Phagocytosis by dendritic cells rather than MHC IIhigh macrophages is associated with skin tumour regression

Tumour-infiltrating Langerhans cells in non-melanoma skin cancer, a clinical and immunohistochemical study

Non-melanoma skin cancer, including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) represents 78.5% of all skin malignant tumours in Egypt. Dendritic cells can be found in almost all human tumours, they play an important role in antitumour immunity. The aim of the present study was to evaluate the percentage of Langerhans cells using CD1a in non-melanoma skin cancer, including BCC and SCC and to correlate this percentage with their clinicopathological features. The current study was performed on surgically excised specimens of 41 patients presented with non-melanoma skin cancer (26 BCC and 15 SCC) and 16 healthy volunteer control subjects. The mean and median percentage of Langerhans cells were higher in normal epidermis of control compared to malignant tumour tissue (p < 0.0001) and adjacent epidermis overlying malignant tumour tissue (p = 0.007). Langerhans cells were significantly seen in BCC cases more than SCC (p = 0.035) and they were seen in facial lesions more than those arising from other sites (p = 0.007). The reduction of Langerhans cells is a way for non-melanoma skin cancer to develop and progress. Marked reduction of Langerhans cells in SCC compared to BCC could refer to their role as a barrier against metastasis.

Silica Particles Mediate Phenotypic and Functional Alteration of Dendritic Cells and Induce Th2 Cell Polarization

During silicosis, immune cells, including macrophages, T cells, B cells, and NK cells, participate in fibrosis development through alteration of the immune status. Dendritic cells (DCs) are professional antigen-presenting cells (APCs) with a key role in initiating immune responses and sustaining immune tolerance to maintain homeostasis. The relative contribution of DCs to silicosis progression is not well-documented. In the current study, we investigated the phenotypic and functional alterations of peripheral blood mononuclear cell (PBMC)-derived DCs of Sprague-Dawley (SD) rat during immune responses to silica exposure. We established models for direct and indirect exposure of DCs to silica by either treating DCs with silica or coculturing them with alveolar macrophages (AMs) treated with silica, respectively. The functional activity of DCs was analyzed by measuring their expression of costimulatory molecules, fluorescent microparticle uptake, cytokine production, and ability to mediate T cell polarization in vitro. In vivo, we demonstrated that silica could induce DC migration in response to silica exposure. Our results show that cytokine production by DCs was increased in response to direct silica direct exposure, while indirect silica exposure led to reduced cytokine levels. Moreover, the phagocytic capacity of DCs increased in cocultures after silica exposure. Gene and protein expression analyses showed that silica exposure altered the expression levels of Toll-like receptor pathway proteins and inflammatory factors. DC surface expression of the costimulatory molecules, CD80, CD86, and major histocompatibility complex, was inhibited by exposure to silica, which mediated a Th2-polarizing response in vitro. In rats, silica exposure induced migration of DCs from the peripheral blood into the alveoli. These results demonstrate that direct and indirect exposure to silica particles alter the phenotype and function of DCs, thereby regulating immune responses. Such changes may contribute to the development of silicosis by altering DC phenotype, function, and migration and by influencing the balance between Th1 and Th2 cells.

Dermal mast cells affect the development of sunlight-induced skin tumours

Ultraviolet (UV) radiation contained in sunlight is considered a major risk in the induction of skin cancer. While mast cells are best known for their role in allergic responses, they have also been shown to play a crucial role in suppressing the anti-tumour immune response following UV exposure. Evidence is now emerging that UV may also trigger mast cell release of cutaneous tissue remodelling and pro-angiogenic factors. In this review, we will focus on the cellular and molecular mechanisms by which UV recruits and then activates mast cells to initiate and promote skin cancer development.

