BCL-2 expression promotes immunosuppression in chronic lymphocytic leukemia by enhancing regulatory T cell differentiation and cytotoxic T cell exhaustion

Hallmarks of cancer resistance

This review explores the hallmarks of cancer resistance, including drug efflux mediated by ATP-binding cassette (ABC) transporters, metabolic reprogramming characterized by the Warburg effect, and the dynamic interplay between cancer cells and mitochondria. The role of cancer stem cells (CSCs) in treatment resistance and the regulatory influence of non-coding RNAs, such as long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), are studied. The chapter emphasizes future directions, encompassing advancements in immunotherapy, strategies to counter adaptive resistance, integration of artificial intelligence for predictive modeling, and the identification of biomarkers for personalized treatment. The comprehensive exploration of these hallmarks provides a foundation for innovative therapeutic approaches, aiming to navigate the complex landscape of cancer resistance and enhance patient outcomes.

Bulk and single-cell RNA sequencing reveal the contribution of laminin γ2 -CD44 to the immune resistance in lymphocyte-infiltrated squamous lung cancer subtype

The high heterogeneity of lung squamous cell carcinomas (LUSC) and the complex tumor microenvironment lead to non-response to immunotherapy in many patients. Therefore, characterizing the heterogeneity of the tumor microenvironment in patients with LUSC and further exploring the immune features and molecular mechanisms that lead to immune resistance will help improve the efficacy of immunotherapy in such patients. Herein, we retrospectively analyzed the RNA sequencing (RNA-seq) data of 513 LUSC samples with other multiomics and single-cell RNA-seq data and validated key features using multiplex immunohistochemistry. We divided these samples into six subtypes (CS1-CS6) based on the RNA-seq data and found that CS3 activates the immune response with a high level of lymphocyte infiltration and gathers a large number of patients with advanced-stage disease but increases the expression of exhausted markers cytotoxic T-lymphocyte associated protein 4, lymphocyte-activation gene 3, and programmed death-1. The prediction of the response to immunotherapy showed that CS3 is potentially resistant to immune checkpoint blockade therapy, and multi-omic data analysis revealed that CS3 specifically expresses immunosuppression-related proteins B cell lymphoma 2, GRB2-associated binding protein, and dual-specificity phosphatase 4 and has a high mutation ratio of the driver gene ATP binding cassette subfamily A member 13. Furthermore, single-cell RNA-seq verified lymphocyte infiltration in the CS3 subtype and revealed a positive relationship between the expression of LAMC2-CD44 and immune resistance. LAMC2 and CD44 are epithelial-mesenchymal transition-associated genes that modulate tumor proliferation, and multicolor immunofluorescence validated the negative relationship between the expression of LAMC2-CD44 and immune infiltration. Thus, we identified a lymphocyte-infiltrated subtype (CS3) in patients with LUSC that exhibited resistance to immune checkpoint blockade therapy, and the co-hyperexpression of LAMC2-CD44 contributed to immune resistance, which could potentially improve immunological efficacy by targeting this molecule pair in combination with immunotherapy.

Expression and prognostic significance of the PD-1/PD-L1 pathway in AIDS-related non-Hodgkin lymphoma

OBJECTIVE

Immune tolerance and evasion play a critical role in virus-driven malignancies. However, the phenotype and clinical significance of programmed cell death 1 (PD-1) and its ligands, PD-L1 and PD-L2, in aggressive acquired immunodeficiency syndrome (AIDS)-related non-Hodgkin lymphoma (AR-NHL) remain poorly understood, particularly in the Epstein-Barr virus (EBV)-positive subset.

METHODS

We used in situ hybridization with EBV-encoded RNA (EBER) to assess the EBV status. We performed immunohistochemistry and flow cytometry analysis to evaluate components of the PD-1/PD-L1/L2 pathway in a multi-institutional cohort of 58 patients with AR-NHL and compared EBV-positive and EBV-negative cases.

RESULTS

The prevalence of EBV+ in AR-NHL was 56.9% and was associated with a marked increase in the expression of PD-1/PD-L1/PD-L2 in malignant cells. Patients with AR-NHLs who tested positive for both EBER and PD-1 exhibited lower survival rates compared to those negative for these markers (47.4% vs. 93.8%, p = 0.004). Similarly, patients positive for both EBER and PD-L1 also demonstrated poorer survival (56.5% vs. 93.8%, p = 0.043). Importantly, PD-1 tissue-expression demonstrated independent prognostic significance for overall survival in multivariate analysis and was correlated to elevated levels of LDH (r = 0.313, p = 0.031), increased PD-1+ Tregs (p = 0.006), and robust expression of EBER (r = 0.541, p < 0.001) and PD-L1 (r = 0.354, p = 0.014) expression.

