Histidine decarboxylase expression in human melanoma

Pathophysiological role of histamine signaling and its implications in glioblastoma

Glioblastoma (GBM), an extremely aggressive and prevalent malignant brain tumor, remains a challenge to treat. Despite a multimodality treatment approach, GBM recurrence remains inevitable, particularly with the emergence of temozolomide (TMZ) resistance and limited treatment options. Surprisingly, previous studies show that a history of allergies, atopy, or asthma is inversely associated with GBM risk. Further, the electronic medical record at the University Hospital of Lausanne showed that the GBM patients taking antihistamine during treatment had better survival. Histamine is an essential neurotransmitter in the brain and plays a significant role in regulating sleep, hormonal balance, and cognitive functions. Elevated levels of histamine and increased histamine receptor expression have been found in different tumors and their microenvironments, including GBM. High histamine 1 receptor (HRH1) expression has been shown to be inversely related to overall and progression-free survival in GBM patients, further emphasizing the role of histamine in disease progression. This review aims to provide insights into the challenges of GBM treatment, the role of histamine in GBM progression, and the rationale for considering antihistamines as targeted therapy. The review concludes by encouraging further investigation into antihistamine mechanisms and their impact on the tumor microenvironment.

H2 antihistamines: May be useful for combination therapies in cancer?

Cancer morbimortality is still a great concern despite advances in research and therapies. Histamine and its receptors' ligands can modulate different biological responses according to the cell type and the receptor subtype involved. Besides the wide variety of histamine functions in normal tissues, diverse roles in the acquisition of hallmarks of cancer such as sustained proliferative signaling, resistance to cell death, angiogenesis, metastasis, altered immunity and modified microenvironment have been described. This review summarizes the present knowledge of the various roles of histamine H2 receptor (H2R) ligands in neoplasias. A bioinformatic analysis of human tumors showed dissimilar results in the expression of the H2R gene according to tumor type when comparing malignant versus normal tissues. As well, the relationship between patients' survival parameters and H2R gene expression levels also varied, signaling important divergences in the role of H2R in neoplastic progression in different cancer types. Revised experimental evidence showed multiple effects of H2R antihistamines on several of the cited hallmarks of cancer. Interventional and retrospective clinical studies evaluated different H2R antihistamines in cancer patients with two main adjuvant uses: improving antitumor efficacy (which includes regulation of immune response) and preventing toxic adverse effects produced by chemo or radiotherapy. While there is a long path to go, research on H2R antihistamines may provide new opportunities for developing more refined combination therapeutic strategies for certain cancer types to improve patients' survival and health-related quality of life.

Integrated metabolomics revealed the photothermal therapy of melanoma by Mo2C nanosheets: toward rehabilitated homeostasis in metabolome combined lipidome

Melanoma, the most aggressive and life-threatening form of skin cancer, lacks innovative therapeutic approaches and deeper bioinformation. In this study, we developed a photothermal therapy (PTT) based on Mo2C nanosheets to eliminate melanoma while utilizing integrated metabolomics to investigate the metabolic shift of metabolome combined lipidome during PTT at the molecular level. Our results demonstrated that 1 mg ml-1 Mo2C nanosheets could efficiently convert laser energy into heat with a strong and stable photothermal effect (74 ± 0.9 °C within 7 cycles). Furthermore, Mo2C-based PTT led to a rapid decrease in melanoma volume (from 3.299 to 0 cm2) on the sixth day, indicating the effective elimination of melanoma. Subsequent integrated metabolomics analysis revealed significant changes in aqueous metabolites (including organic acids, amino acids, fatty acids, and amines) and lipid classes (including phospholipids, lysophospholipids, and sphingolipids), suggesting that melanoma caused substantial fluctuations in both metabolome and lipidome, while Mo2C-based PTT helped improve amino acid metabolism-related biological events (such as tryptophan metabolism) impaired by melanoma. These findings suggest that Mo2C nanosheets hold significant potential as an effective therapeutic agent for skin tumors, such as melanoma. Moreover, through exploring multidimensional bioinformation, integrated metabolomics technology provides novel insights for studying the metabolic effects of tumors, monitoring the correction of metabolic abnormalities by Mo2C nanosheet therapy, and evaluating the therapeutic effect on tumors.

The association between the neuroendocrine system and the tumor immune microenvironment: Emerging directions for cancer immunotherapy

This review summarizes emerging evidence that the neuroendocrine system is involved in the regulation of the tumor immune microenvironment (TIME) to influence cancer progression. The basis of the interaction between the neuroendocrine system and cancer is usually achieved by the infiltration of nerve fibers into the tumor tissue, which is called neurogenesis; the migration of cancer cells toward nerve fibers, which is called perineural invasion (PNI), and the neurotransmitters. In addition to the traditional role of neurotransmitters in neural communications, neurotransmitters are increasingly recognized as mediators of crosstalk between the nervous system, cancer cells, and the immune system. Recent studies have revealed that not only nerve fibers but also cancer cells and immune cells within the TIME can secrete neurotransmitters, exerting influence on both neurons and themselves. Furthermore, immune cells infiltrating the tumor environment have been found to express a wide array of neurotransmitter receptors. Hence, targeting these neurotransmitter receptors may promote the activity of immune cells in the tumor microenvironment and exert anti-tumor immunity. Herein, we discuss the crosstalk between the neuroendocrine system and tumor-infiltrating immune cells, which may provide feasible cancer immunotherapy options.

Epigallocatechin gallate stimulated histamine production and downregulated histamine H1 receptor in oral cancer cell lines expressing histidine decarboxylase

OBJECTIVES

Increased histamine production and the overexpression of receptors (H1R∼H4R) has been reported in several tumors. The effects of TGFβ1 and epigallocatechin gallate (EGCG) on histamine synthesizing enzymes (HDCs), and the histamine transporter systems and receptors were investigated in this study.

METHODS

Four oral cancer cell lines (HSC2, HSC3, HSC4, and SAS) were treated with or without TGFβ1 or EGCG for 24 h. The expression levels of HDC, SLC22A3, H1R∼H4R, and TAS2R14 were investigated by Western blotting. Histamine concentrations were determined using the enzyme immune assay. Bitter taste receptor (TAS2R14 and TAS2R39) mRNAs were investigated by RT-PCR.

