Abstract 4495: Elucidating BCL11A’s function in triple negative breast cancer

Abstract It has been recently shown that the B-cell CLL/lymphoma 11A (BCL11A) transcription factor is highly expressed in triple-negative breast cancer (TNBC) and has critical functions in promoting tumor growth and mammary stem cell maintenance. Studies in our group have found that the first twelve amino acids (aa 1-12) of BCL11A are a conserved sequence that allows binding to retinoblastoma binding protein 4 (RBBP4). RBBP4, a histone binding protein, is involved in many epigenetic complexes, including the Polycomb repressive complex 2 (PRC2), the nucleosome remodeling and deacetylase (NuRD) complex, and SIN3A complex. Through these interactions BCL11A may exert transcriptional and epigenetic regulation. Herein we investigate the importance of BCL11A’s interaction with RBBP4 and its function in TNBC. BCL11A-complex interactions were observed through pull-down experiments of TNBC cell lysate utilizing aa 2-16 of BCL11A and a scramble control sequence. Our results demonstrate that this 16-amino acid sequence is sufficient to bind to RBBP4 and pull down the PRC2, NuRD, and SIN3A complexes. Furthermore, the NuRD and Sin3a complexes pulled down by BCL11A aa 2-16 retained their functionality as observed through post pull-down histone deacetylase (HDAC) activity assays. These results indicate significantly higher HDAC activity in the wildtype sequence as compared to the scrambled sequence. To further investigate this interaction, protein crystallization was conducted, the results of which validate the binding between BCL11A and RBBP4. Additionally, a BCL11A peptide (aa 2-12) and a scramble control were transfected into the TNBC cell line SUM149. Analysis via flow cytometry shows a reduction of the ALDH+ cell population in the BCL11A peptide transfected cells versus scramble control. We are currently investigating the necessity of this 12-amino acid sequence in interactions with RBBP4, PRC2, NuRD and SIN3A via co-Immunoprecipitation experiments using an N-terminal truncated BCL11A protein (del 2-12). The effects of full-length BCL11A and del 2-12 on the ALDH+ cell population are also being examined. These experiments will further delineate this sequence’s importance in BCL11A-RBBP4 interactions. Citation Format: Nicholas O. Stevers, Samantha L. Tinsley, Rebecca Moody, Chang-Ching Lin, Jennifer Meagher, Jeanne A. Stuckey, Miao-Chia Lo, Duxin Sun. Elucidating BCL11A’s function in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4495. doi:10.1158/1538-7445.AM2017-4495