Long-term treatment of breast cancer cell lines with trastuzumab generates highly enriched CSCs of an EMT phenotype, which allows secretion of over 100-fold more IL-6 than parental cells and promotes resistance development.90 Trastuzumab resistance can be mediated by IL-6-involved inflammatory loop, suggesting that blocking such a loop may help overcome resistance to targeted agents. Here, IL6 is linked to breast cancer.