Abstract C145: Targeted radiosensitization of non-small cell lung cancer (NSCLC) through ADAM17 inhibition

Abstract

Abstract Introduction: Radiotherapy is a mainstay for the treatment of locally advanced NSCLC. However, the response rates and clinical outcomes are still disappointing, with the 5-year survival rate being only approximately 15%. Growth and survival of NSCLC cells are often dependent on ectodomain cleavage of membrane-anchored proteins, which is primarily mediated by metalloproteases such as ADAMs (a disintegrin and metalloproteinase). Among all metalloproteases, ADAM17 is actively associated with this process of proteolytic ‘shedding’ and hence the release of growth factors and cytokines regulating cell proliferation and migration. In the current study, we provide novel insights into activation of ADAM17 and subsequent ligand shedding in response to irradiation. We show for the first time that direct targeting of ADAM17 with a clinically relevant inhibitor radiosensitizes lung carcinoma in vitro and in vivo. Material and methods: Large scale secretome profiling (>300 factors) was performed using antibody arrays for a wide range of secretory factors. Secretion kinetics of selected ADAM17 substrates were determined using ELISA across different established tumor cells and in murine blood serum, derived from irradiated A549 tumor xenograft-carrying mice. Clonogenic survival and xenograft tumor growth delay assays were performed in response to IR in siRNA-targeted tumor cell lines or in combination with small molecular agents. Tumor proliferation and ADAM17 downstream was evaluated employing immunohistochemistry and ex vivo blood serum analysis. Results: Based on a large scale secretome screening, we investigated secretion of auto- or paracrine factors in non–small cell lung cancer in response to irradiation and discovered the ADAM17 network as crucial mediator of resistance to IR. Irradiation triggered secretion of multiple ADAM17 substrates as ALCAM and amphiregulin in a similar IR-induced time- and dose-dependent manner across a panel of NSCLC cell lines and from A549-derived tumor xenografts. Irradiation also induced a dose-dependent increase of furin-mediated cleavage of the proform of ADAM17 to active ADAM17, which resulted in enhanced ADAM17 activity in vitro and in vivo. Genetic or pharmacologic targeting of ADAM17 suppressed IR-induced shedding of secreted factors, downregulated ErbB-signaling in target cells and enhanced IR-induced cytotoxicity in vitro. Furthermore, the combined treatment modality of IR with the ADAM17 inhibitor TMI-005 resulted in a supra-additive antitumor response in A549 tumor xenografts. Inhibition of ADAM17 with TMI-005 also strongly reduced immunohistochemical staining for ADAM17 substrates and MIB1, demonstrating an enduring antiproliferative effect and potency of ADAM17 targeting in combination with radiotherapy to overcome treatment resistance. Conclusions: These findings implicate that radiotherapy significantly activates ADAM17 in non–small cell lung cancer (NSCLC) cells, which results in shedding of multiple survival factors, growth factor pathway activation and contributes to treatment resistance. We provide a sound rationale for repositioning ADAM17 inhibitors as short-term adjuvants to improve the radiotherapy outcome of NSCLC. Citation Format: Ashish Sharma, Sabine Bender, Oliver Riesterer, Angela Broggini-Tenzer, Martin Pruschy. Targeted radiosensitization of non-small cell lung cancer (NSCLC) through ADAM17 inhibition. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C145.