BackgroundFirst-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as erlotinib, have been shown to target tumors with L858R (exon 21) and exon 19 deletions, resulting in significant clinical benefits. However, acquired resistance often occurs due to EGFR mutations. Therefore, novel therapeutic strategies for treatment of patients with EGFR-positive tumors are needed. Berberine (BBR) is an active alkaloid extracted from pharmaceutical plants such asCoptis chinensis. Berberine has been shown to significantly inhibit EGFR activity and mediate anticancer effects in multiple preclinical studies. We investigated whether combining BBR with erlotinib could augment erlotinib-induced cell growth inhibition of EGFR-positive cells in a mouse xenograft model.MethodsWe examined the antitumor activities and potential mechanisms of erlotinib in combination with berberinein vitroandin vivousing the MTT assay, immunoblotting, flow cytometry, and tumor xenograft models.ResultsIn vitrostudies with A431 cells showed that synergistic cell growth inhibition by the combination of BBR and erlotinib was associated with significantly greater inhibition of pEGFR and pAKT, and inhibition of cyclin D and Bcl-2 expression compared to that observed in response to BBR or erlotinib alone. The efficacy of the combination treatment was also investigated in nude mice. Consistent with thein vitroresults, BBR plus erlotinib significantly reduced tumor growth.ConclusionOur data supported use of BBR in combination with erlotinib as a novel strategy for treatment of patients with EGFR positive tumors.