Overcoming EGFR T790M-based Tyrosine Kinase Inhibitor Resistance with an Allele-specific DNAzyme

Blocking of the EGFR-STAT3 signaling pathway through afatinib treatment inhibited the intrahepatic cholangiocarcinoma

Epidermal growth factor receptor (EGFR) and downstream signal transducer and activator of transcription 3 (STAT3) signaling have been extensively implicated in various human neoplasms. Recently, a novel EGFR inhibitor, known as afatinib, has exhibited broad antitumor activities in a variety of tumors. Therefore, the present study attempted to investigate the impact of this agent on intrahepatic cholangiocarcinoma (ICC). Initially, immunohistochemical assays were performed on 15 human ICC specimens and their adjacent tissues in order to assess the protein levels of phosphorylated EGFR (pEGFR) and pSTAT3. Subsequently, the human ICC cell lines JCK and OZ were exposed to different doses of afatinib, and then cell viability and apoptosis were determined by MTT assay and flow cytometry, respectively. Furthermore, immunoblotting was applied to detect any variations in the phosphorylated protein levels of EGFR and STAT3 in afatinib-treated ICC cells. The results of the current study demonstrated that ICC specimens had evidently increased pEGFR and pSTAT3 protein levels as compared with the adjacent noncancerous tissues. Further in vitro experiments indicated that afatinib evidently blocked ICC cell growth and induced cell apoptosis. At the protein level, pEGFR and pSTAT3 were evidently attenuated by afatinib-administration. In conclusion, the present study clearly determined that afatinib exerts an antitumor effect on ICC cells by silencing the EGFR-STAT3 signaling pathway. This novel agent deserves further investigation as a potential therapeutic strategy for ICC.

GLP2 Promotes Directed Differentiation from Osteosarcoma Cells to Osteoblasts and Inhibits Growth of Osteosarcoma Cells

Glucagon-like peptide 2 (GLP2) is a proglucagon-derived peptide that is involved in the regulation of energy absorption and exerts beneficial effects on glucose metabolism. However, the exact mechanisms underlying the GLP2 during osteogenic differentiation has not been illustrated. Herein, we indicated that GLP2 was demonstrated to result in positive action during the osteogenic differentiation of human osteosarcoma cells. Our findings demonstrate that GLP2 inhibis the growth of osteosarcoma cells in vivo and in vitro. Mechanistic investigations reveal GLP2 inhibits the expression and activity of nuclear factor κB (NF-κB), triggering the decrease of c-Myc, PKM2, and CyclinD1 in osteosarcoma cells. In particular, rescued NF-κB abrogates the functions of GLP2 in osteosarcoma cells. Strikingly, GLP2 overexpression significantly increased the expression of osteogenesis-associated genes (e.g., Ocn and PICP) dependent on c-Fos-BMP signaling, which promotes directed differentiation from osteosarcoma cells to osteoblasts with higher alkaline phosphatase activity. Taken together, our results suggested that GLP2 could be a valuable drug to promote directed differentiation from osteosarcoma cells to osteoblasts, which may provide potential therapeutic targets for the treatment of osteosarcoma.

Ibrutinib selectively and irreversibly targets EGFR (L858R, Del19) mutant but is moderately resistant to EGFR (T790M) mutant NSCLC Cells

Through comprehensive comparison study, we found that ibrutinib, a clinically approved covalent BTK kinase inhibitor, was highly active against EGFR (L858R, del19) mutant driven NSCLC cells, but moderately active to the T790M 'gatekeeper' mutant cells and not active to wild-type EGFR NSCLC cells. Ibrutinib strongly affected EGFR mediated signaling pathways and induced apoptosis and cell cycle arrest (G0/G1) in mutant EGFR but not wt EGFR cells. However, ibrutinib only slowed down tumor progression in PC-9 and H1975 xenograft models. MEK kinase inhibitor, GSK1120212, could potentiate ibrutinib's effect against the EGFR (L858R/T790M) mutation in vitro but not in vivo. These results suggest that special drug administration might be required to achieve best clinical response in the ongoing phase I/II clinical trial with ibrutinib for NSCLC.

Sulforaphane attenuates EGFR signaling in NSCLC cells

Background

EGFR, a receptor tyrosine kinase (RTK), is frequently overexpressed and mutated in non-small cell lung cancer (NSCLC). Tyrosine kinase inhibitors (TKIs) have been widely used in the treatment of many cancers, including NSCLC. However, intrinsic and acquired resistance to TKI remains a common obstacle. One strategy that may help overcome EGFR-TKI resistance is to target EGFR for degradation. As EGFR is a client protein of heat-shock protein 90 (HSP90) and sulforaphane is known to functionally regulate HSP90, we hypothesized that sulforaphane could attenuate EGFR-related signaling and potentially be used to treat NSCLC.

Results

Our study revealed that sulforaphane displayed antitumor activity against NSCLC cells both in vitro and in vivo. The sensitivity of NSCLC cells to sulforaphane appeared to positively correlate with the inhibition of EGFR-related signaling, which was attributed to the increased proteasomal degradation of EGFR. Combined treatment of NSCLC cells with sulforaphane plus another HSP90 inhibitor (17-AAG) enhanced the inhibition of EGFR-related signaling both in vitro and in vivo.

Conclusions

We have shown that sulforaphane is a novel inhibitory modulator of EGFR expression and is effective in inhibiting the tumor growth of EGFR-TKI-resistant NSCLC cells. Our findings suggest that sulforaphane should be further explored for its potential clinical applications against NSCLC.