Automated ERCC1 immunohistochemistry in non-small cell lung cancer: comparison of anti-ERCC1 antibodies 8F1, D-10, and FL-297.

INTRODUCTION: The excision repair cross-complementation group 1 (ERCC1) protein is the key enzyme of the nucleotide excision repair (NER) pathway and thus a potential predictor for platinum-based chemotherapy response. We aimed for evaluating different anti-ERCC1 antibodies on formalin-fixed tumor tissue of non-small cell lung cancer patients by automated immunohistochemistry (IHC).
METHODS: ERCC1 protein expression was assessed on a tissue microarray of 491 NSCLC's using 2 monoclonal mouse (Mab 8F1, Mab D-10) and 1 polyclonal rabbit (Rab FL-297) antibody. Two automated IHC platforms with different detection systems and immunofluorescence were used. Protein expression levels were independently scored by 2 pathologists for both intensity and intensity multiplied by percentage of positive cells (H-score).
RESULTS: On both platforms, the 8F1 ab showed best nuclear staining quality. D-10 had additional unspecific background at the plasma membrane and in goblet cells. FL-297 could not be scored owing to high cytoplasmic background. Both 8F1 and D-10 antibodies produced a speckled granular pattern over the whole nuclear compartment. No intranuclear compartmentalization was observed, apart from omission of the nucleolus. Interobserver κ value was good to very good for 8F1 and D-10. Using 8F1, low ERCC1 was correlated with the adenocarcinoma histotype, increased tumor size and clinical stage, high pT and pN category and the presence of metastasis. No relation to progression-free or overall survival was observed.
CONCLUSIONS: In terms of staining quality and restriction to the nuclear compartment, the antibody 8F1 is superior to D-10 or FL-297 on automated IHC platforms.