Cancer in Systemic Sclerosis: Analysis of Antibodies Against Components of the Th/To Complex

Anti-Th/To Antibodies in Scleroderma: Good Prognosis or Serious Concern?

Systemic sclerosis (SSc) represents a rare and intricate autoimmune connective tissue disease, the pathophysiology of which has not been fully understood. Its key features include progressive fibrosis of the skin and internal organs, vasculopathy and aberrant immune activation. While various anti-nuclear antibodies can serve as biomarkers for the classification and prognosis of SSc, their direct role in organ dysfunction remains unclear. Anti-Th/To antibodies are present in approximately 5% of SSc patients, and are particularly prevalent among those with the limited subtype of the disease. Although the presence of these autoantibodies is associated with a mild course of the disease, there is a strong connection between them and severe clinical manifestations of SSc, including interstitial lung disease, pulmonary arterial hypertension and gastrointestinal involvement. Also, the additional clinical correlations, particularly with malignancies, need further research. Moreover, the disease's course seems to be influenced by antibodies, specific serum cytokines and TLR signaling pathways. Understanding the relationships between presence of anti-Th/To, its molecular aspects and response to treatment options is crucial for the development of novel, personalized therapeutic techniques and should undergo profound analysis in future studies.

Distinct Scleroderma Autoantibody Profiles Stratify Patients for Cancer Risk at Scleroderma Onset and During the Disease Course

OBJECTIVES

We examined whether an array of scleroderma autoantibodies associates with risk of cancer and could be useful tools for risk stratification.

METHODS

Scleroderma cancer cases and scleroderma controls without cancer from the Johns Hopkins Scleroderma Center and the University of Pittsburgh Scleroderma Center were studied. Sera were assayed by Lineblot and enzyme-linked immunosorbent assay (ELISA) for autoantibodies against centromere, topoisomerase 1, RNA polymerase (POLR) 3, PM/Scl, Th/To, NOR90, U3 RNP, Ku, Ro52, U1RNP, and RNPC3. Logistic regression models were constructed to examine whether distinct autoantibodies associated with overall cancer at any time and cancer-associated scleroderma (cancer occurring three years before and after scleroderma onset). The effects of having more than one autoantibody on cancer were further examined using random forest analysis.

RESULTS

A total of 676 cases and 687 controls were studied. After adjusting for relevant covariates, anti-POLR3 (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.03-2.11) and monospecific anti-Ro52 (OR 2.19, 95% CI 1.29-3.74) were associated with an increased overall cancer risk, whereas anticentromere (OR 0.69, 95% CI 0.51-0.93) and anti-U1RNP (OR 0.63, 95% CI 0.43-0.93) were associated with lower risk. When examining risk of cancer-associated scleroderma, these immune responses remained associated with increased or decreased risk: anti-POLR3 (OR 2.28, 95% CI 1.33-3.91), monospecific anti-Ro52 (OR 2.58, 95% CI 1.05-6.30), anticentromere (OR 0.39, 95% CI 0.20-0.74), and anti-U1RNP (OR 0.32, 95% CI 0.11-0.93). Anti-Ro52 plus anti-U1RNP or anti-Th/To was associated with decreased cancer risk compared with anti-Ro52 alone.

CONCLUSIONS

These data suggest that five distinct scleroderma immune responses, alone or in combination, may be useful tools to stratify the risk of cancer for scleroderma patients. Further study examining cancer risk in autoantibody subgroups relative to the general population is warranted.

Association between anti-SSSCA1 antibodies and cancer in systemic sclerosis

OBJECTIVE

To define the clinical phenotype of SSc patients with antibodies against Sjogren's syndrome (SS)/scleroderma autoantigen 1 (SSSCA1), and to examine the association between these antibodies and cancer in SSc patients.

METHODS

We conducted a case-control study using data from 209 patients with SSc and cancer, and 205 SSc patients without cancer. All were randomly selected from the Johns Hopkins Scleroderma Center Research Registry. Antibodies against SSSCA1 were assayed by immunoprecipitation of 35S-methionine-labelled protein generated by in vitro transcription and translation. We performed logistic regression analysis to examine the relationship between anti-SSSCA1 antibodies and cancer.

