High Expression of Trophoblast Cell Surface Antigen 2 in Triple-negative Breast Cancer Identifies a Novel Therapeutic Target. (11th September 2019)

• Record Type: Journal Article
• Authors: Makhoul, Elias; Dadmanesh, Farnaz
• Is Part Of: American journal of clinical pathology. Volume 152(2019)Supplement 1
• Page Start: S37
• Page End: S37
• Publication Date: 2019-09-11
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqz113.001
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Objectives: Patients with triple-negative breast cancer (TNBC) respond poorly to current therapeutic modalities. The newly FDA-approved drug conjugate, Sacituzumab Govitecan, targeting antitrophoblastic cell surface antigen 2 (Trop-2), offers a new modality to treat these subtypes of breast carcinoma (BC). Our study examines expression of Trop-2 by immunohistochemistry (IHC) in TNBC. Methods: Forty cases of TNBC were selected from our files (34 ductal, 4 pleomorphic lobular, 1 metaplastic, and 1 mixed ductal and lobular carcinoma). A control group included 11 luminal A-like, 11 luminal B-like, and 8 HER2-like BC. Immunostaining for Trop-2 was performed on 4-micron-thick tissue sections using goat polyclonal antibody (R&D Systems). Three pathologists individually scored the % and intensity of membranous staining. The % of staining was defined as <10%, 10%-50%, and >50%. The intensity of staining was scored as 3+ (crisp circumferential membranous staining), 2+ (medium membranous staining), 1+ (patchy weak membranous staining), and 0 (no staining). A Kruskal-Wallis H-test and pairwise comparison with Bonferroni correction was performed to compare % and intensity of staining in TNBC to control group. Results: TNBC exhibited stronger Trop-2 staining in both intensity and extent when compared to the control. The result was significantly different, χ 2 (4) = 17.427, P = .001. A pairwise comparison with Bonferroni correction found significant difference between TNBC (42.55) and luminal A (16.65) ( P < .001). There was significant agreement ( P < .001) among 3 independent pathologists for assessing % and intensity of staining. Conclusion: The extent and intensity of staining for Trop-2 is higher in TNBC than in other molecular subtypes of BC. These findings suggest that patients with TNBC may potentially benefit from this targeted therapy. Furthermore, identification of Trop-2 in other molecular subtypes may expand the therapeutic potential of this new drug. Further studies are needed to determine the efficacy of this marker.