Abstract 2017: Blocking ErbB-c-Met-FAK signaling axis suppresses brain metastasis of breast cancer
Authors: Gautam Shailendra K. , Kanchan Ranjana , Atri Pranita , Siddiqui Jawed , Rauth Sanchita , Mahapatra Sidharth , Jain Maneesh , Moorthy Ponnusamy P. , Salgia Ravi , Band Vimla , Batra Surinder K. , Nasser Mohd W. 
Published: August 2019

Abstract
Background: Brain metastasis is associated with the leading cause of cancer related death and worse quality of life in the breast cancer (BC) patients. Among different molecular subtypes, ErbB2-positive patients show highest incidences of brain metastases. Inability of trastuzumab to cross blood-brain barrier and altered phenotype of metastasizing cells lead to poor therapeutic outcome in ErbB2-positive BC brain metastatic patients. In this regard, new approaches are warranted to overcome challenges associated with brain metastasis.
Experimental design:To understand the molecular expression profile in ErbB2+BC brain metastasis, we compared RNA-Seq expression data of ErbB2+ BC brain-seeking cell line (SKBR3-BrM3) to its parental cell line. Highly expressed targets, epidermal growth factor receptor (EGFR), tyrosine kinase receptor c-Met, and focal adhesion kinase (FAK) were selected for therapeutic intervention. In vitroanalysis of combination therapies was performed using parental and their brain seeking derivative BC cell lines. Neratinib in combination with c-Met inhibitor (Cabozantinib) or FAK inhibitor (PF-573,228) was tested in Hu-ErbB2-postive transgenic (Tg)-mouse derived organoids and in orthotopic nude mouse models.
Results: RNA-Seq data revealed that ErbB2 expression is substantially decreased in ErbB2+ BC brain seeking SKBR3-BrM3 cell line as compared to its parental counterpart SKBR3 cell line. In contrast, EGFR, c-Met and their downstream target, FAK are significantly upregulated in SKBR3-BrM3 cell line, suggesting their role in brain metastasis. Altered expression of these selected targets was further validated by western blotting and immunofluorescence assays. When tested in combination with FDA approved EGFR inhibitor neratinib, both c-Met or FAK inhibitor synergistically inhibited the proliferation and metastasis of metastatic cell lines as observed in colony formation assay and invasion assays, respectively. In addition, the combinational therapy showed efficacy in various preclinical models of breast cancer brain metastasis.
Conclusions:These studies conclude that EGFR, c-Met, and FAK are potential targets in ErbB2-positive brain metastasis. These studies also demonstrate that FDA approved drugs such as Neratinib or c-Met inhibitor and preclinical FAK-inhibitor in different combinations could be used as a novel preventive strategy to attenuate breast cancer brain metastasis.
Citation Format: Shailendra K. Gautam, Ranjana Kanchan, Pranita Atri, Jawed Siddiqui, Sanchita Rauth, Sidharth Mahapatra, Maneesh Jain, Ponnusamy P. Moorthy, Ravi Salgia, Vimla Band, Surinder K. Batra, Mohd W. Nasser. Blocking ErbB-c-Met-FAK signaling axis suppresses brain metastasis of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2017.