Spontaneous Transformation of Murine Oviductal Epithelial Cells: A Model System to Investigate the Onset of Fallopian-Derived Tumors

Abstract

High-grade serous carcinoma (HGSC) is the most lethal ovarian cancer histotype. The fallopian tube secretory epithelial cells (FTSECs) are a proposed progenitor cell type. Genetically altered FTSECs form tumors in mice; however, a spontaneous HGSC model has not been described. Apart from a subpopulation of genetically predisposed women, most women develop ovarian cancer spontaneously, which is associated with aging and lifetime ovulations. A murine oviductal cell line (MOELOW) was developed and continuously passaged in culture to mimic cellular aging (MOEHIGH). The MOEHIGH cellular model exhibited a loss of acetylated tubulin consistent with an outgrowth of secretory epithelial cells in culture. MOEHIGH cells proliferated significantly faster than MOELOW, and the MOEHIGH cells produced more 2D foci and 3D soft agar colonies as compared to MOELOW MOEHIGH were xenografted into athymic female nude mice both in the subcutaneous and the intraperitoneal compartments. Only the subcutaneous grafts formed tumors that were negative for cytokeratin, but positive for oviductal markers, such as oviductal glycoprotein 1 and Pax8. These tumors were considered to be poorly differentiated carcinoma. The differential molecular profiles between MOEHIGH and MOELOW were determined using RNA-Seq and confirmed by protein expression to uncover pathways important in transformation, like the p53 pathway, the FOXM1 pathway, WNT signaling, and splicing. MOEHIGH had enhanced protein expression of c-myc, Cyclin E, p53, and FOXM1 with reduced expression of p21. MOEHIGH were also less sensitive to cisplatin and DMBA, which induce lesions typically repaired by base-excision repair. A model of spontaneous tumorogenesis was generated starting with normal oviductal cells. Their transition to cancer involved alterations in pathways associated with high-grade serous cancer in humans.

PAX2 function, regulation and targeting in fallopian tube-derived high-grade serous ovarian cancer

“…Serial passaging of the MOE cells harboring both alterations resulted in an increase in all functional characteristics. These data are consistent with a previous study performed in serially passaged fallopian tube cells that indicate that aging is sufficient to induce functional alterations(16). In contrast to the tumorigenic model of serially passaging MOE cells on a CD1 background, the current model with PAX2 knocked down and p53 mutated did not form tumors after serial passaging.…”

“…Several studies have demonstrated that the fallopian tube is likely one of the sources of origin of HGSC(9, 11, 13, 16, 38). However, no models of SCOUTs or of fallopian tube cells lacking PAX2 have been reported.…”

“…showed that PAX2 was present in the tumors derived from transgenic animal models(12). Similarly, another high-grade carcinoma animal model presented with higher PAX2 expression as the cells became tumorigenic(16). These data along with those in this report suggest that loss of PAX2 alone is not sufficient for tumor progression from fallopian tube cells.…”

“…Fut8 protein is highly expressed in MOE:PAX2 shRNA-1 cells and this increased expression is progressively inhibited when combined with p53 mutation. Interestingly, a recently published undifferentiated high-grade carcinoma mouse model that expressed PAX2 and a p53 splice variant(16), failed to express fut8. In contrast, MOE cells harboring mutation of p53 and overexpression of KRAS G12V , that formed poorly differentiated carcinomas in vivo (15), did not express PAX2, but expressed fut8 (Supplementary Fig.…”

“…Although these models mimic human disease and affirm FTE as the source of origin, they fail to address the role of SCOUTS, which often lack PAX2 protein expression. Interestingly, several high-grade carcinoma animal models have also been developed that have retained PAX2 expression in tumor samples (12, 16). …”