Functional Characterization of Forkhead-Domain Missense Mutations of FOXA1 in Driving Prostate Cancer Progression
Abstract
Scientific Objective and Rationale: Male hormone androgen is the fuel that drives the disease progression in prostate cancer (PCa). Biologically, androgen binds to a nuclear receptor called androgen receptor (AR). AR will translocate to the nucleus and form transcriptional machinery to regulate gene expression via binding to the androgen responsive elements (AREs) on the chromatin. However, prior to AR activation, a protein that functions as a “pioneer” factor, called FOXA1, will have to bind the DNA and loosen the tight DNA for AR incoming. FOXA1 contains a Forkhead DNA binding domain that enables it to directly associate with the DNA and serves as a major regulator of AR transcriptional activity. Hormonal therapies (including chemical or surgical castration) aim to disrupt AR activity and stand in the mainstream of PCa therapy. Unfortunately, those therapies eventually fail, and the disease relapses to a deadly stage called castration-resistant prostate cancer (CRPC) that commonly metastasizes to bone tissue. Large-scale sequencing studies using PCa patient tumor tissues have identified increasing frequency of FOXA1 mutations in the CRPC patients and African American group. In particular, more than half of these mutations are missense mutations (change of amino acid from one to another) in the Forkhead DNA binding domain, indicating altered DNA binding ability and concomitant AR activity. I propose in this study to elucidate the biological functions of FOXA1 mutants and identify downstream targets that can be translated into therapeutic interventions specifically for patients carrying these mutants. Applicability of the Research: In this study, we generated a series of PCa cell lines that stably express different FOXA1 Forkhead missense mutations. Our preliminary data have shown there is a broad decrease of AR activity in cells expressing the mutants in comparison to wildtype. This is not surprising, as the CRPC patients have gone through treatments for blocking AR activity. In contrast to loss of DNA binding on the AR-regulated gene loci, we found that these mutants gain binding on a subset of genes mediating metastasis. This could explain how these mutant tumor cells become more aggressive in an androgen-deprived condition. In the proposed work, we are going to further delineate the mechanisms and characterize the function of the missense mutations. We have identified protein Met as a potential “culprit” for mediating the invasiveness of tumor cells expressing the mutants. The specific Met inhibitor, crizotinib (trade name Xalkori, Pfizer), for treating small cell lung cancer has been tested in PCa, but did not show promising output. Our preliminary data show cells expressing the mutant FOXA1 are more sensitive to crizotinib than wildtype. We will further test it in the mice model and explore other potential “culprits.” More importantly, we will also determine the correlation between FKHD-MS and AR activity and metastasis signaling in the high-risk PCa patients, particularly African American males, by analyzing the DNA and RNA obtained from this group of patients. This study is of special importance for patients at the CRPC stage who carry FOXA1 mutations. We aim to accomplish the proposed studies in 3 years, and patients should benefit fairly quickly because a lot of the inhibitors targeting metastasis have been approved by the Food and Drug Administration for treating other diseases. The potential risks could be the side effects from taking the drugs, which should be compensated by careful medication. Contributions of This Study: Studying the function of FOAX1 mutations will further our understanding on how tumor cells evade AR signaling to develop drug resistance. The output from this proposed study will clearly delineate a subgroup of CRPC patients who will no longer respond to therapies targeting AR action, but will benefit from a subset of metastasis inhibitors. This study will also p
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910777
Entities
People
- Shuai Gao
Organizations
- United States Army
- University of Massachusetts Boston