MET and breast cancer: In MCF-7 and T47D breast cancer cells, the acquisition of fulvestrant resistance was accompanied by an increase in c-Met expression, which promoted the response to CAF-secreted HGF.76 In TNBCs, CAF-released HGF improves survival of breast cancer cells in the presence of EGFR inhibitors gefitinib and erlotinib.77 In Her2-positive breast cancers, HGF is able to restore PI3K and Ras/Raf/MEK/ERK pathway activities that were lost upon treatment with the EGFR/Her2 kinase inhibitor lapatinib, thereby inducing drug resistance.8 Several other growth factors also play active roles in cancer resistance.