Indeed, none of the anti-RPA194-positive patients manifested scleroderma renal crisis (present in 14% of the anti-RPC155-only group), and severe gastrointestinal disease was present significantly less frequently in the anti-RPC155/RPA194 subgroup than in the anti-RPC155-only subgroup (26% vs 51%). cancer (16/88, 18.2%) than the group with cancer (3/80, 3.8%; p=0.003). Patients with anti-RPA194 and anti-RPC155 were significantly less likely to have severe gastrointestinal disease (26.3% vs 51.0%, p=0.043) than patients with only anti-RPC155. Conclusions: Anti-RPA194 antibodies are enriched in anti-RPC155-positive scleroderma patients without cancer. Since somatic mutations in the gene encoding in scleroderma patient cancers appears to play a role in immune response initiation against RPC155 in those patients, these data raise the possibility that the development of immune responses to both RPC155 and RPA194 may influence clinical cancer emergence. Further study is required to define whether different autoantibody combinations have utility as tools for cancer risk stratification in scleroderma. locus) that encodes for RPC155 in some of these patients cancers, with development of both mutation-specific and cross-reactive immune responses (9). While these data strongly suggest a model of cancer-induced autoimmunity, it is notable that ~85% of scleroderma patients with anti-RPC155 antibodies do not manifest a cancer clinically over extensive follow-up (8). These data raise the tantalizing possibility that cancer may be an underlying trigger for scleroderma in most patients with anti-RPC155 antibodies, with the anti-tumor immune response being variably successful in eliminating the cancer or maintaining it in equilibrium such that it does not emerge (10). In this context, an important relevant property of the immune response is its ability to diversify to additional epitopes within the primary target (intramolecular spreading) and also to additional proteins that bind to the primary target at some stage in its functional Norepinephrine hydrochloride cycle (intermolecular spreading) (11). It is noteworthy that many targets of the autoimmune response in scleroderma (e.g. RNA polymerases, the minor spliceosome and the centromere) are multi-component complexes. Furthermore, multiple components of these complexes are recognized by autoantibodies, suggesting antigenic spreading (12). We hypothesized that the immune response in anti-RPC155 positive scleroderma patients in whom cancer does not emerge might target additional autoantigens. To address Norepinephrine hydrochloride this, we initially studied a small group of patients with anti-RPC155 antibodies with and without cancer, and compared the autoantibody specificities in these 2 groups by immunoprecipitation. Interestingly, in anti-RPC155 antibody positive patients without cancer, a 194 kDa protein was enriched. Noting the molecular weight, the prior description of RNA polymerase I as an autoantigen in scleroderma (13), and the observation that an inhibitor inducing destruction of the catalytic subunit of RNA polymerase I Norepinephrine hydrochloride (RPA194) is itself an effective anti-cancer agent (14), we pursued whether, and then rapidly confirmed, that the 194 kDa protein was RPA194. When the frequency of RPA194 antibodies was assayed in a large cohort of anti-RPC155-positive scleroderma patients with and without cancer, we confirmed that anti-RPA194 antibodies were enriched Rabbit Polyclonal to MRPS21 among anti-RPC155 patients without Norepinephrine hydrochloride cancer. These data strongly suggest that scleroderma patients targeting the Norepinephrine hydrochloride catalytic components of both RNA polymerase I and III complexes (that is, RPA194 and RPC155, respectively) are associated with decreased emergence of cancer, raising the possibility that the combined immune responses may affect cancer survival and fitness. These observations have important implications for understanding the mechanisms underlying the association of cancer and scleroderma, as well as control of cancer by the immune system. Knowing the RPA194 antibody status in anti-RPC155-positive patients may also enable improved precision in cancer prediction in this subgroup. Methods Study population. Patients with systemic sclerosis (scleroderma), as defined by the 2013 ACR/EULAR classification criteria, 1980 ACR criteria, or having at least 3 of 5 CREST (calcinosis, Raynauds phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia) criteria, and a banked serum sample were included for study (15, 16). One hundred sixty-eight scleroderma patients with anti-RPC155 antibodies were identified for this study (RPC155 antibody status was determined by clinically obtained assays): 80 with a history of cancer and 88 who had no history of cancer after at least 5 years of follow up. Anti-RPC155 antibody status was subsequently confirmed in all 168 patients using ELISA (INOVA Diagnostics), using 20 units as the cutoff.