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P1.05 - Poster Session 1 - Preclinical Models of Therapeutics/Imaging (ID 156)
- Event: WCLC 2013
- Type: Poster Session
- Track: Biology
- Presentations: 1
- Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P1.05-001 - EGFR-TKI resistance due to BIM polymorphism can be circumvented in combination with HDAC inhibition (ID 685)
09:30 - 16:30 | Author(s): S. Takeuchi
BIM (BCL2L11) is a BH3-only pro-apoptotic member of the Bcl-2 protein family. BIM upregulation is required for apoptosis induction by EGFR tyrosine kinase inhibitors (EGFR-TKIs) in EGFR-mutant forms of non-small cell lung cancer (NSCLC). Notably, a BIM deletion polymorphism occurs naturally in 12.9% of East Asian individuals, impairing the generation of the pro-apoptotic isoform required for the EGFR-TKIs gefitinib and erlotinib and therefore conferring an inherent drug resistant phenotype. Indeed, NSCLC patients who harbored this host BIM polymorphism exhibited significantly inferior responses to EGFR-TKI treatment than individuals lacking this polymorphism. In attempt to correct this response defect in the resistant group, we investigated whether the histone deacetylase (HDAC) inhibitor vorinostat could circumvent EGFR-TKI resistance in EGFR mutant NSCLC cell lines that also harbored the BIM polymorphism.
We found that such cells with BIM polymorphism were much less sensitive to gefitinib-induced apoptosis than EGFR mutant cells which did not harbor the polymorphism. Notably, vorinostat increased expression in a dose-dependent manner of the pro-apoptotic BH3 domain-containing isoform of BIM, which was sufficient to restore gefitinib death sensitivity in the EGFR mutant, EGFR-TKI resistant cells. In xenograft models, while gefitinib induced marked regression, via apoptosis, of tumors without the BIM polymorphism, its combination with vorinostat was needed to induce marked regression of tumors with the BIM polymorphism in the same manner.
Our results show how HDAC inhibition can epigenetically restore BIM function and death sensitivity of EGFR-TKI, in cases of EGFR mutant NSCLC where resistance to EGFR-TKI is associated with a common BIM polymorphism.