RESULTS

Among the 414 study patients, 31 (7%) were anti-SSSCA1 antibody positive. Antibody-positive patients were more likely to have severe RP, a lower minimum ejection fraction, a trend towards more severe heart involvement and a lower baseline diffusing capacity of the lungs for carbon monoxide percent predicted than anti-SSSCA1-negative patients. Patients with cancer were significantly more likely to be anti-SSSCA1 positive compared with those without cancer [22/209 (11%) vs 9/205 (4%), respectively; P = 0.018]. Among patients with cancer, there was a trend towards longer cancer-SSc interval in anti-SSSCA1-positive patients compared with anti-SSSCA1-negative patients. Patients with anti-SSSCA1 antibodies had an increased adjusted risk of cancer (odds ratio 2.46, 95% CI 1.06, 5.70) compared with anti-SSSCA1-negative patients.

CONCLUSIONS

These data suggest anti-SSSCA1 antibody status may be of utility as a cancer biomarker in SSc. Anti-SSSCA1-positive patients with SSc may be more likely to have severe Raynaud's and cardiac involvement.

Preventative Care in Scleroderma: What Is the Best Approach to Bone Health and Cancer Screening?

Systemic sclerosis (SSc) is a rare multisystem autoimmune disease characterized by fibrosis, vasculopathy, and autoimmunity. Lesser known complications inherent to SSc, such as malignancies and osteoporosis, can lead to decreased quality of life and increased morbidity and mortality. Patients with SSc have a greater risk of developing malignancies than the general population. In addition, they are more likely to be vitamin D deficient and are at great risk of osteoporosis-related fractures. However, these complications can be addressed through preventative measures. The purpose of this review is to provide clinicians with an approach to bone health and cancer screening in SSc.

Autoantibodies and Cancer Association: the Case of Systemic Sclerosis and Dermatomyositis

Several rheumatic diseases have a perplexing association with cancer. Unraveling this mysterious connection is likely to provide deeper understanding regarding mechanisms governing the onset of both autoimmunity and cancer immunity, in addition to providing clinicians much needed guidance around whom and when to screen for occult malignancy. Systemic sclerosis (scleroderma) and dermatomyositis are two diseases in which the association with internal malignancy is well-described and can be considered as models from which to gain important insights that likely have broader applicability. The past 15 years have witnessed a striking acceleration in understanding how these two diseases are related to cancer emergence-an important crack in this inscrutable armor has been the discovery and characterization of disease-specific autoantigens that are closely tied with risk of cancer emergence. The best-described examples of this are antibodies against anti-RNA polymerase III (anti-POL3) and transcription intermediary factor 1-gamma (anti-TIF1γ). Patients with systemic sclerosis and cancer that are diagnosed within a short time interval of each other frequently have anti-POL3 antibodies. Antibodies against the minor spliceosome protein RNA-Binding Region Containing 3 (RNPC3) are also associated with increased cancer incidence in systemic sclerosis. Similarly, in the dermatomyositis spectrum, the majority of anti-TIF1γ-associated cancers are detected around the time of DM onset (most often within 1 year). Antibodies against Nuclear Matrix Protein 2 are also potentially associated with increased cancer emergence in dermatomyositis. The systemic sclerosis/anti-POL3 connection with close cancer onset led to the first experiments directly supporting the concept that rheumatic disease may in fact be a manifestation of cancer. It is now clear that studying these diseases through the lens of autoantibodies can reveal relationships and insights that would otherwise remain obscured. Extending these studies, new findings show that antibodies against RNA polymerase I large subunit are associated with protection against short interval cancers in anti-POL3-positive systemic sclerosis patients. These insights highlight the fact that autoantigen discovery related to cancer emergence remains an important priority; such new tools will enable the testing of specific hypotheses regarding mechanisms governing disease emergence and development of effective anti-tumor responses. Autoantibody phenotype will likely play an important role in the development of cancer screening guidelines that are critically needed by clinicians taking care of these patients. In this review, we will summarize the current state of knowledge regarding the different ways in which autoantibodies are connected with systemic sclerosis/dermatomyositis and malignancy and highlight potential paths forward.

