The Potential Role of Innate Immunity in the Pathogenesis of Hodgkin's Lymphoma

The Effect of the Tumor Microenvironment on Lymphoid Neoplasms Derived from B Cells

Lymphomas are characteristic tumors surrounded by an inflammatory microenvironment. The cells of the microenvironment are essential for the growth and survival of neoplastic cells and are recruited through the effect of cytokines/chemokines. Lymphomas include heterogeneous groups of neoplasms infiltrating various lymphoid structures which may arise from B lymphocytes, T lymphocytes, and natural killer (NK) cells at various stages of their differentiation state. In this review article, we analyze the literature data concerning the involvement of the tumor microenvironment (TME) in the progression of lymphomas and the recent advances in the analysis of microenvironment components in the most common forms: some mature B cell lymphoma neoplasms and classic Hodgkin lymphomas. The complex crosstalk between the TME and tumor cells led to the discovery of many mechanisms usable as molecular-targeted therapy through the control of diverse elements of the TME, varying from inhibitors of angiogenic cytokines and their receptors to the regulation of cells' activities and the novel immune checkpoint inhibitors.

Hodgkin Lymphoma: A Special Microenvironment

Classical Hodgkin's lymphoma (cHL) is one of the most particular lymphomas for the few tumor cells surrounded by an inflammatory microenvironment. Reed-Sternberg (RS) and Hodgkin (H) cells reprogram and evade antitumor mechanisms of the normal cells present in the microenvironment. The cells of microenvironment are essential for growth and survival of the RS/H cells and are recruited through the effect of cytokines/chemokines. We summarize recent advances in gene expression profiling (GEP) analysis applied to study microenvironment component in cHL. We also describe the main therapies that target not only the neoplastic cells but also the cellular components of the background.

Proteomic Exploration of Plasma Exosomes and Other Small Extracellular Vesicles in Pediatric Hodgkin Lymphoma: A Potential Source of Biomarkers for Relapse Occurrence

Exosomes and other small extracellular vesicles (EVs) are potential sources of cancer biomarkers. Plasma-derived EVs have not yet been studied in pediatric Hodgkin lymphoma (HL), for which predictive biomarkers of relapse are greatly needed. In this two-part proteomic study, we used two-dimensional difference gel electrophoresis (2D-DIGE) followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) to analyze EV proteins of plasma collected at diagnosis from children with nodular sclerosis HL, relapsed or not. EVs isolated using membrane affinity had radii ranging from 20 to 130 nm and contained the programmed cell death 6-interacting (ALIX) and the tumor susceptibility gene 101 (TSG101) proteins, whereas calnexin (CANX) was not detected. 2D-DIGE identified 16 spots as differentially abundant between non-relapsed and relapsed HL (|fold change| ≥ 1.5, p < 0.05). LC–MS/MS identified these spots as 11 unique proteins, including five more abundant in non-relapsed HL (e.g., complement C4b, C4B; fibrinogen γ chain, FGG) and six more abundant in relapsed HL (e.g., transthyretin, TTR). Shotgun LC–MS/MS on pooled EV proteins from non-relapsed HL identified 161 proteins, including 127 already identified in human exosomes (ExoCarta data). This EV cargo included 89 proteins not yet identified in exosomes from healthy plasma. Functional interrogation by the Database for Annotation, Visualization and Integrated Discovery (DAVID) revealed that the EV proteins participate in platelet degranulation and serine-type endopeptidase activity as the most significant Gene Ontology (GO) biological process and molecular function (p < 0.01).

