Anti-nuclear valosin-containing protein-like autoantibody is associated with calcinosis and higher risk of cancer in systemic sclerosis

Abstract

Objectives: Systemic sclerosis (SSc)-specific autoantibodies allow the diagnosis and predict the prognosis of SSc patients with different clinical characteristics. The aim of this study was to describe new SSc-related autoantibodies by a novel protein immunoprecipitation (IP) assay. Methods: Serum samples and clinical data were collected from 307 SSc patients. Antinuclear autoantibodies were tested in all patients by indirect immunofluorescence (IIF) on HEp-2 cells. SSc-specific autoantibodies were evaluated with a commercial immunoblot and chemiluminescence immunoassay, and traditional RNA-IP. Patients negative for all these autoantibodies (n ¼ 51) were further tested with a non-radioactive protein IP assay. Protein bands detected on SDS–PAGE were then analysed by mass spectrometry (MS) and confirmed by western blot (WB). Additional 56 patients with nucleolar pattern by IIF were tested by protein IP-WB. Results: Five patients who underwent protein IP testing showed a 110-115kDa molecular weight band on SDS–PAGE and a homogeneous nucleolar pattern by IIF. MS identified the bands as nuclear valosin-containing protein-like (NVL). An additional positive patient was detected by IP-WB. As compared with the remaining 101 negative patients, anti-NVL positive patients showed a greater prevalence of calcinosis (100% vs 18.9%, P < 0.001), and cancer (66.7% vs 8.9%, P ¼ 0.002), with a particular association with synchronous cancer (OR ¼ 16.3; P ¼ 0.024). Conclusion: We identified NVL as a new autoantibody target by a novel protein IP assay in SSc patients with a homogeneous nucleolar IIF pattern, testing negative for all known SSc-specific autoantibodies by commercial assays and RNA IP. Anti-NVL identifies a new clinical phenotype, characterized by calcinosis and cancer.