Targeting TNFR2, an immune checkpoint stimulator and oncoprotein, is a promising treatment for cancer

TNFR2-expressing CD4+Foxp3+ regulatory T cells in cancer immunology and immunotherapy

CD4⁺Foxp3⁺ regulatory T cells (Tregs) represent a major cellular mechanism in tumor immune evasion. Elimination of Treg activity has become a strategy to devise an effective tumor immunotherapy. We reported that TNF receptor type II (TNFR2), one of two receptors transducing TNF biological activity, is preferentially expressed by the most suppressive subset of Tregs. By interaction with TNFR2, TNF plays a decisive role in the activation, expansion and phenotype stability of Tregs. We also found that highly suppressive TNFR2-expressing Tregs appear to be tumor-associated Tregs. This finding has been supported by recent studies in mouse tumor models and in cancer patients. In this chapter, published data revealing the important role of TNFR2⁺ Tregs in tumor development and metastasis in different tumor types are reviewed and analyzed. The therapeutic potential of targeting TNF-TNFR2 interaction as means to eliminate Treg activity, and consequently to enhance anti-tumor immune responses, also is discussed.

Expression of tumor necrosis factor receptor 2 in human non-small cell lung cancer and its role as a potential prognostic biomarker

BACKGROUND

Tumor necrosis factor receptor 2 (TNFR2) promotes tumor cell proliferation, activates immunosuppressive cells, and supports immune escape. However, its role in non-small cell lung cancer (NSCLC) has not been reported.

METHODS

Quantitative real-time PCR and Western blotting were used to evaluate TNFR2 in three NSCLC cell lines (A549, H1299, H1975) and normal lung epithelial cells (BEAS-2B). TNFR2 was evaluated in 71 tumor tissues and 25 adjacent normal lung tissues by immunohistochemistry and analyzed with respect to clinical parameters.

RESULTS

The messenger RNA and protein levels of TNFR2 were significantly higher in A549, H1299, and H1975 cells than in BEAS-2B cells (P < 0.05) and differed significantly between NSCLC tissues and adjacent normal lung tissues by immunohistochemistry (P < 0.0001). TNFR2 is a independent prognostic factor in NSCLC. There have significantly differences in overall survival (OS) (P = 0.006) and disease-free survival (DFS) (P = 0.000) of NSCLC patients between TNFR2 low expression groups and TNFR2 high expression group.

CONCLUSION

TNFR2 is expressed in human NSCLC tissues and cell lines and is related to poor prognosis. TNFR2 may represent a new auxiliary index for patients with NSCLC.

Engineering lymphocytes with RNAi

Lymphocytes are the gatekeepers of the body's immune system and are involved in pathogenesis if their surveillance is stalled by inhibitory molecules or when they act as mediators for viral entry. Engineering lymphocytes in order to restore their functions is an unmet need in immunological disorders, cancer and in lymphotropic viral infections. Recently, the FDA approved several therapeutic antibodies for blocking inhibitory signals on T cells. This has revolutionized the field of solid tumor care, together with chimeric antigen receptor T cell (CAR-T) therapy that did the same for hematological malignancies. RNA interference (RNAi) is a promising approach where gene function can be inhibited in almost all types of cells. However, manipulation of genes in lymphocyte subsets are difficult due to their hard-to-transfect nature and in vivo targeting remains challenging as they are dispersed throughout the body. The ability of RNAi molecules to gain entry into cells is almost impossible without delivery strategy. Nanotechnology approaches are rapidly growing and their impact in the field of drug and gene delivery applications to transport payloads inside cells have been extensively studied. Here we discuss various technologies available for RNAi delivery to lymphocytes. We shed light on the importance of targeting molecules in order to target lymphocytes in vivo. In addition, we discuss recent developments of RNAi delivery to lymphocyte subsets, and detail the potential implication for the future of molecular medicine in leukocytes implicated diseases.

