Fc Receptor-Like Proteins in Pathophysiology of B-cell Disorder

The Increased FCRL mRNA Expression in Patients with Graves' Disease Is Associated with Hyperthyroidism (But Not with Positive Thyroid Antibodies)

Background: Fc receptor-like (FCRL) genes play a role in the immune system by encoding proteins that function as receptors on the surface of immune cells. The clinical significance of FCRL gene expression in Graves' Disease (GD) and Graves' Orbitopathy (GO) remains unclear. We evaluated the expression of FCRL 2, 3, 4 mRNA in patients with GD and GO and its role in the development and activity of these diseases. Methods: Peripheral blood samples from patients with GD (n = 24) or GO (n = 49) hospitalized in the Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, were collected. Expressions of FCRL2, FCRL3 and FCRL4 were measured by real-time PCR. Results: FCRL3 expression was higher in patients with GD compared to GO (1.375 vs. 0.673, p = 0.004) and, specifically, active GO (1.375 vs. 0.639, p = 0.005). Regarding FCRL4, mRNA expression was higher in GD compared to Control (3.078 vs. 0.916, p = 0.003), GO (3.078 vs. 1.178, p < 0.001), active GO (3.078 vs. 1.186, p = 0.002) and inactive GO (3.078 vs. 1.171, p = 0.008). In turn, FCRL4 mRNA expression was higher in patients with hyperthyroidism (subclinical + overt) than in euthyroid patients (2.509 vs. 0.995, p = 0.001 when the whole group of individuals was considered; 2.509 vs. 1.073, p = 0.004 when GO + GD was considered). Conclusions: The increased FCRL mRNA expression in patients with GD is associated with hyperthyroidism (but not with positive TSHRAbs), and our study is the first one to confirm this relationship.

Fc receptor-like A promotes malignant behavior in renal cell carcinoma and correlates with tumor immune infiltration

BACKGROUND

Our study aims to investigate the mechanisms through which Fc receptor-like A (FCRLA) promotes renal cell carcinoma (RCC) and to examine its significance in relation to tumor immune infiltration.

MATERIALS AND METHODS

The correlation between FCRLA and data clinically related to RCC was explored using The Cancer Genome Atlas (TCGA), then validated using Gene Expression Omnibus (GEO) gene chip data. Enrichment and protein-protein interaction (PPI) network analyses were performed for FCRLA and its co-expressed genes. FCRLA was knocked down in RCC cell lines to evaluate its impact on biological behavior. Then the potential downstream regulators of FCRLA were determined by western blotting, and rescue experiments were performed for verification. The relevance between FCRLA and various immune cells was analyzed through GSEA, TIMER, and GEPIA tools. TIDE and ESTIMATE algorithms were used to predict the effect of FCRLA in immunotherapy.

RESULTS

Fc receptor-like A was associated with clinical and T stages and could predict the M stage (AUC = 0.692) and 1-3- and 5-year survival rates (AUC = 0.823, 0.834, and 0.862) of RCC patients. Higher expression of FCLRA predicted an unfavorable overall survival (OS) in TCGA-RCC and GSE167573 datasets (p = 0.03, p = 0.04). FCRLA promoted the malignant biological behavior of RCC cells through the pERK1/2/-MMP2 pathway and was associated with tumor immune microenvironment in RCC.

CONCLUSION

Fc receptor-like A is positively correlated with poor outcomes in RCC patients and plays an oncogenic role in RCC through the pERK1/2-MMP2 pathway. Patients with RCC might benefit from immunotherapy targeting FCRLA.

FCRL3 expression is upregulated and closely correlates with TIGIT expression in regulatory T cells of patients with systemic lupus erythematosus

Using data from single-cell RNA sequencing and flow cytometry, we initially examined the expression of FCRL3, finding it to be elevated and positively associated with TIGIT expression in the regulatory T cells of patients with systemic lupus erythematosus. This also suggests that the co-expression of FCRL3 and TIGIT warrants further attention.

