Fig 1: YAP1 induces invadopodia and tumor metastasis in vivo.A Cell lysates from MDA-MB-231 control (NC) and YAP1 knockout clones (YAP1-KO1#, 2#, and 3#) cells were analyzed using Western blot and probed for YAP1, CTGF, CYR61, TKS5, cortactin, and GAPDH. B Five-week-old female NOD-SCID mice were orthotopically injected with MDA-MB-231 YAP1 knockout cells (YAP1-KOs) or control cells (WT), into gland fat pad. Four weeks after tumor implantation, the xenografted tumors were resected and the tumor volumes were measured. n = 5 per group. C Images of sections of xenografted tumors stained with TKS5 (red), cortactin (green), and DAPI (blue). Invadopodia were visualized by colocalization of cortactin and TKS5 (white arrow). Percentage of cells with invadopodia was quantified. N = 100 cells per sample (n = 5 per group). **p < 0.01. Scale bar: 20 µm. D Eight weeks after tumor implantation, mice were sacrificed and the lung lobes were collected and examined. E H&E staining of the lung lobes showed that lung metastasis occurred in two mice in the WT group, while no nodal metastasis was detected in the YAP1-KOs groups. Scale bar: 5 mm in the upper images and 500 µm in the below images. F H&E and YAP1 IHC staining of clinical breast specimens. YAP1 expression level was presented as IHC score, YAP1 nucleus accumulation level was presented as IHC nucleus score. H&E hematoxylin–eosin staining, IHC immunohistochemistry. Normal/benign normal tissue or benign lesion (n = 6), primary IBC primary invasive breast cancer specimen (n = 21), metastatic IBC (LN) metastatic lymph node of IBC (n = 6), metastatic IBC (distant) distant metastatic tumor of IBC (n = 9). *p < 0.05; **p < 0.01, Scale bar: 50 µm.