Abstract 421: Potential biomarkers for monitoring therapy with Denosumab in patients affected by giant cell tumor of bone
Authors: Conti Amalia , Luchini Alessandra , Castellani Gastone , Giampieri Enrico , Pazzaglia Laura , Pollino Serena , Magagnoli Giovanna , Palmerini Emanuela , Liotta Lance L. , Picci Piero , Rhoden Kerry J , Benassi Maria Serena 
Published: August 2019

Abstract
Giant Cell Tumor (GCT) of Bone is an intramedullary tumor histologically composed by spindle-shaped mononuclear stromal cells, that are the neoplastic and proliferative component of the lesion, and osteoclast-like multinucleated giant cells, that express receptor activator of nuclear factor κB (RANK). The mononuclear stromal cells express RANK ligand, a mediator of osteoclast activation. GCT represents 5% of all bone tumors and 20% of all benign tumors. It usually affects young adults and 2-3% is metastatic, generally to the lung. Curettage is the preferred surgery, while current therapeutic treatment is represented by Denosumab, an anti-RANK-L monoclonal antibody that blocks RANKL binding to RANK, thereby stopping the ‘vicious cycle’ involved in the biological process of GCT. Identification of circulating biomarkers could provide tools for monitoring the effectiveness of therapy and to better understand its biological mechanism. Low molecular weight (LMW) serum proteins or protein fragments, considered to be a rich source of new potential biomarkers and often masked by the presence of abundant proteins, were detected in serum of 25 GCT patients before and after 9 months of treatment with Denosumab, using the hydrogel nanoparticle technique followed by Mass Spectrometry (MS). 25 healthy sera were also analyzed. Hydrogel core-shell nanoparticles selectively entrap LMW proteins by size exclusion and affinity chromatography, protecting them from degradation and amplifying their concentration for subsequent MS detection. Statistical differences in LMW protein abundance between the three groups (GCT pre-treatment, GCT post-treatment, and healthy) were analyzed using the Wilcoxon test or Mann-Whitney U test as appropriate, with the Benjamini-Hochberg False Discovery Rate for multiple test correction. Proteomic analysis revealed 14 differentially expressed analytes in sera from patients pre- and post-treatment, including Complement factor H, Immunoglobulin kappa variable 4-1, Insulin-like growth factor-binding protein 4, Insulin-like growth factor II, Beta-2-glycoprotein 1 and Immunoglobulin lambda constant 6, while 6 proteins were unaltered by the treatment. Furthermore, 52 proteins showed differential abundance in GCT patients before treatment compared to the healthy group, including several (Vitamin D binding protein, Ceruloplasmin, CD5 antigen-like, Serum amyloid A-4 protein, Complement factor D and Apolipoprotein B-100) that we previously identified in a smaller subset of GCT patients and controls, validating our former results. In conclusion, using a noninvasive proteomic technique, we have identified candidate serum biomarkers that could be useful to monitor Denosumab therapy in patients with GCT of bone, for patient management and to better understand its molecular mechanism.
Citation Format: Amalia Conti, Alessandra Luchini, Gastone Castellani, Enrico Giampieri, Laura Pazzaglia, Serena Pollino, Giovanna Magagnoli, Emanuela Palmerini, Lance L. Liotta, Piero Picci, Kerry J Rhoden, Maria Serena Benassi. Potential biomarkers for monitoring therapy with Denosumab in patients affected by giant cell tumor of bone [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 421.