Mast cells and dendritic cells in basal cell carcinoma stroma

The Complex Role of Mast Cells in Head and Neck Squamous Cell Carcinoma: A Systematic Review

Background and Objectives: Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous malignancy influenced by various genetic and environmental factors. Mast cells (MCs), typically associated with allergic responses, have recently emerged as key regulators of the HNSCC tumor microenvironment (TME). This systematic review explores the role of MCs in HNSCC pathogenesis and their potential as prognostic markers and therapeutic targets. Materials and Methods: A systematic search was conducted in the PubMed, Scopus and ClinicalTrials.gov databases until 31 December 2023, using "Mast cells" AND "Head and neck squamous cell carcinoma" as search terms. Studies in English which reported on MCs and HNSCC were included. Screening, data extraction and analysis followed PRISMA guidelines. No new experiments were conducted. Results: Out of 201 articles, 52 studies met the inclusion criteria, 43 of which were published between 2020 and 2023. A total of 28821 HNSCC and 9570 non-cancerous tissue samples had been examined. MC density and activation varied among normal tissues and HNSCC. Genetic alterations associated with MCs were identified, with specific gene expressions correlating with prognosis. Prognostic gene signatures associated with MC density were established. Conclusions: MCs have arisen as multifaceted TME modulators, impacting various aspects of HNSCC development and progression. Possible site-specific or HPV-related differences in MC density and activation should be further elucidated. Despite conflicting findings on their prognostic role, MCs represent promising targets for novel therapeutic strategies, necessitating further research and clinical validation for personalized HNSCC treatment.

Human Melanoma-Associated Mast Cells Display a Distinct Transcriptional Signature Characterized by an Upregulation of the Complement Component 3 That Correlates With Poor Prognosis

Cutaneous melanoma is one of the most aggressive human malignancies and shows increasing incidence. Mast cells (MCs), long-lived tissue-resident cells that are particularly abundant in human skin where they regulate both innate and adaptive immunity, are associated with melanoma stroma (MAMCs). Thus, MAMCs could impact melanoma development, progression, and metastasis by secreting proteases, pro-angiogenic factors, and both pro-inflammatory and immuno-inhibitory mediators. To interrogate the as-yet poorly characterized role of human MAMCs, we have purified MCs from melanoma skin biopsies and performed RNA-seq analysis. Here, we demonstrate that MAMCs display a unique transcriptome signature defined by the downregulation of the FcεRI signaling pathway, a distinct expression pattern of proteases and pro-angiogenic factors, and a profound upregulation of complement component C3. Furthermore, in melanoma tissue, we observe a significantly increased number of C3+ MCs in stage IV melanoma. Moreover, in patients, C3 expression significantly correlates with the MC-specific marker TPSAB1, and the high expression of both markers is linked with poorer melanoma survival. In vitro, we show that melanoma cell supernatants and tumor microenvironment (TME) mediators such as TGF-β, IL-33, and IL-1β induce some of the changes found in MAMCs and significantly modulate C3 expression and activity in MCs. Taken together, these data suggest that melanoma-secreted cytokines such as TGF-β and IL-1β contribute to the melanoma microenvironment by upregulating C3 expression in MAMCs, thus inducing an MC phenotype switch that negatively impacts melanoma prognosis.

Research on Correlation Between Psychological Factors, Mast Cells, and PAR-2 Signal Pathway in Irritable Bowel syndrome

PURPOSE

The study aimed to explore the level of psychological stress factors, mast cell (MC), and neuropeptide in the occurrence of irritable bowel syndrome (IBS) and the correlation among them, and to identify representative and effective indicators for the pathogenesis and clinical medication development of IBS.

SUBJECTS AND METHODS

Twenty-eight patients (20-64 years old) with diarrhea-predominant IBS (IBS-D) were included in the IBS-D group and 8 healthy subjects (35-63 years old) were enrolled in the control group. All subjects accepted the colonoscopic biopsies, self-rating depression scale (SDS) and self-rating anxiety scale (SAS) assessment. MC degranulation, neuropeptide S (NPS), neuropeptide Y (NPY), NPY receptor 2 (NPY2R) and Protease-activated receptor 2 (PAR-2) in colon tissues were performed by Strept Avidin-Biot complex (SABC) immunohistochemistry. Enzyme-linked immunosorbent assay (ELISA) detection was used to test the expression of NPS and NPY in peripheral blood plasma and colon tissues. Western blot was applied to examine the level of NPY2R and PAR-2.

RESULTS

The level of anxiety and depression of patients with IBS-D was more serious than that in the control. The expression of NPS, NPY and NPY2R was down-regulated in the IBS-D. The total MC and tryptase-positive MC increased significantly in the colon tissue of IBS-D and the expression level of PAR-2 was significantly up-regulated.

CONCLUSION

There has been a close connection among those indicators that the activated MC may up-regulate the function of PAR-2, resulting in the change of neuropeptide (NPS and NPY), successively leading to clinical symptoms and psychological negative changes in the IBS.

