Abstract A126: Analysis of excision repair cross complementing group 1 (ERCC1) expression in squamous cell carcinoma of the head and neck (SCCHN)

Abstract Introduction: ERCC1 is a key enzyme in the nucleotide excision repair pathway and increased expression of ERCC1 is associated with cisplatin resistance in some cancers. Given the widespread use of platinum therapy for the treatment of SCCHN, we characterized the range of ERCC1 expression in SCCHN specimens using an immunofluorescence-based assay (automated quantitative analysis-tissue microarray [AQUA-TMA]). There is currently inadequate data regarding the range of ERCC1 expression in SCCHN, and how ERCC1 levels correlates with treatment outcomes, ERCC1 has been studied in SCCHN by standard immunohistochemistry, however, this method is limited by variability of techniques and subjectivity of interpretation, Therefore, there is a need for a highly quantitative technique which can be accomplished on formalin fixed paraffin embedded tissue and small samples, Our goal is to develop a reproducible assay that can eventually be incorporated into standard patient care practice. Methods: Tissue microarrays containing head and neck squamous cell carcinoma samples obtained from patients treated at Fox Chase Cancer Center from 1999–2006 were constructed. Slides were stained by a modified indirect immunofluorescence method. Sections were incubated with ERCC1 antibody (8F1, Lab Vision) and wide-spectrum screening rabbit cytokeratin antibody (Dako Z0622). Prolong Gold mounting medium (P36931; Molecular Probes) containing 4,6-Diamidino-2-phenylindole (DAPI) was used to define tissue nuclei. A binary image (tumor mask) was created from the cytokeratin image of each histospot. ERCC1 levels were measured using fluorescent immunohistochemistry on the HistoRx PM-2000 image analysis platform and the data analyzed using AQUA algorithms. The in situ biomarker profiling system generated quantitative measurements of patient protein levels based on AQUA scores derived from fluorescent output of labeled markers. Both nuclear and non-nuclear (i.e., non-membrane/cytoplasmic) ERCC1 expression was measured Results: 41 SCCHN specimens (24 oral cavity, 7 oropharynx, 5 glottic tumors, 3 unknown primary, 2 other) were analyzed. There were 25 males and 16 females and age at diagnosis ranged from 25 to 80 years (mean 64). The majority of patients were treated primarily by surgery. The range of AQUA scores was 33.66 to 1696.39 (mean 501.78, stnd deviation 284). The 25th percentile was 337.35, and the 75th percentile was 639.37. ERCC1 was predominantly nuclear (i.e., non-membrane/cytoplasmic) in the SCCHN tissue samples. Conclusions: 1) It is feasible to determine a quantitative value of ERCC1 expression with AQUA. 2) There is a wide range of ERCC1 expression in SCCHN. 3) ERCC1 is predominantly localized to the nuclear compartment. 4) Ongoing work is being done to correlate ERCC1 levels with clinical features, sensitivity to platinum therapy, and survival. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A126.