Eosinophils in the Tumor Microenvironment

Eosinophils are rare blood-circulating and tissue-infiltrating immune cells studied for decades in the context of allergic diseases and parasitic infections. Eosinophils can secrete a wide array of soluble mediators and effector molecules, with potential immunoregulatory activities in the tumor microenvironment (TME). These findings imply that these cells may play a role in cancer immunity. Despite these cells were known to infiltrate tumors since many years ago, their role in TME is gaining attention only recently. In this chapter, we will review the main biological functions of eosinophils that can be relevant within the TME. We will discuss how these cells may undergo phenotypic changes acquiring pro- or antitumoricidal properties according to the surrounding stimuli. Moreover, we will analyze canonical (i.e., degranulation) and unconventional mechanisms (i.e., DNA traps, exosome secretion) employed by eosinophils in inflammatory contexts, which can be relevant for tumor immune responses. Finally, we will review the available preclinical models that could be employed for the study of the role in vivo of eosinophils in cancer.

Epstein-Barr virus LMP2A utilizes Syk and PI3K to activate NF-κB in B-cell lymphomas to increase MIP-1α production

The incidence of Hodgkin's lymphoma (HL) is growing due to an increase in Epstein-Barr virus (EBV)-associated HL in AIDS patients. The HL tumor microenvironment is vital for the survival of the malignant Hodgkin-Reed Sternberg (HRS) cells of HL, which express the EBV protein latent membrane protein 2A (LMP2A). While previous work shows that LMP2A mimics B-cell receptor (BCR) signaling to promote the survival of HRS cells, the ability of LMP2A to establish and maintain the tumor microenvironment through the production of chemokines remains unknown. Since BCR signaling induces the production of the chemokine macrophage inflammatory protein-1α (MIP-1α), and since LMP2A is a BCR mimic, we hypothesized that LMP2A increases MIP-1α levels. A comparison of multiple LMP2A-negative and -positive cell lines demonstrates that LMP2A increases MIP-1α. Additionally, LMP2A-mutant cell lines and pharmacologic inhibitors indicate that LMP2A activates a Syk/PI3K/NF-κB pathway to enhance MIP-1α. Finally, based on the finding that an NF-κB inhibitor decreased MIP-1α RNA/protein in LMP2A-positive cells, we are the first to demonstrate that LMP2A increases the nuclear localization of the NF-κB p65 subunit using DNA-binding assays and confocal microscopy in human B cells. These findings not only have implications for the treatment of HL, but also other LMP2A-expressing B-cell tumors that overexpress NF-κB.

An anergic immune signature in the tumor microenvironment of classical Hodgkin lymphoma is associated with inferior outcome

OBJECTIVE

The classical Hodgkin lymphoma (cHL) tumor microenvironment shows an ongoing inflammatory response consisting of varying degrees of infiltrating eosinophils, mast cells, macrophages, regulatory T lymphocytes (Tregs), and activated lymphocytes surrounding the malignant cells. Herein, different immune signatures are characterized and correlated with treatment outcome.

METHODS

Tumor-infiltrating leukocytes were phenotyped in biopsies from 459 patients with cHL. Time to progression (TTP) (primary progression, relapse, or death from cHL) and overall survival were analyzed using Cox proportional hazards regression.

RESULTS

The leukocyte infiltration in the microenvironment was highly diverse between patients and was categorized in 4 immune signatures (active, anergic, innate, or mixed). A high proportion of Tregs (anergic) resulted in shorter TTP (median 12.9-year follow-up) in age-adjusted analyses (hazard ratio = 1.82; 95% confidence interval 1.05-3-15). Epstein-Barr virus (EBV)-positive cases had higher proportions of macrophages and activated lymphocytes than EBV negative, but neither of those leukocytes predicted prognosis.

CONCLUSIONS

Abundant Tregs (anergic signature) indicate a shorter TTP, particularly in younger patients. This is probably due to a reduced ability of the immune system to attack the tumor cells. Our data warrant further investigation if these suggested immune signatures could predict outcome of immunotherapy such as immune checkpoint inhibitors.

