FGFR1, 2 and 3 protein overexpression and molecular aberrations of FGFR3 in early stage non-small cell lung cancer

Abstract

This study aimed to determine protein expression levels of fibroblast growth factor receptors (FGFR) 1, 2 and 3 in early stage non-small cell lung cancer (NSCLC). Additionally, a screen to define the frequency of FGFR3-TACC3 translocation and FGFR3 amplification was performed. Archived tissues from 653 NSCLC samples (adenocarcinoma (AC), squamous cell carcinoma (SCC) and large cell carcinoma (LCC)) were analysed with immunohistochemistry (IHC) for expression of FGFR1, 2 and 3. Expression levels of FGFR1, 2 and 3 were correlated with clinicopathological features. The presence of FGFR3-TACC3 translocation was detected by RT-PCR and FGFR3 amplification was detected by fluorescence in situ hybridization. FGFR1, 2 and 3 proteins were highly expressed in 64 (10.6%), 76 (12.9%) and 20 (3.3%) NSCLC tumour samples, respectively. Protein expression of FGFR1 was significantly related to worse overall survival in NSCLC. Furthermore, FGFR1 protein expression was associated with light smoking and histological subtype (AC), FGFR2 protein expression with female gender, younger age, histological subtype (AC) and lower tumour stage, and FGFR3 protein was significantly overexpressed in tumours of older patients and SCC histology. The FGFR3-TACC3 fusion was detected in 3.0% (6/200) of NSCLC samples and the FGFR3 gene was amplified in 4.7% of IHC positive NSCLC samples (2/43). FGFR1, 2 and 3 proteins are expressed in a high number of early stage NSCLC and FGFR1 protein expression may serve as a prognostic biomarker. Recurrent translocations and amplifications in FGFR3 can be found in NSCLC. This study shows that FGFR family members are frequently aberrant in NSCLC and could be interesting therapeutic targets for the treatment of NSCLC.

Keywords: FGFR3 amplification; FGFR3‐TACC3 translocation; fibroblast growth factor receptor (FGFR); immunohistochemistry (IHC); non‐small cell lung cancer (NSCLC).

Figure 1

FGFR1, 2 and 3 protein expression by immunohistochemistry and FGFR3 copy numbers by FISH in non‐small cell lung cancer. (A, B, C) Representative immunohistochemical staining of FGFR1, 2 and 3 negative samples versus FGFR1, 2 and 3 positive (high expression) samples, respectively. FGFR1: ab10646, abcam; FGFR2: ab10648, abcam; FGFR3: Clone B‐9, sc‐13121, Santa Cruz Biotechnology. (D, E) FGFR3 amplification and FGFR3 gain, respectively, assessed by dual‐colour FISH analysis using an IGH/FGFR3 translocation dual fusion FISH probe (Cytocell).

Figure 2

FGFR protein expression differs significantly between histological subtypes in non‐small cell lung cancer. (A, B) The asterisks (*) represents statistical significance. FGFR1 and 2 protein expression used as a continuous variable in a Wilcoxon‐Mann‐Whitney test. (C) The asterisks (*) represents statistical significance. FGFR3 protein expression used as a categorical variable in a Fisher's exact test. AC, adenocarcinoma; SCC, squamous cell carcinoma; LCC, large cell carcinoma.

Figure 3

FGFR1 protein expression is related to poor overall in non‐small cell lung cancer. Survival curves by Kaplan‐Meier method. (A, B) FGFR1 and 2 compared as an ordinal four‐level variable by Logrank test. (C) FGFR3 compared as an ordinal three‐level variable by Logrank test. FGFR3 high protein expression is a rare event (n = 20), which might have influenced the statistical significance of this test.