Adaptive upregulation of EGFR limits attenuation of tumor growth by neutralizing IL-6 antibodies with implications for combined therapy in ovarian cancer.

Cancer Research

PubMedID: 25670170

Milagre CS, Gopinathan G, Everitt G, Thompson RG, Kulbe H, Zhong H, Hollingsworth RE, Grose R, Bowtell DD, Hochhauser D, Balkwill FR. Adaptive upregulation of EGFR limits attenuation of tumor growth by neutralizing IL-6 antibodies with implications for combined therapy in ovarian cancer. Cancer Res. 2015;75(7):1255-64.
Excess production of the pro-inflammatory interleukin IL-6 has both local and systemic tumor-promoting activity in many cancers, including ovarian cancer. However, treatment of advanced ovarian cancer patients with a neutralizing IL-6 antibody yielded little efficacy in a previous Phase II clinical trial. Here we report results that may explain this outcome, based on the finding that neutralizing antibodies to IL-6 and STAT3 inhibition are sufficient to up-regulate the EGFR pathway in high-grade serous and other ovarian cancer cells. Cell treatment with the EGFR inhibitor gefitinib abolished upregulation of the EGFR pathway. Combining neutralizing IL-6 antibodies and gefitinib inhibited malignant cell growth in 2D and 3D culture. We found that ErbB-1 was localized predominantly in the nucleus of ovarian cancer cells examined, contrasting with plasma membrane localization in lung cancer cells. Treatment with anti-IL-6, gefitinib or their combination all led to partial restoration of ErbB-1 on the plasma membrane. In vivo experiments confirmed the effects of IL-6 inhibition on the EGFR pathway and the enhanced activity of a combination of anti-IL-6 antibodies and gefitinib on malignant cell growth. Taken together, our results offer a preclinical rationale to combine anti-IL-6 and gefitinib to treat patients with advanced stage ovarian cancer.