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J. Bertrán-Alamillo
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P1.02 - Poster Session with Presenters Present (ID 454)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Biology/Pathology
- Presentations: 2
- 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): J. Bertrán-Alamillo
- 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.
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P1.02-064 - MET-Dependent Activation of STAT3 as Mediator of Resistance to MEK Inhibitors in KRAS-Mutant Lung Cancer (ID 4240)
14:30 - 15:45 | Author(s): J. Bertrán-Alamillo
- Abstract
Background:
Targeting the MAPK pathway by MEK inhibition results in limited activity in patients with KRAS-mutant non-small cell lung cancer (NSCLC). The lack of effectiveness may be associated with activation of other effectors including STAT3, as well as MEK inhibition relief from negative feedback loops. Indeed, in KRAS-mutant colorectal cancer, MEK inhibition decreases the activity of the metalloprotease ADAM17, which normally inhibits MET signaling and STAT3 activation by promoting shedding of MET endogenous antagonist, soluble "decoy" MET. Herein, we explore the MET-dependent activation of STAT3 as a mediator of resistance to MEK inhibitors, and whether MET or STAT3 inhibitors can synergistically increase MEK-inhibitor-induced growth inhibition in KRAS-mutant NSCLC cells in vitro.
Methods:
Cell viability was assessed by MTT (thiazolyl blue) assay after treatment with the allosteric MEK inhibitor, selumetinib, the small-molecule dual inhibitor of the MET and ALK receptor tyrosine kinases, crizotinib, and evodiamine, an alkaloid isolated from the dried, unripe Evodia rutaecarpa (Juss.) Benth fruit, that exerts an anticancer effect by inhibiting STAT3. RNA was isolated from four KRAS cell lines and the STAT3 and MET mRNA expression analysis was performed by TaqMan based qRT-PCR. Western blotting was used to assess the effect of selumetinb on ERK, AKT and STAT3 phosphorylation.
Results:
We first evaluated the efficacy of the MEK inhibitor selumetinib in our KRAS-mutant NSCLC cell line panel using an MTT cell proliferation assay. H460 cells were relatively insensitive to selumetinib. Following 48-hour treatment with selumetinib, ERK1/2 and AKT phosphorylation were suppressed but a rebound activation of STAT3 occurred in H460 cells. We next investigated whether MET expression was related to the feedback activation of STAT3 signaling following MEK inhibitor treatment. We compared gene expression profiles of the H460 cell line before and after treatment with selumetinib. Interestingly, we found significant upregulation of MET and STAT3 mRNA expression after seven days of selumetinib treatment. To further interrogate the relationship between MEK inhibition and MET-mediated STAT3 reactivation, H460 cells were treated with the combination of selumetinib and crizotinib or selumetinib and evodiamine. A 72-hour exposure to both combinations resulted in a clear cell synergism, as measured by the combination index (CI) analysis, with a CI of 0.79 and 0.78 respectively.
Conclusion:
Collectively our results showed that the feedback STAT3 activation induced by MET, mitigates the effect of MEK inhibition, and provides rationale for further assessment of combined MEK and MET or STAT3 inhibition in KRAS-mutant NSCLC.
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P3.01 - Poster Session with Presenters Present (ID 469)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
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P3.01-038 - STAT3 and Src-YAP1 Inhibition Results in Greater Necitumumab Sensitivity in Lung Squamous Cell Carcinoma (ID 4242)
14:30 - 15:45 | Author(s): J. Bertrán-Alamillo
- Abstract
Background:
The anti-EGFR monoclonal antibody (mAb), necitumumab, has been recently approved in combination with chemotherapy, as 1st-line treatment for advanced lung squamous cell carcinoma (LSCC) patients, but with minimal survival benefit. Evidence continues to accumulate that signal transducer and activator of transcription 3 (STAT3) is a promising molecular target for cancer therapies. STAT3 is activated by tyrosine phosphorylation in response to EGF and interleukin-6 (IL-6). In addition to STAT3, IL-6 activates the Src family kinases, and subsequently YES-associated protein 1 (YAP1). STAT3 and Src-YAP1 activation contributes to EGFR inhibitor resistance and concomitant targeting of EGFR and STAT3-Src may represent an effective treatment strategy for LSCC.
Methods:
RNA was isolated from six LSCC cell lines and the mRNA expression analysis of EGFR, STAT3, Src and YAP1 was performed by TaqMan based qRT-PCR. Cell viability was assessed by MTT (thiazolyl blue) assay after treatment with necitumumab and evodiamine, an alkaloid isolated from the dried, unripe Evodia rutaecarpa (Juss.) Benth fruit that exerts an anticancer effect by inhibiting STAT3 and Src. Western blotting was performed to assess the effect of necitumumab on EGFR downstream signaling pathways.
Results:
We first evaluated the expression of EGFR in our panel of LSCC cell lines. We found that almost all of them homogeneously express high levels of EGFR. We then assessed the effect of necitumumab on EGFR downstream signaling in the SK-MES1 cell line. Treatment of SK-MES1 cells with 25ug/ml of necitumumab for seven days was unable to ablate STAT3, Src or YAP1 mRNA expression. Consistent with this, we found that necitumumab suppressed EGFR, ERK1/2 and AKT phosphorylation but increased STAT3 phosphorylation on the critical tyrosine residue 705 in a time and dose-dependent manner. We examined the growth inhibitory effect of the necitumumab and evodiamine combination. We performed an MTT cell proliferation assay on SK-MES1 cells and we used a constant ratio drug combination method to determine synergy, additivity, or antagonism. The combination of necitumumab and evodiamine resulted in a clear synergism in SK-MES1 cells as measured by the combination index (CI) analysis, with a CI of 0.74. Experiments in the rest of our LSCC cell lines are ongoing.
Conclusion:
Herein we have examined the role of STAT3 and Src-YAP1 in the context of treatment with the FDA-approved EGFR mAb, necitumumab. Our data provide initial evidence that co-activation of STAT3 and Src-YAP1 may limit the cellular response to EGFR inhibition in LSCC.
