Abstract 6645: Anti-EGF antibodies significantly improve the activity of RET, BRAF, MEK and PI3K kinase inhibitors in preclinical models

Background: We have recently shown that antibodies generated by vaccination (anti-EGF VacAbs) potentiate the effects of tyrosine kinase inhibitors (TKIs) in epidermal growth factor receptor mutant (EGFR-mut) cell lines (1) and a Phase I/II clinical trial of an anti-EGF vaccine in combination with afatinib has been initiated. In this study we aimed to determine the efficacy of anti-EGF VacAbs to improve the antitumor activity of RET, BRAF, MEK and PI3K inhibitors in non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) cell lines.

Methods: Cell lines with RET translocations (LC-2/ad) and BRAF, KRAS and PIK3CA mutations (HT29, DLD1, LS174T and H508) were used. Anti-EGF VacAbs were obtained by immunizing rabbits with recombinant human EGF. Cell lines were treated with anti-EGF VacAbs alone and in combination with RET, BRAF, MEK and PI3K inhibitors. Cell viability was determined by MTT, cell cycle was analyzed by flow cytometry, changes of total and phosphorylated proteins by Western blot and emergence of resistance by direct microscopic examination in low density cultures.

Results: Anti-EGF VacAbs suppressed EGF-induced cell proliferation and blocked EGFR transduction signaling pathway in all cell lines tested. In combination, the anti-EGF VacAbs significantly enhanced the antitumor activity of BLU667 in LC-2/ad, trametinib and encorafenib in HT29, trametinib in DLD1 and LS174T and trametinib, taselisib, alpelisib and copanlisib in H508 cells. In these cell lines, anti-EGF VacAbs in combination with kinase inhibitors suppressed EGFR, Akt and Erk 1/2 phosphorylation. Cell cycle experiments revealed that anti-EGF VacAbs significantly increased the antiproliferative effects of the kinase inhibitors, measured as the percentage of cells in G2+M. Finally, the addition of the anti-EGF VacAbs to the culture medium significantly delayed the emergence resistant clones to trametinib in DLD1 cells.

Conclusions: Anti-EGF VacAbs potentiate the antitumor effects of RET, MEK, BRAF and PI3K inhibitors in tumor cell lines. Our data provide a rationale for clinical trials testing the combination of anti-EGF VacAbs with kinase inhibitors in RET-translocated, KRAS, BRAF and PIK3CA mutant NSCLC and CRC patients.(1)“Anti-Epidermal Growth Factor Vaccine Antibodies Enhance the Efficacy of Tyrosine Kinase Inhibitors and Delay the Emergence of Resistance in EGFR Mutant Lung Cancer Cells” Codony-Servat J, García-Roman S, Molina-Vila MA, et al. J Thorac Oncol. 2018.

Citation Format: Silvia Garcia Roman, Jordi Codony Servat, Miguel Angel Molina Vila, Jordi Bertran Alamillo, Monica Garzon, Alejandro Martínez Bueno, Santiago Viteri, María González Cao, Andrés Aguilar, Juan José García, Erik d'Hondt, Rafael Rosell. Anti-EGF antibodies significantly improve the activity of RET, BRAF, MEK and PI3K kinase inhibitors in preclinical models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6645.

Common Co-activation of AXL and CDCP1 in EGFR-mutation-positive Non-smallcell Lung Cancer Associated With Poor Prognosis

Epidermal growth factor receptor (EGFR)-mutation-positive non-small cell lung cancer (NSCLC) is incurable, despite high rates of response to EGFR tyrosine kinase inhibitors (TKIs). We investigated receptor tyrosine kinases (RTKs), Src family kinases and focal adhesion kinase (FAK) as genetic modifiers of innate resistance in EGFR-mutation-positive NSCLC. We performed gene expression analysis in two cohorts (Cohort 1 and Cohort 2) of EGFR-mutation-positive NSCLC patients treated with EGFR TKI. We evaluated the efficacy of gefitinib or osimertinib with the Src/FAK/Janus kinase 2 (JAK2) inhibitor, TPX0005 in vitro and in vivo. In Cohort 1, CUB domain-containing protein-1 (CDCP1) was an independent negative prognostic factor for progression-free survival (hazard ratio of 1.79, p = 0.0407) and overall survival (hazard ratio of 2.23, p = 0.0192). A two-gene model based on AXL and CDCP1 expression was strongly associated with the clinical outcome to EGFR TKIs, in both cohorts of patients. Our preclinical experiments revealed that several RTKs and non-RTKs, were up-regulated at baseline or after treatment with gefitinib or osimertinib. TPX-0005 plus EGFR TKI suppressed expression and activation of RTKs and downstream signaling intermediates. Co-expression of CDCP1 and AXL is often observed in EGFR-mutation-positive tumors, limiting the efficacy of EGFR TKIs. Co-treatment with EGFR TKI and TPX-0005 warrants testing.

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AXL and CDCP1 are co-expressed in treatment-naïve EGFR-mutation-positive NSCLC patients.

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AXL and CDCP1 are related to shorter progression-free survival with EGFR inhibitors and shorter overall survival.

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Src family kinases and YAP1 are regulatory nodes for AXL and CDCP1 expression.

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The combination of EGFR TKI with TPX-0005 is synergistic in EGFR-mutation-positive lung tumors in culture and in vivo.

We explore the molecular changes that occur after the application of an EGFR inhibitor in EGFR-mutation positive tumors. The tumors do not acquire secondary drivers to overcome a primary driver but, counter-regulatory nodes observable before treatment, are immediately made apparent by pathway-specific intervention. The expression of the receptor tyrosine kinase AXL and the transmembrane protein CDCP1 in baseline samples of EGFR-mutation positive NSCLC patients can provide us with information on the treatment outcome. The upfront combination of an EGFR inhibitor with a multikinase inhibitor, that controls the regulatory nodes for RTKs activation, is a therapeutic approach that deserves to be further explored.

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

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.