CONCLUSIONS

These data emphasize the importance of PD-1-mediated immune evasion in the complex landscape of immune oncology in AR-NHL co-infected with EBV, and contribute to the diagnostic classification and possible definition of immunotherapeutic strategies for this unique subgroup.

The role of Bach2 in regulating CD8 + T cell development and function

Bach2 was initially discovered in B cells, where it was revealed to control the transcription involved in cell differentiation. Bach2 is intimately connected to CD8 + T lymphocytes in various differentiation states and subsets according to recent findings. Bach2 can regulate primitive T cells, stimulate the development and differentiation of memory CD8 + T cells, inhibit the differentiation of effector CD8 + T cells, and play a significant role in the exhaustion of CD8 + T cells. The appearance and development of diseases are tightly linked to irregular CD8 + T cell differentiation and function. Accordingly, Bach2 offers novel approaches and possible targets for the clinical treatment of associated disorders based on research on these pathways. Here, we summarize the role of Bach2 in the function and differentiation of CD8 + T cells and its potential clinical applications.

T-cell infiltration and its regulatory mechanisms in cancers: insights at single-cell resolution

Tumor-infiltrating T cells recognize, attack, and clear tumor cells, playing a central role in antitumor immune response. However, certain immune cells can impair this response and help tumor immune escape. Therefore, exploring the factors that influence T-cell infiltration is crucial to understand tumor immunity and improve therapeutic effect of cancer immunotherapy. The use of single-cell RNA sequencing (scRNA-seq) allows the high-resolution analysis of the precise composition of immune cells with different phenotypes and other microenvironmental factors, including non-immune stromal cells and the related molecules in the tumor microenvironment of various cancer types. In this review, we summarized the research progress on T-cell infiltration and the crosstalk of other stromal cells and cytokines during T-cell infiltration using scRNA-seq to provide insights into the mechanisms regulating T-cell infiltration and contribute new perspectives on tumor immunotherapy.

Decoding leukemia at the single-cell level: clonal architecture, classification, microenvironment, and drug resistance

Leukemias are refractory hematological malignancies, characterized by marked intrinsic heterogeneity which poses significant obstacles to effective treatment. However, traditional bulk sequencing techniques have not been able to effectively unravel the heterogeneity among individual tumor cells. With the emergence of single-cell sequencing technology, it has bestowed upon us an unprecedented resolution to comprehend the mechanisms underlying leukemogenesis and drug resistance across various levels, including the genome, epigenome, transcriptome and proteome. Here, we provide an overview of the currently prevalent single-cell sequencing technologies and a detailed summary of single-cell studies conducted on leukemia, with a specific focus on four key aspects: (1) leukemia's clonal architecture, (2) frameworks to determine leukemia subtypes, (3) tumor microenvironment (TME) and (4) the drug-resistant mechanisms of leukemia. This review provides a comprehensive summary of current single-cell studies on leukemia and highlights the markers and mechanisms that show promising clinical implications for the diagnosis and treatment of leukemia.

TCF7 and LEF-1 downregulation in sepsis promotes immune suppression by inhibiting CD4+ T cell proliferation

BACKGROUND

Previous studies have shown that sepsis is implicated in a reduction in the number and function of CD4+ T cells. TCF7 and LEF-1 facilitate early T cell development and lineage selection of CD4+ T cells. However, the function and mechanism of TCF7 and LEF-1 in sepsis are uncharacterized. This study intended to delineate effect of TCF7 and LEF-1 on sepsis and the impact on proliferation of CD4+ T cells in sepsis.

METHODS

A mouse sepsis model was constructed by cecal ligation and puncture (CLP) method. Expression of TCF7 and LEF-1 in sepsis was investigated using bioinformatics analysis and molecular experiments. We then constructed TCF7 and LEF-1 overexpression cell lines to investigate their effects on proliferation, apoptosis, effector activation, and immunosuppressive molecules of CD4+ T cells in sepsis.

RESULTS

TCF7 and LEF-1 were downregulated in sepsis. As the duration of sepsis induction increased, the levels of TCF7 and LEF-1 gradually decreased, as did the number of CD4+ T cells. Cell experiments showed that overexpression of TCF7 and LEF-1 enhanced proliferation and effector activation of CD4+ T cells, reduced apoptosis, decreased PD-1 and LAG3 expression, and promoted immune response in sepsis.

