Trophoblast Cell Surface Antigen 2 Expression in Thymic Carcinoma: Brief Report.

Introduction: Trophoblast cell surface antigen 2 (TROP2) is a transmembrane glycoprotein overexpressed in various cancer types. Although TROP2-targeting therapy is currently attracting attention, little is known about TROP2 expression in thymic carcinoma.
Methods: TROP2 gene expression in thymic epithelial tumors was analyzed using RNA-sequencing (RNA-seq) data for 122 cases obtained from The Cancer Genome Atlas. Immunohistochemistry (IHC) staining with anti-TROP2 antibody (SP295) was performed in 26 cases of thymic carcinoma tissues surgically resected at Juntendo University.
Results: RNA-seq data analysis from The Cancer Genome Atlas revealed that TACSTD2 (gene encoding TROP2) expression was significantly higher in thymic carcinoma than in thymoma (adjusted p  = 6.64e-05). There was also a trend of increasing expression in the order of thymoma type B1, B2, B3, and thymic carcinoma. As for IHC in thymic carcinoma, TROP2 expression was localized to the membrane of cancer cells. Intensity 0, 1, and 2 was observed in six (23.1%), 11 (42.3%), and nine (34.6%) cases, respectively, leading to TROP2 positivity in 20 cases (76.9%). The median proportion of TROP2-positive tumor cells and the median H-score were 25.0% (range: 0%-100%) and 25.0 (range: 0-200), respectively. No relevant factors were identified in the analysis of TROP2 expression and patient background. Although not significant, high TROP2 expression (H-score ≥ 50) tended to be associated with shorter survival.
Conclusions: TROP2 expression in thymic carcinoma was confirmed by both RNA-seq and IHC, with high expression observed in IHC for intensity (76.9%) and proportion. TROP2 could be a potential target in thymic carcinoma.
Competing Interests: Dr. Asao reports honoraria from AstraZeneca K.K., Bristol-Myers K.K., Chugai Pharmaceutical Co., Ltd., Daiichi Sankyo Co., Ltd., Eli Lilly Japan K.K, Merck Biopharma Co., Ltd., Merck Sharp & Dohme K.K, Nippon Boehringer Ingelheim Co., Ltd., Nippon Kayaku Co., Ltd., Ono Pharmaceutical Co., Ltd., Pfizer Inc., Taiho Pharmaceutical Co., Ltd., and Takeda Pharmaceutical Company Limited outside of the submitted work. Dr. Shukuya reports grants and honoraria from AstraZeneca K.K., Chugai Pharmaceutical Co., Ltd., Nippon Boehringer Ingelheim Co., Ltd., Novartis Pharma K.K., and Merck Sharp & Dohme K.K. and honoraria from Taiho Pharmaceutical Co., Ltd., Daiichi Sankyo Co., Ltd., Ono Pharmaceutical Co., Ltd., Bristol-Myers Squibb Company, Nippon Kayaku Co., Ltd., Takeda Pharmaceutical Company, Pfizer Inc., and Eisai Co., Ltd. outside of the submitted work. Dr. Fumiyuki Takahashi reports grants from 10.13039/100004325AstraZeneca, 10.13039/100017346Nippon Boehringer Ingelheim, 10.13039/100009947Merck Sharp & Dohme, 10.13039/100004336Novartis, and Lilly Japan outside of the submitted work. Dr. Kazuhisa Takahashi reports grants and honoraria from Chugai Pharmaceutical Co., Ltd., Nippon Boehringer Ingelheim Co., Ltd., Pfizer Inc., Taiho Pharmaceutical Co., Ltd., Kyorin Pharmaceutical Co., Ltd., Ono Pharmaceutical Co., Ltd., Novartis Pharma K.K., Eli Lilly Japan K.K., Nippon Kayaku Co., Ltd., Takeda Pharmaceutical Company Limited, and grants from 10.13039/100018036Nippon Shinyaku Co., Ltd., Tsumura & Co., Teijin Pharma Limited, 10.13039/100015990Sanofi K.K., Shionogi & Co., Ltd., Bayer Yakuhin, Ltd., 10.13039/501100002973Daiichi Sankyo Co., Ltd., Nipro Pharma Corporation, 10.13039/100010740Asahi Kasei Pharma Corporation, Kyowa Kirin Co., Ltd., and honoraria from Merck Sharp & Dohme K.K., AstraZeneca K.K., Merck Biopharma Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Bristol-Myers K.K., Meiji Seika Pharma Co., Ltd., Viatris Inc., Janssen Pharmaceutical K.K., Abbott Japan LLC, and Thermo Fisher Scientific Inc. outside the submitted work. The remaining authors declare no conflict of interest.
(© 2024 The Authors.)