Date of Award
Master of Science
Molecular Cellular and Systemic Physiology
E-&ndashcadherin (CDH1) is a cell adhesion molecule that coordinates key morphogenetic processes regulating cell growth, cell proliferation and apoptosis. Loss of CDH1 is a trademark of the cellular event epithelial to mesenchymal transition (EMT), which increases the metastatic potential of malignant cells. PTEN is a tumor suppressor gene commonly mutated in many human cancers, including endometrial cancer. In the mouse uterus, ablation of Pten induces epithelial hyperplasia, leading to endometrial carcinomas. However, loss of Pten alone does not affect longevity until around 5 months. Similarly, conditional ablation of Cdh1 alone does not predispose mice to cancer. We characterized the impact of dual Cdh1 and Pten ablation using Pgr-Cre (Cdh1d/d Ptend/d) in the mouse uterus. We observed that Cdh1d/d Ptend/d mice died at postnatal day 15-&ndash19 with massive blood loss from their reproductive tract (abnormal metrorrhagia) with prevalent vascularization in both the endometrium and myometrium. Their uteri were abnormally structured with curly horns, disorganized epithelial structure, and increased cell proliferation. Co-&ndashimmunostaining of KRT8 and ACTA2 showed invasion of epithelial cells into the myometrium. Further, the uteri of Cdh1d/d Ptend/d mice had prevalent vascularization in both the endometrium and myometrium. We also observed reduced expression of estrogen and progesterone receptors, loss of cell adherens and tight junction molecules (CTNNB1 and claudin), as well as activation of AKT in the uteri of Cdh1d/d Ptend/d mice. However, complex hyperplasia was not found in the uteri of Cdh1d/d Ptend/d. Collectively, these findings suggest that ablation of Pten with Cdh1 in the uterus accelerates cellular invasiveness and angiogenesis, and causes early death. Thus, this model does not allow sufficient time for the emergence of advanced, clinically over aggressive endometrial tumorigenesis and metastasis. Additionally, we looked at a new Cre system to ablate Pten and Cdh1 only in the epithelial cells of the uterus. Sprr2f, an estrogen dependent gene that is found highly expressed in the uterus, helps with structure and barrier function of epithelial cells. Prg-Cre turns on at postnatal day 3-5 before development of the uterus; whereas, Sprr2f-Cre is active around 3 weeks which is after uterine development. We have driven the ablation of Cdh1d/d Ptend/d using the Sprr2f-Cre. The Sprr2f-Cre Cdh1d/d Ptend/d mice successfully lived to 2 months. The Sprr2f-Cre Ptend/d mice displayed hyperplastic epithelial cells, most prominently in the glandular like structures of the uterus. Lack of cellular structure was observed in the Sprr2f-Cre Cdh1d/d Ptend/d mice. We also developed a model of orthotopic tumor transplantation to study further tumor development including cell invasion, dissemination and metastasis. The uteri of control, Cdhd/d, Ptend/d and Cdhd/d Ptend/d mice were collected and dissected to approximately ~1 mm in diameter. Then, the tissue fragments were orthotopically implanted into the uterine wall (endometrium) of wild-type syngeneic host mice. We have observed successful implantation and sustainability of the tissue through this technique. The tissue viability was successfully verified by implanting donor uterine pieces under the kidney capsule of recipient wild type mice. This study has shown that the ablation of Cdh1 and Pten in the mouse uterus initiates a more aggressive form of type I endometrial carcinoma when using Pgr-Cre as well as Sprr2f-Cre. However, neither conditional ablation approaches allowed us to fully observe the progression of the carcinoma to a metastatic disease. Our intrauterine endometrial/myometrial implantation technique proved to be an incomplete method to further study the metastatic potential of the PgrCre/+ Cdh1f/f Ptenf/f mice.
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