Fc receptor-like 1 (FCRL1) is a novel biomarker for prognosis and a possible therapeutic target in diffuse large B-cell lymphoma

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin's lymphoma, which can involve various types of mature B-cells. Considering that the incidence of DLBCL has increased, additional research is required to identify novel and effective prognostic and therapeutic molecules. Fc receptor-like 1 (FCRL1) acts as an activation co-receptor of human B-cells. Aberrant expression of this molecule has been reported in a number of B-cell-related disorders. Moreover, the clinical significance and prognosis value of FCRL1 in DLBCL are not completely identified.

METHODS

In this study, the expression levels of FCRL1 were determined in thirty patients with DLBCL and 15 healthy controls (HCs). In addition, the correlation between FCRL1 expressions with clinicopathological variables of DLBCL patients were examined. Then, the potential roles of FCRL1 in proliferation, apoptosis, and cell cycle distribution of B-cells from DLBCL patients were determined using flow cytometry analysis, after knockdown of this marker using retroviral short hairpin RNA interference. Quantitative real time-PCR, western blotting, and enzyme-linked immunosorbent assay were also used to identify the possible effects of FCRL1 knockdown on the expression levels of BCL-2, BID, BAX, intracellular signaling pathway PI3K/p-Akt, and p65 nuclear factor-kappa B (NF-κB) in the B-cells of DLBCL.

RESULTS

Statistical analysis revealed higher levels of FCRL1 expression in the B-cells of DLBCL patients compared to HCs at both protein and mRNA levels. A positive correlation was observed between the FCRL1 expression and some clinicopathological parameters of DLBCL patients. In addition, FCRL1 knockdown significantly decreased cell proliferation and stimulated apoptosis as well as G1 cell cycle arrest in the B-cells of DLBCL patients. The levels of p65 NF-κB and PI3K/p-Akt expressions were markedly reduced after knockdown of FCRL1 expression.

CONCLUSIONS

These results suggested that FCRL1 could be a potential novel biomarker for prognosis and/or a possible effective therapeutic target for treatment of patients with DLBCL.

Variants of Novel Immunomodulatory Fc Receptor Like 5 Gene Are Associated With Multiple Sclerosis Susceptibility in the Polish Population

Fc receptors have been shown to play a role in several autoimmune diseases. We aimed to test, for the first time, whether some of the single nucleotide variants in the FCRL5 gene were associated with multiple sclerosis (MS) susceptibility and clinical manifestations in the Polish population. The case-control study included 94 individuals with MS and 160 healthy subjects. We genotyped two single nucleotide variants of the FCRL5 gene: rs2012199 and rs6679793. The age of onset, disease duration, and clinical condition of the MS subjects were analyzed. For statistical analysis, we used the chi-squared test confirmed with Fisher's exact test. We observed the significant differences in the distribution of investigated FCRL5 genotypes between MS subjects and healthy controls. The CC and CT genotypes, as well as the C allele of rs2012199, were significantly more common in the MS subjects, as were genotypes AA and AG, and allele A of rs6679793. We noted that decreased MS susceptibility was associated with the T allele rs2012199 (OR = 0.37, p = 0.0002) and G allele rs6679793 (OR = 0.6, p = 0.02). Our results support the role of the FCRL5 locus in MS predisposition and extend the evidence of its influence on autoimmunity.

Expression profile of Fc receptor-like molecules in patients with IgA nephropathy

BACKGROUND

Fc receptor-like (FCRL) molecules were considered to play a role in the pathogenesis of certain autoimmune diseases. Nonetheless, the clinical significance of FCRLs in IgA nephropathy (IgAN) remains unclear.

OBJECTIVE

This study is aimed at investigating the expression levels of FCRLs molecules in IgAN patients and determining its relevance to disease activity.

