Fig. 1

YAP overexpression and activation were associated with lymphatic metastasis and poor prognosis in breast cancer patients. (a) Immunohistochemistry staining of YAP protein in paired primary and lymphatic metastatic specimens from one breast cancer patient. Lymphatic metastasis revealed a higher expression level of YAP. Scale bar: 20 μm. (b) Immunohistochemistry staining score (IHC score) of YAP expression in 101 paired primary/lymphatic metastatic breast cancer specimens from a breast cancer tissue microarray. The expression level of YAP was significantly higher in lymphatic metastases than in primary lesions (**p < 0.01 by paired Student’s t-test). Primary: primary lesion; Metastasis: lymphatic metastasis. (c) Immunohistochemistry cytoplasm expression (cytoplasmic score, left panel) and nucleus accommodation (nucleus score, right panel) of YAP in the 101 paired primary/lymphatic metastatic breast cancer specimens. The cytoplasm expression and nucleus accumulation of YAP was significantly higher in lymphatic metastases than in primary lesions (*p < 0.05 by paired Student’s t-test). Primary: primary lesion; Metastasis: lymphatic metastasis. (d) Analysis of TCGA breast invasive carcinoma dataset (n = 962) via SurvExpress program. Left: Heat map summarizing the expression values of YAP and its target genes (CTGF, CYR61, AXL and MYC) in breast cancer specimens from the TCGA dataset. Patients were sorted by prognostic index and divided into “Low Risk” and “High Risk” groups, according to the “Maximized Risk Groups” algorithm (see reference [32]). Middle: patients in the “High Risk” group presented a significantly higher expression level of YAP and its downstream genes (p < 0.01). Right: Kaplan-Meier analysis revealed that patients in the “High Risk” group suffered from poor prognosis (p < 0.01)