Human non-small cell lung cancer cells A549, human fetal lung fibroblasts HFL1, and human umbilical vein endothelial cells (HUVECs) were co-cultured on the chip to evaluate the efficacy of gefitinib, an epidermal growth factor receptor (EGFR)-targeted drug, and to investigate the mechanisms underlying drug resistance in A549 cells (Fig. 3A). Here, EGFR is linked to non-small cell lung carcinoma.