METHODS

The mRNA expression levels of FCRLs were determined in peripheral blood mononuclear cells (PBMCs) of 42 IgAN patients and 48 healthy controls by quantitative real-time PCR (qRT-PCR). FCRLs proteins expression in B cells of 25 IgAN patients, 14 patients with non-IgAN glomerulonephritis, and 29 healthy controls were detected by Flow cytometry. The Spearman correlation test was used to assess the correlation of FCRLs expression with clinical parameters of IgAN patients.

RESULTS

Our results indicated significant down-regulation of FCRL2 and FCRL3 mRNA levels in IgAN patients compared to healthy subjects. Surface protein expression of FCRLs molecules confirmed the qRT-PCR results. But FCRL2 and FCRL3 protein levels did not correlate with clinicopathologic phenotypes of IgAN patients. However, we found a significant positively correlation of FCRL2 and FCRL3 mRNA expression with the core 1 β1,3-galactosyltransferase (C1GALT1) and its molecular chaperone (Cosmc) mRNA levels in IgAN patients.

CONCLUSIONS

FCRL2 and FCRL3 expression levels in IgAN patients are significantly decreased and correlated with CIGALT1 and Cosmc mRNA expression.

Two genetic variants explain the association of European ancestry with multiple sclerosis risk in African-Americans

Epidemiological studies have suggested differences in the rate of multiple sclerosis (MS) in individuals of European ancestry compared to African ancestry, motivating genetic scans to identify variants that could contribute to such patterns. In a whole-genome scan in 899 African-American cases and 1155 African-American controls, we confirm that African-Americans who inherit segments of the genome of European ancestry at a chromosome 1 locus are at increased risk for MS [logarithm of odds (LOD) = 9.8], although the signal weakens when adding an additional 406 cases, reflecting heterogeneity in the two sets of cases [logarithm of odds (LOD) = 2.7]. The association in the 899 individuals can be fully explained by two variants previously associated with MS in European ancestry individuals. These variants tag a MS susceptibility haplotype associated with decreased CD58 gene expression (odds ratio of 1.37; frequency of 84% in Europeans and 22% in West Africans for the tagging variant) as well as another haplotype near the FCRL3 gene (odds ratio of 1.07; frequency of 49% in Europeans and 8% in West Africans). Controlling for all other genetic and environmental factors, the two variants predict a 1.44-fold higher rate of MS in European-Americans compared to African-Americans.

Considerations for the Design of Antibody-Based Therapeutics

Antibody-based proteins have become an important class of biologic therapeutics, due in large part to the stability, specificity, and adaptability of the antibody framework. Indeed, antibodies not only have the inherent ability to bind both antigens and endogenous immune receptors but also have proven extremely amenable to protein engineering. Thus, several derivatives of the monoclonal antibody format, including bispecific antibodies, antibody-drug conjugates, and antibody fragments, have demonstrated efficacy for treating human disease, particularly in the fields of immunology and oncology. Reviewed here are considerations for the design of antibody-based therapeutics, including immunological context, therapeutic mechanisms, and engineering strategies. First, characteristics of antibodies are introduced, with emphasis on structural domains, functionally important receptors, isotypic and allotypic differences, and modifications such as glycosylation. Then, aspects of therapeutic antibody design are discussed, including identification of antigen-specific variable regions, choice of expression system, use of multispecific formats, and design of antibody derivatives based on fragmentation, oligomerization, or conjugation to other functional moieties. Finally, strategies to enhance antibody function through protein engineering are reviewed while highlighting the impact of fundamental biophysical properties on protein developability.