CONCLUSION

In conclusion, this study confirmed that downregulation of TCF7 and LEF-1 expression in sepsis inhibited proliferation of CD4+ T cells, leading to immune suppression. This finding suggested that TCF7 and LEF-1 were potential biological targets for sepsis and indicated that immunotherapy aimed at improving CD4+ T cell proliferation may be a new strategy for immune therapy in sepsis patients.

Aberrant frequency of TNFR2-expressing CD4+ FoxP3+ regulatory T cells in nasopharyngeal carcinoma patients

TNFR2 is a surface marker of highly suppressive subset of CD4+ FoxP3+ regulatory T cells (Tregs) in humans and mice. This study examined the TNFR2 expression by Tregs of nasopharyngeal carcinoma (NPC) patients and healthy controls. The proliferation, migration, survival of TNFR2+ Tregs, and association with clinicopathological characteristics were assessed. The expression levels of selected cytokines were also determined. The results demonstrated that in both peripheral blood (PB) (10.45 ± 5.71%) and tumour microenvironment (TME) (54.38 ± 16.15%) of NPC patients, Tregs expressed TNFR2 at noticeably greater levels than conventional T cells (Tconvs) (3.91 ± 2.62%, p < 0.0001), akin to healthy controls. Expression of TNFR2 (1.06 ± 0.99%) was correlated better than CD25+ (0.40 ± 0.46%) and CD127-/low (1.00 ± 0.83% ) with FoxP3 expression in NPC PB (p = 0.0005). Though there was no significant association between TNFR2 expression with the functional capacity (proliferation, migration and survival) of Tregs (p > 0.05), the proportions of PB and TME TNFR2+ Tregs in NPC patients showed more proliferative, higher migration capacity, and better survival ability, as compared to those in healthy controls. Furthermore, TNFR2+ Tregs from NPC patients expressed significantly higher amounts of IL-6 (p = 0.0077), IL-10 (p = 0.0001), IFN-γ (p = 0.0105) and TNF-α (p < 0.0001) than those from healthy controls. Most significantly, TNFR2 expression in maximally suppressive Tregs population were linked to WHO Type III histological type, distant metastasis, progressive disease status, and poor prognosis for NPC patients. Hence, our research implies that TNFR2 expression by PB and TME Tregs may be a useful predictive indicator in NPC patients.

Recent revelations and future directions using single-cell technologies in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a clinically and biologically heterogeneous disease with varying outcomes. In the last decade, the application of next-generation sequencing technologies has allowed extensive mapping of disease-specific genomic, epigenomic, immunogenetic, and transcriptomic signatures linked to CLL pathogenesis. These technologies have improved our understanding of the impact of tumor heterogeneity and evolution on disease outcome, although they have mostly been performed on bulk preparations of nucleic acids. As a further development, new technologies have emerged in recent years that allow high-resolution mapping at the single-cell level. These include single-cell RNA sequencing for assessment of the transcriptome, both of leukemic and non-malignant cells in the tumor microenvironment; immunogenetic profiling of B and T cell receptor rearrangements; single-cell sequencing methods for investigation of methylation and chromatin accessibility across the genome; and targeted single-cell DNA sequencing for analysis of copy-number alterations and single nucleotide variants. In addition, concomitant profiling of cellular subpopulations, based on protein expression, can also be obtained by various antibody-based approaches. In this review, we discuss different single-cell sequencing technologies and how they have been applied so far to study CLL onset and progression, also in response to treatment. This latter aspect is particularly relevant considering that we are moving away from chemoimmunotherapy to targeted therapies, with a potentially distinct impact on clonal dynamics. We also discuss new possibilities, such as integrative multi-omics analysis, as well as inherent limitations of the different single-cell technologies, from sample preparation to data interpretation using available bioinformatic pipelines. Finally, we discuss future directions in this rapidly evolving field.

