Evaluation of P63 Autoantibodies as a Biomarker for Head & Neck Squamous Cell Carcinoma
Haifa Gallai, Richard O Wein, Karl Kelsey, Lynn W Solomon. Tufts University, Boston, MA; Tufts Medical Center, Boston, MA; Brown University, Providence, RI; Emory University, Atlanta, GA
Background: Amplification and overexpression of the p63 gene on chromosome 3q27–29 is reported in 85% of head and neck squamous cell carcinomas (HNSCC). Overexpressed p63 functions as an oncogene. Protein overexpression can override host immune self-tolerance and produce a humoral immune response to self proteins. Previous studies detected serum p63 autoantibodies in 18% of patients with HNSCC. A case of HNSCC was serendipitously found to have p63 overexpression in the tumor cells by immunohistochemistry and serum autoantibodies to p63 by immunofluorescence studies and enzyme-linked immunosorbent assay (ELISA) (titer >0.8 OD/controls <0.1 OD; OD = optical density 450nm). Our hypothesis is that some patients with HNSCC will have serum autoantibodies to p63 that are detectable by ELISA.
Design: A case control study was designed to test serum from HNSCC patients for the presence of p63 autoantibodies. A validated ELISA was developed using recombinantly expressed p63 protein (N-terminal aa 1-205 of the ΔNp63 isoform) as the antibody capture agent. nQuery V7.0 software determined the sample size of 100 HNSCC cases and 100 age and sex matched controls (α = 0.05; power = 99%). Each serum was independently tested for IgG and IgA antibodies. Samples were tested in triplicate and the OD results averaged. SPSS for Windows V16 software was used for all statistical analyses. Receiver operator characteristic (ROC) curves were constructed to determine the optimal cut-off for classifying the disease state; the cut-off value that maximized the Youden Index was selected as the optimal cut-off. An independent-samples t-test was used and p-values less than 0.05 are considered statistically significant. The sensitivity/specificity and positive/negative predictive values were calculated.
Results: The ELISA test revealed a sensitivity of 54%, specificity of 72%, positive predictive value of 67% and a negative predictive value of 61% for IgG antibodies. Testing for IgA antibodies had a sensitivity of 75%, specificity of 47%, positive predictive value of 58.6% and a negative predictive value of 65%.
Conclusions: Testing for p63 autoantibodies by ELISA is not specific or sensitive enough to be used for screening, prognosis, treatment response monitoring or detection of disease recurrence in HNSCC. Serum p63 autoantibodies are not a reliable biomaker for HNSCC.
Category: Head & Neck
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 176, Wednesday Morning