EGFR inhibitors (EGFRIs)  including EGFR monoclonal antibodies (mAbs) are a well-established targeted therapy for several cancers. However, EGFRIs frequently cause cutaneous adverse effects such as papulo-pustular eruption, xerosis and chronic paronychia. We previously reported that EGFR mAbs suppress the production of human β-defensin (hBD)  induced by staphylococci in vitro. In this study, we investigated that whether EGFR mAbs have an influence on innate immune response in actual skin of patients. 
Stratum corneum samples were obtained from 26 patients treated with EGFR mAbs. Samples were taken from cheeks of the patients by tape stripping before and after onset of treatments. Total protein was extracted from the stratum corneum and the levels of hBD1, 2 and 3  were evaluated by ELISA. 
We found that hBD productions were decreased in patients treated with EGFR mAbs, and the suppression of hBD productions by EGFR mAbs were correlated with the development of papulo-pustular eruptions. 
Our results suggest that these suppressive effects of EGFR mAbs on hBD productions may be involved with pathological mechanism of cutaneous adverse effects caused by EGFR mAbs.

Human β-defensins are involved with pathological mechanism of cutaneous adverse effects caused by EGFR inhibitors