CD25: A potential tumor therapeutic target

CD25 is the alpha-chain of the heterotrimer IL-2 receptor. CD25 is expressed on the surface of both immune and non-immune cells with different frequencies. For cancers, CD25 is expressed at high levels in many types of hematological malignancies, but at low levels in most solid tumors. CD25 is also highly expressed in activated circulating immune cells and regulatory T cells (Tregs). Infiltration of Tregs in the tumor microenvironment can lead to an imbalanced ratio of effector T cells (Teffs) and Tregs, which is associated with the progression of cancers. A rescued Teff/Treg cell ratio indicates an efficient anti-tumor response to immunotherapy. CD25 as a potential target for the depletion of Tregs is critical in developing new immunotherapeutic strategies. Few articles have summarized the relationships between CD25 and tumors, or the recent progress of drugs targeting CD25. In this paper, we will discuss the structures of IL-2 and IL-2R, the biological function of CD25 and its important role in tumor therapy. In addition, the latest research on drugs targeting CD25 has been summarized, providing guidance for future drug development.

Increased sIL-2Rα leads to obstruction of IL-2 biological function and Treg cells differentiation in SLE patients via binding to IL-2

Background

The decrease of IL-2 level is believed to play an important role in the disease occurrence and development of SLE, but the relevant mechanisms have not been fully clarified. Many studies have found that the level of soluble interleukin 2 receptor α (sIL-2Rα) in SLE patients is significantly increased. Considering the fact that sIL-2Rα has the ability to bind IL-2, we want to know whether the increased sIL-2Rα has some impact on the level and function of IL-2 in SLE patients.

Methods

New onset SLE patients, treated SLE patients and healthy volunteers were recruited. The levels of serum IL-2, IL-2 mRNA in CD3⁺ T cells and serum sIL-2Rα were detected and compared in these subjects. Two mixed solid-phase sandwich ELISA system were designed to measure exclusively the heterodimers complex of sIL-2Rα/IL-2. The sera from SLE patients were pretreated with or without immune complex dissociation solution and detected for IL-2 levels. IL-2 standard or serum from HCs were used to co-incubate with recombinant sIL-2Rα or serum samples with high levels of sIL-2Rα and detected for IL-2 levels by ELISA. The inhibitory effect of sIL-2Rα on IL-2 biological activity was investigated by CTLL-2 cell proliferation assay. The frequencies and absolute counts of Treg cells were detected by flow cytometry before and after the addition of recombinant sIL-2Rα.

Results

The levels of serum IL-2 in SLE patients were significantly decreased and negatively correlated with SLEDAI. However, there was no significant difference in IL-2 mRNA levels in CD3⁺ T cells between SLE patients and healthy controls. The levels of serum sIL-2Rα in SLE patients were significantly increased, positively correlated with the SLEDAI and negatively correlated with the levels of serum IL-2. sIL-2Rα was shown to bind to IL-2 to form immune complex, resulting in false reduction in the detection level of serum IL-2 and significant decrease in biological activity of IL-2. The increase of sIL-2Rα was demonstrated to be one of the important mechanisms for the obstruction of Treg cells differentiation in SLE patients.

Conclusion

Increased serum sIL-2Rα can bind to IL-2, leading to obstruction of IL-2 activity and Treg cells differentiation.

Biology of Tumor Associated Macrophages in Diffuse Large B Cell Lymphoma

The tumor associated microenvironment is known to play a vital role during the development and progression of different malignant tumors. As a part of tumor microenvironment, tumor associated macrophages (TAMs) are crucial for the genesis, proliferation, metastasis, and survival of tumor cells. Recently, more and more studies showed that TAMs were related with poor clinical status and survival in patients with diffuse large B cell lymphoma (DLBCL). Considering the complex roles which TAMs play in the tumor microenvironment of DLBCL, the aim of this study was to review the biological mechanisms between TAMs and DLBCL cells, including extracellular matrix remodeling and angiogenesis promotion, tumor promotion, immune suppression, and phagocytosis inhibition. This review will help us to further understand the comprehensive impact of TAMs on DLBCL and explore possible prognostic markers and therapeutic targets.

