Expression of cancer cell-derived IgG and extra domain A-containing fibronectin in salivary adenoid cystic carcinoma

IgG expressed by renal tubular epithelial cells in epithelial mesenchymal transformation and interstitial fibrosis in diabetic kidney disease

Studies have reported that immunoglobulin G (IgG) "deposited" in the basement membrane of renal tubules is associated with tubulointerstitial damage in patients with diabetic kidney disease (DKD). Our previous study found that renal tubular epithelial cells (RTECs) can express and secrete IgG (RTEC-IgG) which may be associated with fibrosis. The present study aimed to explore the role of RTEC-IgG in renal tubulointerstitial fibrosis (TIF) in DKD. The results showed that RTEC-IgG expression was up-regulated in the renal tubulointerstitium of DKD patients and was associated with worse kidney function, more severe anemia, and higher interstitial fibrosis and tubular atrophy (IFTA) scores, and positively correlated with tubular epithelial mesenchymal transition (EMT) and TIF. IgG expression was also enhanced in the renal tubulointerstitium of DKD mice, which was positively correlated with TIF. High glucose induced an over expression of IgG in human renal tubular epithelial cells, and knockdown of IgG with siRNA relieved the expression of α-smooth muscle actin (SMA), collagen IV, fibronectin, and transforming growth factor (TGF)-β1 under high glucose conditions. In conclusion, our study suggests that RTEC-IgG is involved in the development of DKD by promoting EMT and interstitial fibrosis via TGF-β1.

The Expression of Non B Cell-Derived Immunoglobulins

Although V(D)J recombination and immunoglobulin (Ig) production are traditionally recognised to occur only in B lymphocytes and plasma cells, the expression of Igs in non-lymphoid cells, which we call non B cell-derived Igs (non B Igs), has been documented by growing studies. It has been demonstrated that non B-Igs can be widely expressed in most cell types, including, but not limited to, epithelial cells, cardiomyocytes, hematopoietic stem/progenitor cells, myeloid cells, and cells from immune-privileged sites, such as neurons and spermatogenic cells. In particular, malignant tumour cells express high level of IgG. Moreover, different from B-Igs that mainly localised on the B cell membrane and in the serum and perform immune defence function mainly, non B-Igs have been found to distribute more widely and play critical roles in immune defence, maintaining cell proliferation and survival, and promoting progression. The findings of non B-Igs may provide a wealthier breakthrough point for more therapeutic strategies for a wide range of immune-related diseases.

Functional analysis of tumor-derived immunoglobulin lambda and its interacting proteins in cervical cancer

BACKGROUND

Immunoglobulin lambda (Igλ) has been reported to be expressed in many normal and tumor tissues and cells. However, the function and clinical significance of tumor-derived Igλ remain unclear.

METHODS

The differential expressions of Immunoglobulin Lambda Constants (IGLCs) in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) were examined with The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Human Protein Atlas (HPA) databases. The effects of IGLCs on patient clinical phenotypes and prognosis were explored via bioinformatics analyses based on the TCGA databases. We used the bioinformatics analyses based on the TCGA and GTEx databases to elucidate the correlations among IGLC expressions, immunomodulator expressions, tumor stemness, and infiltration scores of tumor infiltrating immune cells. Co-immunoprecipitation (Co-IP) and silver staining combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to obtain potential tumor-derived Igλ-interacting proteins. Functional annotation of candidate proteins identified by LC-MS/MS was performed in Database for Annotation, Visualization and Integrated Discovery (DAVID). The bioinformatics analyses of 7 IGLCs in CESC and normal cervical tissues were performed based on TCGA, GTEx, and Gene Expression Profiling Interactive Analysis 2 (GEPIA2) databases. Protein-protein interaction (PPI) network was analyzed based on tumor-derived Igλ-interacting proteins in Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. Immunohistochemistry (IHC) was used to validate the expressions of IGLCs in CESC.

