Title

The Addition of Melatonin to 17beta-Estradiol and Progesterone Modulated Markers Relevant to Mammary Tumor Development and Modulated Steroid Receptors Relevant to Uterine Protection in a Mouse Model of Breast Cancer

Defense Date

5-15-2013

Graduation Date

Summer 1-1-2013

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Pharmacology-Toxicology

School

School of Pharmacy

Committee Chair

Paula Witt-Enderby

Committee Member

David Johnson

Committee Member

Jane Cavanaugh

Committee Member

Rehana Leak

Committee Member

Melissa Melan

Keywords

Breast cancer, Gene Expression, Melatonin, MMTV-Neu mice, Tertiary side-branching, Uterus

Abstract

The use of hormone replacement therapy (HRT) is important to relieve menopausal symptoms. However, HRT use declined after an increased risk of breast cancer was reported by the Women's Health Initiative. With the ultimate goal of developing a novel replacement therapy to relieve menopausal symptoms without increasing the risk of breast cancer, we postulated that a novel replacement therapy containing 17β-estradiol (E2) and half the recommended dose of progesterone (P4) along with nocturnal melatonin supplementation (EPMRT) would be protective against mammary tumor development. Previously, in a mouse model of HER2+ breast cancer, our laboratory demonstrated that EPMRT was protective against mammary cancer by increasing mammary tumor latency, decreasing tumor incidence and weight, and decreasing gross lung metastases while not increasing uterine weight. A pre-tumor study was conducted to gain insight into these protective effects. Randomized, non-ovariectomized, 60-day old female MMTV/unactivated Neu mice were provided therapies comprised of E2 and P4, with or without nocturnal melatonin supplementation, given continually for 30 days. To investigate actions on mammary tissues, whole mount, microarray, and real-time RT-PCR analyses were performed. To assess impact on the uterus, uterine wet weight, luminal epithelial height, estrogen receptor (ERα) and progesterone receptor (PR) expression, as well as Ki67 expression were performed. Tertiary side-branching, the initial step in the process of mammary ductal differentiation, was significantly increased by Melatonin and EPMRT as compared to Control. Also, EPMRT displayed significantly decreased expression of the cancer-related genes encoding amphiregulin and indoleamine 2, 3-dioxygenase. In the uterus, there were no differences detected in wet weight, luminal epithelial height, and proliferation. Also, there was no effect on serum E2 or P4 levels; however, EPMRT increased the time in estrus. Moreover, the increase in expression of aromatase mRNA by low dose P4 was abolished by increasing doses of P4 and by addition of melatonin. Overall, these data provide important insight into the protective actions of EPMRT on Neu-induced mammary cancer. These findings provide a rationale for future investigations with the ultimate goal of having women use this novel therapy to relieve menopausal symptoms while providing protective actions on the breast and the uterus.

Format

PDF

Language

English

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