Abstract 3338: BP1 induces an epithelial to mesenchymal transition in breast cancer cells by modulating the Twist/IL6 pathway
Authors: Farhad Vesuna, Bin-Jin Hwang, Jinguen Rheey, Mamta Giri, Mandeep Gill, Sidney W. Fu, Ashley Irving, Ala Lisok, Yehudit Bergman, Venu Raman, Patricia E. Berg
Journal: Cancer Research (2018)

Abstract Background. BP1 (Beta Protein 1) belongs to the Distal-less family of homeobox genes. We have demonstrated that BP1 is activated in over 80% of invasive ductal breast tumors, where it is associated with breast cancer progression. The mechanism(s) of BP1 involvement in breast cancer progression, invasion and metastasis are still not known. Homeobox genes contribute to the epithelial to mesenchymal transition (EMT). During EMT, epithelial cells acquire mesenchymal features which lead to motility, invasiveness and resistance to apoptosis. EMT is also characterized by changes in apico-basal polarity and a dramatic remodeling of the cytoskeleton. During progression toward metastasis, cancer cells acquire a mesenchymal gene expression phenotype and increased motility. This transition allows the tumor cells to metastasize and establish secondary tumors at distant sites. One of the drivers of the EMT is the transcription factor Twist. Twist is a member of highly conserved family of basic helix-loop-helix transcription factors and is involved in the specification and differentiation of mesenchymal tissue in embryos. Twist overexpression can induce EMT, generate cancer stem cells, and promote metastasis in vivo. We hypothesized that BP1 might promote cancer metastasis and invasiveness mediated though Twist and the EMT. Methods. We generated BP1 overexpressing cell lines, MCF-7/BP1 and HS578T/BP1, along with the associated vector controls. Expression of BP1 was tested by both protein and transcript levels by Western blotting and qRT-PCR, respectively. BP1 binding to Twist was assayed by chromatin immunoprecipitation. Confocal microscopy was used to localize BP1 expression and Boyden chamber assays were employed to assess the migratory and invasive ability of these cells. ELISA assays were employed to study IL6 expression in BP1 expressing cells. Results. BP1 expression led to an increase in Twist expression. Mechanistically, we demonstrated that BP1 bound proximally to the Twist promoter and regulated its expression. BP1 induced an EMT in both cell lines as seen by (a) lack of expression of E-cadherin, and an increase of vimentin and fibronectin expression, as well as (b) morphological changes, including a spindle-like, and more migratory phenotype. We also observed that BP1 induced expression of the cytokine IL6 in both cell lines. We conclude that BP1 regulates the EMT in breast cancer cells via the Twist and IL6 pathways. Citation Format: Farhad Vesuna, Bin-Jin Hwang, Jinguen Rheey, Mamta Giri, Mandeep Gill, Sidney W. Fu, Ashley Irving, Ala Lisok, Yehudit Bergman, Venu Raman, Patricia E. Berg. BP1 induces an epithelial to mesenchymal transition in breast cancer cells by modulating the Twist/IL6 pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3338.