Through human kinase arrays, we found that STAT3 signaling was activated in EGFR+ HER2+ breast cancer and that the inhibition of STAT3 led to the downregulation of SUSD2 levels, indicating that STAT3 was responsible for upregulated SUSD2 levels in EGFR+ HER2+ breast cancer. This evidence concerns the gene ERBB2 and breast carcinoma.