RESULTS

We found that the expressions of the majority of IGLCs (IGLC1, IGLC2, IGLC3, IGLC4, IGLC5, IGLC6, and IGLC7) were upregulated in CESC tissues, compared with those in normal cervical tissues. The expressions of IGLC5 and IGLC7 had significant difference in different pathologic metastasis (M), one of tumor, node, and metastasis (TNM) staging system, categories of CESC. Except for disease-free interval (DFI), 4 IGLC (IGLC1, IGLC2, IGLC3, and IGLC7) expression levels were positively associated with patient overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) respectively in CESC tissues. 5 IGLC (IGLC1, IGLC2, IGLC3, IGLC6, and IGLC7) expressions were positively correlated with the expressions of a majority of immunomodulators respectively in CESC tissues. Tumor stemness was negatively correlated with the expressions of 4 IGLCs (IGLC1, IGLC2, IGLC3, and IGLC7) respectively in CESC tissues. Except for IGLC4, IGLC5, and IGLC7, 4 IGLC (IGLC1, IGLC2, IGLC3, and IGLC6) expressions were positively correlated with infiltration scores of 6 tumor-infiltrating immune cells (B cell, T cell CD4, T cell CD8, neutrophil, macrophage, and DC). After analyses of the above bioinformatics data of tumor-derived Igλ, Co-IP and LC-MS/MS were used to confirm that 4 proteins (RPL7, RPS3, H1-5, and H1-6) might interact with tumor-derived Igλ in cervical cancer cells. Functional analyses of these candidate proteins showed that they interacted with many proteins and were involved in various cellular biological processes. Finally, IHC was used to further confirm the above bioinformatics results, it was indicated that the expression level of Igλ in cervical adenocarcinoma and cervical squamous cell carcinoma was higher than that in normal cervical tissue.

CONCLUSION

This study comprehensively investigated the functions of tumor-derived Igλ and its interacting proteins based on bioinformatics analysis and the potential value of Igλ as a prognostic and therapeutic marker for CESC, providing new direction and evidence for CESC therapy.

Molecular insight in intrarenal inflammation affecting four main types of cells in nephrons in IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis and the leading cause of kidney failure in the world. The current widely accepted framework for its pathogenesis is the "multi-hit hypothesis." In this review, we mainly discussed the intrarenal inflammation in IgAN, which is initiated by immune complex deposition with complement molecule activation, by focusing on four main types of cells in nephrons including mesangial cells, endothelial cells, podocytes, and tubular epithelial cells (TECs). Galactose-deficient IgA1 (Gd-IgA1)-containing immune complexes deposit in the mesangium and activate complement molecules and mesangial cells. Activation of mesangial cells by Gd-IgA1 deposition with enhanced cellular proliferation, extracellular matrix (ECM) expansion, and inflammatory response plays a central role in the pathogenesis of IgAN. Regional immune complex deposition and mesangial-endothelial crosstalk result in hyperpermeability of endothelium with loss of endothelial cells and infiltration barrier proteins, and recruitment of inflammatory cells. Podocyte damage is mainly derived from mesangial-podocyte crosstalk, in which tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), renin-angiotensin-aldosterone system (RAAS), and micro-RNAs are the major players in podocyte apoptosis and disorganization of slit diaphragm (SD) related to proteinuria in patients with IgAN. In addition to filtrated proteins into tubulointerstitium and mesangial-tubular crosstalk involved in the injury of TECs, retinoic acid has been discovered innovatively participating in TEC injury.

Cancer-Cell-Derived IgG and Its Potential Role in Tumor Development

Human immunoglobulin G (IgG) is the primary component of the human serum antibody fraction, representing about 75% of the immunoglobulins and 10-20% of the total circulating plasma proteins. Generally, IgG sequences are highly conserved, yet the four subclasses, IgG1, IgG2, IgG3, and IgG4, differ in their physiological effector functions by binding to different IgG-Fc receptors (FcγR). Thus, despite a similarity of about 90% on the amino acid level, each subclass possesses a unique manner of antigen binding and immune complex formation. Triggering FcγR-expressing cells results in a wide range of responses, including phagocytosis, antibody-dependent cell-mediated cytotoxicity, and complement activation. Textbook knowledge implies that only B lymphocytes are capable of producing antibodies, which recognize specific antigenic structures derived from pathogens and infected endogenous or tumorigenic cells. Here, we review recent discoveries, including our own observations, about misplaced IgG expression in tumor cells. Various studies described the presence of IgG in tumor cells using immunohistology and established correlations between high antibody levels and promotion of cancer cell proliferation, invasion, and poor clinical prognosis for the respective tumor patients. Furthermore, blocking tumor-cell-derived IgG inhibited tumor cells. Tumor-cell-derived IgG might impede antigen-dependent cellular cytotoxicity by binding antigens while, at the same time, lacking the capacity for complement activation. These findings recommend tumor-cell-derived IgG as a potential therapeutic target. The observed uniqueness of Ig heavy chains expressed by tumor cells, using PCR with V(D)J rearrangement specific primers, suggests that this specific part of IgG may additionally play a role as a potential tumor marker and, thus, also qualify for the neoantigen category.

