Background Chemoradiotherapy‐induced PD‐L1 upregulation leads to therapeutic resistance and treatment failure. The PD‐1/PD‐L1 blocking antibodies sensitize cancers to chemoradiotherapy by blocking extracellular PD‐1 and PD‐L1 binding without affecting the oncogenic function of intracellular PD‐L1. Reversing the chemoradiation‐induced PD‐L1 expression could provide a new strategy to achieve a greater anti‐tumour effect of chemoradiotherapy. Here, we aimed to identify candidate small molecular inhibitors that might boost the anti‐tumour immunity of chemoradiotherapy by decreasing treatment‐induced PD‐L1 expression in non‐small cell lung cancer (NSCLC). Methods A drug array was used to recognize compounds that can suppress the cisplatin‐induced and radiation‐induced PD‐L1 expression in NSCLC via the flow cytometry‐based assay. We examined whether and how targeting bromodomain containing 4 (BRD4) inhibits chemoradiation‐induced PD‐L1 expression and evaluated the effect of BRD4 inhibition and chemoradiation combination in vivo. Results BRD4 inhibitors JQ1 and ARV‐771 were identified as the most promising drugs both in the cisplatin and radiation screening projects in two NSCLC cell lines. Targeting BRD4 was supposed to block chemoradiotherapy inducible PD‐L1 expression by disrupting the recruitment of BRD4‐IRF1 complex to PD‐L1 promoter. A positive correlation between BRD4 and PD‐L1 expression was observed in human NSCLC tissues. Moreover, BRD4 inhibition synergized with chemoradiotherapy and PD‐1 blockade to show a robust anti‐tumour immunity dependent on CD8+ T cell through limiting chemoradiation‐induced tumour cell surface PD‐L1 upregulation in vivo. Notably, the BRD4‐targeted combinatory treatments did not show increased toxicities. Conclusion The data showed that BRD4‐targeted therapy synergized with chemoradiotherapy and anti‐PD‐1 antibody by boosting anti‐tumour immunity in NSCLC.
Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) tyrosine kinase inhibitors (TKIs) have achieved remarkable clinical progress in the treatment of non-small-cell lung cancer; however, resistance has limited their therapeutic efficacy. Therefore, understanding the mechanisms of VEGF-TKI and ICI resistance will help to develop effective treatment strategies for patients with advanced NSCLC. Our results suggested that treatment with VEGFR2-TKIs upregulated ADRB2 expression in NSCLC cells. Propranolol, a common ADRB2 antagonist, significantly enhanced the therapeutic effect of VEGFR2-TKIs by inhibiting the ADRB2 signaling pathway in NSCLC cells in vitro and in vivo. Mechanically, the treatment-induced ADRB2 upregulation and the enhancement of ADRB2/VEGFR2 interaction caused resistance to VEGFR2-TKIs in NSCLC. And the inhibition of the ADRB2/CREB/PSAT1 signaling pathway sensitized cells to VEGFR2-TKIs. We demonstrated that ADRB2 signaling is crucial in mediating resistance to VEGFR2-TKIs and provided a novel promising combinatory approach to enhance the antitumor effect of VEGFR2-TKIs in NSCLC combining with propranolol.
The efficacy of apatinib has been confirmed in the treatment of solid tumors, including non-small-cell lung cancer (NSCLC). However, the direct functional mechanisms of tumor lethality mediated by apatinib and the precise mechanisms of drug resistance are largely unknown. In this study, we demonstrated that apatinib could reprogram glutamine metabolism in human NSCLC via a mechanism involved in amino acid metabolic imbalances. Apatinib repressed the expression of GLS1, the initial and rate-limiting enzyme of glutamine catabolism. However, the broken metabolic balance led to the activation of the amino acid response (AAR) pathway, known as the GCN2/eIF2α/ATF4 pathway. Moreover, activation of ATF4 was responsible for the induction of SLC1A5 and ASNS, which promoted the consumption and metabolization of glutamine. Interestingly, the combination of apatinib and ATF4 silencing abolished glutamine metabolism in NSCLC cells. Moreover, knockdown of ATF4 enhanced the antitumor effect of apatinib both in vitro and in vivo. In summary, this study showed that apatinib could reprogram glutamine metabolism through the activation of the AAR pathway in human NSCLC cells and indicated that targeting ATF4 is a potential therapeutic strategy for relieving apatinib resistance.
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