Exclusive expression of transmembrane TNF aggravates acute glomerulonephritis despite reduced leukocyte infiltration and inflammation

Tumor necrosis factor-α (TNF) is a cytokine mediating inflammatory kidney diseases such as immune complex glomerulonephritis. Its two receptors, TNFR1 and TNFR2, play distinct roles in this process, with TNFR2 strongly required for induction of disease. In contrast to soluble TNF (sTNF), transmembrane TNF robustly activates TNFR2. Thus, we examined the functional role of transmembrane TNF by inducing heterologous nephrotoxic serum nephritis in wild-type and transgenic TNFΔ1-9,K11E knock-in mice expressing transmembrane TNF but no sTNF (memTNF mice). Compared to wild-type, nephritis was exacerbated in memTNF mice on day 5, indicated by increased albuminuria, higher serum urea levels, and more pronounced glomerular deposits, together with higher numbers of dying and proliferating glomerular cells. This was associated with greater loss of glomerular endothelial cells, increased podocyte stress, and signs of augmented necroptosis in memTNF kidneys. Aggravation of nephritis was dependent on transmembrane TNF expression in parenchymal cells, but not leukocytes. Surprisingly, increased kidney injury was associated with reduced renal leukocyte infiltration in memTNF mice, which correlated with decreased renal mRNA expression of pro-inflammatory mediators. This effect was also present in isolated memTNF glomeruli stimulated with interleukin-1β in vitro. Thus, uncleaved transmembrane TNF is an important mediator of renal tissue damage characterized by increased renal cell death and loss of glomerular endothelial cells in murine glomerulonephritis. In contrast, sTNF predominantly mediates renal leukocyte recruitment and inflammation. These findings highlight the importance of transmembrane TNF in inflammatory kidney disease as a possible therapeutic target.

BCMA (TNFRSF17) Induces APRIL and BAFF Mediated Breast Cancer Cell Stemness

Recent advances in cancer immunology revealed immune-related properties of cancer cells as novel promising therapeutic targets. The two TNF superfamily members, APRIL (TNFSF13), and BAFF (TNFSF13B), which are type II membrane proteins, released in active forms by proteolytic cleavage and are primarily involved in B-lymphocyte maturation, have also been associated with tumor growth and aggressiveness in several solid tumors, including breast cancer. In the present work we studied the effect of APRIL and BAFF on epithelial to mesenchymal transition, migration, and stemness of breast cancer cells. Our findings show that both molecules increase epithelial to mesenchymal transition and migratory capacity of breast cancer cells, as well as cancer stem cell numbers, by increasing the expression of pluripotency genes such as ALDH1A1, KLF4, and NANOG. These effects are mediated by their common receptor BCMA (TNFRSF17) and the JNK signaling pathway. Interestingly, transcriptional data analysis from breast cancer cells and patients revealed that androgens can increase APRIL transcription and subsequently, in an autocrine/paracrine manner, enhance its pluripotency effect. In conclusion, our data suggest a possible role of APRIL and BAFF in breast cancer disease progression and provide evidence for a new possible mechanism of therapy resistance, that could be particularly relevant in aromatase inhibitors-treated patients, were local androgen is increased.

The p38 MAPK Inhibitor SB203580 Abrogates Tumor Necrosis Factor-Induced Proliferative Expansion of Mouse CD4+Foxp3+ Regulatory T Cells

