Abstract
Abstract Introduction Tumor-associated calcium signal transducer 2 (TROP-2) is a transmembrane glycoprotein overexpressed in various types of epithelial carcinomas from lung, breast, stomach, ovary, cervix, colon and pancreas. A recent immunohistochemical (IHC) study indicated that TROP-2 is also overexpressed in thyroid papillary carcinoma, but the sensitivity is only 82% in formalin-fixed and paraffin-embedded thyroid (FFPE) tissues when a polyclonal anti-TROP-2 antibody was used. A high quality of TROP-2 antibody for IHC applications is needed to improve the sensitivity of the detection of thyroid papillary carcinoma in FFPE tissues. Methodology A rabbit monoclonal antibody (clone SP295) against human TROP-2 protein was developed. Western blot was performed using SK-BR-3 cell lysates to verify the specificity of the TROP-2 antibody. An IHC study of TROP-2 was performed on normal tissue and tumor arrays from the thyroid and other organs. TROP-2 staining intensity was semi-quantitatively scored using a 0-3 scale. The sensitivity and specificity of the TROP-2 IHC assay for detecting papillary carcinoma were determined using 65 cases of thyroid papillary carcinoma, 29 cases of follicular carcinoma, and 31 cases of other thyroid conditions (normal, adenoma, Grave's disease, thyroiditis, Goiter, medullary carcinoma, clear cell carcinoma, squamous cell carcinoma, and undifferentiated carcinoma). Results A single band at 33 kDa was detected by SP295 on a western blot. In normal tissues, TROP-2 is detectable by IHC mostly in squamous epithelia of many normal organs (skin, pharynx, esophagus, and cervix) and cuboidal and columnar epithelium (breast, kidney, liver, uterus, pancreas, prostate and transitional epithelium of the bladder). In thyroid lesions, the TROP-2 positive rate is 100% (65/65) in papillary adenocarcinoma and it is negative in all other thyroid conditions (normal, adenoma, Grave's disease, thyroiditis, Goiter, medullary carcinoma, clear cell carcinoma, squamous cell carcinoma, and undifferentiated carcinoma). The sensitivity and specificity of TROP-2 IHC for detecting papillary carcinoma were both 100% in this study. Conclusions Rabbit monoclonal TROP-2 antibody (clone SP295) is highly sensitive and specific for detecting TROP-2 in FFPE tissues and it can be used to identify thyroid papillary carcinoma. Citation Format: Zhiming Liao. Immunohistochemical study of TROP-2 protein expression in thyroid lesions. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 463.
Published Version
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