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EGFR tyrosine kinase inhibition induces autophagy in cancer cells.

ABSTRACT: The epidermal growth factor receptor (EGFR) signaling pathway is frequently dysregulated in a variety of human malignancies. As a result, agents have been developed to selectively inhibit the tyrosine kinase function of EGFR (EGFR-TKI) for cancer therapy. However, the clinical efficacy of these drugs to date has been limited by both acquired and intrinsic resistance. Macroautophagy, a process of intracellular proteolysis, has been shown to be activated in response to EGFR targeted therapy. However, the specific role of the induction of autophagy remains controversial. Here we show that autophagy is induced in a dose-dependent manner by in vitro treatment of multiple cancer cell lines with EGFR-TKI. Additionally, we find that in cells highly resistant to EGFR-TKI, autophagy is not robustly activated and that co-treatment of these cells with rapamycin, a known inducer of autophagy, can partially restore sensitivity to EGFR-TKI. Finally, we demonstrate that, in resistant cell lines, EGFR-TKI sensitivity can be further inhibited by siRNA-mediated depletion of the critical autophagy protein ATG7. Thus, our data suggests that defective autophagy may be an EGFR-TKI resistance mechanism and that activation of autophagy may be a viable strategy to augment the cytotoxic effect of EGFR-TKIs.

SUBMITTER: Fung C

PROVIDER: S-EPMC3542232 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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EGFR tyrosine kinase inhibition induces autophagy in cancer cells.

Fung Christopher C Chen Xing X Grandis Jennifer R JR Duvvuri Umamaheswar U

Cancer biology & therapy 20120906 14

The epidermal growth factor receptor (EGFR) signaling pathway is frequently dysregulated in a variety of human malignancies. As a result, agents have been developed to selectively inhibit the tyrosine kinase function of EGFR (EGFR-TKI) for cancer therapy. However, the clinical efficacy of these drugs to date has been limited by both acquired and intrinsic resistance. Macroautophagy, a process of intracellular proteolysis, has been shown to be activated in response to EGFR targeted therapy. Howev ...[more]

PMID: 22954701

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Project description:OBJECTIVE:To investigate the inhibitory effect of epidermal growth factor receptor tyrosine kinase inhibitor (EGFRTKI) HS-10296 on the proliferation of triple-negative breast cancer (TNBC) MDA-MB-231 cells and explore the possible molecular mechanism. METHODS:MDA-MB-231 cells were treated with HS-10296 for 24, 48, or 72 h, and CCK-8 assay was used to assess the changes in the cell viability. The inhibitory effect of HS-10296 on cell proliferation was determined by clonogenic assay. JC-1 and flow cytometry were employed for analyzing the cell apoptosis, and the ultrastructure of the cells was observed under electron microscope. After pretreatment with autophagy inhibitor chloroquine (CQ), MDA-MB-231 cells were divided into control group, CQ treatment group, HS-10296 (4 and 6 ?mol/L) treatment groups and combined treatment groups, and the sensitivity of the treated cells to HS-10296 was determined using CCK-8 assay. The effects of HS-10296 on EGFR pathway and apoptosis- and autophagy-related proteins in MDA-MB-231 cells were investigated using Western blotting. RESULTS:HS-10296 significantly inhibited the proliferation of MDA-MB-231 cells with IC50 values at 24, 48 and 72 h of 8.393, 2.777 and 2.016 ?mol/L, respectively. JC-1 and flow cytometry showed that HS-10296 induced obvious apoptosis of MDA-MB-231 cells, which showed an apoptosis rate of (21.63 ± 2.97)% following treatment with 8 ?mol/L HS-10296. Autophagy vesicles were observed in the cells treated with HS-10296 under electron microscope. In MDA-MB-231 cells pretreated with CQ, inhibition of autophagy significantly enhanced HS-10296-induced cell death. Western blotting showed that the apoptosis-related protein caspase-3 was activated after HS-10296 treatment to cut its substrate PARP. The expression of autophagy-related protein light chain 3B (LC3B) was significantly enhanced after HS-10296 treatment (P < 0.01), which also resulted in inhibited phosphorylation of EGFR and AKT proteins in the cells. CONCLUSIONS:HS-10296 can inhibit the proliferation and induce autophagy and apoptosis of MDA-MB-231 cells by inhibiting the EGFR/PI3K/AKT signaling pathway.

Project description:Asparagine (N)-linked glycosylation is a posttranslational modification essential for the function of complex transmembrane proteins. However, targeting glycosylation for cancer therapy has not been feasible due to generalized effects on all glycoproteins. Here, we perform sensitivity screening of 94 lung cancer cell lines using NGI-1, a small-molecule inhibitor of the oligosaccharyltransferase (OST) that partially disrupts N-linked glycosylation, and demonstrate a selective loss of tumor cell viability. This screen revealed NGI-1 sensitivity in just 11 of 94 (12%) cell lines, with a significant correlation between OST and EGFR inhibitors. In EGFR-mutant non-small cell lung cancer with EGFR tyrosine kinase inhibitor (TKI) resistance (PC9-GR, HCC827-GR, and H1975-OR), OST inhibition maintained its ability to induce cell-cycle arrest and a proliferative block. Addition of NGI-1 to EGFR TKI treatment was synthetic lethal in cells resistant to gefitinib, erlotinib, or osimertinib. OST inhibition invariably disrupted EGFR N-linked glycosylation and reduced activation of receptors either with or without the T790M TKI resistance mutation. OST inhibition also dissociated EGFR signaling from other coexpressed receptors like MET via altered receptor compartmentalization. Translation of this approach to preclinical models was accomplished through synthesis and delivery of NGI-1 nanoparticles, confirmation of in vivo activity through molecular imaging, and demonstration of significant tumor growth delay in TKI-resistant HCC827 and H1975 xenografts. This therapeutic strategy breaks from kinase-targeted approaches and validates N-linked glycosylation as an effective target in tumors driven by glycoprotein signaling.Significance:EGFR-mutant NSCLC is incurable despite the marked sensitivity of these tumors to EGFR TKIs. These findings identify N-linked glycosylation, a posttranslational modification common to EGFR and other oncogenic signaling proteins, as an effective therapeutic target that enhances tumor responses for EGFR-mutant NSCLC. Cancer Res; 78(17); 5094-106. ©2018 AACR.

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EGFR tyrosine kinase inhibition induces autophagy in cancer cells.

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EGFR tyrosine kinase inhibition induces autophagy in cancer cells.

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