STAT3 and breast cancer: In this study, we revealed that STAT3 inhibition significantly increased the antitumor effect of trastuzumab on EGFRvIII+HER2+ breast cancers (Figure 2), implicating that STAT3 inhibitors might be used to increase the antitumor effect of trastuzumab on EGFRvIII+HER2+ breast cancers..