New insights into the role of ribonuclease P protein subunit p30 from tumor to internal reference

Ribonuclease P protein subunit p30 (RPP30) is a highly conserved housekeeping gene that exists in many species and tissues throughout the three life kingdoms (archaea, bacteria, and eukaryotes). RPP30 is closely related to a few types of tumors in human diseases but has a very stable transcription level in most cases. Based on this feature, increasing number of studies have used RPP30 as an internal reference gene. Here, the structure and basic functions of RPP30 are summarized and the likely relationship between RPP30 and various diseases in plants and human is outlined. Finally, the current application of RPP30 as an internal reference gene and its advantages over traditional internal reference genes are reviewed. RPP30 characteristics suggest that it has a good prospect of being selected as an internal reference; more work is needed to develop this research avenue.

Systemic Sclerosis Association with Malignancy

The association of systemic sclerosis (SSc) and cancer is well known from several decades suggesting common genetic and environmental risk factors involved in the development of both diseases. Immunosuppressive drugs widely used in SSc may increase the risk of cancer occurrence and different SSc clinical and serological features identify patients at major risk to develop malignancy. In this context, among serological features, presence of anti-RNA polymerase III and anti-topoisomerase I autoantibodies seems to increase cancer frequency in SSc patients (particularly lung and breast cancers). Lung fibrosis and a long standing SSc pulmonary involvement have been largely proposed as lung cancer risk factors, and the exposure to cyclophosphamide and an upper gastrointestinal involvement have been traditionally linked to bladder and oesophagus cancers, respectively. Furthermore, immune checkpoint inhibitors used for cancer therapy can induce immune-related adverse events, which are more frequent and severe in patients with pre-existing autoimmune diseases such as SSc. The strong association between SSc and cancer occurrence steers clinicians to carefully survey SSc patients performing periodical malignancy screening. In the present review, the most relevant bilateral relationships between SSc and cancer will be addressed.

Development of Pulmonary Hypertension in Over One-Third of Patients With Th/To Antibody-Positive Scleroderma in Long-Term Follow-Up

OBJECTIVE

This study was undertaken to describe clinical manifestations in patients with Th/To antibody-positive systemic sclerosis (SSc) during long-term follow-up.

METHODS

We performed a case-control study involving anti-Th/To antibody-positive patients with SSc who were newly referred to the University of Pittsburgh Medical Center and the Pittsburgh Scleroderma Center from 1980 to 2015. For every case, 2 anti-Th/To antibody-negative SSc patients (the first 2 consecutively seen after a case) were used as controls. Long-term disease manifestations and survival were then compared between cases and controls.

RESULTS

A total of 204 anti-Th/To antibody-positive SSc patients and 408 controls were identified. The cohort had a mean ± SD age of 52 ± 12.9 years, and 76% of individuals were women. Anti-Th/To antibody-positive patients more often presented without skin thickening (P < 0.0001) and had a higher rate of pulmonary hypertension (PH) (P < 0.0001) and interstitial lung disease (P = 0.05) compared to anti-Th/To antibody-negative SSc controls. Anti-Th/To antibody-positive SSc patients also had less frequent muscle and joint involvement than anti-Th/To antibody-negative SSc controls (P < 0.0001). After a median clinical follow-up period of 6.1 years (interquartile range 2.4-12.7), 38% of anti-Th/To-positive patients had developed PH compared to 15% of anti-Th/To antibody-negative SSc controls (P < 0.0001). The rate of PH classified as World Health Organization (WHO) Group 1 pulmonary arterial hypertension [PAH] was 23% in anti-Th/To-positive patients compared to 9% in anti-Th/To antibody-negative SSc controls (P < 0.0001). After adjusting for age and sex, anti-Th/To antibody positivity was associated with a hazard ratio (HR) of 3.3 (95% confidence interval 2.3-4.9) for increased risk of developing PH at 10 years of follow-up from the first scleroderma center visit.

CONCLUSION

This is the largest cohort of patients with anti-Th/To antibody-positive SSc with long-term follow-up data. The very high rate (38%) and associated independent risk of anti-Th/To antibody-positive patients developing PH in follow-up, particularly in WHO Group 1 PAH patients, is striking. Patients presenting with limited skin involvement should be tested for Th/To antibodies, and if present, careful monitoring for PH is warranted.

Insights into origins and specificities of autoantibodies in systemic sclerosis

PURPOSE OF REVIEW

Autoantibodies are hallmark findings in systemic sclerosis (SSc), often present prior to disease onset. Clinical diagnosis and prognosis of SSc have long relied on the antitopoisomerase - anticentromere - anti-RNA polymerase antibody trichotomy. However, many more autoantibodies found in SSc are being actively investigated for insights into triggering events, mechanisms of tolerance break, and connections to tissue damage. This review examines recent studies on SSc autoantibodies and the early events that lead to their development.

