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Permanent link (DOI): https://doi.org/10.7939/R39P2WB9W

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MOLECULAR AND PHENOTYPIC CHARACTERIZATION OF DISTINCT BREAST CANCER CELL SUBPOPULATIONS PURIFIED USING A SOX2 REGULATORY REGION 2 TRANSCRIPTION ACTIVITY REPORTER Open Access

Descriptions

Other title
Subject/Keyword
breast cancer
Sox2
estrogen receptor positive (ER+)
cancer stem cells
triple negative breast cancer (TNBC)
transcription activity
Myc
intra-tumour heterogeneity
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Jung, Karen KT
Supervisor and department
Lai, Raymond (Laboratory Medicine and Pathology)
Abdulkarim, Bassam (Oncology)
Examining committee member and department
Park, Morag (Biochemistry, McGill University)
Godbout, Roseline (Oncology)
Hugh, Judith (Laboratory Medicine and Pathology)
Shaw, Andrew (Oncology)
Department
Department of Oncology
Specialization
Experimental Oncology
Date accepted
2015-08-28T12:05:31Z
Graduation date
2015-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Sex-determining Region Y-box 2 (Sox2) is a transcription factor integral to the maintenance of pluripotency in embryonic stem cells. In recent years, Sox2 expression has been detected and implicated in the pathogenesis of breast and other cancers. Clinically, Sox2 expression has been associated with higher tumour grade, tumour size, lymph node metastases, tamoxifen resistance, disease recurrence, and poor overall survival in breast cancer (BC) patients. Many studies have focused on Sox2 as a marker of enhanced tumourigenic capacity and stem cell-like features in heterogeneous tumour cell subpopulations but little is known about its functional role or transcription activity in tumour cells. Our group has recently identified in estrogen receptor-positive (ER+) BC cells, two phenotypically distinct BC cell subsets separated based on their differential activation of Sox2 regulatory region 2 (SRR2) enhancer transcription activity reporter, the reporter-unresponsive (RU) and the more tumorigenic reporter-responsive (RR) cells. We hypothesize that the cell subsets purified by the SRR2 reporter will exhibit distinct molecular mechanisms underlying their differential phenotypes. Firstly, we show that Y-box binding protein-1 (YB-1), another oncogenic transcription factor, negatively regulates Sox2 expression in ER+ RU and RR cells. Consequentially, loss of YB-1 induced increased Sox2 activity only in the RR cells, providing the RR cells with the unique ability to maintain tumourigenic capacity in the absence of YB-1. Secondly, using chromatin immunoprecipitation and a human genome-wide promoter microarray chip (ChIP-chip), we found a largely mutually exclusive profile of gene promoters bound by Sox2 in the ER+ RU and RR cells. Sox2 was bound to 1830 and 456 unique gene promoters in the RU and RR cells respectively, with only 62 overlapping gene promoters. Intriguingly, Sox2 was bound to many stem cell- and cancer-associated genes only in RR cells, mediating the enhanced stem-like, tumourigenic phenotype in RR cells. Thirdly, we observed that triple negative breast cancer (TNBC) cells also exhibited heterogeneous activation of the SRR2 reporter and were comprised of RU and RR cell subsets. Similar to the ER+ BC cells, RR cells showed enhanced tumourigenic capacity in vitro and in vivo, particularly within the CD44High/CD24- TNBC cells. Unlike ER+ cells, however, Sox2 was not a major contributor to the SRR2 activity. Fourthly, we discovered that Myc is a novel transcriptional activator the SRR2 reporter in the RR TNBC cells, and contributes to the RR stem-like, tumourigenic phenotype, providing a therapeutic opportunity. Taken together, ER+ and ER- BC cells exhibit heterogeneous response to the SRR2 enhancer reporter, and the SRR2 reporter is an invaluable tool to distinguish cells with differential tumourigenic properties and distinct Sox2 and Myc molecular mechanisms that can be exploited for novel targeted therapies in the treatment of BC patients.
Language
English
DOI
doi:10.7939/R39P2WB9W
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Jung K, Sabri S, Hanson J, Xu Y, Wang YW, Lai R, Abdulkarim BS. Elevated ARG1 expression in primary monocytes-derived macrophages as a predictor of radiation-induced acute skin toxicities in early breast cancer patients. Cancer Biol Ther. 2015. Epub ahead of print.Jung K*, Gupta N*, Wang P, Lewis JT, Gopal K, Wu F, Ye X, Alshareef A, Abdulkarim BS, Douglas DN, Kneteman NM, Lai R. Triple negative breast cancers comprise a highly tumorigenic cell subpopulation detectable by its high responsiveness to a Sox2 regulatory region 2 (SRR2) reporter. Oncotarget. 2015, 6(12):10366-73. *Co-first authors.Jung K, Wang P, Gupta N, Gopal K, Wu F, Ye X, Alshareef A, Bigras G, McMullen TP, Abdulkarim BS, Lai R. Profiling gene promoter occupancy of Sox2 in two phenotypically distinct breast cancer cell subsets using chromatin immunoprecipitation and genome-wide promoter microarrays (ChIP-chip). Breast Cancer Res. 2014, 16(6):470.Jung K, Wu F, Wang P, Ye X, Abdulkarim BS, Lai R. YB-1 regulates Sox2 to coordinately sustain stemness and tumorigenic properties in a phenotypically distinct subset of breast cancer cells. BMC Cancer. 2014, 14:328.

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