Abstract 3563: Unlocking the potential of CD70 as a therapeutic target in non-small cell lung cancer
Authors: Jacobs Julie , Pauwels Patrick , Rolfo Christian , Lardon Filip , Deschoolmeester Vanessa , Deben Christophe , Van den Bossche Jolien , Zwaenepoel Karen , Hermans Christophe , Silence Karen , Thibault Alain 
Published: August 2015

Abstract
Introduction: Upon interaction of CD70, a type II transmembrane protein, with its receptor CD27, the NFκB pathway is activated, leading to proliferation and survival. Hence, CD70 expression is tightly regulated and only transient on cells of the lymphoid lineage. In contrast, constitutive overexpression of CD70 has been documented in malignancies, where it appears to mediate immune escape through recruitment of CD27+ regulatory cells. Soluble CD27 (sCD27), the extracellular domain of CD27, can be released after lymphocyte activation and has been detected at increased levels in serum samples of lymphoid malignancies. To our knowledge, expression of CD70 has never been systematically characterized in non-small cell lung cancer (NSCLC).
Methods: Fourty-nine primary NSCLC formalin-fixed paraffin embedded and 9 metastatic biopsies were stained by immunohistochemistry (IHC) for expression of CD70 (Clone 301731, 1/40) and CD27 (Clone 137B4, 1/40), using the Dako autostainer Link and Ventana ultra, respectively. Additionally, sCD27 levels were analyzed in 19 serum samples, taken before of biopsy, with the PeliKine Compact™ human sCD27 ELISA kit. Finally, we tested the efficacy of ARGX-110, a CD70-blocking monoclonal IgG1 SIMPLE Antibody™ endowed with enhanced ADCC properties (POTELLIGENT®), using the xCELLigence RTCA technology in CD70+ and CD70- cell lines.
Results: In tumor cells, CD70 positivity (&gt;10%) was detected in 16% of cases with a higher percentage in squamous NSCLC (27%) than in adenocarcinoma (9%). Additionally, one neuro-endocrine NSCLC was CD70+. We demonstrated identical CD70 patterns in primary and metastatic tissue in 8/10 biopsies. Furthermore, CD70 was found in the micro-environment of the tumor (23/49). IHC revealed high levels of CD27 expressing tumor infiltrating lymphocytes (TIL) in all NSCLC biopsies, with increasing FOXP3 expression and higher CD4/CD8 ratios in stromal tissue adjacent to CD70+ tumor cells. High sCD27 levels (&gt;500U/ml) were found to be significantly associated with poor overall survival and even though sCD27 levels did not show potential as a blood-based biomarker for CD70 overexpression on tumor cells, dual positivity of CD70 and sCD27 marked even worse prognosis. We also showed that a low concentration of ARGX-110 (0.5μg/ml) induces efficient NK cell based tumor lysis in CD70+ cell lines.
Conclusion: Expression of CD70 was demonstrated in tumor cells and TILs of NSCLC. Moreover, all biopsies revealed infiltration of CD27+ TIL in the micro-environment of the tumor and a trend towards increased FOXP3 expression and higher CD4/CD8 ratios in CD70+ biopsies. In addition, serum sCD27 levels have potential as a prognostic marker for NSCLC. Lastly, our in vitro results showed a maximum ADCC of ARGX-110 in CD70+ target cells stained by IHC. Hence, our data suggest that CD70 might be an interesting therapeutic target in NSCLC.
Citation Format: Julie Jacobs, Patrick Pauwels, Christian Rolfo, Filip Lardon, Vanessa Deschoolmeester, Christophe Deben, Jolien Van den Bossche, Karen Zwaenepoel, Christophe Hermans, Karen Silence, Alain Thibault. Unlocking the potential of CD70 as a therapeutic target in non-small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3563. doi:10.1158/1538-7445.AM2015-3563