Establishment and comprehensive analysis of a new human cell line (NK-NJ) with NK-cell characteristics established from extranodal natural killer cell lymphoma/leukemia

Extranodal NK/T cell lymphoma, nasal type (ENKTL) is an aggressive and heterogeneous disease. With standard treatment containing pegaspargase-based regimen, patients who were resistant to pegaspargase have rapidly disease progression and worse prognosis. Thus, there is an urgent requirement for constructing ENKTL cell line model to explore the mechanism of pegaspargase resistance and new molecular targeted drugs to improve prognosis. We report here on the establishment of a novel ENKTL cell line, NK-NJ. The cells were isolated from a 52-year-old Chinese man who was diagnosed with relapse/refractory (R/R) ENKTL and grow steadily in vitro. The NK-NJ cells express CD56, CD2, CD45RA with no expression of CD3, CD16, CD57, CD4, CD8, CD26, CD28, CD5, TCR, CD45RO and CD161 and showed a TCR gene unrearrangement, which suggested an origin in the NK-lineage but not T-lineage. The immunophenotypes of NK-NJ cells were consistent with the patient. Moreover, short tandem repeat (STR) profiling results also demonstrated that NK-NJ originated from the patient. NK-NJ showed complex karyotype. Target sequencing method indicated that the main mutation genes of the first-time disease progression of lymph nodal were the same as main mutation genes of the primary nasal lesions. Moreover, NK-NJ was recognized as latency I with EBER positivity and carried high EBV-DNA viral load. The chemosensitivity results suggested synthetic lethality of epigenetic drugs and PD-1 inhibitor for ENKTL patients by reasons of epigenetic drugs promoting PD-L1 expression. In conclusion, we established a new ENKTL cell line in the era of new targeted drugs. We hope that this cell line can help to further understand underlying pathogenesis of ENKTL especially for advanced ENKTL and the functional role of EBV in ENKTL pathogenetic process.

Identification and Validation of Ferroptosis-Related LncRNAs Signature as a Novel Prognostic Model for Chronic Lymphocytic Leukemia

Background

Chronic lymphocytic leukemia (CLL) is a subtype of B-cell malignancy with high heterogeneity. Ferroptosis is a novel cell death induced by iron and lipid peroxidation and exhibits prognostic value in many cancers. Emerging studies on long non-coding RNAs (lncRNAs) and ferroptosis reveal the unique value in tumorigenesis. However, the prognostic value of ferroptosis-related lncRNAs (FRLs) remains unclear in CLL.

Aim

We aimed to construct a FRLs risk model to predict prognosis and improve prognostic stratification for clinical practice.

Methods

RNA-sequencing data and clinical characteristics of CLL patients were downloaded from the GEO database. Based on ferroptosis-related genes from FerrDb database, differentially expressed FRLs with prognostic significance were identified and used to generate the risk model. The capability of the risk model was assessed and evaluated. GO and KEGG analyses were performed to confirm biological roles and potential pathways.

Results

A novel ferroptosis-related lncRNAs prognostic score (FPS) model containing six FRLs (PRKCQ, TRG.AS1, LNC00467, LNC01096, PCAT6 and SBF2.AS1) was identified. Patients in the training and validation cohort were evenly divided into high- and low-risk groups. Our results indicated that patients in the high-risk group had worse survival than those in the low-risk group. Functional enrichment analyses showed that the differently expressed genes (DEGs) between the two groups were enriched in the chemokine signaling pathway, hematopoietic cell lineage, T cell differentiation, TCR pathway and NF-κB pathway. Moreover, significant differences in immune cell infiltration were also observed. Surprisingly, FPS was proved to be an independent prognostic indicator for OS.

Conclusion

We established and evaluated a novel prognostic risk model with 6 FRLs that could predict prognosis accurately and describe the distinct immune infiltration in CLL.

Mechanisms and Strategies to Overcome PD-1/PD-L1 Blockade Resistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by a high rate of systemic metastasis, insensitivity to conventional treatment and susceptibility to drug resistance, resulting in a poor patient prognosis. The immune checkpoint inhibitors (ICIs) represented by antibodies of programmed death receptor 1 (PD-1) and programmed death receptor ligand 1 (PD-L1) have provided new therapeutic options for TNBC. However, the efficacy of PD-1/PD-L1 blockade monotherapy is suboptimal immune response, which may be caused by reduced antigen presentation, immunosuppressive tumor microenvironment, interplay with other immune checkpoints and aberrant activation of oncological signaling in tumor cells. Therefore, to improve the sensitivity of TNBC to ICIs, suitable patients are selected based on reliable predictive markers and treated with a combination of ICIs with other therapies such as chemotherapy, radiotherapy, targeted therapy, oncologic virus and neoantigen-based therapies. This review discusses the current mechanisms underlying the resistance of TNBC to PD-1/PD-L1 inhibitors, the potential biomarkers for predicting the efficacy of anti-PD-1/PD-L1 immunotherapy and recent advances in the combination therapies to increase response rates, the depth of remission and the durability of the benefit of TNBC to ICIs.

