Genetic evidence of PTPN22 effects on chronic lymphocytic leukemia

Metabolic Gatekeepers of Pathological B Cell Activation

Unlike other cell types, B cells undergo multiple rounds of V(D)J recombination and hypermutation to evolve high-affinity antibodies. Reflecting high frequencies of DNA double-strand breaks, adaptive immune protection by B cells comes with an increased risk of malignant transformation. In addition, the vast majority of newly generated B cells express an autoreactive B cell receptor (BCR). Thus, B cells are under intense selective pressure to remove autoreactive and premalignant clones. Despite stringent negative selection, B cells frequently give rise to autoimmune disease and B cell malignancies. In this review, we discuss mechanisms that we term metabolic gatekeepers to eliminate pathogenic B cell clones on the basis of energy depletion. Chronic activation signals from autoreactive BCRs or transforming oncogenes increase energy demands in autoreactive and premalignant B cells. Thus, metabolic gatekeepers limit energy supply to levels that are insufficient to fuel either a transforming oncogene or hyperactive signaling from an autoreactive BCR.

Modulation of TCR Signaling by Tyrosine Phosphatases: From Autoimmunity to Immunotherapy

Early TCR signaling is dependent on rapid phosphorylation and dephosphorylation of multiple signaling and adaptor proteins, leading to T cell activation. This process is tightly regulated by an intricate web of interactions between kinases and phosphatases. A number of tyrosine phosphatases have been shown to modulate T cell responses and thus alter T cell fate by negatively regulating early TCR signaling. Mutations in some of these enzymes are associated with enhanced predisposition to autoimmunity in humans, and mouse models deficient in orthologous genes often show T cell hyper-activation. Therefore, phosphatases are emerging as potential targets in situations where it is desirable to enhance T cell responses, such as immune responses to tumors. In this review, we summarize the current knowledge about tyrosine phosphatases that regulate early TCR signaling and discuss their involvement in autoimmunity and their potential as targets for tumor immunotherapy.

PTPN22 Silencing in Human Acute T-Cell Leukemia Cell Line (Jurkat Cell) and its Effect on the Expression of miR-181a and miR-181b

Purpose: T-cell acute lymphoblastic leukemia (T-ALL) is one of the most common malignancies associated with T-lymphocytes, accounting for 10 to 15 percent of ALL cases in children and 25 percent in adults. Innovative therapeutic approaches that overcome ineffective treatments on tumor cells may be a potential source of improvement in therapeutic approaches. Suppression of gene expression at transfusion level is one of the important strategies in gene therapy. The expression of PTPN22 and miR-181 genes in all types of hematologic malignancies increases and is likely to contribute to the survival and death of cells by affecting a variety of signaling pathways. The purpose of this study was to determine the role of PTPN22 inhibition by siRNA, and alteration in miR-181a and miR-181b in Jurkat cell line.

Methods: Jurkat cells were transfected with 80 pmol of siRNA to inhibit PTPN22. After that, expression of PTPN22 mRNA and transcript levels of miR-181a and miR-181b were measured with Real-time PCR after 48hrs.

Results: Experiments demonstrated that siRNA transfection resulted in significant downregulation of PTPN22 mRNA after 48 hrs in 80 pmol dose of siRNA. Moreover, transcript levels of both miR-181a and miR-181b was decreased after transfection.

Conclusion: PTPN22, miR-181a and miR-181b might be involved in progression of Jurkat cells and targeting these molecules by RNAi might confer promising tool in treatment of T-ALL.

Autoimmunity checkpoints as therapeutic targets in B cell malignancies

Targeted therapy of cancer typically focuses on inhibitors (for example, tyrosine kinase inhibitors) that suppress oncogenic signalling below a minimum threshold required for survival and proliferation of cancer cells. B cell acute lymphoblastic leukaemia and B cell lymphomas originate from various stages of development of B cells, which, unlike other cell types, are under intense selective pressure. The vast majority of newly generated B cells are autoreactive and die by negative selection at autoimmunity checkpoints (AICs). Owing to ubiquitous encounters with self-antigen, autoreactive B cells are eliminated by the overwhelming signalling strength of their autoreactive B cell receptor (BCR). A series of recent findings suggests that, despite malignant transformation, AICs are fully functional in B cell malignancies. This Opinion article proposes targeted engagement of AICs as a previously unrecognized therapeutic opportunity to overcome drug resistance in B cell malignancies.

