Is there a general autoantibody signature for cancer?

Antibody Profiling and In Silico Functional Analysis of Differentially Reactive Antibody Signatures of Glioblastomas and Meningiomas

Studies on tumor-associated antigens in brain tumors are sparse. There is scope for enhancing our understanding of molecular pathology, in order to improve on existing forms, and discover new forms, of treatment, which could be particularly relevant to immuno-oncological strategies. To elucidate immunological differences, and to provide another level of biological information, we performed antibody profiling, based on a high-density protein array (containing 8173 human transcripts), using IgG isolated from the sera of n = 12 preoperative and n = 16 postoperative glioblastomas, n = 26 preoperative and n = 29 postoperative meningiomas, and n = 27 healthy, cancer-free controls. Differentially reactive antigens were compared to gene expression data from an alternate public GBM data set from OncoDB, and were analyzed using the Reactome pathway browser. Protein array analysis identified approximately 350-800 differentially reactive antigens, and revealed different antigen profiles in the glioblastomas and meningiomas, with approximately 20-30%-similar and 10-15%-similar antigens in preoperative and postoperative sera, respectively. Seroreactivity did not correlate with OncoDB-derived gene expression. Antigens in the preoperative glioblastoma sera were enriched for signaling pathways, such as signaling by Rho-GTPases, COPI-mediated anterograde transport and vesicle-mediated transport, while the infectious disease, SRP-dependent membrane targeting cotranslational proteins were enriched in the meningiomas. The pre-vs. postoperative seroreactivity in the glioblastomas was enriched for antigens, e.g., platelet degranulation and metabolism of lipid pathways; in the meningiomas, the antigens were enriched in infectious diseases, metabolism of amino acids and derivatives, and cell cycle. Antibody profiling in both tumor entities elucidated several hundred antigens and characteristic signaling pathways that may provide new insights into molecular pathology and may be of interest for the development of new treatment strategies.

Impact of Autoantibodies against Glycolytic Enzymes on Pathogenicity of Autoimmune Retinopathy and Other Autoimmune Disorders

Autoantibodies (AAbs) against glycolytic enzymes: aldolase, α-enolase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase are prevalent in sera of patients with blinding retinal diseases, such as paraneoplastic [cancer-associated retinopathy (CAR)] and non-paraneoplastic autoimmune retinopathies, as well as in many other autoimmune diseases. CAR is a degenerative disease of the retina characterized by sudden vision loss in patients with cancer and serum anti-retinal AAbs. In this review, we discuss the widespread serum presence of anti-glycolytic enzyme AAbs and their significance in autoimmune diseases. There are multiple mechanisms responsible for antibody generation, including the innate anti-microbial response, anti-tumor response, or autoimmune response against released self-antigens from damaged, inflamed tissue. AAbs against enolase, GADPH, and aldolase exist in a single patient in elevated titers, suggesting their participation in pathogenicity. The lack of restriction of AAbs to one disease may be related to an increased expression of glycolytic enzymes in various metabolically active tissues that triggers an autoimmune response and generation of AAbs with the same specificity in several chronic and autoimmune conditions. In CAR, the importance of serum anti-glycolytic enzyme AAbs had been previously dismissed, but the retina may be without pathological consequence until a failure of the blood–retinal barrier function, which would then allow pathogenic AAbs access to their retinal targets, ultimately leading to damaging effects.

Autoantibody signatures defined by serological proteome analysis in sera from patients with cholangiocarcinoma

BACKGROUND

The challenging diagnosis and poor prognosis of cholangiocarcinoma require the determination of biomarkers. Autoantibodies could be used in the clinic as diagnostic markers for the early detection of tumours. By proteomic approaches, several autoantibodies were proposed as potential markers. We tried in this study, to perform a serological proteome analysis, using various antigenic substrates, including tumours and human liver.

METHODS

Sera from patients (n = 13) and healthy donors (n = 10) were probed on immunoblots performed using 2-dimensionally separated proteins from cholangiocarcinoma cell lines (CCLP1 and CCSW1), from the liver of healthy subject and interestingly, from tumour and adjacent non-tumour liver tissues from five patients with cholangiocarcinoma and tested with their corresponding serum. Spots of interest were identified using mass spectrometry and classified according gene ontology analysis.