RESULTS

Varying expression levels of HDC, SLC22A3, H1R∼H4R, and TAS2R14 were observed in the four cell lines, where histamine concentrations were found to be ∼500 fmol/ml in cell culture media and induced 2-2.5 times higher amounts of histamine following EGCG treatment. TGFβ1 increased HDC expression in three cell lines, SLC22A3 expression in three cell lines, H1R expression in two cell lines, H2R expression in three cell lines, H3R expression in three cell lines, and H4R expression in three cell lines. EGCG decreased HDC expression in all four cell lines, SLC22A3 expression in three expression, H1R expression in all four cell lines, H2R expression in two cell lines, H3R expression in three cell lines, and H4R expression in two cell lines.

CONCLUSIONS

EGCG upregulated histamine production and decreased the expression level of H1R in the oral cancer cell lines. It might prove useful for cancer therapy during histamine regulation.

The allergy mediator histamine confers resistance to immunotherapy in cancer patients via activation of the macrophage histamine receptor H1

Reinvigoration of antitumor immunity remains an unmet challenge. Our retrospective analyses revealed that cancer patients who took antihistamines during immunotherapy treatment had significantly improved survival. We uncovered that histamine and histamine receptor H1 (HRH1) are frequently increased in the tumor microenvironment and induce T cell dysfunction. Mechanistically, HRH1-activated macrophages polarize toward an M2-like immunosuppressive phenotype with increased expression of the immune checkpoint VISTA, rendering T cells dysfunctional. HRH1 knockout or antihistamine treatment reverted macrophage immunosuppression, revitalized T cell cytotoxic function, and restored immunotherapy response. Allergy, via the histamine-HRH1 axis, facilitated tumor growth and induced immunotherapy resistance in mice and humans. Importantly, cancer patients with low plasma histamine levels had a more than tripled objective response rate to anti-PD-1 treatment compared with patients with high plasma histamine. Altogether, pre-existing allergy or high histamine levels in cancer patients can dampen immunotherapy responses and warrant prospectively exploring antihistamines as adjuvant agents for combinatorial immunotherapy.

Uncovering the anti-NSCLC effects and mechanisms of gypenosides by metabolomics and network pharmacology analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Lung cancer is the chief reason of cancer death worldwide, and non-small cell lung cancer (NSCLC) make up the majority of lung cancers. Gypenosides are the main active constituents from Gynostemma pentaphyllum. Previous studies showed that they were used to remedy many cancers. The effect of gypenosides on NSCLC has never been studied from the perspective of network pharmacology and metabolomics. The mechanism is still not clear and remains to be explored.

AIM OF THE STUDY

To explore the anti-NSCLC activity and mechanism of gypenosides in A549 cells.

MATERIAL/METHODS

Gypenosides of G. pentaphyllum were detected by HPLC-MS. The cytotoxicity was detected by MTT assay. The migration, cell cycle and apoptosis of gypenosides were studied by wound healing assay, JC-1 assay and flow cytometry. The mechanism of gypenosides on NSCLC was studied by metabolomics and network pharmacology. Some key proteins and pathways were further confirmed by Western blot.

RESULTS

Eleven gypenosides were detected by HPLC-MS. Gypenosides could suppress the proliferation of A549 cells, inhibit the migration of A549 cells, induce apoptosis and arrest cell cycle in G0/G1 phase. Metabolomics and network pharmacology approach revealed that gypenosides might affect 17 metabolite related proteins by acting on 9 candidate targets (STAT3, VEGFA, EGFR, MMP9, IL2, TYMS, FGF2, HPSE, LGALS3), thus resulting in the changes of two metabolites (uridine 5'-monophosphate, D-4'-Phosphopantothenate) and two metabolic pathways (pyrimidine metabolism; pantothenate and CoA biosynthesis). Western blotting indicated that gypenosides might inhibit A549 cells through MMP9, STAT3 and TYMS to indirectly affect the pathways of pyrimidine metabolism, pantothenate and CoA biosynthesis.

CONCLUSIONS

This study revealed that metabolomics combined with network pharmacology was conducive to understand the anti-NSCLC mechanism of gypenosides.

Expression of histidine decarboxylase in melanocytes of the human skin

Histamine-producing cells include storage-type cells (e.g., mast cells and basophils), which store histamine intracellularly, and inducible-type cells (e.g., keratinocytes and macrophages), which induce histidine decarboxylase (HDC, a key enzyme for histamine biosynthesis) activity but do not have a storage pool of histamine. Most of the studies focused on identifying HDC-expressing cells by using cultured cells, and few on investigating the localization of HDC by using skin tissues. Hence, this study conducted immunohistochemical studies using human healthy skin samples. HDC-positive and cytokeratin 14 (a marker of basal keratinocytes)-negative cells were present around the basal layer of the epidermis. These cells did not immunohistochemically react with mast cell tryptase but expressed tyrosinase (a key enzyme for melanin biosynthesis) and microphthalmia-associated transcription factor (MITF, a transcription factor controlling the expression of tyrosinase genes). Melanin granules were clearly observed around HDC-positive and MITF-positive cells. Moreover, HDC mRNA and protein were both detected in cultured normal human epidermal melanocytes. In conclusion, HDC-positive and cytokeratin 14-negative cells around the basal layer of the epidermis are melanocytes.