Differential Lipid Response to Statins Is Associated With Variants in the BUD13-APOA5 Gene Region

Genetic variants within the BUD13-APOA5 gene region are known to be associated with high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) levels. Recent studies suggest that single nucleotide polymorphisms (SNPs) within this region affect HDL-C response to statin-fibrate combination therapy and low-density lipoprotein cholesterol (LDL-C) response to statin therapy. We hypothesized that SNPs within the BUD13-APOA5 region are associated with TG, HDL-C, and LDL-C response to statin therapy. We examined 1520 observations for 1086 patients from the Personalized Medicine Research Project, a large biorepository at the Marshfield Clinic Research Foundation, who had received statin therapy and been previously genotyped for polymorphisms in the 11q23 chromosomal region. A significant differential response to statin therapy was observed for 3 SNPs. The minor allele at rs11605293 significantly attenuated TG-lowering response to pravastatin (P = 0.000159), whereas the minor allele at rs12806755 was associated with a similar response to lovastatin (P = 0.000192). Genotypes at rs947990 significantly attenuated LDL-C reduction to atorvastatin therapy (P = 0.000668) with some patients with the minor allele having LDL-C increase after therapy. No SNPs within the BUD13-APOA5 region were associated with a significant effect on HDL-C reduction in response to statin therapy. In conclusion, this study suggests that common SNPs within the BUD13-APOA5 can affect TG and LDL-C response to statin therapy in a North American population.

PTPN22: the archetypal non-HLA autoimmunity gene

PTPN22 encodes a tyrosine phosphatase that is expressed by haematopoietic cells and functions as a key regulator of immune homeostasis by inhibiting T-cell receptor signalling and by selectively promoting type I interferon responses after activation of myeloid-cell pattern-recognition receptors. A single nucleotide polymorphism of PTPN22, 1858C>T (rs2476601), disrupts an interaction motif in the protein, and is the most important non-HLA genetic risk factor for rheumatoid arthritis and the second most important for juvenile idiopathic arthritis. PTPN22 exemplifies a shared autoimmunity gene, affecting the pathogenesis of systemic lupus erythematosus, vasculitis and other autoimmune diseases. In this Review, we explore the role of PTPN22 in autoimmune connective tissue disease, with particular emphasis on candidate-gene and genome-wide association studies and clinical variability of disease. We also propose a number of PTPN22-dependent functional models of the pathogenesis of autoimmune diseases.

Genome wide association study of SNP-, gene-, and pathway-based approaches to identify genes influencing susceptibility to Staphylococcus aureus infections

Background: We conducted a genome-wide association study (GWAS) to identify specific genetic variants that underlie susceptibility to diseases caused by Staphylococcus aureus in humans.

Methods: Cases (n = 309) and controls (n = 2925) were genotyped at 508,921 single nucleotide polymorphisms (SNPs). Cases had at least one laboratory and clinician confirmed disease caused by S. aureus whereas controls did not. R-package (for SNP association), EIGENSOFT (to estimate and adjust for population stratification) and gene- (VEGAS) and pathway-based (DAVID, PANTHER, and Ingenuity Pathway Analysis) analyses were performed.

Results: No SNP reached genome-wide significance. Four SNPs exceeded the p < 10⁻⁵ threshold including two (rs2455012 and rs7152530) reaching a p-value < 10⁻⁷. The nearby genes were PDE4B (rs2455012), TXNRD2 (rs3804047), VRK1 and BCL11B (rs7152530), and PNPLA5 (rs470093). The top two findings from the gene-based analysis were NMRK2 (p_gene = 1.20E-05), which codes an integrin binding molecule (focal adhesion), and DAPK3 (p_gene = 5.10E-05), a serine/threonine kinase (apoptosis and cytokinesis). The pathway analyses identified epithelial cell responses to mechanical and non-mechanical stress.

Conclusion: We identified potential susceptibility genes for S. aureus diseases in this preliminary study but confirmation by other studies is needed. The observed associations could be relevant given the complexity of S. aureus as a pathogen and its ability to exploit multiple biological pathways to cause infections in humans.

Tyrosine phosphatase PTPN22: multifunctional regulator of immune signaling, development, and disease

Inheritance of a coding variant of the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is associated with increased susceptibility to autoimmunity and infection. Efforts to elucidate the mechanisms by which the PTPN22-C1858T variant modulates disease risk revealed that PTPN22 performs a signaling function in multiple biochemical pathways and cell types. Capable of both enzymatic activity and adaptor functions, PTPN22 modulates signaling through antigen and innate immune receptors. PTPN22 plays roles in lymphocyte development and activation, establishment of tolerance, and innate immune cell-mediated host defense and immunoregulation. The disease-associated PTPN22-R620W variant protein is likely involved in multiple stages of the pathogenesis of autoimmunity. Establishment of a tolerant B cell repertoire is disrupted by PTPN22-R620W action during immature B cell selection, and PTPN22-R620W alters mature T cell responsiveness. However, after autoimmune attack has initiated tissue injury, PTPN22-R620W may foster inflammation through modulating the balance of myeloid cell-produced cytokines.