Abstract C14: Tissue expression profile of novel tumor biomarkers identified by monoclonal antibodies.

Abstract Background: Monoclonal antibodies (mAbs) were raised against human colon tumor tissue extracts. Antibodies that specifically recognized tumor tissues, but did not cross-react with normal tissues, were selected for further characterization and development as diagnostic reagents and therapeutic candidates. Three mAbs that react with variant forms of MUC5AC, CEACAM molecules, and A33 were identified. The immunohistochemical staining profiles of these antibodies (NEO-101, NEO-201, and NEO-301) will be discussed. Methods: The three antibodies (NEO-101, NEO-201, and NEO-301) were each biotin-labeled, and used to stain a variety of tumor and normal human tissue types, typically at 10 ug/mL. Binding of the primary antibody was detected using streptavidin-HRP conjugate. Slides were reviewed and scored by light microscopy. Results: The NEO-101 antibody recognizes a variant form of MUC5AC expressed by colorectal (79%) and pancreatic (48%) cancer tissues. NEO-101 did not significantly cross-react with normal colon or pancreas tissues. Staining appeared to be cytoplasmic, membrane-associated, and elaborated into the lumenal spaces of positively stained tissues. The NEO-201 antibody recognizes variant forms of both CEACAM-5 and CEACAM-6. NEO-201 reacts with a wider variety of tumor tissue types including colorectal (98%), pancreatic (80%), lung (71%), stomach (100%), esophagus (61%), breast (31%), and ovarian (31%). Cross-reactivity to normal tissues was weak and sporadic. The NEO-301 antibody recognizes a variant form of A33, that is expressed by colorectal (46%), pancreatic (52%), lung (65%), and breast (45%) tumor tissues. NEO-301 also does not cross-react significantly with normal tissues. Antibodies NEO-201 and NEO-301 stained both cytoplasm and membranes of tissues examined. Conclusions: NEO-101, NEO-201, and NEO-301 antibodies react specifically with tumor tissues without significant cross-reactivity to normal tissues, an attractive characteristic for developing effective therapeutic and diagnostic products for oncology indications. We suggest that the antigens they react with are novel variants of commonly known wild type proteins that can be used as biomarker since they do not cross-react with healthy tissues. Interestingly, although these 3 antibodies were generated from extracts of pooled human colon tumor tissues, the variant antigens they cross-react with are not restricted to expression by colon tumor tissues, supporting the idea that variant protein expression may be a general property of tumor cells compared to normal cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C14.