J Pathol Transl Med.  2018 Jan;52(1):14-20. 10.4132/jptm.2017.10.17.

The Significance of TROP2 Expression in Predicting BRAF Mutations in Papillary Thyroid Carcinoma

• Kong JS
• Kim HJ
• Kim MJ
• Kim A
• Lee D
• Han K
• Park S
• Koh JS
• Myung JK

• KMID: 2403253
• DOI: http://doi.org/10.4132/jptm.2017.10.17

Abstract

BACKGROUND
Trophoblast antigen 2 (TROP2) is a human trophoblast cell-surface glycoprotein that is overexpressed in several types of epithelial cancers, and is suggested to be associated with an unfavorable prognosis. BRAF mutations are the most common genetic alteration in papillary thyroid carcinoma (PTC). We evaluated the correlation between TROP2 expression and BRAF mutation in PTC.
METHODS
First, we carried out pyrosequencing for BRAF mutations and immunohistochemistry for TROP2 expression with a tissue microarray consisting of 52 PTC cases. Membranous staining in at least 5% of tumor cells was designated as positive staining and we analyzed the relationship between TROP2 expression and diverse clinicopathological factors, including BRAF mutation. Second, we tested TROP2 mRNA expression in three thyroid cancer cell lines with BRAF mutations (BCPAP, SNU790, and 8505C) and a normal thyroid cell line. Additionally, we checked TROP2 protein levels in a normal thyroid cell line after introduction of the BRAF V600E mutation.
RESULTS
In this study, 21 of 26 cases with BRAF mutation showed TROP2 immunoreactivity, whereas all 26 cases without BRAF mutation showed no immunoreactivity for TROP2 with a statistically significant difference (p<.001). Upregulation of TROP2 mRNA was observed in all three thyroid cancer cell lines, but not in the normal thyroid cell line. Interestingly, however, the TROP2 expression was increased in the normal thyroid cell line after introduction of the BRAF V600E mutation.
CONCLUSIONS
Based on these results, we concluded that TROP2 expression is significantly associated with BRAF mutation and that TROP2 immunohistochemistry could be used for predicting BRAF mutations or diagnosing papillary thyroid carcinoma.

Keyword

TROP2; BRAF mutation; Papillary thyroid carcinoma

MeSH Terms

Cell Line
Glycoproteins
Humans
Immunohistochemistry
Prognosis
RNA, Messenger
Thyroid Gland*
Thyroid Neoplasms*
Trophoblasts
Up-Regulation
Glycoproteins
RNA, Messenger

Figure

• 

  Fig. 1. Representative image of trophoblast antigen 2 (TROP2) immunohistochemistry. Membranous staining of TROP2 in more than 5% area of entire field was considered positive (A) and no immunoreactivity for TROP2 expression or case showing the area of staining in less than 5% were negative (B).

• 

  Fig. 2. Expression of trophoblast antigen 2 (TROP2) in vitro. (A) Reverse transcription polymerase chain reaction. High levels of TROP2 expression were observed in all three thyroid cancer cell lines (BCPAP, SNU790, and 8505C) compared to normal thyroid cell line (Nthy). Expression of glyceraldehyde 3-phosphate dehydrogenase was used as an internal control. (B) Western blot analysis. TROP2 protein levels were increased in the normal thyroid cell line after expression of BRAF V600E mutant. The levels of p-ERK and ERK were also elevated with increasing BRAF mutational status.

Reference

1. Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics. CA Cancer J Clin. 2011; 61:69–90.

2. Shvartsur A, Bonavida B. Trop2 and its overexpression in cancers: regulation and clinical/therapeutic implications. Genes Cancer. 2015; 6:84–105.

3. McDougall AR, Tolcos M, Hooper SB, Cole TJ, Wallace MJ. Trop2: from development to disease. Dev Dyn. 2015; 244:99–109.

4. Lipinski M, Parks DR, Rouse RV, Herzenberg LA. Human trophoblast cell-surface antigens defined by monoclonal antibodies. Proc Natl Acad Sci U S A. 1981; 78:5147–50.

