Overcoming Linsitinib intrinsic resistance through inhibition of nuclear factor‐κB signaling in esophageal squamous cell carcinoma

The aim of this study is to evaluate the efficacy of insulin‐like growth factor 1 receptor (IGF‐1R) inhibitor Linsitinib, in esophageal squamous cell carcinoma (ESCC), and to characterize special biomarker to screen Linsitinib‐sensitive patients as well as explore the molecular‐resistant mechanism to Linsitinib in ESCC. Our study evaluated the sensitivity of insulin‐like growth factor 1 receptor (IGF‐1R) inhibitor, Linsitinib in ESCC cells with MTT assay. After Linsitinib treatment, the expressions of downstream signaling molecules and apoptosis pathways were measured by western blot. And the antitumor effect of Linsitinib and JSH‐23, an inhibitor of nuclear factor‐κB transcriptional activity, was analyzed both as single agent and in combination in ESCC. Apoptosis, cell viability, and clonogenic survival analysis were also investigated. The sensitivity of Linsitinib was relatively variable in patient‐derived primary ESCC cells as well as in human commercial cell lines. And the downstream AKT/mTOR and ERK signaling pathways were inhibited by Linsitinib, while phosphorylation level of NF‐κB p65 was obviously activated to reduce apoptosis effect in Linsitinib‐resistant cell lines. Most importantly, blockage of NF‐κB activity by JSH‐23 could sensitize resistant cells to Linsitinib treatment. Results from this study demonstrated that the intrinsic resistance to Linsitinib was predominantly mediated by NF‐κB activation in ESCC. Moreover, combination of Linsitinib and JSH‐23 as therapy provides a novel strategy to overcome resistance to Linsitinib in ESCC.