All ETDs from UAB

Advisory Committee Chair

Douglas R Hurst

Advisory Committee Members

Andra R Frost

Ralph D Sanderson

Hengbin Wang

Kurt R Zinn

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Metastasis continues to be the most difficult clinical challenge for breast cancer. Survival rates for patients with metastatic breast cancer have not significantly changed in the past 20 years. Therefore, we need a better understanding of the molecular mechanisms that regulate breast cancer metastasis to develop effective therapies. SIN3 chromatin remodeling complexes have been implicated in breast cancer progression. Mammalian cells have two paralogs of SIN3 (SIN3A and SIN3B) that are encoded by distinct genes and have unique functions during development. However, specific roles for SIN3A and SIN3B in breast cancer progression have not been characterized. To better understand how SIN3 chromatin complexes functionally regulate breast cancer progression, we generated stable knockdown of SIN3 paralogs individually and in combination using three non-overlapping shRNA in two different triple negative metastatic breast cancer cell lines. Knockdown of SIN3A resulted in increased metastatic potential whereas knockdown of SIN3B decreased metastatic potential of triple negative breast cancer cells both in vitro and in vivo. Analysis of publically available microarray datasets indicated that high mRNA expression of SIN3A and low mRNA expression of   SIN3B correlates with relapse free survival in patients with triple negative breast cancer consistent with our in vitro and in vivo data. Previous studies indicated that intracellular localization may play an important role in SIN3 function. Using immunofluorescence and confocal microscopy, we discovered that SIN3A is localized to the nucleus in metastatic cells and is more dispersed in “normal” breast epithelial cells. In situ proximity ligation assays demonstrated that the interaction of SIN3B with HDAC2 was predominantly nuclear in metastatic cells and both nuclear and non-nuclear in normal cells. Overall, these results demonstrate key functional differences between SIN3 paralogs in regulating the process of breast cancer metastasis and suggest metastasis-suppressive roles for SIN3A and metastasis-promoting roles for SIN3B. Our results further support the notion that intracellular localization of SIN3 protein interactions is an important component in determining SIN3 paralog function. A deeper understanding of independent, compensating, and redundant functions of SIN3A and SIN3B may prove to be critical in assessing how they regulate breast cancer progression and metastasis.

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