Myelin expression factor 2 expression is associated with aggressive phenotype in triple-negative breast cancer

Triple-negative breast cancers (TNBCs) are characterized by an aggressive clinical course with frequent recurrence and short survival and an absence of molecular targets. Myelin expression factor 2 (MYEF2) is suggested to play a role in carcinogenesis by in silico analysis; however, the function of MYEF2 in cancer is largely unknown. The purpose of this study was to investigate MYEF2 expression in TNBC. Immunohistochemistry for MYEF2 was performed on tissue microarray sections from 132 patients with TNBC and interpreted using a semiquantitative immunoreactive score (IRS). Association of MYEF2 expression with various clinicopathologic characteristics, including patient survival, was analyzed. MYEF2 expression was localized in the nucleus of tumor cells, and positive staining was observed in 90.15% of TNBCs. Expression of MYEF2 was positively correlated with tumor size (P = 0.027), AJCC stage (P = 0.013), and Ki-67 proliferation index (P < 0.001). Survival analyses using Cox proportional regression model revealed that lymphovascular invasion, lymph node metastasis, and AJCC stage were prognostic factors for disease-free and overall survival. Patients with high MYEF2-expressing tumors showed a decreased estimated survival time (96 months) compared with patients with absent or low MYEF2 expression (101 months), however, the difference was not statistically significant (P = 0.178). Expression of MYEF2 is significantly correlated with aggressive phenotypes of TNBC, such as larger tumor size, high AJCC stage, and Ki-67 proliferation index. Further functional studies will be required to define the role of MYEF2 in cancers.