ERBB2 and breast cancer: The HER2-positive breast cancer cell line, SKBR-3, in co-culture with NHOst cells induced the TGF-β gene and a set of TGF-β response genes (including up-regulation of the tropomyosins TPM1, TPM2, TPM4), supporting previous studies that have demonstrated the critical role of TGF-β signaling during formation of bone metastases [29].