RECENT FINDINGS

Recent work has elucidated potential connections between human cytomegalovirus infection, silicone breast implants, and malignancy to SSc autoantibody development. At the level of the dendritic cell:T cell interaction, where tolerance is broken, new studies identified shared motifs in the peptide-binding domains of SSc-associated human leukocyte antigen alleles. Immunological analysis of SSc patient B cells has uncovered several anomalies in the regulatory capacities of SSc naïve and memory B cell populations. Expanding efforts to uncover new SSc autoantibodies revealed anti-CXCL4, anticollagen V, and other autoantibodies as potential players in disease pathogenesis.

SUMMARY

Further research into the role of autoantibodies in SSc development may uncover new mechanism-guided therapeutic targets. In addition, a better understanding of autoantibody associations with SSc disease outcomes will improve clinical care.

Association between autoantibodies in systemic sclerosis and cancer in a national registry

OBJECTIVE

A close temporal relationship between systemic sclerosis (SSc) onset and cancer has been reported in anti-RNA polymerase III-positive patients. We investigated the association between cancer and other SSc autoantibodies in a national SSc registry.

METHODS

SSc patients enrolled in the Canadian Scleroderma Research Group registry from 2004 to 2019 were characterized according to autoantibodies to centromere, topoisomerase I/Scl70, RNA polymerase III, fibrillarin, Th/To (hPOP1), PM/Scl, Ku, NOR90, Ro52/TRIM21 and U1RNP. Logistic regression was used to examine the association between a close cancer-SSc interval and autoantibody status, adjusted for age, sex, race and smoking history.

RESULTS

Of 1698 SSc patients, 1481 (87%) had available autoantibody data. Cancer was diagnosed within 2, 3 and 5 years of the first non-Raynaud manifestation in 1.3%, 2.1% and 3.5% of patients. The most frequent cancers diagnosed within 2 years were breast (33%), gynaecological (19%) and haematological (14%) cancers. The risk of cancer within 2 years was increased among anti-topoisomerase I (OR 3.43, 95% CI 1.04-10.05) and anti-U1-RNP-positive patients (OR 5.54, 95% CI 1.16-20.40), but not with anti-RNA polymerase III. None of the anti-fibrillarin, Th/To, PM/Scl, Ku and NOR90-positive patients had cancer within 2 years. Patients with anti-centromere or none of the tested autoantibodies had numerically lower risks of developing cancer within two years.

CONCLUSION

Synchronous cancer was rare in this large cohort of predominantly female and White SSc patients. The risk of cancer within 2 years was increased among anti-topoisomerase I and anti-U1-RNP-positive patients. Screening strategies guided by autoantibodies require further careful consideration.

A Master Autoantigen-ome Links Alternative Splicing, Female Predilection, and COVID-19 to Autoimmune Diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare but reported adverse effects of the currently available COVID vaccines.

Clinical significance of anti-NOR90 antibodies in systemic sclerosis and idiopathic interstitial pneumonia

OBJECTIVE

Anti-NOR90 antibodies are usually found in patients with systemic sclerosis (SSc); however, their clinical relevance remains obscure. We developed an enzyme-linked immunosorbent assay (ELISA) for measuring them to investigate the clinical features of patients with anti-NOR90 antibodies.

METHODS

Serum samples from 1,252 patients with various conditions from Nagoya University Hospital and 244 patients with idiopathic interstitial pneumonia (IIP) from Tosei General Hospital were included. Anti-NOR90 antibodies were assayed by an ELISA using the recombinant protein produced by in vitro transcription/translation.

RESULTS

Five (0.4%) patients in the Nagoya University Hospital cohort had anti-NOR90 antibodies. One patient with diffuse cutaneous SSc, 3 with limited cutaneous SSc, and 1 with Raynaud's disease were positive for anti-NOR90 antibodies. Anti-NOR90 antibodies were found more frequently in patients with systemic scleroderma-spectrum disorders (SSDs) than without SSDs (5/316 vs. 0/936, P<0.00101) and were found more frequently in patients with SSc than without SSc (4/249 vs. 0/528, P<0.0104) in the systemic autoimmune rheumatic diseases cohort. Three of the 4 anti-NOR90-positive SSc patients had interstitial lung disease (ILD), and 2 of those 4 had cancer. Three (1.2%) patients in the Tosei General Hospital cohort had anti-NOR90 antibodies. All 3 of the anti-NOR90-positive IIP patients had gastrointestinal tract involvement, and 2 of those 3 had cancer or skin lesions observed in SSc.

