The Molecular Mechanisms Of Interferon-alpha Enhancing The Antitumour Activity Of EGFR Targeted Therapies In Head And Neck Squamous Cell Carcinoma

Objectives:The epidermal growth factor receptor(EGFR)-targeted therapies have been tested in the clinic as treatments for head and neck squamous cell carcinoma(HNSCC).Owing to intrinsic or acquired resistance,EGFR-targeted therapies often lead to a low response rate and treatment failure.Interferon-alpha(IFN?)is a multi-functional cytokine and chemosensitising agent with a tumour inhibitory effect.However,the synergic effect of IFN?and EGFR-targeted therapies(erlotinib and nimotuzumab)and their mechanisms in HNSCC remain unclear.Methods:The interactions between IFN?,erlotinib,and nimotuzumab were evaluated in vitro in HNSCC cells.The synergistic effect of IFN?(20 000 IU per day,s.c.),erlotinib(50 mg kg^-1 per day,i.g.)and nimotuzumab(10 mg kg^-1 per day,i.p.)was further confirmed in vivo using HNSCC xenografts in nude mice.The upregulation of retinoic-acid inducible gene I(RIG-I)induced by IFN? and EGFR-targeted therapies and its mechanism were detected in vitro and in vivo.Tumorsphere formation assay was conducted under incubation with IFN?for 2weeks.The expression of programmed death ligand 1(PDL1)on tumor cells was detected under endogenous or exogenous IFN?in vitro and in vivo.Results:IFN? enhances the antitumour effects of erlotinib and nimotuzumab on HNSCC cells both in vitro and in vivo.Importantly,both IFN?and EGFR-targeted therapies promote the expression of RIG-I by activating signal transducers and activators of transcription 1(Stat1)in HNSCC cells.RIG-I knockdown reduced the sensitivity of HN4 and HN30 cells to IFN?,erlotinib,and nimotuzumab.Moreover,IFN? transcriptionally induced RIG-I expression in HNSCC cells through Stat1.IFN?transcriptionally activated the expression of CD44 and aldehyde dehydrogenase 1(ALDH1A1)expression both in vivo and in vitro.Low dose of IFN?(2 and 20 ng/ml)promoted the tumorsphere formation in vitro.2 ng/ml IFN?-primed enhanced the cytotoxic inhibition effect of CDDP,erlotinib and nimotuzumab on HNSCC cells.IFN?transcriptionally activated the expression of PDL1 through p-Stat1(Tyr701).Moreover,IFN?promoted programmed death 1(PD1)expression on immune cells,especially in patients with HNSCC.Conclusions:IFN? enhances the effect of EGFR-targeted therapies by upregulating RIG-I,and its expression may represent a predictor of the effectiveness of a combination treatment including IFN?in HNSCC.Low dose of IFN?promoted expression of cancer stem cells biomarkers in HNSCC.Endogenous IFN?promoted PDL1 expression on tumor cells and PD1on immune cells,leading to immunosuppression.