The role of mast cells in human skin cancers

Mast cells (MCs) are immune cells derived from myeloid lineage present in all classes of vertebrates and have emerged preceding much time the development of adaptive immunity. MCs are involved in inflammatory processes, allergic reactions, and host responses to parasites and bacteria infectious diseases. MCs are located at the host-environment interface, at many sites of initial antigen entry, including skin, lung and gastrointestinal tract, and have part of a protective mechanism. Skin has an important role in protecting the host from invasion both as physical barriers and by employing an intricate network of resident immune and non-immune cells include macrophages, T and B lymphocytes, MCs, neutrophils, eosinophils, and Langerhans cells. In this review we discussed the role of MCs in human skin cancers.

Silibinin inhibits ultraviolet B radiation-induced mast cells recruitment and bone morphogenetic protein 2 expression in the skin at early stages in Ptch(+/-) mouse model of basal cell carcinoma

Around 80% of nonmelanoma skin cancers (NMSCs) are basal cell carcinoma (BCC), still studies evaluating the efficacy of chemopreventive agents during early stage/s of BCC development are lacking. Accordingly, utilizing the well-established patched (Ptch)+/- mouse model of ultraviolet B (UVB) radiation-induced BCC formation, we excised skin samples from UVB exposed Ptch+/- and Ptch+/+ mice before tumor formation to study the promotion/progression of BCC and to determine the efficacy and target/s of silibinin, a well-known skin cancer chemopreventive agent. UVB exposure for 1 month increased the number of mast cells in Ptch+/- mice by ~48% (P < 0.05), which was completely inhibited by silibinin. Polymerase chain reaction profiler array analysis of skin samples showed strong molecular differences between Ptch+/+ and Ptch+/- mice which were either unexposed or UVB irradiated+/- silibinin treatment. Most notably, silibinin treatment significant decreased the expression of BMP-2, Bbc3, PUMA, and Ccnd1 in Ptch+/- mice irradiated with silibinin + UVB. Additional studies showed that silibinin targets UVB-induced expression of bone morphogenetic protein 2 (BMP-2) in Ptch+/- mouse skin. Last, our studies found that silibinin strongly attenuates UVB-induced BMP-2 expression and DNA damage in Ptch+/- mouse skin ex vivo only after single UVB exposure. Together, our results suggest a possible role of mast cell recruitment and BMP-2 activation in the early stages of BCC development; these are strongly inhibited by silibinin suggesting its possible chemopreventive efficacy against BCC formation in long-term UVB exposure regimen.

Keratinocyte Cytokine Networks Associated with Human Melanocytic Nevus Development

Melanocytes can group together in nevi, commonly thought to form because of intrinsic somatic mutations involving MAPK pathway activation. However, the role of the microenvironment, in particular keratinocytes, in nevogenesis is rarely studied. Melanocytes proliferate during the hair follicle growth phase and in some basal cell carcinomas, allowing us to construct keratinocyte gene expression clusters correlated with melanocyte activation. We asked whether such correlations are evident in the more subtle context of regulation of melanocyte behavior in normal skin. We considered genes which, when mutated in keratinocytes in mice, lead to nevogenesis. Across the human GTEx normal skin database, their expression was correlated with that of keratinocyte cytokines KITLG, HGF, FGF2, EDN1, and melanocyte markers. These cytokines have pleiotropic effects on melanocyte-specific and pigmentation genes and also influence mast cell gene expression. We show five classes of keratinocyte genes that, via germline genetic variation, influence melanocyte activity. These include genes involved in SHH signaling, structural keratins, ribosomal biogenesis, and stem cell governance. In agreement with the finding of KITLG linked to nevogenesis in human genome-wide association studies, we provide evidence that specific keratinocyte cytokines are components of networks that may drive or exacerbate nevus development.

Neuroendocrine factors: The missing link in non‑melanoma skin cancer (Review)

Non‑melanoma skin cancer (NMSC) is the most common form of cancer worldwide, comprising 95% of all cutaneous malignancies and approximately 40% of all cancers. In spite of intensive efforts aimed towards awareness campaigns and sun‑protective measures, epidemiological data indicate an increase in the incidence of NMSC. This category of skin cancers has many common environmental triggers. Arising primarily on sun‑exposed skin, it has been shown that ultraviolet radiation is, in the majority of cases, the main trigger involved in the pathogenesis of NMSC. Aside from the well‑known etiopathogenic factors, studies have indicated that several neuroactive factors are involved in the carcinogenesis of two of the most common types of NMSC, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with the exception of penile SCC, for which a paucity of specific data on their pathogenic role exists. The complex interaction between the peripheral nervous system and target cells in the skin appears to be mediated by locally released neuroendocrine factors, such as catecholamines, substance P, calcitonin gene‑related peptide and somatostatin, as well as neurohormones, such as proopiomelanocortin and its derived peptides, α‑melanocyte‑stimulating hormone and adrenocorticotropin. All these factors have been, at least at some point, a subject of debate regarding their precise role in the pathogenesis of NMSC. There is also a significant body of evidence indicating that psychological stress is a crucial impact factor influencing the course of skin cancers, including SCC and BCC. Numerous studies have suggested that neuroendocrine factor dysregulation, as observed in stress reactions, may be involved in tumorigenesis, accelerating the development and progression, and suppressing the regression of NMSC. Further studies are required in order to elucidate the exact mechanisms through which neuroactive molecules promote or inhibit cutaneous carcinogenesis, as this could lead to the development of more sophisticated and tailored treatment protocols, as well as open new perspectives in skin cancer research.

