A novel polyclonal antibody library for expression profiling of poorly characterized, membrane and secreted human proteins

Novel biomarkers for primary biliary cholangitis to improve diagnosis and understand underlying regulatory mechanisms

BACKGROUND AND AIMS

Primary biliary cholangitis is an autoimmune biliary disease characterized by injury of bile ducts, eventually leading to cirrhosis and death. In most cases, anti-mitochondrial antibodies and persistently elevated serum alkaline phosphatase are the basis for the serological diagnosis. Anti-nuclear antibodies are also useful and may indicate a more aggressive diseases course. In patients in which anti-mitochondrial antibodies are not detected, an accurate diagnosis requires liver histology. This study aims at identifying specific biomarkers for the serological diagnosis of primary biliary cholangitis.

METHODS

Sera from patients affected by primary biliary cholangitis, primary sclerosing cholangitis, hepatitis C virus (with and without cryoglobulinemia), hepatocarcinoma and healthy donors were tested on a protein array representing 1658 human proteins. The most reactive autoantigens were confirmed by DELFIA analysis on expanded cohorts of the same mentioned serum classes, and on autoimmune hepatitis sera, using anti-PDC-E2 as reference biomarker.

RESULTS

Two autoantigens, SPATA31A3 and GARP, showed high reactivity with primary biliary cholangitis sera, containing or not anti-mitochondrial antibodies. Their combination with PDC-E2 allowed to discriminate primary biliary cholangitis from all tested control classes with high sensitivity and specificity. We found that GARP expression is upregulated upon exposure to biliary salts in human cholangiocytes, an event involving EGFR and insulin pathways. GARP expression was also detected in biliary duct cells of PBC patients.

CONCLUSIONS

This study highlighted SPATA31A3 and GARP as new biomarkers for primary biliary cholangitis and unravelled molecular stimuli underlying GARP expression in human cholangiocytes.

ERMP1, a novel potential oncogene involved in UPR and oxidative stress defense, is highly expressed in human cancer

Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are highly activated in cancer and involved in tumorigenesis and resistance to anti-cancer therapy. UPR is becoming a promising target of anti-cancer therapies. Thus, the identification of UPR components that are highly expressed in cancer could offer new therapeutic opportunity.

In this study, we demonstrate that Endoplasmic Reticulum Metallo Protease 1 (ERMP1) is broadly expressed in a high percentage of breast, colo-rectal, lung, and ovary cancers, regardless of their stage and grade. Moreover, we show that loss of ERMP1 expression significantly hampers proliferation, migration and invasiveness of cancer cells. Furthermore, we show that this protein is an important player in the UPR and defense against oxidative stress. ERMP1 expression is strongly affected by reticular stress induced by thapsigargin and other oxidative stresses. ERMP1 silencing during reticular stress impairs the activation of PERK, a key sensor of the UPR activation. Loss of ERMP1 also prevents the expression of GRP78/BiP, a UPR stress marker involved in the activation of the survival pathway. Finally, ERMP1 silencing in cells exposed to hypoxia leads to inhibition of the Nrf2-mediated anti-oxidant response and to reduction of accumulation of HIF-1, the master transcription factor instructing cells to respond to hypoxic stress. Our results suggest that ERMP1 could act as a molecular starter to the survival response induced by extracellular stresses. Moreover, they provide the rationale for the design of ERMP1-targeting drugs that could act by inhibiting the UPR initial adaptive response of cancer cells and impair cell survival.

TCTN2: a novel tumor marker with oncogenic properties

Tectonic family member 2 (TCTN2) encodes a transmembrane protein that belongs to the tectonic family, which is involved in ciliary functions. Previous studies have demonstrated the role of tectonics in regulating a variety of signaling pathways at the transition zone of cilia. However, the role of tectonics in cancer is still unclear. Here we identify that TCTN2 is overexpressed in colorectal, lung and ovary cancers. We show that different cancer cell lines express the protein that localizes at the plasma membrane, facing the intracellular milieu. TCTN2 over-expression in cancer cells resulted in an increased ability to form colonies in an anchorage independent way. On the other hand, downregulation of TCTN2 using targeted epigenetic editing in cancer cells significantly reduced colony formation, cell invasiveness, increased apoptosis and impaired assembly of primary cilia. Taken together, our results indicate that TCTN2 acts as an oncogene, making it an interesting cancer-associated protein and a potential candidate for therapeutic applications.

