Evaluation of HER-2/neu gene amplification and protein expression in non-small cell lung carcinomas

Abstract

HER-2/neu gene amplification and cell surface overexpression are important factors in breast cancer for prognosis and prediction of sensitivity to anti-HER-2/neu monoclonal antibody therapy. In lung cancer, the clinical significance of HER-2/neu expression is currently under evaluation. We investigated 238 non-small lung carcinomas for HER-2/neu protein overexpression by immunohistochemistry using the HercepTest. We found 2+ or 3+ overexpression in 39 patients (16%), including 35% in adenocarcinomas and 20% in large cell carcinomas, but only 1% of squamous cell carcinomas. Marked (3+) overexpression was uncommon (4%). The association between protein expression and gene copy number per cell, as determined by fluorescence in situ hybridisation assay, was investigated in 51 of these NSCLC tumours. Twenty-seven tumours (53%) were negative by both tests. Marked (3+) protein expression and gene amplification were present in only 4% of samples. In 11 tumours (21%), gene gain was accompanied by chromosomal aneusomy and did not result in high protein levels while in 7 (14%) the score 2+ was associated with maximum number of signals per cell <9. The prognostic implication of HER-2/neu protein expression was studied in 187 surgically resected tumours. No statistical difference in survival was observed comparing patients with positive (2+/3+) and negative tumours (0/1+), although 3+ patients showed a tendency to shorter survival. The therapeutic implications of protein expression and gene amplification in lung cancer need to be examined in prospective clinical trials.

Figure 3

Kaplan–Meier survival curves according to the results of HercepTest.

Figure 1

Typical staining patterns by immunohistochemistry (HercepTest, Dako, Denmark): Normal epithelium with apical/lateral staining, but no basocellular staining (Upper left). Modified 2+with a strong basolateral staining seen in some adenocarcinomas, but without complete membrane staining (Upper right). A moderate near complete membrane staining in more than 10% of the cells, considered as 2+(lower left). Complete strong membrane staining, considered as 3+(lower right).

Figure 2

Dual-colour FISH assay using the PathVysion DNA probe (Vysis) in lung tissue sections. HER-2/neu probe is labelled in red (SpectrumOrange) and chromosome 17 probe is labelled in green (SpectrumGreen). Chromatin in staining in blue (DAPI). Gene amplification (Gene/Chromosome ratio >2.0) is illustrated in patients with adenocarcinomas with HercepTest score 0 in (A) and HercepTest score 3+ in (B). Small HER-2/neu clusters (Gene/Chromosome ratio 1.2) are illustrated in (C) for a patient with squamous cell carcinoma and HercepTest 1+. Balanced aneusomy (Gene/Chromosome ratio 1.0) is shown in an adenocarcinoma patient with HercepTest score 2+ (D).