Detection of tumor-specific autoantibodies in sera of patients with lung cancer.

The presence of autoantibodies (AAs) in sera from two pulmonary carcinoma patients, adenocarcinoma (AD) and small cell carcinoma (SCLC) was screened by immunoblotting using cell lysate of four cell lines (LCN1, large cell neuroendocrine carcinoma (LCNEC); N231, SCLC; A549, AD; RERF-LC-AI, squamous cell carcinoma (SCC)). To identify the antigens recognized by AAs, two-dimensional gel electrophoresis was immunoblotted and target spots were cut out from the membrane and gel. After trypsin digestion, the proteins were analyzed by mass-spectrometry using a liquid chromatography-tandem mass spectrometer. By this method, cytokeratin18 (CK18) and villin1 were identified with AAs in sera from patients with AD and SCLC, respectively. Thus, the expressions of CK18 and villin1 were further immunohistochemically studied on 124 formalin-fixed and paraffin-embedded pulmonary carcinomas of various histologic types (44 AD, 27 SCC, 29 SCLC, and 34 LCNEC) using commercially available CK18 and villin1 antibodies. Positive CK18 immunostaining was observed in almost all cases with staining intensities significantly higher in AD and LCNEC than in SCC and SCLC. Villin1 was detected in 17/44 (38.6%) of AD and 21/34 (61.8%) of LCNEC, respectively, while in only one each of SCLC and SCC. Thus, villin1 and CK18 may be useful markers to distinguish LCNEC/AD from SCLC/SCC, and the present method might be useful to identify specific tumor-associated molecules in sera from pulmonary carcinoma patients with different histologic types.