Components of the histone modifying CoREST/LSD1 complex regulate breast tumorigenesis and breast cell biology.
Mazumdar, Sohini.
2013
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Abstract:
Multiprotein complexes that regulate histone modifications and chromatin structure play
critical roles in determining gene expression patterns important for cellular
differentiation and neoplasia. This work explores the role of CoREST1 (corepressor of
REST—1) and LSD1 (Lysine specific demethylase 1) in breast cancer tumorigenesis
and epithelial breast cell differentiation, respectively. ... read moreCoREST1 and LSD1 are
associated in multiprotein complexes, and CoREST1 is important for LSD1 enzymatic
activity as a histone lysine demethylase (Lee et al., 2005; Ouyang et al., 2009; Shi et
al., 2005). While high levels of LSD1 have been observed in aggressive, basal-type
breast cancers (Lim et al., 2010), nothing is known about the role of CoREST1 in breast
cancer initiation and/or progression. We investigated the role of CoREST1 in
tumorigenesis by knocking down CoREST1 in the invasive, metastatic cell line, MDA MB 231
that lacks expression of hormone receptors, estrogen receptor (ER), progesterone
receptor (PR) and HER2. In xenograft studies, we observed that CoREST1 knockdown cells
led to significantly smaller tumors with a marked decrease in angiogenesis. Levels of
several secreted pro—angiogenic and pro—inflammatory factors were reduced
in CoREST1 depleted cells. Many of these changes occurred at the transcriptional level,
indicating that CoREST1 acts to promote expression of pro—angiogenic and
pro—inflammatory genes. We further showed that, upon CoREST1 depletion, the MDA
MB 231 secretome had reduced ability to stimulate endothelial cell tube formation and
migration. These findings underscore an unanticipated function for a chromatin modifier
acting in tumor cells to exert profound non-cell autonomous effects on the tumor
microenvironment. In a collaborative study with the Kuperwasser lab, we also
investigated the role of LSD1 in breast cell differentiation. We observed an interaction
between LSD1 and the EMT transcription factor Slug, which has an important role in
mammary epithelial cell differentiation (Come et al., 2004; Nassour et al., 2012). Based
on this observation, we hypothesized that elevated levels of the LSD1/Slug complex
contribute to breast cell fate determination by repressing transcription of luminal
differentiation genes favoring maintenance of a basal cell state. To investigate this,
we depleted LSD1 and Slug in human mammary epithelial cells (HMECs). Gene expression
profiling identified 30% overlap between LSD1 and Slug target genes. Endogenous
coimmunoprecipitations confirmed that LSD1 and Slug formed a complex in HMECs, and
additional binding partners, including CoREST3, were identified. FACS analyses revealed
a more pronounced luminal phenotype upon LSD1 or Slug knockdown and chromatin
immunoprecipitation studies demonstrated that LSD1 and Slug were recruited to luminal
gene promoters such as CK18. Taken together, these studies advance understanding of the
molecular changes in breast cell fate determination and lend a better understanding of
the factors that promote basal cell fate, which will inform us about better treatment of
treatment refractory basal—like breast cancers. Taken together, the studies
presented here reveal novel and important roles of CoREST1 and LSD1 in tumorigenesis and
epithelial cell specification, respectively. Further, our studies suggest that there are
multiple LSD1 and/or CoREST1 complexes with distinct functions. Our findings illustrate
the complexity of regulation that multiprotein complexes with epigenetic modifier
activity have in development. Further understanding of those processes will potentially
aid in the development of sophisticated cancer therapies like targeting anti-angiogenic
therapies specifically to tumors, and reprogramming the molecular phenotype of a tumor
from a refractory to a more tractable one.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Genetics.
Advisor: Grace Gill.
Committee: Philip Hinds, Charlotte Kuperwasser, and Claire Moore.
Keywords: Genetics, and Oncology.read less - ID:
- c247f464h
- Component ID:
- tufts:20441
- To Cite:
- TARC Citation Guide EndNote