RESULTS

A comparison of the whole immunoblotting patterns given by cholangiocarcinoma sera against those obtained with normal control sera enabled the definition of 862 spots. Forty-five different proteins were further analysed, corresponding to (1) spots stained with more than four of 13 (30 %) sera tested with the CCLP1 or the CCSW1 cell line and with the normal liver, and (2) to spots immunoreactive with at least two of the five sera probed with their tumour and non-tumour counter-part of cholangiocarcinoma. Immunoreactive proteins with catalytic activity as molecular function were detected at rates of 93 and 64 % in liver from healthy subjects or cholangiocarcinoma non-tumour tissues respectively, compared to 43, 33, 33 % in tumour tissues, or CCSW1 and CCLP1 cell lines. A second pattern was represented by structural proteins with rates of 7 and 7 % in normal liver or non-tumour tissues compared to 14, 33 and 67 % in tumour tissue, CCSW1 or CCLP1 cell lines. Proteins with a binding function were detected at rates of 7 % in non-tumour tissue and 14 % in tumour tissue. Using the extracted tumour tissue, serotransferrin was targeted by all cholangiocarcinoma-related sera.

CONCLUSIONS

Immunological patterns depended on the type of antigen substrate used; i.e. tumour versus non tumour specimens. Nevertheless, a combination of multiple autoantibodies tested with the most appropriate substrate might be more sensitive and specific for the diagnosis of cholangiocarcinoma.

Study of circulating IgG antibodies to BIRC5 and MYC in non-small cell lung cancer

•

An in-house ELISA was developed to detect circulating antibodies to peptide antigens.

•

Circulating anti-MYC IgG levels were significantly increased in patients with NSCLC.

•

Neither anti-MYC nor anti-BIRC5 IgG levels significantly changed in early stage NSCLC.

•

Altered anti-MYC IgG levels were observed only in patients with late stage NSCLC.

An in-house enzyme-linked immunosorbent assay (ELISA) was developed in this study to detect circulating IgG antibodies to peptide antigens derived from baculoviral IAP repeat-containing protein 5 isoform 2 (BIRC5) and myc proto-oncogene protein (MYC) in non-small cell lung cancer (NSCLC). Student’s t-test revealed that circulating anti-MYC IgG levels were significantly increased in patients with NSCLC compared with control subjects in the discovery sample (t = 3.96, P = 0.0001) but not in the validation sample (t = 1.24, P = 0.217), generating a combined P-value of 0.0003. Neither the discovery sample nor the validation sample showed a significant change in anti-BIRC5 IgG levels in NSCLC. Further analysis was performed to investigate whether circulating IgG antibodies to these two tumor-associated antigens (TAAs) significantly changed with early (stages I + II) and late (stages III + IV) NSCLC stages. The results showed that neither anti-MYC IgG nor anti-BIRC5 IgG levels significantly changed in patients with early stage NSCLC, while patients with late stage NSCLC had higher levels of circulating anti-MYC IgG than control subjects in the discovery sample (t = 4.74, P < 0.0001) but not in the validation sample (t = 0.80, P = 0.423), generating a combined P-value of 0.00003 (X² = 26.13, df = 4). In conclusion, circulating IgG antibodies to MYC and BIRC5 do not appear to serve as biomarkers for early diagnosis of lung cancer but anti-MYC IgG might have a prognostic value.

Immune-Signatures for Lung Cancer Diagnostics: Evaluation of Protein Microarray Data Normalization Strategies

New minimal invasive diagnostic methods for early detection of lung cancer are urgently needed. It is known that the immune system responds to tumors with production of tumor-autoantibodies. Protein microarrays are a suitable highly multiplexed platform for identification of autoantibody signatures against tumor-associated antigens (TAA). These microarrays can be probed using 0.1 mg immunoglobulin G (IgG), purified from 10 µL of plasma. We used a microarray comprising recombinant proteins derived from 15,417 cDNA clones for the screening of 100 lung cancer samples, including 25 samples of each main histological entity of lung cancer, and 100 controls. Since this number of samples cannot be processed at once, the resulting data showed non-biological variances due to “batch effects”. Our aim was to evaluate quantile normalization, “distance-weighted discrimination” (DWD), and “ComBat” for their effectiveness in data pre-processing for elucidating diagnostic immune-signatures. “ComBat” data adjustment outperformed the other methods and allowed us to identify classifiers for all lung cancer cases versus controls and small-cell, squamous cell, large-cell, and adenocarcinoma of the lung with an accuracy of 85%, 94%, 96%, 92%, and 83% (sensitivity of 0.85, 0.92, 0.96, 0.88, 0.83; specificity of 0.85, 0.96, 0.96, 0.96, 0.83), respectively. These promising data would be the basis for further validation using targeted autoantibody tests.

Study of circulating IgG antibodies to peptide antigens derived from BIRC5 and MYC in cervical cancer

•

Autoantibodies to BIRC5 and MYC were measured in cervical cancer patients and a control group.