Controversial role of mast cells in skin cancers

Cancer development is a multistep process characterized by genetic and epigenetic alterations during tumor initiation and progression. The stromal microenvironment can promote tumor development. Mast cells, widely distributed throughout all tissues, are a stromal component of many solid and haematologic tumors. Mast cells can be found in human and mouse models of skin cancers such as melanoma, basal and squamous cell carcinomas, primary cutaneous lymphomas, haemangiomas and Merkel cell carcinoma. However, human and animal studies addressing potential functions of mast cells and their mediators in skin cancers have provided conflicting results. In several studies, mast cells play a pro-tumorigenic role, whereas in others, they play an anti-tumorigenic role. Other studies have failed to demonstrate a clear role for tumor-associated mast cells. Many unanswered questions need to be addressed before we understand whether tumor-associated mast cells are adversaries, allies or simply innocent bystanders in different types and subtypes of skin cancers.

Variable stromal periductular expression of CD34 and smooth muscle actin (SMA) in intraductal carcinoma of the breast

In breast carcinoma, the stromal loss of CD34 expression and acquisition of SMA myofibroblastic features may constitute a prerequisite for tumor invasiveness. However, this hypothesis remains controversial, with some authors describing the loss of CD34 fibrocytes in the absence of SMA myofibroblastic-like cells in the stroma of invasive carcinoma. Others have also described the disappearance of CD34 fibrocytes from in situ carcinoma. To clarify this issue, we compared the distribution of CD34 fibrocytes and SMA reactive myofibroblasts between stromal areas of tumor-free mammary tissue, ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC). In addition to 28 IDC, 300 normal duct–lobular units and 600 ducts with DCIS (158 low-grade, 266 intermediate, and 176 high-grade) were scored. The relationships between staining patterns and different histological features (grade of DCIS and presence or absence of necrosis) were compared. Loss of CD34 expression and acquisition of SMA expression were more frequent in high-grade in situ lesions than in intermediate and low-grade lesions (p<0.001). When necrosis was found in association with grade 2 or 3 DCIS, the decrease in CD34 expression was higher than in lesions without necrosis and that independently of the grade of DCIS (p<0.05). Necrosis did not appear to play a significant role in the expression of SMA (p = 0.35). In all cases, the stroma of invasive carcinomas showed a complete loss of CD34 fibrocytes. Future research on both CD34 fibrocytes and mechanisms stromal changes are essential in the future and may potentially lead to new treatment approaches.

Morphometric characteristics of basal cell carcinoma peritumoral stroma varies among basal cell carcinoma subtypes

BACKGROUND

The role that the peritumoral stroma plays in the growth of tumours is currently poorly understood. In this manuscript the morphometric characteristics of basal cell carcinoma subtypes and their associated peritumoral stromas are presented.

METHODS

Ninety eight digitized basal cell carcinoma histology slides were categorized as infiltrative, nodular, or superficial subtypes, and were analysed using a combination of manual and computer-assisted approaches. The morphometric characteristics of the tumour nests and their associated peritumoral stroma were quantified, and the presence of a marked immune reaction or elastosis was noted.

RESULTS

The tumour to stroma ratio was different among each tumour subtype. Elastosis was identified in a greater proportion of the infiltrative tumours.

CONCLUSIONS

Quantitative differences exist between the peritumoral stroma of basal cell carcinoma subtypes. Future work exploring the relation between these morphometric differences and biochemical variations in peritumoral stroma may further our understanding of the biology of carcinoma development.

TRIAL REGISTRATION

Not applicable.

Distribution of mast cells in benign odontogenic tumors

The aim of this study was to investigate the presence of mast cells in a series of odontogenic tumors. Forty-five cases of odontogenic tumors were investigated using immunohistochemistry for mast cell triptase, and differences between groups were statistically evaluated. Mast cells were present in 96% of odontogenic tumors. Mast cells present in solid ameloblastoma were observed in the tumor stroma surrounding more solid and follicular epithelial islands, with or without squamous metaplasia. The odontogenic mixoma showed few mast cells. In odontogenic tumors with a cystic structure, the mast cells were distributed throughout all areas of the lesions, mainly in keratocystic odontogenic tumor. In addition, the total density of mast cells between all odontogenic tumors showed no significant difference (p > 0.05). A greater mast cells distribution was found in keratocystic odontogenic tumor in relation to adenomatoid odontogenic tumor (p < 0.01), and when the unicystic ameloblastoma and keratocistic odontogenic tumor were compared to the odontogenic myxoma (p < 0.05). Syndrome keratocystic odontogenic tumor showed a higher mean of mast cells when compared with the other tumors of the sample. Mast cells values presented by syndrome keratocystic odontogenic tumor were significantly greater than those of the sporadic keratocystic odontogenic tumor that were not associated with the syndrome (p = 0.03). Mast cells are probably one of the major components of the stromal scaffold in odontogenic tumors. We found significant differences of mast cells between syndrome nonsyndrome keratocystic odontogenic tumors, although their distribution did not seem to have any influence on the biologic behavior of benign odontogenic tumors.

