Trichostatin A downregulates bromodomain and extra-terminal proteins to suppress osimertinib resistant non-small cell lung carcinoma

Yuting Meng,Xixi Qian,Xuerong Wang,Nan Li,Tong Sun,Baoan Chen,Shengjie Wu,Li Zhao

doi:10.1186/s12935-021-01914-y

Abstract

BackgroundThe third-generation epithelial growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have shown significant therapeutic effects on patients with non-small cell lung carcinoma (NSCLC) who carry active EGFR mutations, as well as those who have developed acquired resistance to the first-generation of EGFR-TKIs due to the T790M mutation. However, most patients develop drug resistance after 8–10 months of treatment. Currently, the mechanism has not been well clarified, and new therapeutic strategies are urgently needed.MethodsOsimertinib resistant cell lines were established by culturing sensitive cells in chronically increasing doses of osimertinib. The anticancer effect of reagents was examined both in vitro and in vivo using the sulforhodamine B assay and a xenograft mouse model. The molecular signals were detected by western blotting. The combination effect was analyzed using CompuSyn software.ResultsWe found that bromodomain and extra-terminal proteins (BETs) were upregulated in osimertinib resistant (H1975-OR) cells compared with those in the paired parental cells (H1975-P), and that knockdown of BETs significantly inhibited the growth of H1975-OR cells. The BET inhibitor JQ1 also exhibited stronger growth-inhibitory effects on H1975-OR cells and a greater expression of BETs and the downstream effector c-Myc than were observed in H1975-P cells. The histone deacetylase (HDAC) inhibitor trichostatin A (TSA) showed stronger growth suppression in H1975-OR cells than in H1975-P cells, but vorinostat, another HDAC inhibitor, showed equal inhibitory efficacy in both cell types. Consistently, downregulation of BET and c-Myc expression was greater with TSA than with vorinostat. TSA restrained the growth of H1975-OR and H1975-P xenograft tumors. The combination of TSA and JQ1 showed synergistic growth-inhibitory effects in parallel with decreased BET and c-Myc expression in both H1975-OR and H1975-P cells and in xenograft nude mouse models. BETs were not upregulated in osimertinib resistant HCC827 cells compared with parental cells, while TSA and vorinostat exhibited equal inhibitory effects on both cell types.ConclusionUpregulation of BETs contributed to the osimertinib resistance of H1975 cells. TSA downregulated BET expression and enhanced the growth inhibitory effect of JQ1 both in vitro and in vivo. Our findings provided new strategies for the treatment of osimertinib resistance.

Highlights

The third-generation epithelial growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have shown significant therapeutic effects on patients with non-small cell lung carcinoma (NSCLC) who carry active epidermal growth factor receptor (EGFR) mutations, as well as those who have developed acquired resistance to the first-generation of EGFR-TKIs due to the T790M mutation
We explored the mechanism of osimertinib resistance by first establishing osimertinib resistant cell lines (H1975-osimertinib resistant, H1975-OR) using an osimertinib sensitive cell line H1975 (H1975-parental, H1975-P), which harbors EGFR L858R and T790M mutations resulting in constitutively activated EGFR signaling and shows sensitivity to osimertinib but resistance to the first-line EGFR-TKI erlotinib
H1975-OR cells were smaller in size than the H1975-P cells (Fig. 1a), but the growth rates were comparable between the two cell lines, as determined by sulforhodamine B (SRB) assays

Summary

Introduction

The third-generation epithelial growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have shown significant therapeutic effects on patients with non-small cell lung carcinoma (NSCLC) who carry active EGFR mutations, as well as those who have developed acquired resistance to the first-generation of EGFR-TKIs due to the T790M mutation. EGFR tyrosine kinase inhibitors (EFGR-TKIs) have achieved clinically significant therapeutic effects, but patients can develop resistance after 8–10 months of TKI treatment [4]. Osimertinib has been recommended as the first-line treatment for patients with advanced or metastatic NSCLC who carry EGFR-sensitive mutations or acquired T790M resistant mutations after using first or second-generation EGFRTKIs [8]. An effective strategy is still needed for treatment of patients who have developed resistance to the third-generation EGFR-TKIs

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Discussion

Conclusion