CONCLUSIONS

Although anti-NOR90 antibodies are rarely found in clinics, our ELISA is useful for their detection. Further studies are needed to confirm the association of anti-NOR90 antibodies with ILD and cancer in SSc and IIP patients.

PM-Scl and Th/To in systemic sclerosis: a comparison of different autoantibody assays

OBJECTIVE

To compare test characteristics of the Euroimmun line blot assay with other assays for two uncommon autoantibody specificities in systemic sclerosis (SSc).

METHODS

Patients from the Johns Hopkins Scleroderma Center were assayed routinely using the Euroimmun platform. Patients positive for anti-Th/To (N = 73) and anti-PM-Scl (PM75 and/or PM100; N = 290) by Euroimmun were compared with SSc patients negative for these autoantibodies. For Th/To antibodies, the comparison assay was immunoprecipitation (IP), performed using 4 Th/To complex components: POP1, RPP40, RPP30, and RPP25. For anti-PM-Scl, IPs were performed with PM100 and PM75. Different Euroimmun cut-offs for assigning antibody positive status (≥ 15/+, ≥ 36/++, ≥ 71/+++) were examined. Kappa statistics were calculated to determine agreement between assays.

RESULTS

The best performing thresholds for defining anti-PM-Scl positivity were both PM75 and PM100 ≥ 15/+ on Euroimmun, corresponding to a kappa statistic of 0.79, sensitivity 72% and specificity 100%. For anti-Th/To, kappa values were lower for all comparisons (κ < 0.5). Given the high sensitivity of defining anti-Th/To by ≥ 15/+ (91-95%), a potential approach is to use Euroimmun screening (15/+ cut-off), followed by confirmatory IP.

CONCLUSION

Given the increasing utilization of Euroimmun and the importance of comparing data across cohorts, continued use of this platform is warranted, acknowledging discordance with IP for some specificities. For these, using a two-step approach (Euroimmun to maximize sensitivity, confirmatory assay to increase specificity) is suggested.

KEY POINTS

• For less common SSc autoantibody specificities, some discordances exist between IP and Euroimmun LIA. • The best performing thresholds for defining anti-PM-Scl positivity were both PM75 and PM100 ≥ 15/+ on Euroimmun. • For Th/To, a two-step approach (Euroimmun to maximize sensitivity, confirmatory assay to increase specificity) is suggested.

An Autoantigen Profile of Human A549 Lung Cells Reveals Viral and Host Etiologic Molecular Attributes of Autoimmunity in COVID-19

We aim to establish a comprehensive COVID-19 autoantigen atlas in order to understand autoimmune diseases caused by SARS-CoV-2 infection. Based on the unique affinity between dermatan sulfate and autoantigens, we identified 348 proteins from human lung A549 cells, of which 198 are known targets of autoantibodies. Comparison with current COVID data identified 291 proteins that are altered at protein or transcript level in SARS-CoV-2 infection, with 191 being known autoantigens. These known and putative autoantigens are significantly associated with viral replication and trafficking processes, including gene expression, ribonucleoprotein biogenesis, mRNA metabolism, translation, vesicle and vesicle-mediated transport, and apoptosis. They are also associated with cytoskeleton, platelet degranulation, IL-12 signaling, and smooth muscle contraction. Host proteins that interact with and that are perturbed by viral proteins are a major source of autoantigens. Orf3 induces the largest number of protein alterations, Orf9 affects the mitochondrial ribosome, and they and E, M, N, and Nsp proteins affect protein localization to membrane, immune responses, and apoptosis. Phosphorylation and ubiquitination alterations by viral infection define major molecular changes in autoantigen origination. This study provides a large list of autoantigens as well as new targets for future investigation, e.g., UBA1, UCHL1, USP7, CDK11A, PRKDC, PLD3, PSAT1, RAB1A, SLC2A1, platelet activating factor acetylhydrolase, and mitochondrial ribosomal proteins. This study illustrates how viral infection can modify host cellular proteins extensively, yield diverse autoantigens, and trigger a myriad of autoimmune sequelae.