EGFR and neoplasm: Erlotinib, which acts as an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) and blocks its downstream signaling cascade to modulate cancer proliferation, differentiation, apoptosis, invasion, and metastasis, has been shown to increase the efficacy of gemcitabine towards radiation or recurrent PDAC tumor growth in mice [46,47,48,49,50].