•

There was a significant difference in circulating levels of these autoantibodies in the patient and control groups.

•

ROC analysis suggests that anti-BIRC5 IgG has a higher sensitivity than anti-MYC IgG.

•

Anti-BIRC5 IgG could serve as a biomarker for the early diagnosis of cervical cancer.

The present study was undertaken to detect circulating IgG antibodies to peptide antigens derived from baculoviral IAP repeat-containing protein 5 isoform 2 (BIRC5) and myc proto-oncogene protein (MYC) in cervical cancer. A total of 107 female patients with cervical cancer of stages I and II, and 130 healthy female subjects were recruited for analysis of circulating IgG antibodies to BIRC5 and MYC. Student’s t-test showed significant differences in circulating levels of anti-BIRC5 IgG (t = −4.27, df = 235, P < 0.0001) and anti-MYC IgG (t = 3.51, df = 232, P = 0.0005) between the patient group and the control group. Receiver operating characteristic (ROC) analysis showed an area under the ROC curve (AUC) of 0.67 with sensitivity of 23.4% against specificity of 90% for the anti-BIRC5 IgG assay and an AUC of 0.66 with sensitivity of 9.4% against specificity of 90.6% for the anti-MYC IgG assay. Analysis of quality control samples gave an inter-assay deviation of 8.9% in the anti-BIRC5 IgG assay and 9.0% in the anti-MYC IgG assay. This work suggests that anti-BIRC5 IgG could serve as a biomarker for early diagnosis of cervical cancer although a panel of such tumor-associated antigens is needed to develop a highly sensitive test.

Circulating antibodies to p16 protein-derived peptides in breast cancer

Overexpression of the p16 protein has been reported in breast cancer and may trigger the secretion of antibodies against itself. Circulating anti-p16 antibodies that were detected with a recombinant protein have been reported in breast cancer. The present study was designed to determine whether the levels of circulating IgG antibody to p16 protein-derived linear antigens are altered in breast cancer. An enzyme-linked immunosorbent assay (ELISA) was developed in-house to determine circulating IgG against peptide antigens derived from the p16 protein in 152 female breast cancer patients and 160 healthy female subjects. The Student's T-test revealed that breast cancer patients exhibited significantly higher levels of anti-p16 IgG antibody compared to control subjects (T=2.02, P=0.045). In addition, ductal cancer appeared to be the main type contributing to the increased levels of circulating anti-p16 antibodies (T=2.08, P=0.038). Of all four stages of breast cancer, stage I was associated with the highest levels of IgG antibody (T=2.02, P=0.045) and receiver operating characteristic (ROC) analysis demonstrated that the area under the ROC curve was 0.74 (95% confidence interval: 0.65-083) and that the sensitivity against a specificity of 90% was 30.3%. Therefore, the levels of circulating IgG antibody to the p16 protein may be a potential biomarker for early diagnosis of breast cancer.

A new method combining sequential immunoaffinity depletion and differential in gel electrophoresis to identify autoantibodies as cancer biomarkers

Easily measurable biomarkers are urgently required to detect early stages of cancer progression. Autoantibodies (aAbs), as a component of the humoral immune response against tumor cells, have such potential of diagnostic markers since they are circulating and stable proteins, produced rapidly and easily amenable to in vitro dosage. The identification of aAbs is based on the characterization of tumor-associated antigens (TAA) against which they are directed. Here, we propose a new method for an unbiased identification of TAA and thereby of aAbs as cancer biomarkers. This method that we called sequential immunoaffinity depletion-differential in gel electrophoresis (SID-DIGE) is based on the immunodepletion of tumor cell lysates with IgG from control and tumor-bearing mice and direct matching of the flow throughs of these immunoaffinity separations on the same 2D format. This strategy reduces the complexity of the samples to be analyzed and maximizes the interest of assessing hundreds of proteins simultaneously. SID-DIGE has also the potential, contrary to existing serological proteome analysis (SERPA) techniques, to detect immunogenic proteins with conformational epitopes, including those resulting from post-translational modifications. Using a model of human colorectal tumors in mice for the proof of principle, we showed that SID-DIGE outperforms the conventional SERPA technique, with the identification of 7 common TAA (validating our approach) and 18 additional aAbs proving the potential of this new method. In particular, the identification of aAbs directed against key enzymes supporting glycolysis gives credential to the role of hypoxia as a major determinant of the tumor proteome and thus as a source of immunogenicity. Overall, the developed methodology allowed efficient screening of sera for the identification of aAbs as potential biomarkers.