Low-frequency ultrasound irradiation increases paclitaxel-induced sarcoma cells apoptosis and facilitates the transmembrane delivery of drugs

Sarcoma is a malignant tumor derived from interstitial tissues and requires comprehensive treatment including chemotherapy. Paclitaxel (PTX) is an active agent against sarcoma, but its effect is not sufficiently acceptable and needs to be improved. Low-frequency ultrasound (LFU) has been documented to improve the efficacy of drugs by inducing reversible changes in membrane permeability; however, the effects of the combined use of LFU and PTX for sarcoma tumors remain unclear and warrant further investigation. We investigated the effects of 30 kHz LFU treatment combined with PTX on sarcoma cells A-204 and HT-1080 by analyzing in vitro apoptosis and cell growth inhibition rates, and determined their antitumor effects by examining tumor weights with or without LFU in the S180 sarcoma xenograft model. Drug concentrations in the subcutaneous tumors were measured using high performance liquid chromatography (HPLC). LFU combined with PTX significantly induced cell apoptosis, and blocked the cell cycle of sarcoma cells in G2/M phase, and furthermore, inhibited the activation of JAK2/STAT3 signaling pathway. Meanwhile, LFU combined with PTX inhibited the expression of PD-L1 in vitro, suggesting the potential of enhanced antitumor immunity by this treatment. LFU combined with PTX significantly inhibited the growth of S180 tumors transplanted subcutaneously in Institute of Cancer Research (ICR) mice, and its enhanced effect may be associated with increased local concentrations of PTX in tumor tissues in vivo, with no significant adverse subsequences on body weight observed. We conclude that the combination of LFU and PTX has synergistic antitumor effects and is a candidate for subcutaneous treatment of sarcoma by further increasing the intracellular concentration of PTX.

Prime, shock and kill: BCL-2 inhibition for HIV cure

While modern HIV therapy can effectively suppress viral replication, the persistence of the latent reservoir posits the greatest hurdle to complete cure. The "shock and kill" strategy is under investigation for HIV therapy, aiming to reactivate latent HIV, and subsequently eliminate it through anti-retroviral therapy and host immune function. However, thus far, studies have yielded suboptimal results, stemming from a combination of ineffective latency reversal and poor immune clearance. Concomitantly, studies have now revealed the importance of the BCL-2 anti-apoptotic protein as a critical mediator of infected cell survival, reservoir maintenance and immune evasion in HIV. Furthermore, BCL-2 inhibitors are now recognized for their anti-HIV effects in pre-clinical studies. This minireview aims to examine the intersection of BCL-2 inhibition and current shock and kill efforts, hoping to inform future studies which may ultimately yield a cure for HIV.

Omega-3 polyunsaturated fatty acids reverse the impact of western diets on regulatory T cell responses through averting ceramide-mediated pathways

Western diet (WD), high in sugar and fat, promotes obesity and associated chronic low-grade pro-inflammatory environment, leading to impaired immune function, reprogramming of innate and adaptive immune cells, and development of chronic degenerative diseases, including cardiovascular disease. Increased concentrations of circulating and tissue ceramides contribute to inflammation and cellular dysfunction common in immune metabolic and cardiometabolic disease. Therefore, ceramide-lowering interventions have been considered as strategies to improve adipose tissue health. Here, we report the ability of omega-3 polyunsaturated fatty acids (n-3PUFA) to attenuate inflammatory phenotypes promoted by WD, through ceramide-dependent pathways. Using an animal model, we show that enrichment of WD diet with n-3PUFA, reduced the expression of ceramide synthase 2 (CerS2), and lowered the concentration of long-chain ceramides (C23-C26) in plasma and adipose tissues. N-3PUFA also increased prevalence of the anti-inflammatory CD4+Foxp3+ and CD4+Foxp3+CD25+ Treg subtypes in lymphoid organs. The CerS inhibitor FTY720 mirrored the effect of n-3PUFA. Treatment of animal and human T cells with ceramide C24 in vitro, reduced CD4+Foxp3+ Treg polarisation and IL-10 production, and increased IL-17, while it decreased Erk and Akt phosphorylation downstream of T cell antigen receptors (TCR). These findings suggest that molecular mechanisms mediating the adverse effect of ceramides on regulatory T lymphocytes, progress through reduced TCR signalling. Our findings suggest that nutritional enrichment of WD with fish oil n-3PUFA can partially mitigate its detrimental effects, potentially improving the low-grade inflammation associated with immune metabolic disease. Compared to pharmacological interventions, n-3PUFA offer a simpler approach that can be accommodated as lifestyle choice.