Prognostication of diffuse large B-cell lymphoma in the molecular era: moving beyond the IPI

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with variable outcomes. Despite the majority of patients being cured with combination chemoimmunotherapy, up to 30% eventually succumb to the disease. Until recently, baseline prognostic assessment has centred on the International Prognostic Index (IPI), although this index is yet to impact strongly on treatment choice. Molecular features such as cell of origin, MYC and BCL-2 genetic alterations and protein overexpression were identified over a decade ago, yet their prognostic value is still not fully elucidated. Adding complexity are the plethora of new clinical, biological and molecular prognostic markers described in the recent literature, most of which lack independent validation, likely act as surrogate markers for those already in common use and have yet to substantially impact on therapeutic decision making. This review comprehensively assesses the value of individual prognostic markers in the clinical setting and their potential to predict response to novel agents, and ways to optimise their use in future research.

Association of Soluble Interleukin-2 Receptor and C-Reactive Protein with the Efficacy of Bendamustine Salvage Treatment for Indolent Lymphomas and Mantle Cell Lymphoma

Bendamustine has demonstrated favourable efficacy in relapsed or refractory indolent lymphoma and mantle cell lymphoma. We retrospectively evaluated the pre-treatment clinical and laboratory factors and their correlation with the clinical outcome of these lymphomas. We analysed 53 patients who had been treated with bendamustine alone (n = 6) or rituximab plus bendamustine (n = 47). The overall response rate was 81.1%, with a complete response (CR) rate of 39.6%. The CR rate was significantly low in patients who had elevated levels of soluble interleukin-2 receptor (p = 0.024) and C-reactive protein (CRP; p = 0.004). The 1-year overall survival (OS) rate was 79.3%. An elevated CRP was associated with a short OS (p = 0.056). The present findings suggest that the lymphoma microenvironment and immune response were involved in the effects of bendamustine. These findings are also important in order to understand the pathophysiology of refractory lymphoma and to find effective strategies using bendamustine.

The emerging role of anti-CD25 directed therapies as both immune modulators and targeted agents in cancer

CD25 (also termed IL2RA) forms one component of the high-affinity heterotrimeric interleukin 2 (IL2) receptor on activated T cells. Its affinity for IL2 and cellular function are tightly regulated and vary in different cell types. The high frequency of CD25 on the surface of many different haematological tumour cells is now well established and, apart from its prognostic significance, CD25 may be present on leukaemic stem cells and enable oncogenic signalling pathways in leukaemic cells. Additionally, high CD25 expression in activated circulating immune cells and Tregs is a factor that has already been exploited by IL2 immunotherapies for treatment of tumours and autoimmune disease. The relative clinical safety and efficacy of administering anti-CD25 radioimmunoconjugates and immunotoxins in various haematological tumour indications has been established and clinical trials of a novel CD25-directed antibody drug conjugate are underway.

A case series of histoplasmosis patients with elevated serum soluble interleukin-2 receptor levels

Histoplasmosis is a common endemic mycosis that is usually asymptomatic but occasionally results in severe illness. Histoplasmosis and its causative agent, Histoplasma capsulatum, are found worldwide but rarely in Japan. In recent years, however, the number of histoplasmosis patients in Japan has increased. In addition, to our knowledge, there are no previous reports of increased serum soluble interleukin-2 receptor (sIL-2R) levels in patients with histoplasmosis. We report a case series of histoplasmosis in three Japanese temporary workers in Manzanillo, Mexico. All three patients developed a persistent high fever and general fatigue. Laboratory tests showed increased C-reactive protein levels and mild liver dysfunction. All patients also showed increased soluble interleukin-2 receptor (sIL-2R) levels. Chest computed tomography revealed multiple nodules in both lung fields. All patients were positive for serum anti-Histoplasma antibodies, and two patients were positive for Histoplasma on polymerase chain reaction tests. After treatment that included antifungals, their conditions gradually improved and laboratory data normalized. Although one patient developed respiratory failure, this patient recovered with antifungal therapy in combination with methylprednisolone. Serum sIL-2R levels in all patients gradually declined to normal levels, indicating their recovery from Histoplasma infection. From our experience with these patients, sIL-2R levels may be a useful biomarker for patients with histoplasmosis.