Current insights into the expression and functions of tumor-derived immunoglobulins

Numerous studies have reported expressions of immunoglobulins (Igs) in many human tumor tissues and cells. Tumor-derived Igs have displayed multiple significant functions which are different from classical Igs produced by B lymphocytes and plasma cells. This review will concentrate on major progress in expressions, functions, and mechanisms of tumor-derived Igs, similarities and differences between tumor-derived Igs and B-cell-derived Igs. We also discuss the future research directions of tumor-derived Igs, including their structural characteristics, physicochemical properties, mechanisms for rearrangement and expression regulation, signaling pathways involved, and clinical applications.

Immunoglobulin Expression in Cancer Cells and Its Critical Roles in Tumorigenesis

Traditionally, immunoglobulin (Ig) was believed to be produced by only B-lineage cells. However, increasing evidence has revealed a high level of Ig expression in cancer cells, and this Ig is named cancer-derived Ig. Further studies have shown that cancer-derived Ig shares identical basic structures with B cell-derived Ig but exhibits several distinct characteristics, including restricted variable region sequences and aberrant glycosylation. In contrast to B cell-derived Ig, which functions as an antibody in the humoral immune response, cancer-derived Ig exerts profound protumorigenic effects via multiple mechanisms, including promoting the malignant behaviors of cancer cells, mediating tumor immune escape, inducing inflammation, and activating the aggregation of platelets. Importantly, cancer-derived Ig shows promising potential for application as a diagnostic and therapeutic target in cancer patients. In this review, we summarize progress in the research area of cancer-derived Ig and discuss the perspectives of applying this novel target for the management of cancer patients.

Cancer-driven IgG promotes the development of prostate cancer though the SOX2-CIgG pathway

BACKGROUND

Although androgen deprivation therapy (ADT) is the initial treatment strategy for prostate cancer (PCa), recurrent castration-resistant prostate cancer (CRPC) eventually ensues. In this study, cancer-derived immunoglobulin G (CIgG) is found to be induced after ADT, identifying CIgG as a potential CRPC driver gene.

METHODS

The expression of CIgG and its clinical significance in PCa tissue was analyzed by The Cancer Genome Atlas database and immunohistochemistry. Subsequently, the sequence features of prostate cell line VHDJH rearrangements were analyzed. We also assessed the effect of CIgG on the migratory, invasive and proliferative abilities of PCa cells in vitro and vivo. Suspended microsphere, colony formation and drug-resistant assays were performed using PC3 cells with high CIgG expression (CIgG^high ) and low CIgG expression (CIgG^-/low ), and A nonobese diabetic/severe combined immunodeficiency mouse tumor xenograft model was developed for the study of the tumorigenic effects of the different cell populations. The SOX2-CIgG signaling pathway was validated by immunohistochemistry, immunofluorescence, quantitative reverse transcription-polymerase chain reaction, Western blot, luciferase, and chromatin immunoprecipitation assays and bioinformatics analyses. Finally, we investigated the effect of RP215 inhibition on the progression of PCa in vivo using a Babl/c nude mouse xenograft model.

RESULTS

CIgG is frequently expressed in PCa and associated with clinicopathological characteristics, moreover, CIgG transcripts with unique patterns of VHDJH rearrangements are found in PCa cells. Functional analyses identified that CIgG was induced by ADT and upregulated by SOX2 (SRY (sex determining region Y)-box 2) in PCa, promoting the development of PCa. In addition, our findings underscore a novel role of CIgG signaling in the maintenance of stemness and the progression of cancer through mitogen activated protein kinase/extracellular-signal-regulated kinase and AKT in PCa. In vivo experiments further demonstrated that depleting CIgG significantly suppressed the growth of PCa cell xenografts. Furthermore, a CIgG monoclonal antibody named RP215 exhibits tumor inhibitory effect as well.

CONCLUSION

Our data suggests that CIgG could be a driver of PCa development, and that targeting the SOX2-CIgG axis may therefore inhibit PCa development after ADT.

[Expression and Clinical Significance of Cancer-derived Immunoglobulin G in Non-small Cell Lung Cancer by Bioinformatics and Immunohistochemistry]

背景与目的

经典免疫学理论认为，免疫球蛋白G（immunoglobulin G, IgG）仅由B细胞合成。近年来研究发现恶性肿瘤细胞也可以合成IgG（cancer-IgG）。本研究分析了cancer-IgG在非小细胞肺癌（non-small cell lung cancer, NSCLC）中的表达及临床意义，并初步探究其机制。

方法

应用数据库分析IgG1重链编码基因（immunoglobulin heavy constant gamma 1, IGHG1）、免疫组化分析cancer-IgG在NSCLC中的表达及与预后的关系；基因富集分析（gene set enrichment analysis, GSEA）方法探究与IGHG1调控相关的信号通路。