Histamine receptors and cancer pharmacology: an update

In the present review, we will discuss the recent advances in the understanding of the role of histamine and histamine receptors in cancer biology. The controversial role of the histaminergic system in different neoplasias including gastric, colorectal, oesophageal, oral, pancreatic, liver, lung, skin, blood and breast cancers will be reviewed. The expression of histamine receptor subtypes, with special emphasis on the histamine H4 receptor, in different cell lines and human tumours, the signal transduction pathways and the associated biological responses as well as the in vivo treatment of experimental tumours with pharmacological ligands will be described. The presented evidence demonstrates that histamine regulates cancer-associated biological processes during cancer development in multiple cell types, including neoplastic cells and cells in the tumour micro-environment. The outcome will depend on tumour cell type, the level of expression of histamine receptors, signal transduction associated with these receptors, tumour micro-environment and histamine metabolism, reinforcing the complexity of cancer disease. Findings show the pivotal role of H4 receptors in the development and progression of many types of cancers, and considering its immunomodulatory properties, the H4 receptor appears to be the most promising molecular therapeutic target for cancer treatment within the histamine receptor family. Furthermore, the H4 receptor is differentially expressed in tumours compared with normal tissues, and in most cancer types in which data are available, H4 receptor expression is associated with clinicopathological characteristics, suggesting that H4 receptors might represent a novel cancer biomarker. LINKED ARTICLES: This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

Repurposing a Histamine Detection Platform for High-Throughput Screening of Histidine Decarboxylase

Histidine decarboxylase (HDC) is the primary enzyme that catalyzes the conversion of histidine to histamine. HDC contributes to many physiological responses as histamine plays important roles in allergic reaction, neurological response, gastric acid secretion, and cell proliferation and differentiation. Small-molecule modulation of HDC represents a potential therapeutic strategy for a range of histamine-associated diseases, including inflammatory disease, neurological disorders, gastric ulcers, and select cancers. High-throughput screening (HTS) methods for measuring HDC activity are currently limited. Here, we report the development of a time-resolved fluorescence resonance energy transfer (TR-FRET) assay for monitoring HDC activity. The assay is based on competition between HDC-generated histamine and fluorophore-labeled histamine for binding to a Europium cryptate (EuK)-labeled anti-histamine antibody. We demonstrated that the assay is highly sensitive and simple to develop. Assay validation experiments were performed using low-volume 384-well plates and resulted in good statistical parameters. A pilot HTS screen gave a Z' score > 0.5 and a hit rate of 1.1%, and led to the identification of a validated hit series. Overall, the presented assay should facilitate the discovery of therapeutic HDC inhibitors by acting as a novel tool suitable for large-scale HTS and subsequent interrogation of compound structure-activity relationships.

Metabolite marker discovery for the detection of bladder cancer by comparative metabolomics

Bladder cancer is one of the most common urinary tract carcinomas in the world. Urine metabolomics is a promising approach for bladder cancer detection and marker discovery since urine is in direct contact with bladder epithelia cells; metabolites released from bladder cancer cells may be enriched in urine samples. In this study, we applied ultra-performance liquid chromatography time-of-flight mass spectrometry to profile metabolite profiles of 87 samples from bladder cancer patients and 65 samples from hernia patients. An OPLS-DA classification revealed that bladder cancer samples can be discriminated from hernia samples based on the profiles. A marker discovery pipeline selected six putative markers from the metabolomic profiles. An LLE clustering demonstrated the discriminative power of the chosen marker candidates. Two of the six markers were identified as imidazoleacetic acid whose relation to bladder cancer has certain degree of supporting evidence. A machine learning model, decision trees, was built based on the metabolomic profiles and the six marker candidates. The decision tree obtained an accuracy of 76.60%, a sensitivity of 71.88%, and a specificity of 86.67% from an independent test.

Study of early stage non-small-cell lung cancer using Orbitrap-based global serum metabolomics

Purpose

The aim of the project was to apply ultra-high-performance liquid chromatography–quadrupole-Orbitrap-high-resolution mass spectrometry for serum metabolite profiling of non-small-cell lung cancer (NSCLC). This Orbitrap-based methodology has been applied for a study of NSCLC potential markers for the first time.

Methods

After extraction using protein precipitation, sera were separated on the ACE Excel 2 C18-PFP (100 × 2.1 mm, 2.0 µm) column using gradient elution and analyzed within the range of 70–1000 m/z. Only patients with early stage disease (stages IA–IIB) were included in the study, providing opportunity to find biomarkers for early lung cancer detection. The resulting metabolite profiles were subjected to univariate and multivariate statistical tests.

Results

36 features were found significantly changed between NSCLC group and controls after FDR adjustment and 19 were identified using various metabolite databases (in-house library, HMDB, mzCloud). The study revealed a number of NSCLC biomarker candidates which belong to such compound classes as acylcarnitines, organic acids, and amino acids. Multivariate ROC curve built using 12 identified metabolites was characterized by AUC = 0.836 (0.722–0.946). There were no significant differences in the serum metabolite profiles between two most common histological types of lung cancer—adenocarcinoma and squamous cell carcinoma.

Conclusions

Through identification of novel potential tumor markers, Orbitrap-based global metabolic profiling is a useful strategy in cancer research. Our study can accelerate development of new diagnostic and therapeutic strategies in NSCLC. The metabolites involved in discrimination between NSCLC patients and the control subjects should be further explored using a targeted approach.

Electronic supplementary material

The online version of this article (doi:10.1007/s00432-017-2347-0) contains supplementary material, which is available to authorized users.

Low- and high-grade bladder cancer determination via human serum-based metabolomics approach

To address the shortcomings of urine cytology and cystoscopy for probing and grading urinary bladder cancer (BC), we applied (1)H nuclear magnetic resonance (NMR) spectroscopy as a surrogate method for the identification of BC. This study includes 99 serum samples comprising low-grade (LG; n = 36) and high-grade (HG; n = 31) BC as well as healthy controls (HC; n = 32). (1)H NMR-derived serum data were analyzed using orthogonal partial least-squares discriminant analysis (OPLS-DA). OPLS-DA-derived model validity was confirmed using an internal and external cross-validation. Internal validation was performed using the initial samples (n = 99) data set. External validation was performed on a new batch of suspected BC patients (n = 106) through a double-blind study. Receiver operating characteristic (ROC) curve analysis was also performed. OPLS-DA-derived serum metabolomics (six biomarkers, ROC; 0.99) were able to discriminate 95% of BC cases with 96% sensitivity and 94% specificity when compared to HC. Likewise (three biomarkers, ROC; 0.99), 98% of cases of LG were able to differentiate from HG with 97% sensitivity and 99% specificity. External validation reveals comparable results to the internal validation. (1)H NMR-based serum metabolic screening appears to be a promising and less invasive approach for probing and grading BC in contrast to the highly invasive and painful cystoscopic approach for BC detection.