Serum Interleukin-6 and CCL11/Eotaxin May Be Suitable Biomarkers for the Diagnosis of Chronic Nonbacterial Osteomyelitis

OBJECTIVES

Chronic recurrent multifocal osteomyelitis (CRMO), the most severe form of chronic nonbacterial osteomyelitis (CNO), is an autoinflammatory bone disorder. In the absence of diagnostic criteria or biomarkers, CNO/CRMO remains a diagnosis of exclusion. The aim of this study was to identify biomarkers for diagnosing multifocal disease (CRMO).

STUDY DESIGN

Sera from 71 pediatric CRMO patients, 11 patients with osteoarticular infections, 62 patients with juvenile idiopathic arthritis (JIA), 7 patients with para-infectious or reactive arthritis, and 43 patients with acute leukemia or lymphoma, as well as 59 healthy individuals were collected. Multiplex analysis of 18 inflammation- and/or bone remodeling-associated serum proteins was performed. Statistical analysis included univariate ANOVA, discriminant analysis, univariate receiver operating characteristic (ROC) analysis, and logistic regression analyses.

RESULTS

For 14 of 18 blood serum proteins, significant differences were determined between CRMO patients, at least one alternative diagnosis, or healthy controls. Multi-component discriminant analysis delivered five biomarkers (IL-6, CCL11/eotaxin, CCL5/RANTES, collagen Iα, sIL-2R) for the diagnosis of CRMO. ROC analysis allowed further reduction to a core set of 2 biomarkers (CCL11/eotaxin, IL-6) that are sufficient to discern between CRMO, healthy controls, and alternative diagnoses.

CONCLUSION

Serum biomarkers CCL11/eotaxin and IL-6 differentiate between patients with CRMO, healthy controls, and alternative diagnoses (leukemia and lymphoma, osteoarticular infections, para-infectious arthritis, and JIA). Easily accessible biomarkers may aid in diagnosing CRMO. Further studies testing biomarkers in larger unrelated cohorts are warranted.

Encapsulating peritoneal sclerosis is associated with T-cell activation

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is an excessive fibrotic response of the peritoneum that may occur after long-term peritoneal dialysis (PD). The underlying pathophysiology is poorly understood, but involvement of peritoneal inflammatory T helper 1 cells may be pivotal.

METHODS

Soluble interleukin-2 receptor alpha (sCD25) concentration was measured as a marker for T-cell activation in serum and ascites from EPS patients and various control patient groups. Peritoneal biopsies were stained for the presence of T cells, and T cells isolated from ascites of EPS patients were characterized in detail for differentiation status and cytokine expression.

RESULTS

Serum sCD25 concentrations are significantly and specifically increased in EPS patients compared with haemodialysis, PD and predialysis patients. Peritoneal effluent of stable PD patients contains very low levels of sCD25, while sCD25 levels in ascites of EPS patients are high and indicative of local production. In the years preceding the diagnosis of EPS, the serum sCD25 concentrations increased while remaining at stable levels in control PD patients. The peritoneum and ascites of EPS patients showed a significant influx of T cells with relatively increased numbers of CD4(+) T cells. These T cells were fully differentiated and displayed a T helper 1 cell type with a pro-inflammatory cytokine profile.

CONCLUSIONS

Increased serum sCD25 concentrations and peritoneal lymphocytosis in EPS patients indicate the involvement of activated T cells in the pathophysiology of excessive fibrosis.

Role of tumor-associated macrophages in hematological malignancies

The tumor microenvironment consists of many non-tumor cells such as leukocytes, endothelial cells, and fibroblasts, and phenotypic changes in a tumor microenvironment are believed to be involved in tumor progression and resistance to anticancer treatments. In hematological malignancies, tumor-associated macrophages (TAMs) that have infiltrated lymphoma or leukemia tissues may be involved in tumor progression, and many researchers have studied phenotypic changes in TAMs. This review article summarizes the publications related to TAMs in hematological malignancies, with an emphasis on CD163(+) protumoral TAMs, which seem to be associated with disease progression. Cell-cell interactions between protumoral TAMs and lymphoma or leukemia cells may play an important role in lymphoma or leukemia microenvironments. Although detailed molecular mechanisms of these cell-cell interactions have not yet been clarified, phenotypic characterization of TAMs is thought to be a useful approach for evaluating clinical prognosis. In addition, targeting TAMs may be a new strategy for treating malignant hematological diseases.