Bcl-2 expression in Langerhans' cell histiocytosis

Neutralizing Anti-IL-17A Antibody Demonstrates Preclinical Activity Enhanced by Vinblastine in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterised by the accumulation into granulomas of apoptosis-resistant pathological dendritic cells (LCH-DCs). LCH outcome ranges from self-resolving to fatal. Having previously shown that, (i) monocyte-derived DCs (Mo-DCs) from LCH patients differentiate into abnormal and pro-inflammatory IL-17A-producing DCs, and (ii) recombinant IL-17A induces survival and chemoresistance of healthy Mo-DCs, we investigated the link between IL-17A and resistance to apoptosis of LCH-DCs. In LCH granulomas, we uncovered the strong expression of BCL2A1 (alias BFL1), an anti-apoptotic BCL2 family member. In vitro, intracellular IL-17A expression was correlated with BCL2A1 expression and survival of Mo-DCs from LCH patients. Based on the chemotherapeutic drugs routinely used as first or second line LCH therapy, we treated these cells with vinblastine, or cytarabine and cladribine. Our preclinical results indicate that high doses of these drugs decreased the expression of Mcl-1, the main anti-apoptotic BCL2 family member for myeloid cells, and killed Mo-DCs from LCH patients ex vivo, without affecting BCL2A1 expression. Conversely, neutralizing anti-IL-17A antibodies decreased BCL2A1 expression, the downregulation of which lowered the survival rate of Mo-DCs from LCH patients. Interestingly, the in vitro combination of low-dose vinblastine with neutralizing anti-IL-17A antibodies killed Mo-DCs from LCH patients. In conclusion, we show that BCL2A1 expression induced by IL-17A links the inflammatory environment to the unusual pro-survival gene activation in LCH-DCs. Finally, these preclinical data support that targeting both Mcl-1 and BCL2A1 with low-dose vinblastine and anti-IL-17A biotherapy may represent a synergistic combination for managing recurrent or severe forms of LCH.

Immunohistochemical characterization of immune cell infiltration in paediatric and adult Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia commonly affecting children with frequent somatic mutations in MAPK pathway genes including BRAF^V600E and MAP2K1. Some studies suggest that LCH cells can recruit and modulate inflammatory cells, which could provide reciprocal survival signals. To characterize the immune profile of infiltrating inflammatory cells, and to clarify their participation in LCH pathogenesis, a detailed immunohistochemical analysis was performed. Fifteen (10 children, 5 adults) LCH cases were assessed through macrophage (CD68 and CD163), mature dendritic cell (mDC; CD83 and CD208), regulatory T cell (Treg; CD4, CD25 and FOXP3) and cytotoxic lymphocyte (CL; CD56, CD57, perforin and granzyme B) immunomarkers. Moreover, lymphocytic and LCH markers were also analysed. All cases were S100, CD1a, CD207 and CD4-positive. Bcl-2 and cyclin D1 expression was observed in 13 of 15 cases. In the immune microenvironment, M2-polarized macrophages and Tregs were the predominant cell populations, followed by significantly (P < .005) smaller levels of mDCs and CLs. Additionally, the number of CD3 + cells was significantly higher than that of CD20 + cells. In the CD3 + cell population, there were a significantly higher number of CD4 + cells than CD8 + cells. While there were no differences when comparing the paediatric and adult populations, FOXP3 + cells were significantly higher in patients with multisystem involvement and treated with chemotherapy, than single-site cases and those without chemotherapy. Our results suggest that M2-polarized macrophages and Treg infiltration can promote LCH development and survival, probably through pro-tumoral, immunosuppressive and/or cytokine-mediated mechanisms. This work highlights the need for further exploration of immune-targeted therapy for LCH.

Targeting BCL2 family in human myeloid dendritic cells: a challenge to cure diseases with chronic inflammations associated with bone loss

Rheumatoid arthritis (RA) and Langerhans cell histiocytosis (LCH) are common and rare diseases, respectively. They associate myeloid cell recruitment and survival in inflammatory conditions with tissue destruction and bone resorption. Manipulating dendritic cell (DC), and, especially, regulating their half-life and fusion, is a challenge. Indeed, these myeloid cells display pathogenic roles in both diseases and may be an important source of precursors for differentiation of osteoclasts, the bone-resorbing multinucleated giant cells. We have recently documented that the proinflammatory cytokine IL-17A regulates long-term survival of DC by inducing BCL2A1 expression, in addition to the constitutive MCL1 expression. We summarize bibliography of the BCL2 family members and their therapeutic targeting, with a special emphasis on MCL1 and BCL2A1, discussing their potential impact on RA and LCH. Our recent knowledge in the survival pathway, which is activated to perform DC fusion in the presence of IL-17A, suggests that targeting MCL1 and BCL2A1 in infiltrating DC may affect the clinical outcomes in RA and LCH. The development of new therapies, interfering with MCL1 and BCL2A1 expression, to target long-term surviving inflammatory DC should be translated into preclinical studies with the aim to increase the well-being of patients with RA and LCH.