There is now compelling evidence that tumor necrosis factor (TNF) preferentially activates and expands CD4⁺Foxp3⁺ regulatory T cells (Tregs) through TNF receptor type II (TNFR2). However, it remains unclear which signaling transduction pathway(s) of TNFR2 is required for the stimulation of Tregs. Previously, it was shown that the interaction of TNF–TNFR2 resulted in the activation of a number of signaling pathways, including p38 MAPK, NF-κB, in T cells. We thus examined the role of p38 MAPK and NF-κB in TNF-mediated activation of Tregs, by using specific small molecule inhibitors. The results show that treatment with specific p38 MAPK inhibitor SB203580, rather than NF-κB inhibitors (Sulfasalazine and Bay 11-7082), abrogated TNF-induced expansion of Tregs in vitro. Furthermore, upregulation of TNFR2 and Foxp3 expression in Tregs by TNF was also markedly inhibited by SB203580. The proliferative expansion and the upregulation of TNFR2 expression on Tregs in LPS-treated mice were mediated by TNF–TNFR2 interaction, as shown by our previous study. The expansion of Tregs in LPS-treated mice were also markedly inhibited by in vivo treatment with SB203580. Taken together, our data clearly indicate that the activation of p38 MAPK is attributable to TNF/TNFR2-mediated activation and proliferative expansion of Tregs. Our results also suggest that targeting of p38 MAPK by pharmacological agent may represent a novel strategy to up- or downregulation of Treg activity for therapeutic purposes.

Clinical significance of tumor necrosis factor receptor 2 in middle and lower thoracic esophageal squamous cell carcinoma

High expression and role of tumor necrosis factor receptor 2 (TNFR2) in cancer progression and prognosis has been reported in several types of tumors. However, its role in esophageal carcinoma (EC) remains unknown. In the present study, TNFR2 expression in middle and lower thoracic esophageal squamous cell carcinoma (ESCC) was detected using immunohistochemistry (IHC). Chi-square test revealed that TNFR2 was positively correlated with invasion depth, advanced clinical stage and low differentiation degree. Furthermore, survival analysis revealed that TNFR2 was positively correlated with poor overall survival (OS). Moreover, univariate COX regression analysis revealed that clinical stage, lymph node involvement, and invasion depth can affect the OS of ESCC patients, while multivariate COX regression analysis revealed that lymph node involvement and invasion depth can affect the OS of ESCC patients. In middle thoracic ESCC patients, TNFR2 was positively correlated with invasion depth, advanced clinical stage and poor OS. Furthermore, univariate and multivariate COX regression analysis both revealed that clinical stage, lymph node involvement, and invasion depth can affect OS. In lower thoracic ESCC patients, TNFR2 was positively correlated with low differentiation degree. Furthermore, the positive correlation of TNFR2 with poor OS did not reach statistical significance. In addition, univariate COX regression analysis revealed that only lymph node involvement could affect OS. All the results suggest that TNFR2 can play an important role in the progression and poor prognosis of ESCC patients. Moreover, the role of TNFR2 in the prognosis of middle thoracic ESCC patients was earlier and stronger than in lower thoracic ESCC patients.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Modulation of Regulatory T Cell Activity by TNF Receptor Type II-Targeting Pharmacological Agents

There is now compelling evidence that tumor necrosis factor (TNF)-TNF receptor type II (TNFR2) interaction plays a decisive role in the activation, expansion, and phenotypical stability of suppressive CD4⁺Foxp3⁺ regulatory T cells (Tregs). In an effort to translate this basic research finding into a therapeutic benefit, a number of agonistic or antagonistic TNFR2-targeting biological agents with the capacity to activate or inhibit Treg activity have been developed and studied. Recent studies also show that thalidomide analogs, cyclophosphamide, and other small molecules are able to act on TNFR2, resulting in the elimination of TNFR2-expressing Tregs. In contrast, pharmacological agents, such as vitamin D3 and adalimumab, were reported to induce the expansion of Tregs by promoting the interaction of transmembrane TNF (tmTNF) with TNFR2. These studies clearly show that TNFR2-targeting pharmacological agents represent an effective approach to modulating the function of Tregs and thus may be useful in the treatment of major human diseases such as autoimmune disorders, graft-versus-host disease (GVHD), and cancer. In this review, we will summarize and discuss the latest progress in the study of TNFR2-targeting pharmacological agents and their therapeutic potential based on upregulation or downregulation of Treg activity.