LARG links histamine-H1-receptor-activated Gq to Rho-GTPase-dependent signaling pathways

Activation of heterotrimeric G proteins, such as G(12/13) and G(q), by cell surface receptors is coupled to the regulation of numerous cellular functions controlled by activated Rho GTPases. Previous studies have implicated the Rho guanine nucleotide exchange factor (RhoGEF) leukemia-associated RhoGEF (LARG) as a regulatory protein receiving stimulatory inputs from activated Gα(12/13) and Gα(q). However, the molecular mechanisms of the Gα(q)-mediated LARG activation are not fully understood and the structural elements of LARG involved in this process have remained unclear. In the present work, the specific coupling of the histamine H1 receptor (HRH1) exogenously expressed in COS-7 cells to G(q), but not to G(12/13), was used to conduct a detailed analysis of receptor- and Gα(q)-mediated LARG activation and to define its structural requirements. The results show that HRH1-mediated activation of the strictly Rho-dependent transcriptional activity of serum response factor requires the PDZ domain of LARG and can be mimicked by activated Gα(q)(Q209L). The functional interaction between activated Gα(q) and LARG requires no more than the catalytic DH-PH tandem of LARG, and is independent of PLCβ activation and distinct from the mechanisms of Gα(q)-mediated p63RhoGEF and PLCβ(3) activation. Activated Gα(q) physically interacts with the relevant portions of LARG in COS-7 cells and histamine causes activation of LARG in native HeLa cells endogenously expressing HRH1, G(q), and LARG. This work is the first positive demonstration of a stimulatory effect of LARG on the ability of a strictly G(q)-coupled receptor to cause activation of a Rho-GTPase-dependent signaling pathway.

Mast cells and histamine enhance the proliferation of non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is the most common form of lung cancer with an extremely low survival rate. It is characterized by a chronic inflammatory process with intense mast cell infiltrate that is associated with reduced survival. The aim of this study was to test the hypothesis that mast cells have an enhancing effect on NSCLC proliferation. To assess the tumor-promoting potential of mast cells, we used the human alveolar basal adenocarcinoma (A549) and the mouse Lewis lung carcinoma (LLC) cell lines, umbilical cord blood-derived mast cells (CBMC) and the mast cell-deficient mouse Sash model. The proliferation rate of A549/LLC cells was markedly increased by mast cells and histamine. Histamine proliferating activity was mediated via H(1), H(2) and H(4) receptors and caused ERK phosphorylation. LLC induced in Sash mice or in wild-type mice treated with the mast cell stabilizer nedocromil sodium displayed an accelerated growth (number of metastic colonies in the lungs, total lung area and lung/total mice weight ratio). In summary, we have shown a significant effect of mast cells and histamine in enhancing NSCLC/LLCX growth in vitro, while in a mouse LLC model in vivo we have found that mast cells are important negative regulators of cancer development. Therefore our results would indicate a pro-tumorogenic effect of the mast cells in vitro on established lung tumor cell lines, and anti-tumorogenic effect in mice at lung cancer induction. In conclusion, mast cell/anti-histamine targeted therapies should carefully consider this dual effect.

Histamine receptors and cancer pharmacology

Considerable evidence has been collected indicating that histamine can modulate proliferation of different normal and malignant cells. High histamine biosynthesis and content together with histamine receptors have been reported in different human neoplasias including melanoma, colon and breast cancer, as well as in experimental tumours in which histamine has been postulated to behave as an important paracrine and autocrine regulator of proliferation. The discovery of the human histamine H(4) receptor in different tissues has contributed to our understanding of histamine role in numerous physiological and pathological conditions revealing novel functions for histamine and opening new perspectives in histamine pharmacology research. In the present review we aimed to briefly summarize current knowledge on histamine and histamine receptor involvement in cancer before focusing on some recent evidence supporting the novel role of histamine H(4) receptor in cancer progression representing a promising molecular target and avenue for cancer drug development.

Involvement of hydrogen peroxide in histamine-induced modulation of WM35 human malignant melanoma cell proliferation

Histamine is a recognized growth factor in melanoma, and exogenous histamine produces a dual effect on proliferation. We have previously reported that histamine at micromolar concentrations reduces the proliferation of melanoma cell lines. To investigate the mechanism by which histamine inhibits proliferation of WM35 human melanoma cells, we have studied the involvement of histamine in reactive oxygen species production and antioxidant enzyme regulation in these cells. Results indicate that histamine treatment (10 microM) significantly increased hydrogen peroxide levels, whereas it slightly decreased superoxide levels associated with an enhancement of superoxide dismutase and a reduction in catalase activity. Additionally, catalase treatment reversed the inhibitory effect of histamine on proliferation, and various treatments that reduce hydrogen peroxide formation increased proliferation of these cells. Furthermore, we demonstrate that the inhibition of proliferation produced by histamine was mediated at least in part by an induction of cell senescence. We conclude that hydrogen peroxide is involved in histamine-mediated modulation of proliferation in malignant melanoma cells.

Expression of non-mast cell histidine decarboxylase in tumor-associated microvessels in human esophageal squamous cell carcinomas

Histamine is produced by mast cells and many other types of cells. The role of histamine released from mast cells in promoting tumor angiogenesis has been intensively studied; however, the role of non-mast cell histamine in regulating tumor angiogenesis has been largely ignored. In this study, tissue specimen sections from 43 patients with esophageal squamous cell carcinoma (ESCC) and normal esophageal biopsies from 17 heath individuals obtained from a high incidence area of north China were used to assess changes in microvessel density (MVD) and non-mast cell L-histidine decarboxylase (HDC) (the only rate-limiting enzyme that catalyzes the formation of histamine from L-histidine) expression in the tumor microenvironment by immunohistochemistry (IHC). In addition, the cellular characterization of non-mast cell HDC-positive cells in microvessels was examined by double IHC combined with HDC/CD34 and HDC/PCNA antibodies. These IHC analyses revealed a significantly increased HDC-positive MVD in ESCC as compared with normal controls, which accounted for approximately 61% of CD34-labeled general MVD in ESCC. Furthermore, IHC in serial sections and double IHC showed that most of these HDC-positive cells were CD34-positive endothelial cells in microvessels with an increased proliferative capacity. Thus, our results suggest that non-mast cell histamine expressed in endothelial cells of microvessels could be an additional cellular source and might play a role in regulating angiogenesis in ESCC.