Lack of evidence for post-vaccine onset of autoimmune/lymphoproliferative disorders, during a nine-month follow-up in multiply vaccinated Italian military personnel

Anecdotal case reports, amplified by mass media and internet-based opinion groups, have recently indicated vaccinations as possibly responsible for autoimmunity/lymphoproliferation development. Multiply vaccinated Italian military personnel (group 1, operating in Italy, group 2, operating in Lebanon) were followed-up for nine months to monitor possible post-vaccine autoimmunity/lymphoproliferation onset. No serious adverse event was noticed in both groups. Multivariate analysis of intergroup differences only showed a significant association between lymphocyte increase and tetanus/diphtheria vaccine administration. A significant post-vaccine decrease in autoantibody positivity was observed. Autoantibodies were also studied by microarray analysis of self-proteins in subjects exposed to ≥4 concurrent vaccinations, without observing significant difference among baseline and one and nine months post-vaccine. Moreover, HLA-A2 subjects have been analyzed for the possible CD8T-cell response to apoptotic self-epitopes, without observing significant difference between baseline and one month post-vaccine. Multiple vaccinations in young adults are safe and not associated to autoimmunity/lymphoproliferation onset during a nine-month-long follow-up.

FAT1: a potential target for monoclonal antibody therapy in colon cancer

Background:

Colorectal cancer (CRC) is one of the major causes of cancer-associated mortality worldwide. The currently approved therapeutic agents have limited efficacy.

Methods:

The atypical cadherin FAT1 was discovered as a novel CRC-associated protein by using a monoclonal antibody (mAb198.3). FAT1 expression was assessed in CRC cells by immunohistochemistry (IHC), immunoblots, flow cytometry and confocal microscopy. In addition, in vitro and in vivo tumour models were done to assess FAT1 potential value for therapeutic applications.

Results:

The study shows that FAT1 is broadly expressed in primary and metastatic CRC stages and detected by mAb198.3, regardless of KRAS and BRAF mutations. FAT1 mainly accumulates at the plasma membrane of cancer cells, whereas it is only marginally detected in normal human samples. Moreover, the study shows that FAT1 has an important role in cell invasiveness while it does not significantly influence apoptosis. mAb198.3 specifically recognises FAT1 on the surface of colon cancer cells and is efficiently internalised. Furthermore, it reduces cancer growth in a colon cancer xenograft model.

Conclusions:

This study provides evidence that FAT1 and mAb198.3 may offer new therapeutic opportunities for CRC including the tumours resistant to current EGFR-targeted therapies.

Two of Them Do It Better: Novel Serum Biomarkers Improve Autoimmune Hepatitis Diagnosis

BACKGROUND

Autoimmune hepatitis (AIH) is a chronic liver disease of unknown aetiology and characterized by continuing hepatocellular inflammation and necrosis. Autoantibodies represent accessible markers to measure the adaptive immune responses in the clinical investigation. Protein microarrays have become an important tool to discriminate the disease state from control groups, even though there is no agreed-upon standard to analyze the results.

RESULTS

In the present study 15 sera of patients with AIH and 78 healthy donors (HD) have been tested against 1626 proteins by an in house-developed array. Using a Partial Least Squares Discriminant Analysis (PLS-DA) the resulting data interpretation led to the identification of both new and previously identified proteins. Two new proteins AHPA9419 and Chondroadherin precursor (UNQ9419 and CHAD, respectively), and previously identified candidates as well, have been confirmed in a validation phase by DELFIA assay using a new cohort of AIH patients. A receiver operating characteristic analysis was used for the evaluation of biomarker candidates. The sensitivity of each autoantigen in AIH ranged from 65 to 88%; moreover, when the combination of the two new autoantigens was analyzed, the sensitivity increased to 95%.

CONCLUSIONS

Our findings demonstrate that the detection of autoantibodies against the two autoantigens could improve the performance in discriminating AIH patients from control classes and in combination with previously identified autoantigens and they could be used in diagnostic/prognostic markers.

Negatively charged AuNP modified with monoclonal antibody against novel tumor antigen FAT1 for tumor targeting

BACKGROUND

Herein, we demonstrated the use of a newly generated anti FAT1 antibody (clone mAB198.3) for intracellular delivery of anionic gold NPs, to form active targeting Au nanoparticles with high payload characteristics.

METHODS

In vitro characterizations were determined by DLS, confocal microscopy, TEM, western blot, MALDI-TOF MS/MS analysis, MTT, ICP-MS and flow cytometry analysis. In vivo targeting efficacy was investigated by in vivo bio-imaging study and ICP-MS.

RESULTS

The specificity of the FAT1 recognition in colon cancer was confirmed by pre-adsorbing mAb198.3, adsorption dramatically abolished the antibody reactivity on colon cancer, thus confirming the binding specificity. The DLS size distribution profile of the AuCOOH, AuCOOH(Cy5)_ mAb198.3, AuCOOH(Cy5)_isotype has showed that the modified gold nanoparticles are well dispersed in water, PBS buffer and cell culture medium with 10 % FBS. By TEM measurement, the size of Au nanoparticles with spherical morphology is about 10-20 nm. AuCOOH_198.3 NPs were stable in an acidic environment, as well as in PBS buffer, cell culture media and media with 10 % serum. MTT results revealed that Au nanoparticles have well biocompatibility. TEM results indicated that conjugation of mAb198.3 on Au nanoparticles can be an effective delivery vehicle for negatively charged gold nanoparticles and increased its intracellular transport. It was also demonstrated by confocal microscopy that AuCOOH(Cy5)_mAb198.3 could attach to the cell membrane in very short time, then gradually delivered into cells. After 4 h incubation, almost all AuCOOH(Cy5)_mAb198.3 have been uptaken into or surrounding the cytoplasm and nucleus. In vivo results showed that only about 20 % of AuCOOH accumulated in tumor site due to EPR effect, while nearly 90 % of AuCOOH_mAb198.3 was found in tumor, providing sufficient evidence for receptor-specific targeting by mAb198.3.

