CD44v9 as a poor prognostic factor of triple-negative breast cancer treated with neoadjuvant chemotherapy

Background: Neoadjuvant chemotherapy (NAC) is the standard therapeutic strategy for triple-negative breast cancer (TNBC). TNBC patients with residual disease after NAC have a significantly worse survival than those with pathological complete response (pCR); however, there is no apparent prognostic factor for non-pCR patients. Cancer stemness or epithelial–mesenchymal transition (EMT) might influence the sensitivity to chemotherapy. Patients and methods: Forty-eight patients with TNBC who were treated with NAC were available were included in this study. The expressions of stemness marker CD44v9, EMT marker vimentin and BRCA1, and basal phenotype were evaluated with immunohistochemistry. The relationships between the expression of these proteins and the pCR rate and the prognosis, especially in the patients with residual tumors, were investigated. Results: Among the 48 patients, pCR was achieved in 14 cases. High nuclear grade and basal phenotype in the pre-NAC samples were significantly correlated with pCR (p = 0.0458 and 0.0343). There were no significant relationships between the pCR rate and the expression of CD44v9, vimentin, or BRCA1. Achieving pCR was significantly correlated with longer distant metastasis-free survival (DMFS) (p = 0.0206). High CD44v9 expression was significantly associated with shorter DMFS (p = 0.0291). Among the patients in whom pCR was not achieved, high grade in the residual tumor cells, poor pathological response and high CD44v9 expression in the pre-treatment CNB samples were significantly correlated with a poor DMFS (p = 0.0433, 0.0406 and p = 0.0333). In addition, high grade in the residual tumor cells was significantly associated with high CD44v9 expression in the pre-treatment CNB (p = 0.0389). Conclusions: High CD44v9 expression in pre-NAC samples was associated with poor prognosis in TNBC patients treated with NAC, especially for those in whom pCR was not achieved.