EGFR and neoplasm: Tumor-derived EGFR-containing exosomes have been shown to be crucial for the tumor microenvironment, cancer cell proliferation and metastasis, as well as for suppressing host innate immunity.30,32–34 In addition, an increasing number of studies have indicated that exosomes are involved in drug resistance in various cancers,59 and that NCI-H1975 cells harboring EGFRM2 and PC9 cells harboring EGFRD1 are resistant and sensitive to Erlotinib, respectively.