Focal adhesion kinase overexpression in breast cancer molecular subtypes

Abstract #1091 Focal adhesion kinase (FAK) is a protein tyrosine kinase which regulates multiple cellular processes including growth, differentiation, adhesion, motility and apoptosis and is a critical mediator of signalling events between cells and their extracellular matrix. FAK is highly expressed in invasive breast cancer (BC) where its upregulation has been implicated in the acquisition of an invasive tumor phenotype. Hierarchical cluster analysis identified subgroups of BC with separate gene expression profiles which detect four main tumor phenotypes, Luminal A (LA), Luminal B (LB), Basal-like (B), and HER2 subtype (HS) characterized by significant differences in prognosis. Up to now, there are no data concerning FAK distribution within the molecular BC subtypes. In this study FAK overexpression was evaluated, by immunohistochemistry (IHC), in a retrospective series of 193 invasive BC surgically treated at our Institution between 2002 and 2005. Associations with conventional pathological factors and with molecular subtypes were analyzed by Multiple Correspondence Analysis (MCA) and chi square test, aimed to determine the impact of FAK high positivity within BC molecular subtypes and to define a biologic profile associated to aggressive bio-pathologic variables such as tumor size (T), nodal status (N), grading (G), p53, Bcl2, Ki-67, p-AKT, p-MAPK . The anti-FAK 4.47 monoclonal antibody was used to detected FAK expression which was scored as high (2 or 3 intensity and ≥ 90% positive cells) or low (0 or 1 intensity and < 90% positive cells). FAK was overexpressed in 41.7% of LA, 70% of LB, in 48.0% of HER2 subtype and 52.2% of Basal-like BC. The relationships among the bio-pathological factors, analysed by MCA, showed that FAK+ is located in the quadrant containing more aggressive tumor phenotypes such as HER2 and Basal like subtypes together with T3-4, N+, G3 and p53+, high Ki67, Bcl2–, p-MAPK+, p-AKT+. Moreover, in LA tumors, FAK overexpression is significantly related to nodal status (p=0.05), grading (p=0.007), p53 nuclear accumulation (p=0.047) and p-AKT overexpression (p=0.001) and it appears to be a useful tool in identifying BC patients at higher risk of progression. The presence of FAK upregulation in LA subtype, may represent a useful tool in identifying those LA patients who would benefit from more aggressive adjuvant therapy. In this context, further investigations are necessary to better assess the prognostic role of FAK overexpression in low risk BC. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1091.