Rare lung diseases III: pulmonary Langerhans' cell histiocytosis

Pulmonary Langerhans' cell histiocytosis (PLCH) is an unusual cystic lung disease that is also characterized by extrapulmonary manifestations. The current review discusses the presenting features and relevant diagnostic testing and treatment options for PLCH in the context of a clinical case. While the focus of the present article is adult PLCH and its pulmonary manifestations, it is important for clinicians to distinguish the adult and pediatric forms of the disease, as well as to be alert for possible extrapulmonary complications. A major theme of the current series of articles on rare lung diseases has been the translation of insights gained from fundamental research to the clinic. Accordingly, the understanding of dendritic cell biology in this disease has led to important advances in the care of patients with PLCH.

Role of p16 in the pathogenesis of Langerhans cell histiocytosis

Background

It has been hypothesized that genetic alteration at the cellular level may have a significant effect on cellular mechanisms controlling the proliferation and apoptosis of Langerhans cells (LCs).

Methods

We examined whether p16 protein expression can be used to predict the outcome of Langerhans cell histiocytosis (LCH). Archival paraffin blocks from children diagnosed with LCH and followed at the Asan Medical Center and Chungnam National University Hospital between March 1998 and February 2008 were studied.

Results

Slides were stained with p16 antibody and evaluated semi-quantitatively using the following scale: negative, no staining; ±, weakly positive; 1+, staining similar to lymphocytes surrounding the LCs; 2+, stronger staining than lymphocytes; 3+, much stronger staining than lymphocytes. Negative and ± groups were assigned to a lower expression group (LEG) and the 1+, 2+, and 3+ groups were assigned to a higher expression group (HEG). The median age of the 51 patients (24 girls, 27 boys) was 49 (range, 0.6-178) months, and LCH was diagnosed based on CD1a positivity. p16 protein was expressed to varying degrees in all but one specimen. There was a greater tendency toward multisystem disease, risk organ involvement, and relapse in the HEG than in the LEG.

Conclusion

The p16 protein may have a significant effect on cellular mechanisms controlling the proliferation and apoptosis of LCs, and thus may influence the clinical outcome and prognosis of LCH.

Origin, homeostasis and function of Langerhans cells and other langerin-expressing dendritic cells

Langerhans cells (LCs) are a specialized subset of dendritic cells (DCs) that populate the epidermal layer of the skin. Langerin is a lectin that serves as a valuable marker for LCs in mice and humans. In recent years, new mouse models have led to the identification of other langerin(+) DC subsets that are not present in the epidermis, including a subset of DCs that is found in most non-lymphoid tissues. In this Review we describe new developments in the understanding of the biology of LCs and other langerin(+) DCs and discuss the challenges that remain in identifying the role of different DC subsets in tissue immunity.

Association of cell cycle-related gene products and NF-kappaB with clinical parameters in Langerhans cell histiocytosis

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare disorder characterized by the accumulation of abnormal Langerhans cells in one or several organs where they cause local tissue damage. The pathophysiology is not well understood. The aim of this study was to examine expression of various gene products that play a role in cell cycle and cell death and to look for an association with the extent of the disease at the time of diagnosis and with "risk bone" involvement.

PROCEDURE

Histologic slides from cases with biopsy proven disease were stained immunohistochemically for Bcl-2, caspase-3, Ki-67, p53, and nuclear factor-kappaB (NF-kappaB) and the results were quantitated and compared with the clinical extent of the disease.

RESULTS

In patients with multisystem disease and "risk" bone involvement, a higher percentage of Langerhans cells stained with the anti-apoptotic gene product Bcl-2 (P = 0.0004; P = 0.001 respectively) and a lower percentage of these cells stained with the apoptosis marker caspase-3 compared to patients with single system disease (P = 0.0001; P = 0.01 respectively). Proliferation marker Ki-67 was expressed more frequently in multisystem disease compared to single system disease (P = 0.02) but an association with "risk" bone involvement was not found. Expression of p53 and NF-kappaB did not discriminate between clinical subgroups.

CONCLUSIONS

The findings suggest that cell proliferation and suppression of apoptosis may be mechanisms of cell survival in the more aggressive forms of LCH (multisystem, risk bone involvement).

