Publication Date

2018-05-11

Availability

Embargoed

Embargo Period

2020-05-10

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Cancer Biology (Medicine)

Date of Defense

2018-01-04

First Committee Member

J William Harbour, MD

Second Committee Member

Joseph Rosenblatt

Third Committee Member

Mary Lou King

Fourth Committee Member

Marjana Tomic-Canic

Fifth Committee Member

Ralf Landgraf

Abstract

Aberrant gene expression is a feature of cancer. Cancer Testis Antigens (CTAs) which are normally expressed in the gonads are a group of proteins which are abnormally expressed in cancer and whose function remains elusive. Interestingly, the presence of cancer testis antigens is associated with bad prognosis in multiple tumor types. Cutaneous melanoma is a deadly disease which presents aneuploidy which is the aberrant gains and losses of chromosomes. REC8 is a meiotic cohesin that is normally present in testes and ovaries where it participates in meiotic division. In melanoma, REC8 is expressed compared to normal tissue and melanoma cell lines. Furthermore, in a melanocytic model of CIN we observed that REC8 expression paralleled alterations in chromosome number, therefore we hypothesized that the high expression of REC8 could impact chromosome number. We found that REC8 overexpression alone was not sufficient to induce alteration in chromosome number in melanoma lines and E6E7 melanocytes. Evidently, should meiotic proteins be involved in chromosome number alterations via impaired cell division, it requires one or more additional proteins in order to have an effect. By itself REC8 overexpression did not impact chromosome number in melanocytic cell lines. Uveal melanoma is the most common eye malignancy; it represents 3-5% of the melanomas diagnosed. The Harbour Laboratory recently identified high PRAME expression as a biomarker for metastasis in both class 1 and class 2 uveal melanoma. PRAME correlates with chromosome 1q and 6p gain and the PRAME promoter is hypomethylated in metastatic uveal melanoma. Further, PRAME co-localizes with the pioneer transcription factor NFY in ChIP-seq experiments. We hypothesized that PRAME is a modulator of chromatin accessibility by modulating the pioneer transcription factor NFY, leading to an increased expression of genes involved in tumorigenesis. We found by RNA sequencing, that PRAME overexpression causes downregulation of genes associated with chromosome maintenance. Ongoing experiments seek to define the relation of NFY and PRAME and areas of open chromatin utilizing ChIP-Seq and the influence of PRAME in chromatin accessibility utilizing ATAC-Seq. The present work analyzes the role of REC8 in cutaneous melanoma and PRAME in uveal melanoma, the rationale for these CTAs for contributing to tumorigenesis and their potential clinical use.

Keywords

Cutaneous melanoma; uveal melanoma; cancer testis antigens; REC8; PRAME; chromosome instability

Available for download on Sunday, May 10, 2020

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