Poster Presentation 14th International Biennial Conference on Metastasis Research 2012

Breast cancer progression and metastasis regulated by SIN3 chromatin modification complexes (#134)

Douglas R. Hurst 1 , John W. Thomas 1 , Jianzhong Liu 1
  1. University of Alabama at Birmingham, Birmingham, AL, United States
Epigenetic regulation of gene transcription by histone modification and chromatin remodeling has been linked to many biological and pathological events including breast cancer metastasis. SIN3 epigenetically regulates the expression of multiple genes by recruiting protein and DNA modifying enzymes. Altering the protein composition of these large SIN3 complexes leads to suppression of breast cancer metastasis in mouse models without preventing orthotopic tumor growth. We hypothesized that composition of these complexes regulates the metastatic ability of breast cancer cells. Many studies have analyzed SIN3 associated proteins in human cells using systems with a protein of interest ectopically expressed. While these studies have been useful to identify many interacting proteins and possible functions, the complexes are altered with over-expression systems. In order to understand how the complex differs between metastatic and non-metastatic cells, we characterized the endogenous composition of SIN3 complexes. Size exclusion FPLC was used to isolate complexes > 1 MDa in both the nuclear and cytoplasmic lysates. These large complexes were co-immunoprecipitated with anti-SIN3A and all associated proteins were identified by MALDI-TOF mass spectrometry. The intracellular location of these interactions was also determined in situ using a proximity ligation assay (DuoLink). HDAC1 and 2 interactions with SIN3A and B were found to be differentially localized between metastatic MCF10CA cell lines compared to the normal MCF10A breast cell line. Also, the metastasis suppressor BRMS1 was found to associate with SIN3A in the cytoplasm that contributes to functional metastasis suppression. These results identify new roles for the SIN3 chromatin modification complexes that are distinct from chromatin structure and may be critical for breast cancer progression and metastasis.