CONCLUSION

According to in vitro and in vivo research results, the intracellular uptake of negatively charged AuCOOH_mAB198.3 particles is enhanced to a greater extent. Thus, AuCOOH_mAb198.3 holds significant potential to improve the treatment of cancer.

Angiopoietin-like 7, a novel pro-angiogenetic factor over-expressed in cancer

Angiopoietin-like (ANGPTL) proteins are secreted proteins showing structural similarity to members of the angiopoietin family. Some ANGPTL proteins possess pleiotropic activities, being involved in cancer lipid, glucose energy metabolisms, and angiogenesis. ANGPTL7 is the less characterized member of the family whose functional role is only marginally known. In this study, we provide experimental evidences that ANGPTL7 is over-expressed in different human cancers. To understand the role played by ANGPTL7 in tumor biology, we asked whether ANGPTL7 is endogenously expressed by malignant cells or in response to environmental stimuli. We found that ANGPTL7 is marginally expressed under standard growth condition while it is specifically up-regulated by hypoxia. Interestingly, the protein is secreted and partially associated with the exosomal fraction, suggesting that it could be found in the systemic circulation of oncologic patients and act in an endocrine way. Moreover, we found that ANGPTL7 exerts a pro-angiogenetic effect on human differentiated endothelial cells by stimulating their proliferation, motility, invasiveness, and capability to form capillary-like networks while it does not stimulate progenitor endothelial cells. Finally, we showed that ANGPTL7 promotes vascularization in vivo in the mouse Matrigel sponge assay, thereby accrediting this molecule as a pro-angiogenic factor.

Identification of new autoantigens by protein array indicates a role for IL4 neutralization in autoimmune hepatitis

Autoimmune hepatitis (AIH) is an unresolving inflammation of the liver of unknown cause. Diagnosis requires the exclusion of other conditions and the presence of characteristic features such as specific autoantibodies. Presently, these autoantibodies have relatively low sensitivity and specificity and are identified via immunostaining of cells or tissues; therefore, there is a diagnostic need for better and easy-to-assess markers. To identify new AIH-specific autoantigens, we developed a protein microarray comprising 1626 human recombinant proteins, selected in silico for being secreted or membrane associated. We screened sera from AIH patients on this microarray and compared the reactivity with that of sera from healthy donors and patients with chronic viral hepatitis C. We identified six human proteins that are specifically recognized by AIH sera. Serum reactivity to a combination of four of these autoantigens allows identification of AIH patients with high sensitivity (82%) and specificity (92%). Of the six autoantigens, the interleukin-4 (IL4) receptor fibronectin type III domain of the IL4 receptor (CD124), which is expressed on the surface of both lymphocytes and hepatocytes, showed the highest individual sensitivity and specificity for AIH. Remarkably, patients' sera inhibited STAT6 phosphorylation induced by IL4 binding to CD124, demonstrating that these autoantibodies are functional and suggesting that IL4 neutralization has a pathogenetic role in AIH.

Identification of new hematopoietic cell subsets with a polyclonal antibody library specific for neglected proteins

The identification of new markers, the expression of which defines new phenotipically and functionally distinct cell subsets, is a main objective in cell biology. We have addressed the issue of identifying new cell specific markers with a reverse proteomic approach whereby approximately 1700 human open reading frames encoding proteins predicted to be transmembrane or secreted have been selected in silico for being poorly known, cloned and expressed in bacteria. These proteins have been purified and used to immunize mice with the aim of obtaining polyclonal antisera mostly specific for linear epitopes. Such a library, made of about 1600 different polyclonal antisera, has been obtained and screened by flow cytometry on cord blood derived CD34+CD45dim cells and on peripheral blood derived mature lymphocytes (PBLs). We identified three new proteins expressed by fractions of CD34+CD45dim cells and eight new proteins expressed by fractions of PBLs. Remarkably, we identified proteins the presence of which had not been demonstrated previously by transcriptomic analysis. From the functional point of view, looking at new proteins expressed on CD34+CD45dim cells, we identified one cell surface protein (MOSC-1) the expression of which on a minority of CD34+ progenitors marks those CD34+CD45dim cells that will go toward monocyte/granulocyte differentiation. In conclusion, we show a new way of looking at the membranome by assessing expression of generally neglected proteins with a library of polyclonal antisera, and in so doing we have identified new potential subsets of hematopoietic progenitors and of mature PBLs.