DOI

https://doi.org/10.25772/M400-NM10

Author ORCID Identifier

https://orcid.org/0000-0002-3321-3454

Defense Date

2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Clinical and Translational Sciences

First Advisor

Charles V. Clevenger

Abstract

Prolactin (PRL) and its receptor (PRLr) have been implicated in the development and progression of human breast cancer. PRL activates its receptor and induces activation of proximal Janus kinase 2 (Jak2) for signal transduction. Here, we sought to determine the role of PRLr-associated peptidyl-prolyl isomerase, cyclophilin A (CypA), in modulating structure/function relationships of the PRLr. It was demonstrated that CypA mediated PRL-induced conformational change of the CFP- and -YFP tagged forms of the PRLr cytoplasmic-tail, whereas CypA inhibition by NIM811 (N-methyl-4-isoleucine cyclosporin) or knockdown blocked the conformational change of the PRLr assessed by Fluorescence Resonance Energy Transfer (FRET) signal or efficiency. To further investigate the consequences of CypA inhibition or knockdown on the PRLr/Jak2 complex mediated signaling/functions, analyses of phospho-tyrosine residues that are believed to be important for interactions/signaling were investigated. It was found that NIM811 inhibition or CypA shRNA knockdown significantly reduced prolactin-stimulated phosphorylation of PRLr/Jak2 intermediates and their association with the PRLr in breast cancer cells. A microarray analysis revealed that NIM811 inhibited approximately 66% of the top 50 PRL-induced genes. NIM811 inhibited breast cancer cell proliferation, survival, migration and anchorage-independent growth. Subsequent NIM811 treatment of a triple negative breast cancer xenograft inhibited primary tumor growth, outgrowth of macro-metastasis and induced central tumor necrosis. Furthermore, loss of CypA in the MMTV-PyMT mouse model demonstrated inhibition of tumorigenesis with significant reduction in lung and lymph node metastasis. Overall, CypA modulates PRL-induced conformational change of the C-terminus of the PRLr through its isomerase activity, altering PRLr/Jak2 complex signaling/functions in breast/mammary tumorigenesis and metastasis.

Rights

© Shawn Hakim

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-8-2019

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