Mast cells: novel clinical perspectives from recent insights

Mast cells are still generally viewed as mediators of type I allergic or pseudoallergic reactions. Research over the past 10 years revealed that our view was too small and that mast cells are of key importance in innate immunity and also types II, III and IV adaptive immune reactions. Understanding their role in modulating and amplifying of inflammatory responses provides important insights into the pathogenesis of skin diseases such as psoriasis, atopic dermatitis, bullous pemphigoid or the control of infections. This helps us to understand the course of these diseases, their trigger mechanisms, and, the new role of agents, which can modulate the function of mast cells. These insights will help to develop new therapeutic approaches.

Mast cells in tumor growth: angiogenesis, tissue remodelling and immune-modulation

There is a growing acceptance that tumor-infiltrating myeloid cells play an active role in tumor growth and mast cells are one of the earliest cell types to infiltrate developing tumors. Mast cells accumulate at the boundary between healthy tissues and malignancies and are often found in close association with blood vessels within the tumor microenvironment. They express many pro-angiogenic compounds, and may play an early role in angiogenesis within developing tumors. Mast cells also remodel extracellular matrix during wound healing, and this function is subverted in tumor growth, promoting tumor spread and metastasis. In addition, mast cells modulate immune responses by dampening immune rejection or directing immune cell recruitment, depending on local stimuli. In this review, we focus on key roles for mast cells in angiogenesis, tissue remodelling and immune modulation and highlight recent findings on the integral role that mast cells play in tumor growth. New findings suggest that mast cells may serve as a novel therapeutic target for cancer treatment and that inhibiting mast cell function may lead to tumor regression.

Polarized Raman microspectroscopy can reveal structural changes of peritumoral dermis in basal cell carcinoma

Polarized Raman microspectroscopy can provide precious information regarding the orientation and ordering of the molecules in a sample without staining or particular preparation. This technique is used for the first time on a human skin section to probe the molecular modifications of the surrounding dermis in superficial basal cell carcinoma. Spectra using polarized and conventional Raman microspectroscopies were recorded on dermis bordering either the tumor or healthy epidermis. Band areas and spectral decomposition on selected vibrations were computed. Significant differences in dermal collagen vibration bands are detected using both polarized and conventional micro-spectroscopies, but the spectral changes between tumor and healthy tissues are enhanced using polarized Raman microspectroscopy. The analysis of these spectral differences highlights structural modifications of the triple helix of collagen. We see polarized Raman microspectroscopy as a potential tool that could be implemented for clinical analyses to guide clinicians and surgeons in the treatment of aggressive skin cancers. The information obtainable could also help better elucidate the molecular mechanisms induced in basal cell carcinoma development.

CD34(+) fibrocytes in melanocytic nevi and malignant melanomas of the skin

CD34(+) fibrocytes are constitutive elements of the human connective tissue. The stroma associated with invasive carcinomas is characterized by a stereotypic loss of CD34(+) fibrocytes and a phenotype change towards CD34(-) alpha-Smooth muscle actin (SMA)(+) myofibroblasts. Secreted protein acidic and rich in cysteine (SPARC) is an important mediator of tumor-associated stromal remodeling. Melanocytic lesions of the skin have not been investigated as to this aspect up to now. Thus, we investigated a total of 20 malignant melanomas and 29 melanocytic nevi. The normal dermis and benign melanocytic nevi showed numerous CD34(+) fibrocytes, whereas malignant melanomas were devoid of this cell type. alpha-SMA-positive myofibroblasts were absent from the normal dermis, melanocytic nevi, and malignant melanomas. SPARC was positive in malignant melanoma cells and negative in their associated stroma, while all melanocytic nevi were completely negative. The stromal phenotype of malignant melanomas (CD34(-) alpha-SMA(-)) differs from that of invasive carcinomas (CD34(-) alpha-SMA(+)) suggesting different pathogenic mechanisms involved in tumor-associated stromal remodeling. SPARC expression appears to be closely related to malignancy in melanocytic lesions.

