Abstract P4-06-08: Clinical utility of functional analysis of FGFR kinase family for selecting patients who may benefit from FGFR inhibitors

Abstract

Abstract Background: Fibroblast growth factor receptor (FGFR) family of receptor tyrosine kinases (RTKs) are currently under investigation as therapeutic targets for the treatment of breast cancer. Members of this kinase family have been associated with breast cancer progression and resistance to current therapeutics. FGFR1 amplifications range from 7.5–17% in breast cancers and are associated with a shorter overall survival. FGFR1 amplified cell lines drive activation of AKT, ERK, and RSK and are highly sensitive to FGFR1 inhibition, suggesting an oncogenic addiction to FGFR1. FGFR2 is activated in lapatinib-resistant, HER2-positive cells. Likewise, FGFR3 expression levels are elevated in tamoxifen-resistant, ER positive patients. FGFR 4 overexpression correlated with poor response to chemotherapy due to activation of MAPK and increase in B-cell lymphoma extra large (BCL-XL) levels. Using an immuno-microarray system, this study seeks to determine FGFR signal transduction pathway modulation post FGFR inhibitor treatment in breast cancer cell lines expressing varying levels of FGFR1, 2, 3 or 4. Method: FGFR 1, 2, 3, and 4 amplified cell lines (MDA-MB-134VI (KRAS), SNU16, RT112, and MDA-MB-453) were treated with varying dosages (1, 10, 100, and 1000nM) of several FGFR inhibitors (AZD4547 (pan FGFR), PD173074 (FGFR1,3) and Ponatinib-AP24534 (FGFR1)) either in presence or absence of corresponding FGF (FGF1, FGF7, FGF9, and FGF19) stimulation. Expression and activation of FGFR 1, 2, 3, and 4 and downstream signaling proteins FRS2, AKT, ERK, MEK, and RSK were measured utilizing a proximity based immuno-microarray. Results: FGFR1, 2, 3, 4 protein expression was detected in each of the corresponding four FGFR1, 2, 3, 4 amplified cell lines. Total protein levels remained unchanged with or without FGFs stimulation. Levels of FGFR1 phosphorylation increased 5 folds in MDA-MB-134VI stimulated with FGF1. FGFR2 and FGFR3 activation increased by 2–3 folds in SNU16 and RT112 stimulated with FGF7, and FGF9 respectively. FGFR4 activation levels in MDA-MB-453 remained unchanged due to Y367C mutation. ERK was activated in both FGF1 stimulated and unstimulated group in MDA-MB134 due to the KRAS mutation. RSK activation increased in both SNU16 and RT112 when stimulated with FGF7, and FGF9 respectively. FGFR inhibitors treated data analysis is currently in progress and will be presented. Conclusion: We have demonstrated utility of specific FGFR analysis using well defined model systems. FGFR- profiling should be considered during the clinical work-up in order to select patients who may benefit from regimen containing specific FGFR inhibitors. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-08.