The Epstein-Barr virus and the pathogenesis of lymphoma

Since the discovery in 1964 of the Epstein-Barr virus (EBV) in African Burkitt lymphoma, this virus has been associated with a remarkably diverse range of cancer types. Because EBV persists in the B cells of the asymptomatic host, it can easily be envisaged how it contributes to the development of B-cell lymphomas. However, EBV is also found in other cancers, including T-cell/natural killer cell lymphomas and several epithelial malignancies. Explaining the aetiological role of EBV is challenging, partly because the virus probably contributes differently to each tumour and partly because the available disease models cannot adequately recapitulate the subtle variations in the virus-host balance that exist between the different EBV-associated cancers. A further challenge is to identify the co-factors involved; because most persistently infected individuals will never develop an EBV-associated cancer, the virus cannot be working alone. This article will review what is known about the contribution of EBV to lymphoma development.

Epstein-Barr virus and the origin of Hodgkin lymphoma

Although Epstein-Barr virus (EBV) is present in the malignant Hodgkin/Reed-Sternberg (HRS) cells of a proportion of cases of classical Hodgkin lymphoma (cHL), how the virus contributes to the pathogenesis of this disease remains poorly defined. It is clear from the studies of other EBV-associated cancers that the virus is usually not sufficient for tumor development and that other oncogenic co-factors are required. This article reviews what is known about the contribution of EBV to the pathogenesis of cHL and focuses on emerging evidence implicating chronic inflammation as a potential oncogenic co-factor in this malignancy.

Eosinophils regulate peripheral B cell numbers in both mice and humans

The view of eosinophils (Eos) as solely effector cells involved in host parasite defense and in the pathophysiology of allergic diseases has been challenged in recent years. In fact, there is a growing realization that these cells interact with other components of innate and adaptive immunity. For example, mouse Eos were recently demonstrated to promote plasma cell retention in the bone marrow. However, it remains unknown whether Eos influence the biology of normal B lymphocytes. In this study, we specifically assessed the effect of Eos on B cell survival, proliferation, and Ig secretion. Our data first revealed that the genetic deletion of Eos from NJ1638 IL-5 transgenic hypereosinophilic mice (previously shown to display profound B cell expansion) resulted in the near abolishment of the B cell lymphocytosis. In vitro studies using human tissues demonstrated Eos' proximity to B cell follicles and their ability to promote B cell survival, proliferation, and Ig secretion via a contact-independent mechanism. Additionally, this ability of Eos to enhance B cell responsiveness was observed in both T-independent and T-dependent B cell activation and appears to be independent of the activation state of Eos. Finally, a retrospective clinical study of hypereosinophilic patients revealed a direct correlation between peripheral blood eosinophil levels and B cell numbers. Taken together, our study identifies a novel role for Eos in the regulation of humoral immunity via their impact on B cell homeostasis and proliferation upon activation.

Serum levels of interleukins 6, 10, and 13 before and after treatment of classic Hodgkin lymphoma

CONTEXT

Interleukins (ILs) 6, 10, and 13 seem to be important in the pathogenesis of Hodgkin lymphoma (HL), but there is insufficient data on the serum levels of these cytokines in patients with HL.

OBJECTIVES

To evaluate serum levels of IL-6, IL-10, and IL-13 before and after HL treatment and to determine their potential association with clinical and laboratory parameters.

DESIGN

Serum IL-6, IL-10, and IL-13 levels were quantified in the serum of 27 patients with HL by enzyme-linked immunosorbent assay. Results were evaluated against clinical and laboratory parameters, response to treatment, and presence of infection by the Epstein-Barr virus. As a control group, serum samples from 26 healthy blood donors were evaluated the same way.

RESULTS

Pretreatment serum levels of IL-6 and IL-10 were significantly higher in patients with HL (P < .001), and a significant decrease was observed after treatment (P < .001). Serum IL-13 was undetectable in both patient and control groups. Serum IL-6 was higher in patients with abdominal involvement (P  =  .02), hepatomegaly (P  =  .03), B symptoms (P  =  .02), and anemia (P  =  .02). Serum IL-10 levels were higher in patients with hypoalbuminemia (P  =  .04). No association with EBV status was observed. Lymphocytopenia and B symptoms were accurate predictors of IL-6 serum levels before treatment, and higher pretreatment levels of IL-6 were observed in patients with treatment failure (P  =  .03).