Generation of anaphylatoxins by human beta-tryptase from C3, C4, and C5

Both mast cells and complement participate in innate and acquired immunity. The current study examines whether beta-tryptase, the major protease of human mast cells, can directly generate bioactive complement anaphylatoxins. Important variables included pH, monomeric vs tetrameric forms of beta-tryptase, and the beta-tryptase-activating polyanion. The B12 mAb was used to stabilize beta-tryptase in its monomeric form. C3a and C4a were best generated from C3 and C4, respectively, by monomeric beta-tryptase in the presence of low molecular weight dextran sulfate or heparin at acidic pH. High molecular weight polyanions increased degradation of these anaphylatoxins. C5a was optimally generated from C5 at acidic pH by beta-tryptase monomers in the presence of high molecular weight dextran sulfate and heparin polyanions, but also was produced by beta-tryptase tetramers under these conditions. Mass spectrometry verified that the molecular mass of each anaphylatoxin was correct. Both beta-tryptase-generated C5a and C3a (but not C4a) were potent activators of human skin mast cells. These complement anaphylatoxins also could be generated by beta-tryptase in releasates of activated skin mast cells. Of further biologic interest, beta-tryptase also generated C3a from C3 in human plasma at acidic pH. These results suggest beta-tryptase might generate complement anaphylatoxins in vivo at sites of inflammation, such as the airway of active asthma patients where the pH is acidic and where elevated levels of beta-tryptase and complement anaphylatoxins are detected.

Increase in CD30 ligand/CD153 and TNF-alpha expressing mast cells in basal cell carcinoma

Mast cells are a significant source of tumor necrosis factor (TNF) superfamily members, such as TNF-alpha, CD30 ligand/CD153 (CD30L) and CD40L/CD154. Furthermore, the expression of some of these proteins in mast cells has been associated with tumorigenesis, and mast cells have been found to be increased in number in the basal cell carcinoma (BCC) lesion. In this study, we have examined the expression of TNF-alpha, CD30L and CD40L immunoreactivity in mast cells in the healthy-looking skin and lesional skin of ten patients with superficial spreading BCC. Also, the counterparts of these molecules, TNF receptor (TNFR) I and II as well as CD30 and CD40, were analysed immunohistochemically. We found that numbers of mast cells and Kit-positive cells were significantly increased in the dermal BCC lesion. The percentage of CD30L-positive mast cells and the number of CD30-positive cells were significantly increased in the upper dermis of the BCC lesion as well. In addition, the numbers of TNF-alpha-positive mast cells and cells with TNFRI and TNFRII were markedly increased in the upper lesional dermis. In contrast, no mast cells positive for CD40L could be detected, even though the lesional dermis contained increased numbers of CD40 positive cells. The BCC epithelium was positive for TNFRI, TNFRII and CD40, but not for CD30, though the larger basal buds appeared to be less intensely stained for TNFRI and CD40. In conclusion, mast cells positive for CD30L and TNF-alpha, but not CD40L, are increased in number in the lesional dermis in BCC. These data suggest plausible pathways whereby mast cells can be activated and to interact with other cells and thereby contribute to the tumorigenesis in BCC.

The increase in tryptase- and chymase-positive mast cells is associated with partial inactivation of chymase and increase in protease inhibitors in basal cell carcinoma

BACKGROUND

In basal cell carcinoma (BCC), mast cells accumulate in the peritumoral stroma. The serine proteinases tryptase and chymase are the major mediators in mast cell granules and they may exert their enzymatic activity in the BCC lesion by inducing matrix remodeling and epithelial cell detachment.

OBJECTIVE

To analyse the numbers of mast cells showing tryptase enzyme activity, chymase enzyme activity and chymase immunoreactivity as well as the presence of chymase inhibitors alpha(1)-antichymotrypsin (alpha(1)-AC), alpha(1)-proteinase inhibitor (alpha(1)-PI) and squamous cell carcinoma antigen-2 (SCCA-2) in BCC.

METHODS

Eleven biopsies were taken from the lesion and healthy-looking skin of 10 patients with superficial spreading BCC. The frozen biopsies were analysed enzyme- and immunohistochemically, and a sequential double-staining method was applied.

RESULTS

In the BCC lesion, the number of mast cells with tryptase activity and chymase immunoreactivity was significantly increased by 2.2- to 2.3-fold. Practically all tryptase-immunopositive cells contained tryptase activity although occasional tryptase-immunopositive cells (about 1% of total) revealed no activity. However, the ratio of cells with chymase activity to those with chymase immunoreactivity was significantly decreased from 49 +/- 19% in the healthy skin to 33 +/- 19% in the BCC lesion. Instead, the percentage of mast cells displaying alpha(1)-AC or alpha(1)-PI immunoreactivity was significantly increased by 1.7-fold in the BCC lesion. SCCA-2 expression was strongly increased in the malignant BCC epithelium but mostly in the suprabasal layers.

CONCLUSIONS

Tryptase- and chymase-positive mast cells (MC(TC)) increased in the BCC lesion. However, chymase is partially inactivated, possibly by the effective chymase inhibitors alpha(1)-AC and alpha(1)-PI. SCCA-2 increased in BCC, but was localized mostly to the suprabasal layers, and thus it seems not to be crucial in inhibiting chymase.

