osimertinib and navitoclax

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have demonstrated significant benefits to patients with non‑small cell lung cancer (NSCLC) harboring EGFR‑activating mutations; however, acquired resistance limits their long‑term efficacy. Therefore, it remains an urgent requirement to discover the underlying mechanisms and investigate novel therapeutic strategies for overcoming the resistance to EGFR TKIs. The present study aimed to determine the mechanism underlying the resistance of NSCLC cells to osimertinib, a third‑generation EGFR tyrosine kinase inhibitor, the osimertinib‑resistant NSCLC cell sub‑line HCC827/OR was established in the present study. It was found that the expression levels of Bcl‑2 and Bcl‑xL were significantly upregulated in resistant cells compared with sensitive cells. Furthermore, the suppression of Bcl‑2 and Bcl‑xL through small interfering RNA‑mediated gene knockdown or using a small molecule specific inhibitor ABT‑263 re‑sensitized HCC827/OR cells to osimertinib treatment. Moreover, the combined treatment of HCC827/OR cells with ABT‑263 and osimertinib enhanced the rate of cell apoptosis through the mitochondrial apoptotic pathway. Finally, ABT‑263 was able to overcome the resistance of osimertinib in xenograft tumor models. In conclusion, these findings may provide an improved concept for the development of a novel combined therapeutic strategy for the treatment of NSCLC resistance to EGFR TKIs.

Topics: Acrylamides; Aniline Compounds; Animals; Apoptosis; Bcl-2-Like Protein 11; bcl-X Protein; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; ErbB Receptors; Female; Gene Knockdown Techniques; Humans; Lung Neoplasms; Mice, Inbred BALB C; Mice, Nude; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Tumor Stem Cell Assay; Up-Regulation; Xenograft Model Antitumor Assays

In our previous work, PC-9-Br, a PC-9 brain seeking line established via a preclinical animal model of lung cancer brain metastasis (LCBM), exhibited not only resistance to epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) gefitinib in vitro, but also chemotherapy regimens of cisplatin plus etoposide in vivo. Using this cell line, we investigated novel potential targeted therapeutics for treating LCBM in vitro and in vivo to combat drug resistance. Significant increases in mRNA and protein expression levels of Bcl-2 were found in PC-9-Br compared with parental PC-9 (PC-9-P), but no significant changes of Bcl-XL were observed. A remarkable synergistic effect between EGFR-TKI gefitinib and Bcl-2 inhibitors ABT-263 (0.17 ± 0.010 µM at 48 h and 0.02 ± 0.004 µM at 72 h), or ABT-199 (0.22 ± 0.008 µM at 48 h and 0.02 ± 0.001 µM at 72 h) to overcome acquired resistance to gefitinib (> 0.5 µM at 48 h and 0.10 ± 0.007 µM at 72 h) in PC-9-Br was observed in MTT assays. AZD9291 was also shown to overcome acquired resistance to gefitinib in PC-9-Br in MTT assays (0.23 ± 0.031 µM at 48 h and 0.03 ± 0.008 µM at 72 h). Western blot showed significantly decreased phospho-Erk1/2 and increased cleaved-caspase-3 expressions were potential synergistic mechanisms for gefitinib + ABT263/ABT199 in PC-9-Br. Significantly decreased protein expressions of phospho-EGFR, phospho-Akt, p21, and survivin were specific synergistic mechanism for gefitinib + ABT199 in PC-9-Br. In vivo studies demonstrated afatinib (30 mg/kg) and AZD9291 (25 mg/kg) could significantly reduce the LCBM in vivo and increase survival percentages of treated mice compared with mice treated with vehicle and gefitinib (6.25 mg/kg). In conclusion, our study demonstrated gefitinib + ABT263/ABT199, afatinib, and AZD9291 have clinical potential to treat LCBM.

Topics: Acrylamides; Aniline Compounds; Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Brain Neoplasms; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Drug Resistance, Neoplasm; Female; Gefitinib; Lung Neoplasms; Mice; Mice, Nude; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Osimertinib (OSI, also known as AZD9291) is the newest FDA-approved epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor for non-small cell lung cancer (NSCLC) patients with EGFR T790M mutation. However, resistance to OSI is likely to progress and the study of potential OSI-resistant mechanisms in advanced is necessary. Here, the OSI-resistant NCI-H1975/OSIR cells were established. After cells developed resistance to OSI, cell proliferation was decreased while cell migration and invasion were increased. The NCI-H1975/OSIR cells exhibited more resistance to gefitinib, erlotinib, afatinib, rociletinib, doxorubicin, and fluorouracil, meanwhile showing higher sensitivity to paclitaxel, when compared with NCI-H1975 cells. In addition, the NCI-H1975/OSIR cells did not display multidrug resistance phenotype. The activation and expression of EGFR were decreased after cells exhibited resistance. Compared with NCI-H1975 cells, the activation of ERK and AKT in NCI-H1975/OSIR cells could not be significantly inhibited by OSI treatment. Navitoclax (ABT-263)-induced cell viability inhibition and apoptosis were more significant in NCI-H1975/OSIR cells than that in NCI-H1975 cells. Moreover, these effects of navitoclax in NCI-H1975/OSIR cells could be reversed by pretreatment of Z-VAD-FMK. Collectively, loss of EGFR could pose as one of the OSI-resistant mechanisms and navitoclax might be the candidate drug for OSI-resistant NSCLC patients.

Topics: Acrylamides; Amino Acid Chloromethyl Ketones; Aniline Compounds; Antineoplastic Agents; Carcinoma, Non-Small-Cell Lung; Caspase Inhibitors; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; ErbB Receptors; Humans; Lung Neoplasms; Neoplasm Invasiveness; Piperazines; Protein Kinase Inhibitors; Signal Transduction; Sulfonamides; Time Factors