1q23.1 homozygous deletion and downregulation of Fc receptor-like family genes confer poor prognosis in chronic lymphocytic leukemia

The identification of chromosome 1 translocations and deletions is a rare and poorly investigated event in chronic lymphocytic leukemia (CLL). Nevertheless, the identification of novel additional molecular alterations is of great interest, opening to new prognostic and therapeutic strategies for such heterogeneous hematological disease. We here describe a patient affected by CLL with a mutated IGHV status, showing a balanced t(1;3)(q23.1;q21.3) translocation and a der(18)t(1;18)(q24.2;p11.32), accompanying the recurrent 13q14 heterozygous deletion in all analyzed cells at onset. By combining whole-genome sequencing, SNP array, RNA sequencing, and FISH analyses, we defined a 1q23.1 biallelic minimally deleted region flanking translocations breakpoints at both derivative chromosome 1 homologues. The deletion resulted in the downregulation of the Fc receptor-like family genes FCRL1, FCRL2, and FCRL3 and in the lack of expression of FCRL5, observed by RT-qPCR. The mutational status of TP53, NOTCH1, SF3B1, MYD88, FBXW7, and XPO1 was investigated by targeted next-generation sequencing, detecting a frameshift deletion within NOTCH1 (c.7544_7545delCT). We hypothesize a loss of tumor suppressor function for FCRL genes, cooperating with NOTCH1 mutation and 13q14 genomic loss in our patient, both conferring a negative prognosis, independently from the known biological prognostic factors of CLL.

Phase I study of the anti-FcRH5 antibody-drug conjugate DFRF4539A in relapsed or refractory multiple myeloma

FcRH5 is a cell surface marker enriched on malignant plasma cells when compared to other hematologic malignancies and normal tissues. DFRF4539A is an anti-FcRH5 antibody-drug conjugated to monomethyl auristatin E (MMAE), a potent anti-mitotic agent. This phase I study assessed safety, tolerability, maximum tolerated dose (MTD), anti-tumor activity, and pharmacokinetics of DFRF4539A in patients with relapsed/refractory multiple myeloma. DFRF4539A was administered at 0.3-2.4 mg/kg every 3 weeks or 0.8-1.1 mg/kg weekly as a single-agent by intravenous infusion to 39 patients. Exposure of total antibody and antibody-conjugate-MMAE analytes was linear across the doses tested. There were 37 (95%) adverse events (AEs), 8 (21%) serious AEs, and 15 (39%) AEs ≥ grade 3. Anemia (n = 10, 26%) was the most common AE considered related to DFRF4539A. Two cases of grade 3 acute renal failure were attributed to DFRF4539A. There were no deaths; the MTD was not reached. DFRF4539A demonstrated limited activity in patients at the doses tested with 2 (5%) partial response, 1 (3%) minimal response, 18 (46%) stable disease, and 16 (41%) progressive disease. FcRH5 was confirmed to be expressed and occupied by antibody post-treatment and thus remains a valid myeloma target. Nevertheless, this MMAE-based antibody-drug-conjugate targeting FcRH5 was unsuccessful for myeloma.

HBV induces inhibitory FcRL receptor on B cells and dysregulates B cell-T follicular helper cell axis

Spontaneous or treatment induced seroconversion in chronic HBV infection is rare and generation of anti-HBs antibodies is the current goal of HBV therapeutics. Here we investigated B and follicular T helper (Tfh) cell defects that persist in HBV infection despite long-term nucleos(t)ide analog (NUC) treatment and possible mechanisms behind them. RNA sequencing revealed that patient B cells have upregulated expression of multiple inhibitory receptors including members of FcRL family and downregulation of genes involved in antigen presentation. An expansion of atypical memory CD19⁺CD10⁻CD27⁻CD21⁻ subset of B cells, that express high levels of FcRL5, is persistently present in patients. HBs antigen specific IgG response is concentrated in classical memory and not in atypical memory subset, confirming dysfunction of this subset. Activated Tfh, which expressed excessive CD40L upon polyclonal stimulation, were present in patients. Incubation of B cells from healthy individuals with HBV core (HBc) or CD40L resulted in induction of inhibitory receptors FcRL4, FcRL5 and PD-1 on CD19+ cells and resulted in altered B cell phenotypes. Mechanistically, HBc binds B cells and causes proliferation specifically of FcRL5+ B cell subset. Our results provide evidence that HBV directly causes upregulation of inhibitory pathways in B cells resulting in an accumulation of atypical B cells that lack anti-HBs function.