Factor XIIIa-positive dermal dendritic cells in keloids and hypertrophic and mature scars

Keloids and hypertrophic scars have several common features. Both are reddish, firm, slightly protruding lesions that consist of proliferative fibroblastic cells and collagenous tissues. The aim of the present study was to evaluate the contribution of factor XIIIa (FXIIIa)-positive dermal dendritic cells to formation of keloids and hypertrophic scars. The numbers of FXIIIa-positive cells were counted in the keloid, hypertrophic scar and mature scar, each of which was divided into fibrocollagenous area and superficial dermal area overlying the nodular lesion. The features of the FXIIIa-positive cells were examined using immunohistochemical and immunoelectron microscopic techniques. More FXIIIa-positive cells were present in the overlying dermal area than in the fibrocollagenous area, commonly in three types of dermal lesion. The number of FXIIIa-positive dendritic cells was significantly greater in the overlying dermal area of keloids than in the corresponding area of hypertrophic or mature scar. Immunoelectron microscopic examination showed that the immunoreactivity for FXIIIa was seen mainly at the periphery of the cytoplasm of dermal dendritic cells. These results suggest that FXIIIa-positive dendritic cells in the overlying dermal area play active roles in formation of keloids and may contribute to dermal-epidermal interactions in keloids.

The role of circulating fibrocytes in fibrosis

Fibrocytes are cells that circulate in the peripheral blood and produce connective tissue proteins such as vimentin and collagens I and III. Fibrocytes are associated with skin lesions, pulmonary fibrosis, and tumors and they contribute to the remodeling response by secreting matrix metalloproteinases. Fibrocytes can further differentiate, and they are a likely source of the contractile myofibroblast that appears in many fibrotic lesions. There is evidence in the skin for a prominent role for fibrocytes in the development of hypertrophic scars and keloids. In asthma or in experimental models of pulmonary fibrosis, fibrocytes have been shown to infiltrate areas of inflammation and tissue damage. Fibrocytes constitute part of the stromal response to tumor invasion, and there is evidence that these cells may be a prognosticator of malignant potential. IL-1, TGF-beta, chemokines, and serum amyloid P modulate the appearance and function of fibrocytes. Fibrocytes themselves produce inflammatory cytokines, growth factors, and chemokines. The intercellular signals that modulate fibrocyte trafficking, proliferation, and differentiation are only partially defined, but a better understanding of these signals enable new therapies to prevent pathologic fibrosis or to improve the tissue repair response.

Mast cells and cutaneous malignancies

This paper reviews the role of mast cells in the development and progression of basal cell carcinoma, squamous cell carcinoma and malignant melanoma. Mast cells accumulate around cutaneous malignancies. Current evidence suggests that mast cells contribute to the tumorigenesis of cutaneous malignancies through four mechanisms. (1) Immunosuppression: Ultraviolet-B radiation, the most important initiator of cutaneous malignancies, activates mast cells. Upon irradiation of the skin, trans-urocanic acid in the epidermis isomerizes to cis-urocanic acid, which stimulates neuropeptide release from neural c-fibers. These neuropeptides in turn trigger histamine secretion from mast cells, leading to suppression of the cellular immune system. (2) Angiogenesis: Mast cells are the major source of vascular endothelial growth factor in basal cell carcinoma and malignant melanoma. Vascular endothelial growth factor is one of the most potent angiogenic factors, which also induces leakage of other angiogenic factors across the endothelial cell wall into the matrix. Mast cell proteases reorganize the stroma to facilitate endothelial cell migration. As well, heparin, the dominant mast cell proteoglycan, assists in blood-borne metastasis. (3) Degradation of extracellular matrix: Through its own proteases, and indirectly via interaction with other cells, mast cells participate in degradation of the matrix, which is required for tumor spread. (4) Mitogenesis: Mast cell mediators including fibroblast growth factor-2 and interleukin-8 are mitogenic to melanoma cells. Current evidence supports an accessory role for mast cells in the development and progression of cutaneous malignancies. Emerging data, however, also suggest that mast cells might, in fact, have opposing roles in tumor biology, and the microenvironment could polarize mast cells to possess either promoting or inhibitory effects on tumors.

Circulating fibrocytes: collagen-secreting cells of the peripheral blood

Since the original description of circulating fibrocytes in 1994, our knowledge of this unique cell population has grown steadily. While initially described in the context of wound repair, fibrocytes have since been found to participate in granuloma formation, antigen presentation, and various fibrosing disorders. Fibrocytes produce matrix proteins such as vimentin, collagens I and III, and they participate in the remodeling response by secreting matrix metalloproteinases. Fibrocytes also are a rich source of inflammatory cytokines, growth factors, and chemokines that provide important intercellular signals within the context of the local tissue environment. Moreover, fibrocytes express the immunological markers typical of an antigen-presenting cell, and they are fully functional for the presentation of antigen to naïve T cells. Fibrocytes can further differentiate, and they may represent a systemic source of the contractile myofibroblast that appears in many fibrotic lesions. Clinically, there is evidence that patients with hypertrophic scars such as keloids, and those affected by scleroderma and other fibrosing disorders have fibrocytes in their lesions. Recently, a new disease entity called nephrogenic fibrosing dermopathy (NFD) has been described, and the fibrocyte may play an important etiopathogenic role in disease development. Nephrogenic fibrosing dermopathy occurs in patients with renal insufficiency and leads to thickening and hardening of the skin, especially of the extremities. Ongoing research is focusing on the molecular signals that influence fibrocyte migration, proliferation, and function in the context of normal physiology and pathology.