结果

Cancer-IgG在NSCLC中的表达量显著高于正常组织，与预后呈负相关，并与患者的临床分期（P=0.042）、T分期（P=0.044）和转移（P=0.007）密切相关。GSEA分析显示，IGHG1与细胞黏附、细胞因子相互作用和趋化因子信号通路相关。

结论

在NSCLC中，cancer-IgG高表达是预后不良的因素，可能与促进肿瘤的侵袭转移相关。

Cancer-derived sialylated IgG promotes tumor immune escape by binding to Siglecs on effector T cells

To date, IgG in the tumor microenvironment (TME) has been considered a product of B cells and serves as an antitumor antibody. However, in this study, using a monoclonal antibody against cancer-derived IgG (Cancer-IgG), we found that cancer cells could secrete IgG into the TME. Furthermore, Cancer-IgG, which carries an abnormal sialic acid modification in the CH1 domain, directly inhibited effector T-cell proliferation and significantly promoted tumor growth by reducing CD4⁺ and CD8⁺ T-cell infiltration into tumor tissues. Mechanistic studies showed that the immunosuppressive effect of sialylated Cancer-IgG is dependent on its sialylation and binding to sialic acid-binding immunoglobulin-type lectins (Siglecs) on effector CD4⁺ and CD8⁺ T cells. Importantly, we show that several Siglecs are overexpressed on effector T cells from cancer patients, but not those from healthy donors. These findings suggest that sialylated Cancer-IgG may be a ligand for Siglecs, which may serve as potential checkpoint proteins and mediate tumor immune evasion.

Unraveling the Mechanobiology of Extracellular Matrix

Cells need to be anchored to extracellular matrix (ECM) to survive, yet the role of ECM in guiding developmental processes, tissue homeostasis, and aging has long been underestimated. How ECM orchestrates the deterioration of healthy to pathological tissues, including fibrosis and cancer, also remains poorly understood. Inquiring how alterations in ECM fiber tension might drive these processes is timely, as mechanobiology is a rapidly growing field, and many novel mechanisms behind the mechanical forces that can regulate protein, cell, and tissue functions have recently been deciphered. The goal of this article is to review how forces can switch protein functions, and thus cell signaling, and thereby inspire new approaches to exploit the mechanobiology of ECM in regenerative medicine as well as for diagnostic and therapeutic applications. Some of the mechanochemical switching concepts described here for ECM proteins are more general and apply to intracellular proteins as well.

Human colorectal cancer cells frequently express IgG and display unique Ig repertoire

BACKGROUND

There is growing evidence proving that many human carcinomas, including colon cancer, can overexpress immunoglobulin (Ig); the non B cancer cell-derived Ig usually displayed unique V(D)J rearrangement pattern that are distinct from B cell-derived Ig. Especially, the cancer-derived Ig plays important roles in cancer initiation, progression, and metastasis. However, it still remains unclear if the colon cancer-derived Ig can display unique V(D)J pattern and sequencing, which can be used as novel target for colon cancer therapy.

AIM

To investigate the Ig repertoire features expressed in human colon cancer cells.

METHODS

Seven cancerous tissue samples of colon adenocarcinoma and corresponding noncancerous tissue samples were sorted by fluorescence-activated cell sorting using epithelial cell adhesion molecule as a marker for epithelial cells. Ig repertoire sequencing was used to analyze the expression profiles of all 5 classes of Ig heavy chains (IgH) and the Ig repertoire in colon cancer cells and corresponding normal epithelial cells.

RESULTS

We found that all 5 IgH classes can be expressed in both colon cancer cells and normal epithelial cells. Surprisingly, unlike the normal colonic epithelial cells that expressed 5 Ig classes, our results suggested that cancer cells most prominently express IgG. Next, we found that the usage of Ig in cancer cells caused the expression of some unique Ig repertoires compared to normal cells. Some V_H segments, such as V_H3-7, have been used in cancer cells, and V_H3-74 was frequently present in normal epithelial cells. Moreover, compared to the normal cell-derived Ig, most cancer cell-derived Ig showed unique V_HDJ_H patterns. Importantly, even if the same V_HDJ_H pattern was seen in cancer cells and normal cells, cancer cell-derived IgH always displayed distinct hypermutation hot points.

CONCLUSION

We found that colon cancer cells could frequently express IgG and unique IgH repertoires, which may be involved in carcinogenesis of colon cancer. The unique IgH repertoire has the potential to be used as a novel target in immune therapy for colon cancer.