Strategies to overcome CAR-T cell resistance in clinical work: A single-institute experience

The emergence of chimeric antigen receptor (CAR) T cell therapy has shifted the paradigm of malignant tumor treatment, especially the advent of CD19-directed CAR-T cell therapy for the treatment of relapsed/refractory (R/R) B-cell malignancies. Although CAR-T cell therapy has promising effects, some patients are resistant to this treatment, leaving them with limited options. Therefore, strategies to overcome resistance to CAR-T cell therapy are needed. We retrospectively studied three R/R diffuse large B-cell lymphoma patients who were resistant to CAR-T cell therapy and whose disease was controlled after receiving pembrolizumab, 21D4 CAR-T cells, or ibrutinib and venetoclax. Some promising prevention and treatment strategies to overcome treatment resistance are also discussed.

Application of apoptosis-related genes in a multiomics-related prognostic model study of gastric cancer

Gastric cancer (GC) is one of the most common tumors in the world, and apoptosis is closely associated with GC. A number of therapeutic methods have been implemented to increase the survival in GC patients, but the outcomes remain unsatisfactory. Apoptosis is a highly conserved form of cell death, but aberrant regulation of the process also leads to a variety of major human diseases. As variations of apoptotic genes may increase susceptibility to gastric cancer. Thus, it is critical to identify novel and potent tools to predict the overall survival (OS) and treatment efficacy of GC. The expression profiles and clinical characteristics of TCGA-STAD and GSE15459 cohorts were downloaded from TCGA and GEO. Apoptotic genes were extracted from the GeneCards database. Apoptosis risk scores were constructed by combining Cox regression and LASSO regression. The GSE15459 and TCGA internal validation sets were used for external validation. Moreover, we explored the relationship between the apoptosis risk score and clinical characteristics, drug sensitivity, tumor microenvironment (TME) and tumor mutational burden (TMB). Finally, we used GSVA to further explore the signaling pathways associated with apoptosis risk. By performing TCGA-STAD differential analysis, we obtained 839 differentially expressed genes, which were then analyzed by Cox regressions and LASSO regression to establish 23 genes associated with apoptosis risk scores. We used the test validation cohort from TCGA-STAD and the GSE15459 dataset for external validation. The AUC values of the ROC curve for 2-, 3-, and 5-years survival were 0.7, 0.71, and 0.71 in the internal validation cohort from TCGA-STAD and 0.77, 0.74, and 0.75 in the GSE15459 dataset, respectively. We constructed a nomogram by combining the apoptosis risk signature and some clinical characteristics from TCGA-STAD. Analysis of apoptosis risk scores and clinical characteristics demonstrated notable differences in apoptosis risk scores between survival status, sex, grade, stage, and T stage. Finally, the apoptosis risk score was correlated with TME characteristics, drug sensitivity, TMB, and TIDE scores.

Regulatory T cells (Tregs) in lymphoid malignancies and the impact of novel therapies

Regulatory T cells (Tregs) are responsible for maintaining immune homeostasis by controlling immune responses. They can be characterized by concomitant expression of FoxP3, CD25 and inhibitory receptors such as PD-1 and CTLA-4. Tregs are key players in preventing autoimmunity and are dysregulated in cancer, where they facilitate tumor immune escape. B-cell lymphoid malignancies are a group of diseases with heterogenous molecular characteristics and clinical course. Treg levels are increased in patients with B-cell lymphoid malignancies and correlate with clinical outcomes. In this review, we discuss studies investigating Treg immunobiology in B-cell lymphoid malignancies, focusing on clinical correlations, mechanisms of accumulation, phenotype, and function. Overarching trends suggest that Tregs can be induced directly by tumor cells and recruited to the tumor microenvironment where they suppress antitumor immunity to facilitate disease progression. Further, we highlight studies showing that Tregs can be modulated by novel therapeutic agents such as immune checkpoint blockade and targeted therapies. Treg disruption by novel therapeutics may beneficially restore immune competence but has been associated with occurrence of adverse events. Strategies to achieve balance between these two outcomes will be paramount in the future to improve therapeutic efficacy and safety.