The immune-modulating cytokine and endogenous Alarmin interleukin-33 is upregulated in skin exposed to inflammatory UVB radiation

The cellular and molecular mechanisms by which UV radiation modulates inflammation and immunity while simultaneously maintaining skin homeostasis is complex and not completely understood. Similar to the effects of UV, IL-33 has potent immune-modulating properties that are mediated by the downstream induction of cytokines and chemokines. We have discovered that exposure of mice in vivo or human skin samples ex vivo to inflammatory doses of UVB induced IL-33 expression within the epidermal and dermal skin layers. Using a combination of murine cell lines and primary human cells, we demonstrate that both UV and the oxidized lipid platelet activating factor induce IL-33 expression in keratinocytes and dermal fibroblasts. Highlighting the significance of these results, we found that administering IL-33 to mice in vivo suppressed the induction of Th1-mediated contact hypersensitivity responses. This may have consequences for skin cancer growth because UV-induced squamous cell carcinomas that evade immunological destruction were found to express significantly higher levels of IL-33. Finally, we demonstrate that dermal mast cells and skin-infiltrating neutrophils closely associate with UV-induced IL-33-expressing fibroblasts. Our results therefore identify and support a role for IL-33 as an important early danger signal produced in response to inflammation-inducing UV radiation.

New roles for mononuclear phagocytes in cancer biology

The primary focus in the pathogenesis and treatment of human malignancies has been the tumor cell. However, the biologic properties of a malignancy are not all intrinsically determined. Interactions between heterogeneous cell populations influence the growth and survival of both normal and malignant cells. Studies defining the origin of endothelial cells involved in tumor angiogenesis first demonstrated the contributions of normal cellular environment. Recently, the mononuclear phagocyte lineage has been found to have biologically and clinically significant tumor enhancing and tumor suppressive effects. This article reviews the multiple roles of mononuclear phagocytes in cancer biology. A companion manuscript (J Pediatr Hematol Oncol. 2008, in press) describes the targeting of these cells for therapeutic benefit. Incorporating these strategies into future childhood cancer protocols could be an innovative approach for improving patient outcome.

TGFbeta is responsible for skin tumour infiltration by macrophages enabling the tumours to escape immune destruction

Infiltration of skin tumours by macrophages is an important step in tumour progression, although the mechanisms of macrophage recruitment to the tumour mass and the subsequent effects on tumour growth are poorly understood. Transfecting a murine regressing skin tumour with the gene for transforming growth factor (TGF)beta enabled the tumours to grow progressively in vivo thus allowing us to study the role of this cytokine in tumour growth. Flow cytometry was used to show that TGFbeta-mediated tumour progression was accompanied by an increase in tumour-associated macrophages (TAM) and a decrease in tumour-infiltrating dendritic cells (DCs). TAM in TGFbeta-secreting tumours expressed lower levels of major histocompatibility complex II and CD86 compared to DC in control tumours and had a high phagocytic capacity as measured by uptake of latex beads in vivo. Indeed, TGFbeta was directly responsible not only for the enhanced macrophage phagocytosis but also altering the ratio of antigen-presenting cells to favour macrophages over DC. Our results demonstrate that TGFbeta recruitment and retention of macrophages at the tumour site enable effective tumour evasion of the host immune system and reinforces the need to target TGFbeta in human cancer immunotherapy trials.

Cutaneous Metastasis of Renal Cell Carcinoma With Zellballen-Like Inflammatory Reaction Pattern on Immunohistochemical Studies

Skin tumors show variable infiltration by subtypes of inflammatory cells. The composition of these cellular infiltrates, particularly tumor-associated macrophages and dendritic cell numbers, may be responsible for skin tumor progression or regression. In addition, these cells may give rise to diagnostic dilemmas on immunohistochemical studies. The authors report on the local inflammatory reaction to a metastatic renal cell carcinoma to the skin. Histologic examination and immunohistochemical studies demonstrated zellballen-like changes with S-100-positive spindled cells identified around and within tumor cell nests. The role of tumorassociated macrophages and dendritic cells in the skin is discussed.