5. Fang YJ, Lu ZH, Wang GQ, et al. Elevated expressions of MMP7, TROP2, and survivin are associated with survival, disease recurrence, and liver metastasis of colon cancer. Int J Colorectal Dis. 2009; 24:875–84.

6. Fong D, Moser P, Krammel C, et al. High expression of TROP2 correlates with poor prognosis in pancreatic cancer. Br J Cancer. 2008; 99:1290–5.

7. Fong D, Spizzo G, Gostner JM, et al. TROP2: a novel prognostic marker in squamous cell carcinoma of the oral cavity. Mod Pathol. 2008; 21:186–91.

8. Mühlmann G, Spizzo G, Gostner J, et al. TROP2 expression as prognostic marker for gastric carcinoma. J Clin Pathol. 2009; 62:152–8.

9. Guan GF, Zhang DJ, Wen LJ, et al. Prognostic value of TROP2 in human nasopharyngeal carcinoma. Int J Clin Exp Pathol. 2015; 8:10995–1004.

10. Bignotti E, Todeschini P, Calza S, et al. Trop-2 overexpression as an independent marker for poor overall survival in ovarian carcinoma patients. Eur J Cancer. 2010; 46:944–53.

11. Bignotti E, Zanotti L, Calza S, et al. Trop-2 protein overexpression is an independent marker for predicting disease recurrence in endometrioid endometrial carcinoma. BMC Clin Pathol. 2012; 12:22.

12. Addati T, Achille G, Centrone M, et al. TROP-2 expression in papillary thyroid cancer: a preliminary cyto-histological study. Cytopathology. 2015; 26:303–11.

13. Simms A, Jacob RP, Cohen C, Siddiqui MT. TROP-2 expression in papillary thyroid carcinoma: potential diagnostic utility. Diagn Cytopathol. 2016; 44:26–31.

14. Liu H, Shi J, Lin F. The potential diagnostic utility of TROP-2 in thyroid neoplasms. Appl Immunohistochem Mol Morphol. 2017; 25:525–33.

15. Xing M. BRAF mutation in thyroid cancer. Endocr Relat Cancer. 2005; 12:245–62.

16. Schweppe RE, Klopper JP, Korch C, et al. Deoxyribonucleic acid profiling analysis of 40 human thyroid cancer cell lines reveals cross-contamination resulting in cell line redundancy and misidentification. J Clin Endocrinol Metab. 2008; 93:4331–41.

17. Koh CS, Ku JL, Park SY, et al. Establishment and characterization of cell lines from three human thyroid carcinomas: responses to all-trans-retinoic acid and mutations in the BRAF gene. Mol Cell Endocrinol. 2007; 264:118–27.

18. Busca R, Abbe P, Mantoux F, et al. Ras mediates the cAMP-dependent activation of extracellular signal-regulated kinases (ERKs) in melanocytes. EMBO J. 2000; 19:2900–10.

19. Davies H, Bignell GR, Cox C, et al. Mutations of the BRAF gene in human cancer. Nature. 2002; 417:949–54.

20. Peyssonnaux C, Eychène A. The Raf/MEK/ERK pathway: new concepts of activation. Biol Cell. 2001; 93:53–62.

21. Cubas R, Zhang S, Li M, Chen C, Yao Q. Trop2 expression contributes to tumor pathogenesis by activating the ERK MAPK pathway. Mol Cancer. 2010; 9:253.

22. Ahmed N, Oliva K, Wang Y, Quinn M, Rice G. Downregulation of urokinase plasminogen activator receptor expression inhibits Erk signalling with concomitant suppression of invasiveness due to loss of uPAR-beta1 integrin complex in colon cancer cells. Br J Cancer. 2003; 89:374–84.

23. Fang JY, Richardson BC. The MAPK signalling pathways and colorectal cancer. Lancet Oncol. 2005; 6:322–7.