Histamine suppresses fibulin-5 and insulin-like growth factor-II receptor expression in melanoma

We previously showed that transgenic enhancement of histamine production in B16-F10 melanomas strongly supports tumor growth in C57BL/6 mice. In the present study, gene expression profiles of transgenic mouse melanomas, secreting different amounts of histamine, were compared by whole genome microarrays. Array results were validated by real-time PCR, and genes showing histamine-affected behavior were further analyzed by immunohistochemistry. Regulation of histamine-coupled genes was investigated by checking the presence and functional integrity of all four known histamine receptors in experimental melanomas and by administering histamine H1 receptor (H1R) and H2 receptor (H2R) antagonists to tumor-bearing mice. Finally, an attempt was made to integrate histamine-affected genes in known gene regulatory circuits by in silico pathway analysis. Our results show that histamine enhances melanoma growth via H1R rather than through H2R. We show that H1R activation suppresses RNA-level expression of the tumor suppressor insulin-like growth factor II receptor (IGF-IIR) and the antiangiogenic matrix protein fibulin-5 (FBLN5), decreases their intracellular protein levels, and also reduces their availability in the plasma membrane and extracellular matrix, respectively. Pathway analysis suggests that because plasma membrane-bound IGF-IIR is required to activate matrix-bound, latent transforming growth factor-beta1, a factor suggested to sustain FBLN5 expression, the data can be integrated in a known antineoplastic regulatory pathway that is suppressed by H1R. On the other hand, we show that engagement of H2R also reduces intracellular protein pools of IGF-IIR and FBLN5, but being a downstream acting posttranslational effect with minimal consequences on exported IGF-IIR and FBLN5 protein levels, H2R is rather irrelevant compared with H1R in melanoma.

Cervical squamous carcinoma cells are resistant to the combined action of tumor necrosis factor-alpha and histamine whereas normal keratinocytes undergo cytolysis

BACKGROUND

Previous reports showed that mast cells can typically be found in the peritumoral stroma of cervix carcinomas as well as in many other cancers. Both histamine and TNF-alpha are potent preformed mast cell mediators and they can act simultaneously after release from mast cells. Thus, the effect of TNF-alpha and histamine on cervical carcinoma cell lines was studied.

METHODS AND RESULTS

TNF-alpha alone induced slight growth inhibition and cell cycle arrest at G0/G1 phase in SiHa cells, but increased their migration. Histamine alone had no effect on cells. In addition, TNF-alpha and histamine in combination showed no additional effect over that by TNF-alpha alone, although SiHa cells were even pretreated with a protein synthesis inhibitor. Furthermore, TNF-alpha-sensitive ME-180 carcinoma cells were also resistant to the combination effect of TNF-alpha and histamine. In comparison, TNF-alpha or histamine alone induced growth inhibition in a non-cytolytic manner in normal keratinocytes, an effect that was further enhanced to cell cytolysis when both mediators acted in combination. Keratinocytes displayed strong TNF receptor (TNFR) I and II immunoreactivity, whereas SiHa and ME-180 cells did not. Furthermore, cervix carcinoma specimens revealed TNF-alpha immunoreactivity in peritumoral cells and carcinoma cells. However, the immunoreactivity of both TNFRs was less intense in carcinoma cells than that in epithelial cells in cervical specimens with non-specific inflammatory changes.

CONCLUSION

SiHa and ME-180 cells are resistant to the cytolytic effect of TNF-alpha and histamine whereas normal keratinocytes undergo cytolysis, possibly due to the smaller amount of TNFRs in SiHa and ME-180 cells. In the cervix carcinoma, the malignant cells may resist this endogenous cytolytic action and TNF-alpha could even enhance carcinoma cell migration.

Functional genomics of calcium channels in human melanoma cells

Ca(2+)-signaling of human melanoma is in the focus of intensive research since the identification of the role of WNT-signaling in melanomagenesis. Genomic and functional studies pointed to the important role of various Ca(2+) channels in melanoma, but these data were contradictory. In the present study we clearly demonstrate, in a number of different ways including microarray analysis, DNA sequencing and immunocytochemistry, that various human melanoma cell lines and melanoma tissues overexpress ryanodine receptor type 2 (RyR2) and express P2X(7) channel proteins as compared to melanocytes. These channels, although retain some of their usual characteristics and pharmacological properties, display unique features in melanoma cells, including a functional interaction between the two molecules. Unlike P2X(7), RyR2 does not function as a calcium channel. On the other hand, the P2X(7) receptor has an antiapoptotic function in melanoma cells, since ATP-activation suppresses induced apoptosis, while knock down of the gene expression significantly enhances that.

An unexpected inverse correlation between soluble epidermal growth factor receptor and interleukin-6 in metastatic malignant melanoma patients

The exact role of the soluble form of epidermal growth factor receptor (sEGF-R) in melanoma disease remains to be determined. We focused this study on the detection of circulating levels of sEGF-R in metastatic malignant melanoma patients and on the possible relationship between sEGF-R and clinicobiological parameters including circulating interleukin-6 (IL-6) and survival. sEGF-R and IL-6 levels were determined using a highly sensitive enzyme-linked immunosorbent assay in serum from 75 metastatic malignant melanoma patients and 30 healthy controls. In our patients, median sEGF-R level was significantly elevated (P < 0.0001) compared with that of healthy controls (173.4 vs. 91.9 fm/ml). Age or sex was not associated with sEGF-R levels. Regarding tumor burden, in contrary to the detected IL-6 levels, we found that median sEGF-R levels were significantly (P = 0.045) lower in patients with high tumor burden (163 fm/ml) than in those with low tumor burden (193.8 fm/ml). An inverse correlation between IL-6 levels and sEGF-R was observed (r =-0.33; P = 0.040). No relationship between sEGF-R and time to progression or overall survival was observed while circulating IL-6 was found as a predictive factor of survival. Our results showed that sEGF-R level was elevated in metastatic malignant melanoma patients but not related to time to progression or survival and demonstrated an inverse correlation between sEGF-R and IL-6 levels. These findings imply a better understanding of EGF-R and IL-6 cross-talk function in melanoma.

