32P - Effects of BTK inhibitor on gefitinib-resistance non-small cell lung cancer

Date 07 May 2017
Event ELCC 2017
Session Poster Display Session
Topics Immunotherapy
Thoracic Malignancies
Non-Small Cell Lung Cancer
Therapy
Presenter Tse-Ming Hong
Citation Annals of Oncology (2017) 28 (suppl_2): ii9-ii13. 10.1093/annonc/mdx089
Authors T. Hong, Y. Fang, Y. Chen
  • National Cheng Kung University, 70101 - Tainan/TW

Abstract

Background

Lung cancer is the most frequent cause of cancer death in the world. EGFR-mutant lung cancer is a subtype of non–small cell lung cancer (NSCLC) that exhibits sensitivity to EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib (Iressa); however, acquired resistance was developed after a median of 9–14 months. In our previous study, we used two primary TKI-resistant lung cancer cell lines (CL25 and CL100) and a genome-wide human kinase and phosphatase RNAi screening and found that silencing Bruton tyrosine kinase (BTK) significantly inhibited the NSCLC viability. BTK is a non-receptor tyrosine kinase of the Tec kinase family and plays an important role in B-cell receptor signaling. Therefore, we wanted to combine primary TKI (Iressa) with BTK inhibitors (Ibrutinib and CC-292) as a cancer treatment for EGFR TKI-resistant NSCLC patients.

Methods

First, we verified that BTK knockdown decreased cell viability in EGFR TKI-resistant CL25 cells and enhanced the sensitivity to Iressa treatment. Second, we test the 50% inhibitory concentration (IC50) of BTK inhibitors (Ibrutinib and CC-292) in NSCLC cells by WST-1 assay. Next, we analyzed the effects of BTK inhibitors on the downstream signaling of BTK by western blot. Furthermore, we investigated the mechanism of growth inhibition triggered by BTK inhibitors in CL25 cells. The cell cycle distribution and cell death were examined. Finally, we tried to understand whether BTK inhibitors could enhance the gefitinib -induced cell death in EGFR TKI-resistant CL25 cells by combined treatment with gefitinib and BTK inhibitors.

Results

By a genome-wide human kinase and phosphatase RNAi screening and found that BTK may contribute to the primary resistance. Knockdown of BTK expression decreased the NSCLC cell viability in a dose dependent manner and increased the gefitinib-induced cell death in both EGFR TKI-resistant CL25 and CL100 cells. BTK knockdown increased the levels of apoptotic and autophagic markers and cyclinD1 by western blot analysis. Moreover, BTK inhibitors affected BTK, NFkB, PI3K/AKT and EGFR signaling in EGFR TKI-resistant CL25 cells. Besides, treatment with Ibrutinib or CC-292 at the concentration of 4 fold IC50 induced G1 arrest in CL25 cells. Finally, combination of BTK inhibitors and gefitinib could not enhance the gefitinib-induced cell death.

Conclusions

According to above results, we found that BTK may be a candidate contributing to the primary EGFR-TKI resistance in NSCLC cells. Knockdown of BTK induces the autophagic cell death and the G1 arrest in primary EGFR TKI-resistant CL25 cells and enhances the gefitinib-induced cell death while BTK inhibitors induce G1 arrest but cannot enhance the gefitinib-induced cell death.

Clinical trial identification

Legal entity responsible for the study

National Cheng Kung University

Funding

Ministry of Science and Technology, Taiwan.

Disclosure

All authors have declared no conflicts of interest.