Cutaneous leukemia inhibitory factor and its potential role in the development of skin tumors

Leukemia inhibitory factor (LIF) is a polyfunctional cytokine with a variety and a diverse range of biological activities. However, this is a reflection of the fact that the cytokine is expressed in many different tissues, has a wide target cell range, and fulfills different functions in different tissues. The purpose of this article is to examine what is known about LIF expression in the skin and to consider whether LIF plays a role in inflammatory and hyperplastic events in the skin. LIF is strongly expressed in skin tumors, and recent studies indicate that it may affect tumor growth by several different mechanisms. The biological activities of LIF relevant to carcinogenesis, its expression, and signal transduction by the LIF receptor are described. Expression of LIF in normal skin by skin tumors and its induction by ultraviolet radiation and proinflammatory stimuli are discussed, as are possible interactions between LIF, mast cells, and tumor growth. We consider what role LIF and other members of the hemopoietin family of cytokines play in healthy and diseased skin and whether LIF could play a role in hyperplastic skin disorders. LIF appears to be an important cytokine for normal keratinocyte growth and wound healing and may be involved in regulating the proliferation of skin tumors. Accordingly, LIF may be a useful target for anticancer therapy and as a growth factor for normal skin during reconstructive surgery.

CD34+ fibrocytes, alpha-smooth muscle antigen-positive myofibroblasts, and CD117 expression in the stroma of invasive squamous cell carcinomas of the oral cavity, pharynx, and larynx

We investigated tumor-free mucosa and squamous cell carcinomas of the oral cavity, the pharynx, and larynx with respect to the presence of stromal CD34+ fibrocytes and alpha-smooth muscle antigen (SMA)-positive myofibroblasts. Additionally, stromal expression of CD117 was analyzed. A total of 39 squamous cell carcinomas were assessed immunohistochemically. In all cases investigated, CD34+ fibrocytes were found in the tumor-free stroma, whereas alpha-SMA-positive myofibroblasts were lacking. Areas of lymphocytic infiltration disclosed a focal reduction of CD34+ fibrocytes. CD117 expression was absent from the tumor-free stroma. Of 39 squamous cell carcinomas, 33 were free of stromal CD34+ fibrocytes, and, in 31 carcinomas, stromal alpha-SMA-positive myofibroblasts occurred at least focally. CD117-positive stromal spindle cells were found in 25 carcinomas. Compared with tumor-free mucosa, the number of tissue mast cells was significantly increased in carcinomas. We conclude that stromal remodeling induced by invasive carcinomas is characterized by a loss of CD34+ fibrocytes and subsequent gain of alpha-SMA-positive myofibroblasts. The diagnostic impact of this finding is, however, limited by the fact that chronic inflammation may also be accompanied by a focal loss of CD34+ fibrocytes.

Mast cells in testicular lesions

The study was performed on orchidectomized tissue and testicular biopsies sent for histopathological examination which included; 9 cases of orchitis, 6 pyocele, 9 haematocele, 13 seminomas, 5 embryonal cell carcinoma, 2 teratocarcinoma, 2 lymphoma, 4 yolk sac tumor, 17 infertility lesions and 6 normal. Toluidine blue stained sections were examined under high power magnification (hpm) and the number of mast cell present in 10 consecutive fields was counted. There was a considerable variation in the number and distribution of mast cells in various testicular lesions. Mast cells were observed mainly in the areas of inflammatory infiltrate, granulation tissue and immature fibrous tissue. In infertility, interstitium and tubular walls were the areas of predilection for the presence of mast cells. The highest number of mast cells was noted in infertility (23/hpm), compared to inflammatory/reactive lesions (19/hpm) and testicular neoplasms (2/hpm). The highest and the lowest mast cell concentration were observed in infertility and testicular tumours compared to inflammatory/reactive lesions, respectively. The role of mast cells in the pathogenesis of infertility and testicular tumourogenesis requires further investigation.

Are CD34+ cells found in renal interstitial fibrosis?

BACKGROUND

The CD34 antigen is a marker of precursor myeloid cells and endothelial cells, but also of a subset of spindle cells.

METHODS

To establish the possible role of CD34+ cells in the progression of glomerulonephritis, 30 renal biopsies were investigated. Immunohistochemistry for CD34 and smooth muscle actin (SMA) were performed by standard methods. The results were assessed semiquantitatively. The relative interstitial volume (RIV) was evaluated by the point counting method. Clinical data such as sex, age, serum creatinine and urea levels were taken into account.