The Significance of Tumor Necrosis Factor Receptor Type II in CD8+ Regulatory T Cells and CD8+ Effector T Cells

Tumor necrosis factor (TNF) is a pleiotropic cytokine that has both pro-inflammatory and anti-inflammatory functions. The biological functions of TNF are mediated by two receptors, TNF receptor type I (TNFR1) and TNF receptor type II (TNFR2). TNFR1 is expressed universally on almost all cell types and has been extensively studied, whereas TNFR2 is mainly restricted to immune cells and some tumor cells and its role is far from clarified. Studies have shown that TNFR2 mediates the stimulatory activity of TNF on CD4⁺Foxp3⁺ regulatory T cells (Tregs) and CD8⁺Foxp3⁺ Tregs, and is involved in the phenotypic stability, proliferation, activation, and suppressive activity of Tregs. TNFR2 can also be expressed on CD8⁺ effector T cells (Teffs), which delivers an activation signal and cytotoxic ability to CD8⁺ Teffs during the early immune response, as well as an apoptosis signal to terminate the immune response. TNFR2-induced abolition of TNF receptor-associated factor 2 (TRAF2) degradation may play an important role in these processes. Consequently, due to the distribution of TNFR2 and its pleiotropic effects, TNFR2 appears to be critical to keeping the balance between Tregs and Teffs, and may be an efficient therapeutic target for tumor and autoimmune diseases. In this review, we summarize the biological functions of TNFR2 expressed on CD8⁺Foxp3⁺ Tregs and CD8⁺ Teffs, and highlight how TNF uses TNFR2 to coordinate the complex events that ultimately lead to efficient CD8⁺ T cell-mediated immune responses.

Blockade of TNFR2 signaling enhances the immunotherapeutic effect of CpG ODN in a mouse model of colon cancer

Through the tumor necrosis factor (TNF) receptor type II (TNFR2), TNF preferentially activates, expands, and promotes the phenotypic stability of CD4⁺Foxp3⁺ regulatory T (T_reg) cells. Those T_reg cells that have a high abundance of TNFR2 have the maximal immunosuppressive capacity. We investigated whether targeting TNFR2 could effectively suppress the activity of T_reg cells and consequently enhance the efficacy of cancer immunotherapy. We found that, relative to a suboptimal dose of the immunostimulatory Toll-like receptor 9 ligand CpG oligodeoxynucleotide (ODN), the combination of the suboptimal dose of CpG ODN with the TNFR2-blocking antibody M861 more markedly inhibited the growth of subcutaneously grafted mouse CT26 colon tumor cells. This resulted in markedly fewer TNFR2⁺ T_reg cells and more interferon-γ-positive (IFN-γ⁺) CD8⁺ cytotoxic T lymphocytes infiltrating the tumor and improved long-term tumor-free survival in the mouse cohort. Tumor-free mice were resistant to rechallenge by the same but not unrelated (4T1 breast cancer) cells. Treatment with the combination of TNFR2-blocking antibody and a CD25-targeted antibody also resulted in enhanced inhibition of tumor growth in a syngeneic 4T1 mouse model of breast cancer. Thus, the combination of a TNFR2 inhibitor and an immunotherapeutic stimulant may represent a more effective treatment strategy for various cancers.

TNFR2: A Novel Target for Cancer Immunotherapy

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy but exhibit variable efficacy and relapse and can induce autoimmunity. Tumor necrosis factor (TNF) receptor 2 (TNFR2) is a signaling molecule found on the surface of a subset of potent regulatory T cells (T_regs) that can activate the proliferation of these cells through nuclear factor kappa B (NF-κB). TNFR2 is also abundantly expressed on the surface of many human tumors. We propose that blocking TNFR2 might target abundant TNFR2⁺ tumor-infiltrating T_regs and directly kill TNFR2-expressing tumors. We also posit that TNFR2 inhibitors might potentially constitute safer and more targeted alternatives to ICI cancer treatment because the expression of TNFR2 on immune cells, concentrated in the tumor microenvironment of various cancers, appears to be more selective than that of checkpoint molecules.