Vimentin as a poor prognostic factor for triple-negative breast cancer

Triple-negative breast cancer (TNBC), characterized by the absence of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2, is a highly heterogeneous disease. Recent studies suggest that there are links between TNBC and the epithelial-mesenchymal transition (EMT). To identify prognostic biomarkers and novel therapeutic targets, vimentin, one of the most major factors associated with EMT was investigated in TNBC. Sporadic invasive ductal carcinoma specimens were obtained from 659 Japanese patients, and 90 (14 %) cases were diagnosed as TNBC. The vimentin mRNA and protein expression levels were evaluated by quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry. The mRNA expression of vimentin was significantly upregulated in the basal-type breast cancer cell line. Immunohistochemically, the vimentin expression was significantly higher (p = 0.0042) in TNBC compared with the other subtypes. Vimentin expression was associated with a younger age (p = 0.016), high nuclear grade (p = 0.023) and high Ki67 expression (p < 0.0001), and a poorer prognosis in terms of both the recurrence-free survival (RFS) (p = 0.0058) and overall survival (OS) (p = 0.013) in TNBC patients. A multivariate analysis showed that vimentin expression was an independent prognostic factor for the RFS (p = 0.043). Vimentin expression was also associated with a significantly shorter RFS (p = 0.021) and OS (p = 0.017) in patients with basal-like breast cancer (BLBC). The elevated expression of vimentin contributes to the aggressive phenotype and poor prognosis in TNBC. Vimentin expression might be useful as a biomarker for the prognosis of TNBC.