RESULTS

CD34+ spindle cells and SMA+ myofibroblasts were present in the renal interstitium in all but one case. In membranous, membranoproliferative and segmental-proliferative glomerulonephritis, CD34+ cells were seen in clusters, while in IgA nephropathy and in segmental and focal glomerulosclerosis, single, scattered cells were seen. The density of CD34+ cells showed a positive correlation with the myofibroblast density and the RIV. Serum creatinine and urea levels were associated with the RIV of the kidney and to a smaller degree with the number of myofibroblasts and CD34+ cells.

CONCLUSION

These results show that in glomerulonephritis, CD34+ spindle cells appear in the interstitium. At present, their possible role can only be speculated.

Increased dermal mast cell prevalence and susceptibility to development of basal cell carcinoma in humans

Exposure to ultraviolet B (UVB) radiation (280-320 nm) is the primary etiologic factor associated with the development of basal cell carcinoma (BCC). The outgrowth of these keratinocyte-derived skin lesions is enhanced by the ability of UVB to impair an immune response that would otherwise eliminate them. Studies in a range of inbred mouse strains as well as mast cell-depleted mice reconstituted with mast cell precursors support a functional link between histamine-staining dermal mast cells and the extent of susceptibility to UVB-induced systemic immunomodulation. Humans, like mouse strains, display variations in dermal mast cell prevalence. In a study of Danish and South Australian BCC patients and control subjects, one 4-mm punch biopsy of non-sun-exposed buttock skin was sampled from each participant. This skin site was investigated to avoid any changes in mast cell prevalence caused by sun exposure. Two sections (4 microm) per biopsy were immunohistochemically stained for detection of histamine-containing dermal mast cells. Computer-generated image analysis evaluated dermal mast cell prevalence in both sections by quantifying the total number of mast cells according to the total dermal area (expressed as mast cells per square millimeter). This technique enabled us to detect heterogeneity of dermal mast cell prevalence in buttock skin between individuals and provided evidence of an association between high dermal mast cell prevalence and BCC development in two diverse populations. We hypothesize that mast cells function in humans, as in mouse strains, by initiating immunosuppression following UV irradiation and, thereby, allowing a permissive environment for the development of BCC. Thus, a high dermal mast cell prevalence as demonstrable in buttock skin is a significant predisposing factor for development of BCC in humans.

Can smoking and/or occupational UV exposure have any role in the development of the morpheaform basal cell carcinoma? A critical role for peritumoral mast cells

BACKGROUND

The stroma of basal cell carcinoma (BCC) is rich in mast cells. Morpheaform BCC has been reported to contain many more mast cells than the other types of BCC. However, pathogenesis and clinical relevance of this observation are currently unclear. Smoking and ultraviolet (UV) exposure have recently been suggested to be related to the development of morpheaform BCC.

METHODS

With a retrospective study, we aimed to investigate the possible roles of smoking and occupational UV exposure in the development of morpheaform BCC through the quantification of peritumoral mast cells. Our case population consisted of 34 patients with morpheaform BCC and 50 patients with solid BCC. After identification of mast cells with toluidine blue stain, a mast cell index was determined in each case.

RESULTS

Mean mast cell index of morpheaform BCCs was significantly higher than that of solid BCCs (P < 0.02). Increased mast cell indices were associated with smoking (P = 0.003), but not with UV exposure (P > 0.05), irrespective of the tumor type. Morpheaform BCC was significantly more frequent in smokers compared to solid BCC (P < 0.05). In the cases with morpheaform BCC, mean mast cell index of smokers was significantly higher than that of nonsmokers (P = 0.02). Mean mast cell index of smokers with morpheaform BCC was also significantly higher than that of the smokers with solid BCC (P = 0.04). Ultraviolet exposure alone had no significant influence on mast cell indices, nor on the frequency of morpheaform BCC.

CONCLUSION

We suggest that smoking can play a key role in the differentiation of BCC toward its sclerosing form, through the increased peritumoral mast cell numbers.

Characterization of human prostate mast cells and their increase in periprostatic vein thrombosis

Recent data suggest that mast cells (MCs) and their products are involved in the pathophysiology of thrombosis. In the present study, we analyzed the number, distribution, and phenotype of prostate MCs and periprostatic MCs in patients with unilateral periprostatic vein thrombosis (PVT) by immunohistochemical analysis and electron microscopy. MCs reacted with monoclonal antibodies to tryptase, chymase, and c-kit/CD117 and stained positively for tissue-type plasminogen activator (tPA) and urokinase receptor (uPAR/CD87) but did not express detectable urokinase (uPA) or plasminogen activator inhibitors (PAI-1, PAI-2). We found an increase in the mean +/- SEM number of MCs in PVT compared with control (PVT, 14.36 +/- 1.57 vs control, 5.23 +/- 0.57/mm2). The majority of MCs accumulated in the adventitia of thrombosed veins and showed a decrease in chymase expression. As MCs increase in number in PVT and express a profibrinolytic phenotype, we hypothesize that MC-derived molecules have a role in endogenous fibrinolysis.