OP0268 Apoptosis of synovial fibroblasts induced by p53-derived hybrid peptides through dissociating the binding of p73 with iaspp to increase puma and bax expression
Authors: C.-R. Wang, S.-Y. Chen, A.-L. Shiau, C.-L. Wu
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> In rheumatoid arthritis (RA) synovial fibroblasts (SFs), mutant p53 can lead to transformation-like features resistant to the apoptosis induction.<sup><sup>1</sup></sup> Deficiency in p53-mediated suppression by its dominant-negative counterpart is observed in human cancers with activating p73 as a therapeutic strategy in such patients.<sup><sup>2</sup></sup> A p53-derived hybrid peptide 37 amino acid (37AA) can inhibit the p73 binding with inhibitory apoptosis stimulating protein of p53 (iASPP), thus activating the downstream apoptosis signalling pathway in tumour cells.<sup><sup>3</sup></sup> <h3>Objectives</h3> We hypothesised that p73 is involved in the RA pathogenesis, and examined whether p53-derived hybrid peptides can activate p73 to induce apoptosis of SFs by using adenoviral vectors encoding 37AA (Ad37AA) to transduce SFs <i>in vitro</i> and inject collagen-induced arthritis (CIA) joints <i>in vivo</i>. <h3>Methods</h3> Mononuclear cells (MNCs) from RA patients before and after receiving the adalimumab therapy were examined for iASPP expression by real-time RT-PCR. Synovial tissues and SFs from RA patients and CIA rats were subjected to immunohistochemical and immunofluorescent staining and real-time RT-PCR for the p73 and iASPP expression. SFs transduced with Ad37AA, were subjected to TUNEL assay for apoptotic status and real-time RT-PCR for the expression of downstream apoptosis signalling molecule PUMA and Bax. SFs were transduced with lentiviral vectors-encoding short hairpin p73 RNA to produce p73-silenced SF transfectants Therapeutic effects of Ad37AA injection were evaluated on CIA joints. Immunohistochemical staining and TUNEL assay were used to analyse synovial cadherin-11/PUMA/IL-6 expression and apoptotic cells, respectively. <h3>Results</h3> There were reduced iASPP levels by targeting TNF in RA MNCs, and increased p73 with co-localised iASPP expression in synovial lining layers and SFs from RA patients and CIA rats. Enhanced cell apoptosis, increased PUMA and Bax expression and lower iASPP-associated p73 levels were identified in Ad37AA-transduced SFs, and silencing p73 abrogated the increased PUMA and Bax expression. Articular indexes and histologic scores were reduced in Ad37AA-injected joints with decreased SF densities, increased apoptotic cells, higher PUMA expression and lower IL-6 levels. <h3>Conclusions</h3> These results demonstrate that injecting p53-derived hybrid peptides can induce apoptosis of SFs through the activation of p73 in the rheumatoid joint, suggesting that strengthening the p73-dependent apoptotic mechanism is a potential therapeutic strategy in RA patients. <h3>References</h3> [1] Bell HS, et al. J Clin Invest2007;117:1008–18. [2] Bottini N, et al. Nat Rev Rheumatol2013;9:24–33. [3] Lozano G, et al. editor. The p53 protein: from cell regulation to cancer.<i>Cold Spring Harbor Laboratory Press</i>2016;69–94. <h3>Acknowledgements</h3> We thank Dr. Kevin M. Ryan (Cancer Research UK Beatson Institute, Glasgow, UK) for providing pShuttleCMV-37AA adenoviral plasmids, and Drs. Ming-Fei Liu and I-Ming Jou (National Cheng Kung University Hospital) for providing synovial specimens from arthritis patients. <h3>Disclosure of Interest</h3> None declared