Transforming growth factor-beta1 immobilises dendritic cells within skin tumours and facilitates tumour escape from the immune system

Human skin tumours often regress spontaneously due to immune rejection. Murine skin tumours model this behaviour; some regress and others progress in syngeneic immunocompetent hosts. Previous studies have shown that progressor but not regressor skin tumours inhibit dendritic cell (DC) migration from the tumour to draining lymph nodes, and transforming growth factor-beta1 (TGF-beta1) has been identified as a responsible factor. To determine whether increased production of TGF-beta1 in the absence of other differences inhibits DC migration from the tumour and enables it to evade immune destruction, a murine regressor squamous cell carcinoma clone was transfected with the gene for TGF-beta1. This enhanced growth in vitro and in vivo, causing it to become a progressor. TGF-beta1 transfection reduced the number of infiltrating DCs by about 25%. Quantitation of CD11c+ E-cadherin+ (epidermally derived) DCs in lymph nodes determined that TGF-beta1 reduced the number of DCs that migrated from the tumour to undetectable levels. This was supported by showing that TGF-beta1 reduced DC migration from cultured tumour explants by greater than tenfold. TGF-beta1 transfection also reduced the number of infiltrating CD4 and CD8 T cells. Thus, TGF-beta1 production by skin tumours is sufficient to immobilise DCs within the tumour, preventing their migration to lymph nodes. This reduces the number of T cells that infiltrate the tumour, preventing regression. Thus, TGF-beta1 is a key regulator of whether skin tumours regress or progress.

B cells activated in lymph nodes in response to ultraviolet irradiation or by interleukin-10 inhibit dendritic cell induction of immunity

Ultraviolet (UV) radiation suppresses systemic immunity. We explored these cellular mechanisms by exposing mice to systemically immunosuppressive doses of UV radiation and then analyzing cell phenotype and function in the lymphoid organs. Although UV radiation increased total cell number in the draining lymph nodes (DLN), it did not alter the activation state of dendritic cells (DC). Rather, UV radiation selectively activated lymph node B cells, with these cells being larger and expressing higher levels of both anti-major histocompatibility complex II and B220 but not co-stimulatory molecules. This phenotype resembled that of a B cell geared toward immune tolerance. To test whether UV radiation-activated B cells were responsible for immunosuppression, DC and B cells were conjugated to antigen ex vivo and transferred into naive hosts. Although DC by themselves activated T cells, when the B cells from UV radiation-irradiated mice were co-injected with DC, they suppressed DC activation of immunity. Interleukin (IL)-10-activated B cells also suppressed DC induction of immunity, suggesting that IL-10 may be involved in this suppressive effect of UV radiation. These results demonstrate a new mechanism of UV radiation immunosuppression whereby UV radiation activates B cells in the skin-DLN that can suppress DC activation of T cell-mediated immunity.

Prognostic factors in oral cavity and oropharyngeal squamous cell carcinoma

BACKGROUND

The survival of patients with head and neck squamous cell carcinoma (HNSCC) remains unaffected despite recent therapeutic advances. To reverse this trend, reliable and clinically applicable markers of tumor aggressiveness must be identified. One such marker may be the tumor-associated macrophage content. The authors hypothesized that tumor-associated macrophages contribute to HNSCC aggressiveness, and the objective of the current study was to prove this hypothesis using mRNA expression analysis and a large cohort of clinical specimens.

METHODS

Oligonucleotide microarray analysis was performed on a prospective cohort of 20 patients with previously untreated oral cavity or oropharynx squamous cell carcinoma (OC/OP SCCA) and on normal oropharyngeal mucosa from 4 patients. After determining whether macrophage chemoattractants were produced by tumors, conditioned media from three HNSCC cell lines were used to quantify macrophage migration in an in vitro assay. A high-density tissue microarray of 102 patients with previously untreated OC/OP SCCA was stained immunohistochemically for CD68 to identify tissue macrophages, and the results were correlated with clinicopathologic data and survival.

RESULTS

Monocyte chemoattractant protein 1 was up-regulated significantly in tumors compared with normal mucosa (P=0.0025; fold change=1.89). All University of Michigan SCC tumor cell line conditioned media caused a significant increase in macrophage migration (P <0.05). Tissue microarray data revealed that macrophage content of the primary tumor was associated strongly with lymph node metastasis (P <0.0001), extracapsular lymph node spread (P=0.0001), and advanced clinical disease stage (P=0.0002). When it was evaluated along with other clinicopathologic data, the macrophage content was found to be an independent predictor of lymph node metastasis (P <0.0001).

CONCLUSIONS

Primary tumor macrophage content is a strong predictor of tumor aggressiveness in HNSCC.