Author ORCID Identifier
https://orcid.org/0000-0002-7701-4406
Defense Date
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Human and Molecular Genetics
First Advisor
Senthil Radhakrishnan
Abstract
Breast cancer continues to be the second most common cancer in women in the United States. The neuroendocrine hormone human prolactin (hPRL) plays an important role in normal mammary gland development and growth, stimulating normal breast tissue proliferation and differentiation. Considerable evidence has shown that hPRL is involved in the malignant transformation of human breast tissue. hPRL enhances viability, invasiveness, and proliferation of breast cancer cells in vitro. Evidence from epidemiologic and genetic studies also implicates role of hPRL in the pathogenesis of breast cancer. Its cognate receptor the human prolactin receptor (hPRLr) is required for the action of hPRL. hPRLr belongs to the type I cytokine receptor superfamily and lacks intrinsic tyrosine kinase activity. Several hPRLr isoforms exist as the result of alternative splicing and proteolysis. The intermediate form of human PRLr (hPRLrI) induces significant proliferation and anchorage-independent growth of normal mammary epithelia in vitro when co-expressed with the long form human of PRLr (hPRLrL). Furthermore, hPRLrL and hPRLrI co-expression are necessary to induce the transformation of mammary epithelia in vivo. The human intermediate form prolactin receptor isoform which acts as an oncogenic driver, is overexpressed in breast cancer, especially in triple-negative breast cancer. The hPRLrI is produced by alternative splicing which induces a frameshift, resulting in a premature stop codon and a novel 13 amino acid tail ("I-Tail") gain. In studying the function of hPRLrI I-tail, the ubiquitin-like protein neural precursor cell expressed developmentally down-regulated protein 8 (NEDD8) was found to be associated with the I-tail. The goal of this study was to determine the function of the hPRLrI I-tail in hPRLrL/hPRLrI mediated mammary transformation. hPRLrL/hPRLrI, hPRLrL/hPRLrI∆13 (I-tail removal mutant) was delivered to MCF10AT cells. Cell proliferation was decreased when hPRLrI I-tail was removed. I-tail deletion decreased anchorage-independent growth and attenuated cell migration. The I-tail was involved in Ras/MAPK signaling but not PI3K/Akt signaling pathway. I-tail removal resulted in decreased hPRLrI stability. RNA-seq data revealed that I-tail removal resulted in differential gene expression induced by PRL. Ingenuity Pathway Analysis (IPA) revealed that the activity of extracellular signal-regulated kinases (ERK) was attenuated when I-tail was removed. Treatment of breast cancer cells with ERK1/2 inhibitor ulixertinib resulted in decreased colony forming ability and less proliferation. These data suggested that the hPRLrI I-tail contributed to breast oncogenesis and might be a promising target for the development of new breast cancer therapies.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
11-19-2024