CONCLUSIONS

Serum levels of IL-6 and IL-10 were frequently elevated in patients with HL and decreased substantially after conventional chemotherapy. The association of elevated IL-6 and IL-10 levels in serum with some clinical and laboratory features suggests those ILs may be useful biomarkers for monitoring the HL disease and its response to chemotherapy.

Refined prognostic role of CD68-positive tumor macrophages in the context of the cellular micromilieu of classical Hodgkin lymphoma

OBJECTIVE

Classical Hodgkin lymphoma (HL) consists of neoplastic Hodgkin and Reed-Sternberg cells (HRSC) and a nonneoplastic micromilieu that greatly outnumbers the HRSC. Studies on HRSC-related prognostic biomarkers have been unsuccessful, but the microenvironmental composition is of prognostic importance. Recently, the number of CD68-positive macrophages was correlated with adverse survival in HL, and there was a call to validate these results.

METHODS

We utilized immunohistochemistry to analyze the prognostic importance of the CD68-positive macrophage number compared to other cellular environmental components in an unselected series of 105 HLs in tissue microarrays.

RESULTS

Applying a cutoff score of >0.82% tumor macrophages, cases with increased numbers showed worse overall survival (mean 185 months, median 192) compared to cases with lower numbers (mean 285 months, median not reached). Eleven of 62 patients with ≤0.82% tumor macrophages died, compared to 19 of 43 with >0.82% (p < 0.001). The number of macrophages correlated with a low FOXP3-/high granzyme B-/high PD-1-positive micromilieu and patient age, but did not have independent prognostic significance. A combination background score taking into consideration all negative prognostic microenvironmental components (CD68-, PD-1- and granzyme B-positive cells) was of independent prognostic significance (p = 0.002).

CONCLUSION

Increased numbers of CD68-positive tumor macrophages indicate an adverse overall outcome in HL.

Targeting the microenvironment

The microenvironment in which cancer arises plays a critical role in tumorigenesis. Although previously regarded as an innocent bystander, evidence has accumulated over the past 10 years that the microenvironment contributes to tumor growth and progression by providing nutrients and survival signals, and protecting the tumor from normal immune responses and anticancer drugs. Exactly how normal stromal cells, whose function should be to suppress malignant growth, become co-opted into facilitating tumor development is only just beginning to be understood, but a complex story is emerging wherein tumor and stromal cells appear to co-evolve. A better understanding of tumor-stromal interactions and the molecular alterations that result in stromal dysfunction may help to identify patients who will benefit from either more aggressive or risk-adapted therapy regimens, and/or novel compounds that disrupt the tumor microenvironment and re-establishing normal control mechanisms.

Eosinophilia and multifocal vertebral involvement with Hodgkin lymphoma

Patients with Hodgkin lymphoma (HL) usually present with lymphadenopathies. Osseous involvement at presentation is extremely rare. Occurrence of both eosinophilia and osseous involvement has not been reported frequently. We present an adolescent female complaining of lower back pain for 6 months, in whom, multifocal vertebral involvement and peripheral blood eosinophilia preceded the final diagnosis of HL.

Familial Hodgkin's lymphoma from the perspective of HLA

Although the incidence of Hodgkin lymphoma (HL)--a lymphoid tissue malignity--increases in the presence of several viruses, particularly EBV, as well as with autoimmune diseases and following transplantation, although to date, the exact etiopathogenesis is not known. The higher frequency of HL among family members suggests involvement of genetic factors in its etiology. Studies aiming to elucidate the etiopathogenesis of patients with familial HL (FHL) have reported that human leukocyte antigen (HLA) haplotypes might be involved. In this case presentation, the associations between HLs diagnosed in a father of consanguineous marriage and his two children and HLAs in other family members were investigated and the findings are discussed in view of the published literature; no direct association was found between HLA alleles and the development of the disease in the present case with familial HL.