Bcl-2-positive epidermal dendritic cells in inverted follicular keratoses but not squamous cell carcinomas or seborrheic keratoses

AIM

In our previous research, bcl-2-positive dendritic cells were seen in increased numbers in suprabasal areas of inverted follicular keratoses (IFKs) compared to seborrheic keratoses (SKs). The purpose of this study was twofold; firstly, to support that these dendritic cells are Langerhans cells and secondly, to contrast the epidermal dendritic cells in IFKs, squamous cell carcinomas (SCCs), and SKs.

METHODS

Ten IFKs and five SKs previously showing bcl-2-positive dendritic cells within the epidermis were stained with CD1a. Fifteen other IFKs were stained with CD1a alone. Ten SCCs were stained with bcl-2 and CD1a.

RESULTS

In the 10 IFKs stained with both bcl-2 and CD1a, the density of CD1a-positive cells correlated well with the density of bcl-2-positive dendritic cells; in the five SKs, the density of CD1a-positive cells was similar to that seen in IFKs but was higher compared to the density of bcl-2-positive dendritic cells in SKs (p < 0.05). The IFKs had a significantly higher number of CD1a-positive cells compared to SCCs (p < 0.01). SCCs showed bcl-2-positive cells only within the basal layer of the normal epidermis flanking the carcinomas.

CONCLUSIONS

These results suggest that there is different bcl-2 regulation of CD1a-positive cells in IFKs, SKs, and SCCs.

Biology of Langerhans cells and Langerhans cell histiocytosis

Langerhans cells (LC) are epidermal dendritic cells (DC). They play an important role in the initiation of immune responses through antigen uptake, processing, and presentation to T cells. Langerhans cell histiocytosis (LCH) is a rare disease in which accumulation of cells with LC characteristics (LCH cells) occur. LCH lesions are further characterized by the presence of other cell types, such as T cells, multinucleated giant cells (MGC), macrophages (MPhi), eosinophils, stromal cells, and natural killer cells (NK cells). Much has been learned about the pathophysiology of LCH by studying properties of these different cells and their interaction with each other through cytokines/chemokines. In this review we discuss the properties and interactions of the different cells involved in LCH pathophysiology with the hope of better understanding this enigmatic disorder.

Immunohistochemical detection of the apoptosis-related proteins FADD, FLICE, and FLIP in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is characterized by an accumulation of dendritic Langerhans cells in granulomatous lesions in various organs. The etiology of LCH remains enigmatic. Fas/APO-1/CD95 belongs to the "death receptor" family of apoptosis regulators and has been implicated in the downregulation of immune responses. The authors examined the expression of three proteins that are engaged in the Fas signaling cascade-FADD/Fas-associated death domain-containing protein, FLICE/FADD-like interleukin-1beta-converting enzyme (both pro-apoptotic), and FLIP/FLICE-inhibitory protein (anti-apoptotic)-in lesions from LCH patients. Immunohistochemistry was performed on paraffin-embedded tissue specimens from 43 children with LCH. The infiltrates were scored according to the amount of positive pathologic Langerhans cells (pLCs). In all investigated specimens, the majority of the pLCs expressed FADD, active FLICE, and FLIP. The clinical outcome of the disease could not be correlated to the expression of the investigated proteins. This study shows a high expression of the apoptosis-related proteins FADD, active FLICE, and FLIP in pLCs. The authors previously showed that pLCs express Fas and Fas ligand. Taken together, these findings suggest that the Fas signaling pathway may be involved in the pathogenesis of LCH.

Tumor necrosis factor, interleukin 11, and leukemia inhibitory factor produced by Langerhans cells in Langerhans cell histiocytosis

OBJECTIVES

: The etiology and pathophysiology of Langerhans cell histiocytosis (LCH) remain elusive. The 3-year survival in pediatric multisystem LCH is still around 80%, and children with risk organ involvement (i.e., liver, spleen, hematopoietic system, or lungs) have a less favorable outcome. To further elucidate the pathogenesis of LCH in the search for a rationale cure, the authors investigated intracellular synthesis of tumor necrosis factor (TNF), interleukin (IL)-11, and leukemia inhibitory factor (LIF) from biopsied lesions.

METHODS

: Lesional cells were obtained by fine-needle aspiration biopsy from nine children with LCH. The study was accomplished by the use of an immunofluorescence staining method that allowed cytokine-producing cells to be differentiated from cytokine-binding cells.

RESULTS

: All patients had histiocytes expressing TNF. Seven patients had histiocytes expressing IL-11 and six patients had histiocytes expressing LIF. The two children with the highest proportion of histiocytes displaying TNF and the three with the highest proportion of histiocytes expressing IL-11 and LIF all had risk organ involvement. Two-color staining revealed that histiocytes expressing TNF, IL-11, and LIF co-expressed CD1a molecules.

