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Humoral immune response against overexpressed oncogenic or tumor supressor proteins has been demonstrated for many types of cancer. In this study we report on the detection of the autologous antibody response to putative oncogene, human cortactin using serological analysis of breast carcinoma expression library. Cortactin maps to chromosome 11q13, the region ampli®ed in about 15% of primary breast carcinomas and 30% of head and neck squamous cell carcinomas. Cortactin overexpression due to such ampli®cation might a ect adhesive properties of human cancer cells and is associated with poor disease prognosis. Accordingly, we detected overexpression of cortactin transcript in autologous tumor and ampli®ca-tion/overexpression of cortactin in tumors of breast cancer patients serologically positive for this marker. We demonstrate that 15% of breast cancer patients elicit humoral immune response against human cortactin. Oncogene (2000) 19, 5204 ± 5207.Keywords: breast cancer; cortactin; cancer antigen; tumor markerThe development of cancer vaccines requires the identi®cation and characterization of tumor antigens. In the past decade many tumor antigens have been de®ned (reviewed by Old and Chen, 1998;Rosenberg, 1999).In 1991 T Boon and colleagues discovered the ®rst antigen recognized by cytotoxic T-lymphocytes (CTL) in human melanoma (van der Bruggen et al., 1991). In their study tumor antigens have been identi®ed by the transfection of cDNA libraries into cells expressing the appropriate MHC molecule followed by the identi®ca-tion of transfectant using cytokine release or lysis by human T cells with speci®c antitumor reactivity (Boon et al., 1994).An alternative technique for the identi®cation of tumor antigens has been reported by Sahin et al. (1995). This approach of serological analysis of cDNA expression libraries (SEREX), was based on previously described molecular screening techniques (D'Arpa et al., 1988) and exploited patient's B-cell repertoire for the identi®cation of human tumor antigens that show immunogenicity in the autologous host. Many antigens have been isolated by this technique, demonstrating that most, if not all, human cancers express multiple antigens including ampli®ed/overexpressed proteins with known cancer association (reviewed by Old and Chen, 1998;Disis and Cheever, 1996;Brass et al., 1999).In this study we applied the SEREX method to isolate and characterize candidate tumor antigens expressed in breast carcinoma. A cDNA library in phage expression vector (lambda ZAP Express) was prepared from a surgical tumor specimen of a 56-yearold woman with ER-positive breast carcinoma (T 1 M 0 N 0 ). The library was plated and screened with autologous patient's serum diluted 1 : 200 as previously described (Scanlan et al., 1998). Screening of 3610 5 primary recombinant phage clones yielded a total of 70Oncogene (2000) 19, 5204 ± 5207 ã 2000 Macmillan Publishers Ltd All rights reserved 0950 ± 9232/00 $15.00 www.nature.com/onc The deduced amino acid sequence of MOBr-140 represents human cortactin from a...

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