Increased mast cell expression of PAR-2 in skin inflammatory diseases and release of IL-8 upon PAR-2 activation

Mast cells are increasingly present in the lesional skin of chronic skin inflammatory diseases including psoriasis and basal cell carcinoma (BCC). It has previously been shown that proteinase-activated receptor (PAR)-2 is expressed by mast cells, and tryptase is a potent activator of this receptor. In this study, skin biopsies from both healthy-looking and lesional skin of patients with psoriasis and superficial spreading BCC were collected and the expression of PAR-2 immunoreactivity in tryptase-positive mast cells was analysed. PAR-2 expression was confirmed in vitro in different mast cell populations. Cord-blood derived mast cells (CBMC) were stimulated with a PAR-2 activating peptide, 2-furoyl-LIGRLO-NH(2). Consequently, IL-8 and histamine production was analysed in the supernatants. We observed a significant increase in the percentage of mast cells expressing PAR-2 in the lesional skin of psoriasis and BCC patients compared with the healthy-looking skin. HMC-1.2, LAD-2 and CBMC mast cells all expressed PAR-2 both intracellularly and on the cell surface. CBMC activation with the PAR-2 activating peptide resulted in an increased secretion of IL-8, but no histamine release was observed. Furthermore, both PAR-2 and IL-8 were co-localized to the same tryptase-positive mast cells in the lesional BCC skin. These results show that mast cells express increased levels of PAR-2 in chronic skin inflammation. Also, mast cells can be activated by a PAR-2 agonist to secrete IL-8, a chemokine which can contribute to the progress of inflammation.

Pathogenesis of classical and lymphocyte-predominant Hodgkin lymphoma

Hodgkin and Reed-Sternberg (HRS) cells in classical Hodgkin lymphoma (HL) and lymphocytic and histiocytic (L&H) cells in nodular lymphocyte-predominant HL (NLPHL) are derived from germinal-center B cells. HRS cells have, however, largely lost their B cell phenotype and aberrantly express markers and transcriptional regulators of other hematolymphoid cell types. Deregulation of multiple signaling pathways and downstream transcription factors, including receptor tyrosine kinases, nuclear factor-kappa B (NF-kappaB), and Janus kinase/signal transducer and activator of transcription (JAK/STAT), is a further hallmark of HRS cells. These cells harbor genetic lesions that contribute to or cause increases in the activity of transcription factors of the NF-kappaB and STAT families. HRS cells are found within a mixed reactive cellular infiltrate and interact with these nonmalignant cells in a complex fashion that appears to be essential for HRS cell survival and proliferation. Less is known about the pathogenesis of L&H cells in NLPHL, but increases in the activity of receptor tyrosine kinases, NF-kappaB, and JAK/STAT have also been detected.

Beyond the lymphocyte predominant cell: CD4+CD8+ T-cells in nodular lymphocyte predominant Hodgkin lymphoma

Hodgkin lymphomas are characterised by the presence of rare malignant cells in a background of non-neoplastic inflammatory cells. Flow cytometric analysis of involved tissues is generally not thought to be useful in establishing the diagnosis, because of the small number of neoplastic cells present. However, two recent studies describing a CD4+CD8+ (double-positive) T-cell population in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) suggest that flow cytometry could play a role in the diagnosis of this Hodgkin lymphoma subtype. In addition, awareness of this unusual T-cell population is important in avoiding a misdiagnosis of a T-cell neoplasm. Although the function of CD4+CD8+ T-cells in NLPHL is not known, studies of phenotypically similar cells in other settings point to a reactive or regulatory role. CD4+CD8+ T-cells have also been identified in the benign entity progressive transformation of germinal centres (PTGC), suggesting a possible relationship between NLPHL and PTGC.