Expression of ets-1 transcription factor in human head and neck squamous cell carcinoma and effect of histamine on metastatic potential of invasive tumor through the regulation of expression of ets-1 and matrix metalloproteinase-3

BACKGROUND

Ets-1 controls the expression of critical genes involved in matrix remodeling. The matrix metalloproteinase-3 (MMP-3) and urokinase type plasminogen activator (uPA) are typical ets-1 responsive genes. Recent studies have shown an increase in histamine synthesis and content in various human neoplasias. We hypothesized that the increased local histamine overproduction contributed to activation of matrix remodeling through the activation of MMP-3 expression of peritumoral fibroblasts by means of ets-1 regulation in head and neck squamous cell carcinomas (HNSCCs).

METHODS

Paraffin-embedded sections of 30 HNSCCs were immunostained for ets-1. The presence of ets-1 and MMP-3 mRNA in tumor samples was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR). To simulate stromal reaction in vitro, cultured human mucosal fibroblast was used. The level of ets-1 and MMP-3 mRNA was compared by use of RT-PCR, as was their protein with flow-cytometry, in the presence or absence of basic fibroblast growth factor (bFGF) (10 ng/mL) and histamine (1 microM).

RESULTS

Correlation between ets-1 expression and clinicopathologic background was not significant. In all cases, expression of ets-1 was seen in the stroma. In in vitro study, histamine upregulates production of ets-1 and MMP-3 in cultured fibroblast, and bFGF can stimulate histamine expression in fibroblast. Immunofluorescence staining supported the results of RT-PCR and flow cytometry.

CONCLUSIONS

Ets-1 expression in HNSCCs has no prognostic value; however, ets-1 plays an important role in tumor-host interaction. Histamine may accelerate the spread of HNSCC through an ets-1-related mechanism.

The Role of Cyclooxygenase-2 in Mediating the Effects of Histamine on Cell Proliferation and Vascular Endothelial Growth Factor Production in Colorectal Cancer

PURPOSE

Activity of histidine decarboxylase, the key enzyme in the synthesis of histamine, has been shown to be increased in several types of human tumors. We attempted to establish whether the possible involvement of histidine decarboxylase and histamine in colorectal carcinogenesis might be mediated by the activation of the cyclooxygenase-2 (COX-2) pathway.

EXPERIMENTAL DESIGN

Expression/activity of histidine decarboxylase, histamine content, and prostaglandin E2 (PGE2) production were analyzed in 33 colorectal cancer samples and in the HT29, Caco-2, and HCT116 colon cancer cell lines. The effects of histamine, celecoxib, and H1, H2, and H4 receptor antagonists on COX-2 expression/activity, cell proliferation, and vascular endothelial growth factor (VEGF) production were assessed in the three colon cancer lines that showed different constitutive COX-2 expression.

RESULTS

We showed the up-regulation of histidine decarboxylase protein expression and activity in the tumor specimens when compared with normal colonic mucosa. Histidine decarboxylase activity and histamine content were also significantly higher in metastatic tumors than in nonmetastatic ones. These variables significantly correlated with tumor PGE(2) production. The administration of histamine increased COX-2 expression/activity, cell proliferation, and VEGF production in the COX-2-positive HT29 and Caco-2 cells. Treatment with either H2/H4 receptor antagonists or celecoxib prevented these effects. Histamine had no effect on both the COX-2 pathway and VEGF production in the COX-2-negative HCT116 cells.

CONCLUSIONS

Our data showed that histamine exerts both a proproliferative and a proangiogenic effect via H2/H4 receptor activation. These effects are likely to be mediated by increasing COX-2-related PGE2 production in COX-2-expressing colon cancer cells.

Histamine regulates growth of malignant melanoma implants via H2 receptors in mice

The present study examined the effect of histamine H2-receptor antagonists and exogenous histamine on growth of malignant melanoma implant in mice. Drugs were administered to B16BL6 malignant-melanoma-implanted syngeneic mice, and the tumor volume was measured throughout the experiments. Cell proliferation was assessed by MTT assay and mRNA expression was determined by RT-PCR. Both roxatidine and cimetidine significantly suppressed growth of B16BL6 implant compared with vehicle. On the other hand, systemically administered histamine significantly stimulated growth of B16BL6 implants. In addition, the histamine-stimulated B16BL6 implant growth was markedly suppressed by co-administration of cimetidine in a dose-dependent manner. H2-receptor antagonists, however, failed to affect in vitro proliferation of B16BL6 cells. H2-receptor mRNA was detected in B16BL6 implants but not in the cell line. These results indicated that both endogenous and exogenous histamine have ability to stimulate growth of malignant melanoma implants via H2 receptors expressed in host cells.

Phenotypic profiling of engineered mouse melanomas with manipulated histamine production identifies histamine H2 receptor and rho-C as histamine-regulated melanoma progression markers

In the present study, the impact of acquired neoplastic L-histidine decarboxylase (HDC) expression, and its direct consequence, the release of histamine in the tumor environment, was assessed on melanoma tumor progression. B16-F10 mouse melanoma cells were manipulated via stable transfection, and nine novel transgenic variants were generated in triplicates, constitutively expressing the full-length sense mouse HDC mRNA, a mock control, and an antisense HDC RNA segment, respectively. Establishing both primary skin tumors and lung metastases in C57BL/6 mice, the nine variants with different histamine-releasing capacities were subjected to a comprehensive comparative progression profiling in vivo. Our analyses showed trends of markedly accelerated tumor growth (P < 0.001), and moderately increased metastatic colony-forming potential (P = 0.010) along with rising levels of local histamine production. Using RNase protection assay for screening of the melanoma progression profile, and Western blotting for subsequent result validation, we looked for molecular progression markers affected by melanoma histamine secretion. Investigation of 21 functionally clustered markers associated with tumor proliferation, angiogenesis, invasivity, metastasis formation, local or systemic immunomodulation, and histamine signaling revealed positive correlations between histamine production, tumor histamine H2 receptor and rho-C expression (P < 0.001, P = 0.002, respectively). These observations confirm the involvement of histamine in the molecular machinery of melanoma progression.