CONCLUSIONS

: These observations suggest that LCH represents a cytokine-driven condition partially mediated by TNF, IL-11, and LIF. These three cytokines are all osteoclastogenic, suggesting a pathogenetic pathway for the osteolytic lesions in LCH. Furthermore, thrombocytosis in LCH may be explained by IL-11 and LIF activity.

Expression of apoptosis-regulatory proteins in lesions of pulmonary Langerhans cell histiocytosis

AIMS

Pulmonary Langerhans cell histiocytosis (PLCH) is characterized by the presence of lesions containing numerous activated Langerhans cells (LCs). An uncontrolled immune response sustained by activated LCs seems to be involved in the pathogenesis of the disease. The aim of this study was to establish whether disruption of LC apoptosis related to the expression of the Bcl-2 family proteins is implicated in the maintenance of PLCH lesions.

METHODS

Six patients with PLCH were evaluated by morphological and immunohistochemical techniques to explore the incidence of apoptosis in pathological LCs and to characterize the expression of Bcl-2-related proteins by these cells.

RESULTS

Very few LCs present in PLCH lesions exhibited nuclear apoptotic changes or expressed cleaved caspase-3, whereas they all strongly expressed the anti-apoptotic molecule Bcl-x(L). Interestingly, pulmonary LCs present in intervening lung tissue not involved by the pathological process and known to be immature dendritic cells did not express Bcl-2 family proteins.

CONCLUSIONS

These findings suggest that activated LCs present within PLCH lesions are poorly susceptible to apoptosis and, thus, are able to sustain the pathological process by causing continuous local stimulation of T cells. Functional studies are needed, however, to demonstrate that they are actually resistant to programmed cell death.

Expression of cell cycle-related gene products in Langerhans cell histiocytosis

BACKGROUND The pathogenesis of Langerhans cell histiocytosis (LCH), a disease characterized by an abnormal accumulation of the dendritic Langerhans cells, is still unknown. Based on the monoclonality of the CD1a+ cell and reports of familial clustering, it is hypothesized that a genetic alteration at a cellular level may be causative. This genetic change may have an effect on the cellular mechanisms controlling proliferation and apoptosis. MATERIALS AND METHODS LCH-lesions were studied for the expression of Ki-67, present in the nucleus of proliferating cells. Furthermore, the expression of cell cycle-related gene products TGF-beta receptor I and II, MDM2, p53, p21, p16, Rb, and Bcl2 were studied. The TGF-betaR genes play a role in tumor suppression, whereas Bcl2 inhibits apoptosis. The remaining genes are part of either the p53-p21 and/or p16-Rb pathways, which induce cell cycle arrest or apoptosis in response to DNA damage. RESULTS In 30 biopsies the diagnosis of LCH could be confirmed on the basis of CD1a positivity (27 bone and 3 skin). All cases showed scattered nuclear-positive staining for the proliferation marker Ki-67. In more than 90% (n >/=27) of these cases, expression of TGFbeta receptor I and II, MDM2, p53, p21, p16, Rb, and Bcl2 was detected in lesional LCH cells. The overexpression was in general heterogeneous, ranging from limited focal staining of scattered cells within the lesion to strong diffuse staining. CONCLUSIONS These findings suggest that the cellular mechanisms that sense and respond to DNA-damage, namely the p53-p21 pathway and the p16-Rb pathway, are activated. The expression of Ki-67 indicates that the cells in LCH are proliferating. The observed overexpression of Bcl2 may play a role in the activation of p53 and p16 and/or the arrest of apoptosis.

Langerhans cell histiocytosis immunohistochemical expression of fascin, a dendritic cell marker

Langerhans cell histiocytosis (LCH) is a clonal disorder believed to be derivedfrom cells of the dendritic system. Fascin, a 55-kd actin-bundling protein, represents a highly selective marker for dendritic cells of lymphoid tissues and peripheral blood and is involved in the formation of dendritic processes in maturing epidermal Langerhans cells. Since lesional cells of LCH may represent Langerhans cells arrested at an early stage of activation, immunohistochemical expression offascin in epidermal Langerhans cells and in the lesional cells of 34 cases of LCH was evaluated in paraffin sections using an immunoalkaline phosphatase technique. Though epidermal Langerhans cells were nonreactive for fascin, lesional cells in all LCH cases exhibited immunoreactivityforfascin, CD1a, and S-100 protein. Variation in staining intensity was observed in some cases, possibly reflecting differences in cell maturation or activation. Involved tissues included bone, soft tissue, lymph node, thyroid, orbit, and extradural cranial tissue. Immunoreactivity of lesional cells of LCH for fascin supports their derivation from cells of the dendritic system and represents another alteration in the phenotype of Langerhans cells that is associated with maturation, migration, culture, or clonal expansion.