Co-activation of STAT3 and YES-Associated Protein 1 (YAP1) Pathway in EGFR-Mutant NSCLC

Abstract

Background: The efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in EGFR-mutant non–small cell lung cancer (NSCLC) is limited by adaptive activation of cell survival signals. We hypothesized that both signal transducer and activator of transcription 3 (STAT3) and Src-YES-associated protein 1 (YAP1) signaling are dually activated during EGFR TKI treatment to limit therapeutic response. Methods: We used MTT and clonogenic assays, immunoblotting, and quantitative polymerase chain reaction to evaluate the efficacy of EGFR TKI alone and in combination with STAT3 and Src inhibition in three EGFR-mutant NSCLC cell lines. The Chou-Talalay method was used for the quantitative determination of drug interaction. We examined tumor growth inhibition in one EGFR-mutant NSCLC xenograft model (n = 4 mice per group). STAT3 and YAP1 expression was evaluated in tumors from 119 EGFR-mutant NSCLC patients (64 in an initial cohort and 55 in a validation cohort) by quantitative polymerase chain reaction. Kaplan-Meier and Cox regression analyses were used to assess the correlation between survival and gene expression. All statistical tests were two-sided. Results: We discovered that lung cancer cells survive initial EGFR inhibitor treatment through activation of not only STAT3 but also Src-YAP1 signaling. Cotargeting EGFR, STAT3, and Src was synergistic in two EGFR-mutant NSCLC cell lines with a combination index of 0.59 (95% confidence interval [CI] = 0.54 to 0.63) for the PC-9 and 0.59 (95% CI = 0.54 to 0.63) for the H1975 cell line. High expression of STAT3 or YAP1 predicted worse progression-free survival (hazard ratio [HR] = 3.02, 95% CI = 1.54 to 5.93, P = .001, and HR = 2.57, 95% CI = 1.30 to 5.09, P = .007, respectively) in an initial cohort of 64 EGFR-mutant NSCLC patients treated with firstline EGFR TKIs. Similar results were observed in a validation cohort. Conclusions: Our study uncovers a coordinated signaling network centered on both STAT3 and Src-YAP signaling that limits targeted therapy response in lung cancer and identifies an unforeseen rational upfront polytherapy strategy to minimize residual disease and enhance clinical outcomes.

The combination of checkpoint immunotherapy and targeted therapy in cancer

“…This effect can be even stronger in tumors that have undergone epithelial to mesenchymal transition (EMT) and therefore lose the expression of the immunoproteasome, which generates peptides suitable for binding onto HLA I molecules and facilitates antigen presentation for CD8+ T-cell responses (43). STAT1 is a key positive regulator of immunoproteasome subunits whereas STAT3 activation, induced by oncogenic signals (44) or EMT, has an opposing role to STAT1 inhibiting its antitumor effects and immunosurveillance (43). PD-L1 expression is significantly higher in ALK rearranged NSCLCs compared to NSCLCs with EGFR or KRAS mutation or to those with no genetic alteration of ALK, EGFR or KRAS (triple negative) (45,46).…”

Ibrutinib blocks YAP1 activation and reverses BRAFi resistance in melanoma cells

“…carcinoma (51), and non-small-cell lung cancer (52). Despite the importance of YAP1 in cancer, it is still difficult to pharmacologically target YAP1.…”

Immunophenotyping of HER4/YAP axis in breast cancer brain metastasis

“…YAP is a key regulator of the hippo tumour suppressor pathway and is being researched quite extensively in breast cancer. The contextual dependency of YAP's function as either a tumour promoter 28,[56][57][58][59][60] or a tumour suppressor 27,[61][62][63][64] in cancer is widely reported. With respect to breast cancer, one study reported a decrease in YAP levels and genomic depletion of YAP from breast cancer cell lines suppressed anoikis and increased the migratory properties of the cells 63. Similarly, Cao and colleagues showed that at the protein level expression of YAP in 324 breast cancer patients had a favorable prognosis especially in the PR subgroup and Luminal A prognostic subtype.…”