Breast cancer brain metastasis (BCBM) occur in about 10-30% of patients with breast cancer. It has been established that breast cancer is a heterogeneous disease with 3 predominant subtypes (1) ER/PR positive (3) HER2 positive (4) Triple negative breast cancer (TNBC)/Basal subtype. TNBC is associated with the highest incidence of metastasis to brain, mechanism of which is poorly understood. Therefore, in order to understand the proclivity of TNBC to the brain and identify potential targets for treatment BCMB, we employed two widely used paired cell model system, the MDA-MB-231/MDA-MB-231BrM2 and the CN-34/CN34BrM2. The levels of brain predominant markers [ST6GALNAC5 (ST6), Nestin, Tubulin β3 (TUBB3)] in brain-derived clones were assesed by qRT-PCR and found to be overexpressed in brain-derived MDA-MB-231BrM2 and CN34BrM2 in comparison with parental breast cancer cell lines. We also identified hyperactivated TGF-β signaling in brain derived clones in comparison with parental cells. Moreover, the treatment of parental cells with TGF-β increased the expression of ST6, Nestin and TUBB3 indicating that TGF-β plays role in the development of BCBM. To further delineate the role of these markers in BCBM, knockdown experiments using two different shRNA specific to TUBB3 (neuronal specific) were performed. TUBB3 knockdown resulted in a dramatic reduction in tumorspheres formation, migration, invasion and the ability to adhere to laminin in both MDA-MB-231BrM2. Furthermore, the downregulation of expression of β1 and β3 integrins in TUBB3 knockdown cells was discovered as assessed by qPCR and flow cytometry. These results implicate that overexpression of brain specific TUBB3 provides breast cancer cells with migration and invasion abilities and a possible survival advantage in the brain microenvironment.
Citation Format: Deepak P. Kanojia, Purva Sarvaiya, Jian Qiao, Lingjiao Zhang, Irina Balyasnikova, Maciej S. Lesniak. The role of neuronal predominant gene expression in breast cancer brain metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2006. doi:10.1158/1538-7445.AM2014-2006