Expression of epithelial membrane protein (EMP) 1, EMP 2, and EMP 3 in thyroid cancer.

Purpose Epithelial membrane protein (EMP) 1, EMP2, and EMP3 are expressed in various types of tumors and have been reported to be involved in carcinogenesis. In this study, we aimed to investigate the expression of these proteins in primary and metastatic thyroid cancer and its clinical implication. Methods EMP1, EMP2, and EMP3 immunohistochemistry was performed using tissue microarrays of 545 primary thyroid carcinomas [338 papillary thyroid carcinoma (PTC), 111 follicular carcinoma (FC), 69 medullary carcinoma (MC), 23 poorly differentiated carcinoma (PDC), and 4 anaplastic carcinoma (AC)] and 59 recurrent or metastatic PTCs. Results EMP1 showed high expression in AC, PTC, FC (P<0.001), and EMP2 was highly expressed in AC (P<0.001). EMP1 and EMP2 were not expressed in stromal cells. Expression of EMP3 in tumor cells [EMP3 (T)] was higher in PDC, PTC, and AC (P<0.001), and expression in stromal cells [EMP3 (S)] was observed only in AC and PTC (P=0.001). The expression of EMP1 (P=0.002) and EMP3 (T) (P<0.001) was higher in conventional PTC than in follicular variant PTC. PTC with BRAF V600E mutation showed higher expression of EMP1 (P<0.001), EMP3 (T) (P<0.001), and EMP3 (S) (P=0.012) than PTC without BRAF V600E mutation. In the PTC without BRAF V600E mutation group, expression of EMP3 (S) was associated with shorter disease free survival (P=0.004). Metastatic PTC showed higher EMP2 (3.4% vs. 0%, P=0.022) and lower EMP3 (T) (44.1% vs. 66%, P=0.001) than primary PTC. Conclusions Expression of EMP1, EMP2, and EMP3 is different according to the subtypes of thyroid cancer. Further studies are needed to determine their role as prognostic markers and treatment target in thyroid cancer.