Recently, research into the development of new targeted therapies has focused on specific genetic alterations to create advanced, more personalized treatment. One of the target genes, fibroblast growth factor receptor-1 (FGFR1), has been reported to be amplified in estrogen receptor (ER)-positive subtype breast cancer, and is considered one possible mechanism of endocrine resistance through cross-talk between ER and growth factor receptor signaling. We performed a comprehensive analysis of FGFR1 at the levels of gene copy number, transcript and protein expression, and examined the relationships between FGFR1 status and clinicopathological parameters, including prognosis in 307 ER-positive/HER2-negative primary breast cancer patients treated with standard care at our institute. Most notably, a high level of FGFR1 protein expression was observed in 85 patients (27.7%), and was positively associated with invasive tumor size (P = 0.039). Furthermore, univariate analysis revealed that high FGFR1 protein expression was significantly correlated with poor relapse-free survival rate (P = 0.0019, HR: 2.63, 95% confidence interval: 1.17-5.98), and showed a tendency towards an increase in recurrent events if the observation period extended beyond the 5 years of the standard endocrine treatment term. FGFR1 gain/amplification was found in 43 (14.0%) patients, which was only associated with higher nuclear grade (P = 0.010). No correlation was found between FGFR1 mRNA expression levels and any clinicopathological factors. Overall, the level of FGFR1 protein expression may be a biomarker of ER-positive/HER2-negative primary breast cancer with possible resistance to standard treatment, and may be a useful tool to identify more specific patients who would benefit from FGFR-1 targeted therapy.
Keywords: Biomarker; ER-positive/HER2-negative; breast cancer; fibroblast growth factor receptor-1; protein expression.
© 2016 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.