Mammalian histidine decarboxylase: from structure to function

Histamine is a multifunctional biogenic amine with relevant roles in intercellular communication, inflammatory processes and highly prevalent pathologies. Histamine biosynthesis depends on a single decarboxylation step, carried out by a PLP-dependent histidine decarboxylase activity (EC 4.1.1.22), an enzyme that still remains to be fully characterized. Nevertheless, during the last few years, important advances have been made in this field, including the generation and validation of the first three-dimensional model of the enzyme, which allows us to revisit previous results and conclusions. This essay provides a comprehensive review of the current knowledge of the structural and functional characteristics of mammalian histidine decarboxylase.

Melanin pigmentation in mammalian skin and its hormonal regulation

Cutaneous melanin pigment plays a critical role in camouflage, mimicry, social communication, and protection against harmful effects of solar radiation. Melanogenesis is under complex regulatory control by multiple agents interacting via pathways activated by receptor-dependent and -independent mechanisms, in hormonal, auto-, para-, or intracrine fashion. Because of the multidirectional nature and heterogeneous character of the melanogenesis modifying agents, its controlling factors are not organized into simple linear sequences, but they interphase instead in a multidimensional network, with extensive functional overlapping with connections arranged both in series and in parallel. The most important positive regulator of melanogenesis is the MC1 receptor with its ligands melanocortins and ACTH, whereas among the negative regulators agouti protein stands out, determining intensity of melanogenesis and also the type of melanin synthesized. Within the context of the skin as a stress organ, melanogenic activity serves as a unique molecular sensor and transducer of noxious signals and as regulator of local homeostasis. In keeping with these multiple roles, melanogenesis is controlled by a highly structured system, active since early embryogenesis and capable of superselective functional regulation that may reach down to the cellular level represented by single melanocytes. Indeed, the significance of melanogenesis extends beyond the mere assignment of a color trait.

Histamine, part of the metabolome

Histamine, a decarboxylated amino acid with a molecular mass of 112 daltons reveals multicoloured functional activities. Its role in allergy and inflammation is abundantly characterized. Moreover histamine is one of the neuotransmitters, has a role in gastric acid production and in maintenance of blood-brain barrier. In the last decade, many data were collected suggesting an important function of histamine in events of immune response and also in both benign and malignant cell proliferation. Our group collected data on the relevance of histamine as an autocrine factor in human melanoma. The outcome of the action seems to be closely related to the local and actual balance of histamine receptors (H1R, H2R, H3R and H4R) on tumor cells. Recently, using a gene targeted mouse strain (lacking an enzyme, histidine decarboxylase, the only one responsible for histamine production) many phenotype of the histamine-free mice were demonstrated. Our data suggest, that histamine, as part of the poorly characterized metabolome of the mammalian cells plays significant role in many physiological and pathological processes.

Autonomous histamine metabolism in human melanoma cells

Melanoma cells constitutively produce various cytokines as well as growth factors and express their corresponding receptors. Exogenous histamine is known to be a growth factor for some tumours while in other cases histamine inhibits tumour growth, and acts on G protein-coupled H1 and H2 histamine receptors. In previous studies we have detected the expression of the l-histidine decarboxylase (HDC) gene and the presence of HDC protein in human melanoma cell lines. In the present study, the activities of the histamine-forming enzyme HDC and of the degrading enzymes diamine oxidase (DAO) and histamine N-methyltransferase (HNMT) were measured in primary (WM35 and WM983) and metastatic (M1 and HT168) human melanoma cell lines. HDC activity was found in WM35 and WM983 cell lines, while detectable HNMT activity was measured in WM983, M1 and HT168 lines. In contrast, DAO showed very low activity in melanoma cell lines. Melanoma cells release a detectable amount of histamine into the medium without external stimuli. These findings support the possibility of autonomous histamine metabolism in melanoma cells. Our results suggest that not only exogenous histamine but also histamine produced and released by the melanoma cells and acting as an autocrine and paracrine factor may influence cell proliferation and modulate the in situ immune response of the host.

Murine and human hematopoietic colony formation: a possible regulatory role for intracellular histamine

Increasing number of data suggests that locally produced histamine is involved in regulation of hematopoiesis. In this study the granulocyte/macrophage (CFU-GM) colony formation by normal murine or human bone marrow cells, leukaemic colony formation (CFU-L) by a murine leukemia cell line (WEHI 3B), and colony formation by bone marrow cells from patients with chronic myeloid leukemia (CML) have been examined. We detected mRNA and protein expression of histidine decarboxylase (HDC), the only enzyme responsible for histamine synthesis both in normal bone marrow progenitor cells and in leukaemic progenitors. The significance of in situ generated histamine was shown on colony formation by inhibitory action of alphaFMH (blocking HDC activity, i.e. de novo histamine formation) and by N,N-diethyl-2-[4-(phenylmethyl)phenoxy]-ethanamine-HCl (DPPE) disturbing the interference of histamine with intracellular binding sites. These data provide further confirmation of the role of histamine in development and colony formation of bone marrow derived cells.

