel preclinical models are uniquely suited for in vivo combination therapies targeting MUC1, Kras and Pten/PI3K pathways and provide new tools for elucidating the biological behaviors of ovarian cancer cells both in vitro and in vivo.

Citation Format: Lixin Zhang, Raluca Budiu, Joan Brozick, Anda Vlad. Novel ovarian cancer transplantable models generated from MUC1KrasPten tumors show different in vitro and in vivo biological behaviors. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B66.