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S. García
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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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P1.02-020 - The Effect of EGF-Pathway Targeted Immunization (EGF PTI) on STAT3 and Cancer Stem Cells in EGFR Mutant NSCLC Cells (ID 4698)
14:30 - 15:45 | Author(s): S. García
- Abstract
Background:
The vast majority of advanced non-small cell lung cancer (NSCLC) patients with EGFR mutant tumors will develop disease progression following successful treatment with an EGFR tyrosine kinase inhibitor (TKI). Resistance to EGFR-TKIs is due to various mechanisms, such as the secondary mutation (T790M) or the activation of alternative pathways (MET, AXL). What has not been fully appreciated is that EGFR blockade induces an imbalance in favor of survival, increases activity of STAT3 and enriches lung CSCs through Notch3-dependent signaling. EGF-PTI was designed to elicit an antibody response against EGF, in order to reduce EGF receptor signaling and limit tumor growth. We have explored whether EGF-PTI alone or in combination with EGFR TKIs may efficiently inhibit STAT3 and target CSCs.
Methods:
EGF PTI was provided by Bioven (Europe) Ltd. Gefitinib, erlotinib and the recently FDA-approved third-generation EGFR TKI, AZD9291 (osimertinib) were purchased from Selleck chemicals. Western blotting was used to assess the effect of the drugs on ERK, AKT and STAT3 phosphorylation and on Notch and PARP cleavage in EGFR (del19) mutant NSCLC PC9 cells and gefitinib-resistant PC9-GR4 cells. PC9-GR4 cells have been established in our lab and harbor the resistant T790M mutation (T790M+). The protein expression of AXL and CSCs markers such as HES1 (downstream effector of Notch) and Bmi1 was also examined.
Results:
Gefitinib, erlotinib or AZD9291 suppressed EGFR, ERK1/2 and AKT phosphorylation in PC9 cells but increased STAT3 phosphorylation on the tyrosine residue 705 in both PC9 and PC9-GR4 cells. EGF-PTI suppressed STAT3, EGFR and ERK1/2 and the combination of each of the three EGFR TKIs with EGF-PTI lead to more potent inhibition of STAT3, EGFR and ERK1/2. The EGF-PTI induced AKT phosphorylation was reversed when EGF PTI was combined with EGFR TKIs. Interestingly, EGF-PTI blocked Notch cleavage and decreased the expression of HES1. The expression of Bmi1 and AXL were also attenuated with EGF PTI and apoptosis was enhanced through the induction of PARP cleavage.
Conclusion:
EGF PTI may reverse mechanisms of resistance to single EGFR inhibition and the combination of EGF PTI with EGFR TKIs efficiently inhibits downstream signaling pathways in T790M+ cells. Based on these results, the design of a proof-of-concept trial with the combination of EGF PTI with gefitinib for the first line treatment of EGFR mutant NSCLC patients is in progress.
