Trastuzumab treatment is associated with elevated transforming growth factor beta gene expression.

The transforming growth factor beta superfamily, as its name implies, is critical for oncogenesis in multiple cellular contexts (1-8). We found, through mining published microarray and multiplexed gene expression data (9-11), that administration of trastuzumab was associated with increased expression of TGFBR1 and TGFBI. These data serve as one piece of evidence arguing against the use of trastuzumab in human breast cancer, a patient population already prone to difficult-to-treat metastases (12-15).