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Y. Sesumi
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P1.02 - Poster Session with Presenters Present (ID 454)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 12/05/2016, 14:30 - 15:45, Hall B (Poster Area)
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P1.02-047 - Effect of Dasatinib on EMT-Mediated-Mechanism of Resistance against EGFR Inhibitors in Lung Cancer Cells (ID 5809)
14:30 - 14:30 | Author(s): Y. Sesumi
- Abstract
Background:
The epithelial to mesenchymal transition (EMT) is associated with acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in certain non-small cell lung cancers that harbor EGFR mutations. Because no currently available drugs specifically kill cancer cells via EMT, novel treatment strategies that overcome or prevent EMT are needed. A recent report suggested that dasatinib (an ABL/Src kinase inhibitor) inhibits EMT induced by transforming growth factor (TGF)-beta in lung cancer cells. In this study, we analyzed effects of dasatinib on the resistance mechanism in HCC4006 cells harboring EGFR exon 19 deletion, which tend to acquire resistance to EGFR-TKIs via EMT in previous reports.The epithelial to mesenchymal transition (EMT) is associated with acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in certain non-small cell lung cancers that harbor EGFR mutations. Because no currently available drugs specifically kill cancer cells via EMT, novel treatment strategies that overcome or prevent EMT are needed. A recent report suggested that dasatinib (an ABL/Src kinase inhibitor) inhibits EMT induced by transforming growth factor (TGF)-beta in lung cancer cells. In this study, we analyzed effects of dasatinib on the resistance mechanism in HCC4006 cells harboring EGFR exon 19 deletion, which tend to acquire resistance to EGFR-TKIs via EMT in previous reports.
Methods:
HCC4006ER cells with an EMT phenotype were previously established by chronic exposure to increasing concentrations of erlotinib. Sensitivity to dasatinib in parental HCC4006 and HCC4006ER cells was analyzed. Subsequently, HCC4006EDR cells were established by chronic treatment with combination of erlotinib and dasatinib. The expression of EMT markers of these cells and the mechanism of acquired resistance to this combination therapy were analyzed.
Results:
Short-term or long-term, ranging OOhours to XXXmonth, treatment with dasatinib did not reverse EMT in HCC4006ER. In contrast, HCC4006EDR cells maintained an epithelial phenotype, and the mechanism underlying resistance to erlotinib plus dasatinib combination therapy was attributable to a T790M secondary mutation. HCC4006EDR cells, but not HCC4006ER cells, were highly sensitive to a third-generation EGFR-TKI, osimertinib.
Conclusion:
Although dasatinib monotherapy did not reverse EMT in HCC4006ER cells, preemptive combination treatment with erlotinib and dasatinib prevented the emergence of acquired resistance via EMT, and led to the emergence of T790M. Our results indicate that preemptive combination therapy may be a promising strategy to prevent the emergence of EMT-mediated resistance.
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P3.02b - Poster Session with Presenters Present (ID 494)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
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P3.02b-120 - EGFR T790M, L792F, and C797S Mutations as Mechanisms of Acquired Resistance to Afatinib (ID 4818)
14:30 - 14:30 | Author(s): Y. Sesumi
- Abstract
Background:
Afatinib is effective for lung cancers harboring common EGFR mutations, Del19 and L858R. We reported that tumors with exon 18 mutations are especially sensitive to afatinib compared with first generation (1G) EGFR- tyrosine kinase inhibitors (TKIs). However, data on the mechanisms of acquired resistance to afatinib are limited
Methods:
We established afatinib-resistant cells from Ba/F3 cells transfected with common or exon 18 (G719A and Del18) mutations and PC9 (del E746_A750), HCC4006 (del E746_A750), and 11_18 (L858R) cell lines by chronic exposure to increasing concentrations of afatinib. Separately, afatinib-resistant clones were established from above Ba/F3 cells by exposure to fixed concentrations of afatinib using N-ethyl-N-nitrosurea (ENU) mutagenesis. Re-biopsy samples from patients whose tumors acquired resistance to afatinib were collected. EGFR secondary mutations and bypass tracks were analyzed by Sanger sequence, western blot, and real time PCR.
Results:
Afatinib-resistant cells transfected with Del19, L858R, or G719A developed T790M, whereas those with Del18 acquired novel L792F mutation. ENU mutagenesis screening established 84 afatinib-resistant clones. All Del19 clones and most of the other clones acquired only T790M. However, C797S occurred in subsets of L858R, G719A, and Del18 clones. Additionally, subsets of Del18 clones acquired L792F. C797S-acquired cells were sensitive to erlotinib. L792F demonstrated intermediate resistance between T790M and C797S to both 1G and 3G-TKIs, whereas L792F was the least resistant to 2G-TKIs, particularly dacomitinib. Chronic exposure of Del18+L792F cells to dacomitinib induced additional T790M acquisition. T790M was detected in 1 of 4 clinical samples, whereas no EGFR secondary mutations were detected in afatinib-resistant PC9, HCC4006, or 11_18 cell lines. Regarding bypass tracks, IGF1R was over expressed in all of the three afatinib-resistant cell lines compared with parental cells, whereas expression of AXL and PTEN were not changed. Neither mutations in PIK3CA and BRAF nor amplification of MET and FGFR1 were detected in clinical samples and resistant cell lines.
Conclusion:
L792F and C797S, in addition to major T790M, can develop in afatinib-resistant cells, and these minor mutations appear to exhibit sensitivity to dacomitinib and erlotinib, respectively. These secondary mutations should be tested in clinical practice. Bypass track through IGF1R may be associated with acquired resistance to afatinib.
