Publication Date

2019-04-25

Availability

Embargoed

Embargo Period

2021-04-25

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Cancer Biology (Medicine)

Date of Defense

2019-04-02

First Committee Member

Nanette H. Bishopric

Second Committee Member

Eli Gilboa

Third Committee Member

Anthony Capobianco

Fourth Committee Member

Derek M. Dykxhoorn

Fifth Committee Member

Marc E. Lippman

Abstract

Primary breast and prostate cancers can be cured, but the metastatic disease cannot. Identifying cell factors that predict metastatic potential could guide both prognosis and treatment. We used Cell-SELEX to screen an RNA aptamer library for differential binding to prostate cancer cell lines with high vs. low metastatic potential. Mass spectroscopy, immunoblot, and immunohistochemistry were used to identify and validate aptamer targets. Aptamer properties were tested in vitro, in xenograft models, and in clinical biopsies. We identified a novel aptamer (Apt63) that binds to the beta subunit of F1Fo ATP synthase (ATP5B), present on the plasma membrane of cancer cells. Apt63 bound to plasma membranes of multiple aggressive breast and prostate cell lines, but not to normal breast and prostate epithelial cells; binding led to rapid cell death. A single intravenous injection of Apt63 induced rapid cytotoxicity in MDA-MB-231 xenograft tumors, associated with endonuclease G nuclear translocation and DNA fragmentation. Apt63 was not toxic to non-transformed epithelial cells in vitro or adjacent normal tissue in vivo. In breast cancer tissue arrays, plasma membrane staining with Apt63 correlated with tumor stage (p<0.0001, n=416). Across multiple datasets, ATP5B expression was significantly increased in cancer, and negatively correlated with metastasis-free and overall survival. Ecto-ATP5B binding by Apt63 may disrupt an essential survival mechanism in a subset of tumors with high metastatic potential and defines a novel category of cancers with potential vulnerability to ATP5B-targeted therapy. Apt63 is a unique tool for elucidating the function of surface ATP synthase.

Keywords

Ecto-ATP synthase; metastasis; breast cancer; prostate cancer; aptamer

Available for download on Sunday, April 25, 2021

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