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OA10 - EGFR Mutations (ID 382)
- Event: WCLC 2016
- Type: Oral Session
- Track: Biology/Pathology
- Presentations: 1
OA10.03 - YAP-NOTCH and STAT3 Signaling Rebound as a Compensatory Response to Gefitinib or Osimertinib Treatment in EGFR Mutant Lung Cancer (ID 4144)
11:00 - 12:30 | Author(s): A. Drozdowskyj
Preclinical studies provide insights to therapy mechanisms of resistance that are not feasible with clinical studies. We investigated the signaling pathways that could be involved in adaptive resistance to gefitinib and/or osimertinib in EGFR mutant cells.
We performed several laboratory methods to examine the signaling pathways involved in EGFR mutations. Signal transduction pathway analysis was designed using the Ingenuity Pathway Analysis (IPA) software (https://www.ingenuity.com/) Figure 1
Pathways mediating EGFR mutations are: i) ERK1/2 via Ras and MEK1/2 ii) AKT via PI3K and iii) STAT3 via JAK (Figure). By Western blot analysis, phosphorylation of Tyr705 on STAT3 was noted after 2 hours of gefitinib or osimertinib treatment in PC9 and H1975 EGFR mutant cells. Unexpectedly, YAP1 phosphorylation on Tyr357 and Notch activation was detected. Co-targeting STAT3 and Src with gefitinib or osimertinib ablates activation of STAT3 and YAP1-NOTCH3 signaling pathways (Figure). In vitro and in vivo, the combinatory therapy of gefitinib or osimertinib plus TPCA-1 (a dual inhibitor of IKKs and STAT3) plus saracatinib (a SFK inhibitor) leads to significant tumor shrinkage in PC9 and H1975 cells. In tumor samples of 64 EGFR mutant NSCLC patients treated with gefitinib, the median progression free survival (PFS) was significantly shorter in those with high levels of HES1, ALDH1A1, ALDH1A3, Bmi1, AXL, CDCP1, SHP2 and ILK (Figure). However, the mRNA levels of STAT3 and YAP1 stand out in the prediction of shorter PFS with a hazard ratio of 3.02 and 2.57, respectively (P<0.001)
For the first time ever, we reported gefitinib induced activation of theYAP1-NOTCH signaling pathway, in addition to activation of STAT3, in EGFR mutant cells. Secondly, co-targeting STAT3 and Src, together with EGFR, causes significant tumor growth inhibition, in comparison with gefitinib or osimertinib single therapy.
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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
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
P3.02b-047 - Co-Activation of STAT3 and YAP1 Signaling Pathways Limits EGFR Inhibitor Response in Lung Cancer (ID 4168)
14:30 - 15:45 | Author(s): A. Drozdowskyj
EGFR tyrosine kinase inhibitors (TKIs) induce early activation of several signaling pathways. Interleukin-6 (IL-6) and signal transducer and activator of transcription 3 (STAT3) hyper-activation occur following EGFR TKI therapy in EGFR-mutant NSCLC cells. We explored the relevance of co-targeting EGFR, STAT3 and Src-YES-associated protein 1 (YAP1) signaling in EGFR-mutant NSCLC.
We combined in vitro and in vivo approaches to explore whether concomitant activation of STAT3 and Src-YAP1 can limit the effectiveness of EGFR TKIs in EGFR-mutant NSCLC cells and xenograft models. In two cohorts of EGFR-mutant NSCLC patients, we examined messenger RNA (mRNA) gene expression within signaling pathways, leading to EGFR TKI resistance.
Gefitinib suppressed EGFR, ERK1/2 and AKT phosphorylation but increased STAT3 phosphorylation (pSTAT3-Tyr705). In EGFR mutant cells, gefitinib plus TPCA-1 (STAT3 inhibitor) abolished pSTAT3-Tyr705 but not the YAP1 phosphorylation on tyrosine 357 by Src family kinases (SFKs). The triple combination of gefitinib, TPCA-1 and AZD0530 (SFK inhibitor) ablated both STAT3 and YAP1 phosphorylation and was highly synergistic, according to the combination index. In two EGFR mutant xenograft mouse models, the triple combination of gefitinib, TPCA-1 and AZD0530 markedly and safely suppressed tumor growth. High levels of STAT3 or YAP1 mRNA expression were associated with worse outcome to EGFR TKI in 64 EGFR-mutant NSCLC patients. Median progression-free survival (PFS) was 9.6 (95%CI, 5.9-14.1) and 18.4 months (95%CI, 8.8-30.2) for patients with high and low STAT3 mRNA, respectively (p<0.001), (HR for disease progression, 3.02; 95% CI, 1.54-5.93; p=0.0013). Median PFS was 9.6 (95%CI, 7.7-15.2) and 23.4 months (95%CI, 13.0-28.1) for patients with high and low YAP1 mRNA, respectively (p=0.005), (HR for disease progression, 2.57; 95%CI, 1.30-5.09; p=0.0067). The results were similar in the validation cohort of 55 EGFR-mutant NSCLC patients treated with first-line EGFR TKI in the Department of Oncology of Shanghai Pulmonary Hospital.
Our study reveals that STAT3 and Src-YAP1 signaling activation occurs following single EGFR TKI in EGFR-mutant NSCLC. STAT3 and YAP1 mRNA levels were significantly predictive of progression-free survival in the original as well as in the validation cohort of EGFR-mutant NSCLC patients. Co-targeting STAT3 and Src in combination with EGFR TKI could substantially improve survival.