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Characterization of MAX and FOXA2 mutations unique to endometrial cancer

Rush, Craig M
http://rave.ohiolink.edu/etdc/view?acc_num=osu1542204873523922

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Biomedical Sciences.
Endometrial carcinoma (EC) is the most common gynecologic malignancy in the United States and is increasing in incidence. EC is broadly classified as type I or type II based on hormonal dependency and clinical outcomes. Type I tumors tend to be estrogen driven, of endometrioid endometrial carcinoma (EEC) histology, and are associated with endometrial hyperplasia and a good prognosis. Type II tumors include some endometrioid tumors but primarily consists of non-endometrioid histologies, including serous papillary and clear cell histologies, and are associated with poor outcome. ECs are typically diagnosed at early stage and are often cured by surgery with or without adjuvant radio- or chemo-therapy. Recurrent disease is, however, not uncommon and treatment options are limited. Molecular markers to predict recurrence or aggressive disease are sorely lacking. Characterization of specific somatic mutations in EEC and their impact on EC tumor biology is needed to better identify at-risk patients for aggressive disease. The work presented here characterizes mutations in MAX and FOXA2 in EC. Myc-Associated Factor X (MAX) is a transcription factor that functions as the obligate dimerization partner for MYC and MXD family transcription factors by forming and binding to E-box DNA elements to control gene expression. The MYC family members are proto-oncogenes that are frequently aberrantly activated in cancers, while the MXD family of transcription factors have tumor suppressive roles. MAX is central to the opposing activities of the MYC and MXD families. MAX has recently been identified as a target of frequent mutation in EC. The work described here is a characterization of MAX’s role in EC. We demonstrate that MAX mutation is associated with worse progression-free survival, indicating a role for MAX in EC biology. Our functional characterization of MAX in EC focuses on the hotspot missense mutation in MAX’s DNA binding domain, p.His28Arg, that accounts for >50% of MAX mutations and appears to be EC-specific. We show that MAX p.His28Arg binds to DNA with higher affinity using in vitro assays, alters genomic occupancy at gene promoters, and alters gene expression in EC cell lines and primary tumors. Unexpectedly, we observe increased vascularization in EC cell line xenografts expressing MAX p.His28Arg. We hypothesize that MAX p.His28Arg expression alters paracrine angiogenic signals to promote vascularization and show that soluble factors released by MAX p.His28Arg increase endothelial cell sprouting, in part due to increased VEGFA secretion. Furthermore, we demonstrate that MAX p.His28Arg expression leads to dramatic changes in secreted proteins (the secretome). Our work characterizing the MAX p.His28Arg secretome identifies additional proteins with potential biologic impact on the tumor microenvironment and angiogenesis. Our studies provide the first evidence for oncogenic activity of MAX in EC and provide rationale for future studies assessing MAX in EC. Forkhead box A2 (FOXA2) is a pioneer factor that can open condensed chromatin for other transcription factors and can also act as a transcription factor to control gene expression. FOXA2 has important roles in development and is a tumor suppressor in a variety of solid tumors. FOXA2 mutations are frequently observed in EC and endometrial carcinosarcoma. In this work we demonstrate frequent FOXA2 loss-of-function mutations in EEC and propose that FOXA2 is a haploinsufficient tumor suppressor in EC, as few second-hit lesions were identified. We show that expression of FOXA2 in EEC is complex and controlled by multiple mechanisms. In order to better understand the effects of loss-of-function mutations in FOXA2, we functionally characterize several hotspot mutations. Our functional characterization demonstrates that one group of mutations prevents nuclear translocation of FOXA2, blocking its transcription factor function. For mutations that maintained nuclear localization, we observe reduced stability and variable capacity to activate the known FOXA2 controlled CDH1 promoter luciferase reporter. We demonstrate that CDH1 expression was reduced in primary tumors with FOXA2 mutations, confirming loss-of-function of FOXA2 activity. These data represent the first functional characterization of FOXA2 mutation in human EC.
Goodfellow Paul, PhD (Advisor)
Coppola Vincenzo, MD (Committee Member)
Kurita Takeshi, PhD (Committee Member)
Parvin Jeffrey, MD PhD (Committee Member)
299 p.
Biomedical Research; Cellular Biology; Genetics; Gynecology; Molecular Biology; Oncology
endometrial cancer; endometrial carcinoma; MAX; FOXA2; tumor suppressor; oncogene; forkhead box protein a2; myc associated factor x; secretome

Recommended Citations

Citations

  • Rush, C. M. (2018). Characterization of MAX and FOXA2 mutations unique to endometrial cancer [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1542204873523922

    APA Style (7th edition)

  • Rush, Craig. Characterization of MAX and FOXA2 mutations unique to endometrial cancer. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1542204873523922.

    MLA Style (8th edition)

  • Rush, Craig. "Characterization of MAX and FOXA2 mutations unique to endometrial cancer." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1542204873523922

    Chicago Manual of Style (17th edition)

osu1542204873523922
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