Histamine inhibits the production of interferon-induced protein of 10 kDa in human squamous cell carcinoma and melanoma

Interferon-induced protein of (IP-10) inhibits tumor progression. Tumor cells can produce interferon-induced protein of IP-10 in response to interferon-g. Histamine in the vicinity of tumor cells may sustain the tumor progression. We examined the in vitro effects of histamine on interferon-induced protein of IP-10 production in human squamous cell carcinoma and melanoma. Histamine suppressed interferon-g-mediated interferon-induced protein of IP-10 secretion and mRNA expression in SV40-transformed keratinocytes, SCC15, SCC4, and melanoma WM115, WM266-4, and C32. Histamine suppressed interferon-g-induced interferon-mediated protein of IP-10 promoter activation in these cells, and the interferon-stimulated response element on the promoter was responsible for the suppression. Histamine suppressed interferon-g-mediated transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element. Histamine suppressed interferon-g-induced tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine-mediated suppression on the interferon-g-induced interferon-mediated protein of IP-10 synthesis was counteracted by the H2 receptor antagonist cimetidine, adenylate cyclase inhibitor SQ22536, and protein kinase A inhibitor H-89, but were not affected by H1 receptor antagonist mepyramine. Cimetidine, SQ22536, and H-89 also counteracted histamine-mediated suppression on the interferon-g-induced transcription through the interferon-stimulated response element, signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element, and tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine increased intracellular 3',5'-adenosine cyclic monophosphate level and protein kinase A activity in squamous cell carcinoma and melanoma, and the effects of histamine were blocked by cimetidine. These results suggest that histamine may interact with H2 receptor on squamous cell carcinoma and melanoma and generate 3',5'-adenosine cyclic monophosphate, which may activate protein kinase A. The cyclic 3',5'-adenosine monophosphate/protein kinase A signaling pathway induced by histamine may inhibit interferon-g-induced signal transducer and activator of transcription 1alpha activation and suppress interferon-induced protein of IP-10 synthesis.

Inhibition of human primary melanoma cell proliferation by histamine is enhanced by interleukin-6

BACKGROUND

Interleukin-6 (IL-6) is a bifunctional growth factor in malignant melanoma; its expression increases during the malignant progression of the disease. Histamine, detected in large amounts in normal and pathological proliferating tissues, is an important paracrine and autocrine regulator of normal and tumour cell proliferation as well.

MATERIALS AND METHODS

We investigated the presence and function of IL-6 and histamine in the WM35 primary human melanoma cell line with respect to their direct role in cell proliferation and their regulatory interactions.

RESULTS

IL-6 inhibited the proliferation of WM35 melanoma cells and increased significantly the expression of histidine decarboxylase as well as histamine production. It had dose-dependent effects on the proliferation: high concentration (10-5 M) was inhibitory through H1 histamine receptors while low histamine concentration acting on H2 receptors, with a simultaneous increase of cAMP, enhanced colony formation in the monolayer. Furthermore, IL-6 increased the H1- but decreased the H2-histamine receptor expression of the melanoma cells. On the other hand, histamine was locally synthesized by the WM35 melanoma cells.

CONCLUSION

We suggest that the growth arrest induced by IL-6 is in part mediated by its dual action on histamine: a shift toward H1 receptor predominance and an elevation of locally produced histamine with prevalent action on the inhibitory response triggered through the H1 receptor. These findings suggest a local cross-talk between histamine and IL-6 in the regulation of melanoma growth.

Cimetidine and a tamoxifen derivate reduce tumour formation in SCID mice xenotransplanted with a human melanoma cell line

Histamine is produced by many cells expressing histidine decarboxylase (HDC), the enzyme responsible for the synthesis of histamine. Since melanoma cells and tissue contain relatively large amounts of histamine, the functional significance of histamine was examined using specific antihistamines in vitro and in vivo in the human melanoma cell line HT168 and severe combined immunodeficiency (SCID) mice. It was shown that the H2 receptor antagonist cimetidine when combined with N, N-diethyl-2-[4-(phenylmethyl)phenoxy]-ethanamine-HCl (DPPE), a tamoxifen derivate, inhibits the proliferation of HT168 cells. Furthermore, it is suggested that there is a factor(s) that interferes with the exponential growth of HT168 cells xenografted to immunodeficient mice, and cimetidine and DPPE together significantly influence this factor(s). This combination of antihistamines also increases the survival of human melanoma-grafted mice. These changes are accompanied by enhanced infiltration of interferon-gamma- producing mouse macrophages into the tumour tissue. These findings suggest that two different mechanisms are probably acting concordantly: direct inhibition of tumour cell proliferation by the H2 receptor antagonists, and activation of the local immune response characterized by interferon-gamma production. These findings may help to elucidate the possibility of a rationally designed antihistamine strategy in melanoma therapy.

Expression of histidine decarboxylase and synthesis of histamine by human small cell lung carcinoma

We recently found that human small cell lung carcinomas (SCLCs) express, in addition to other neuroendocrine markers, vesicular monoamine transporters. Our present results indicate that SCLCs are histaminergic. We detected the biosynthetic enzyme histidine decarboxylase by immunohistochemistry in paraffin sections of 12 biopsies of SCLC tumors. This finding was supported by immunoblotting and reverse transcription-polymerase chain reaction experiments using established SCLC cell lines, frozen and paraffin-embedded SCLC tumors. Moreover, we found histamine to be synthesized, stored, and released by cultured SCLC cells. Our novel observations may be useful for developing new diagnostic tools for this frequent and highly malignant tumor.

[Regulation of cytokine production by histamine through H2-receptor stimulation]

Histamine is a well known mediator of inflammation including the allergic reaction. Histamine has been suggested to be a immunomodulator. Recent studies revealed that induction of histidine decarboxylase occurs by the stimulation of several cytokines and LPS, suggesting an immunomodulatory role of the inducible histamine. Using human PBMC culture, it was demonstrated that histamine was a potent inducer of IL-18, IFN-gamma in human PBMC. Histamine did not induce the production of IL-12. The effects of histamine on cytokine production were mimicked by H2-selective agonists and inhibited by H2- but not by H1- and H3-antagonists, indicating the involvement of H2-receptors in histamine action. All effects of histamine were abolished by the presence of anti-IL-18 antibody or IL-1b-converting enzyme/caspase-1 inhibitor, indicating that histamine action is dependent on mature IL-18 secretion and that IL-18 production was present most upstream of the cytokine cascade triggered by histamine. Histamine is a very important modulator of Th1 cytokine production in PBMC and is quite unique in triggering the cytokine cascade without inducing IL-12 production.

Suppression of melanoma cell proliferation by histidine decarboxylase specific antisense oligonucleotides

Histidine decarboxylase (HDC) is expressed by the cells of melanoma, in which the histamine content tends to be relatively high. This study shows that elevated expression of HDC was found by western blot analysis of primary and metastatic melanoma tissue using a polyclonal HDC specific antibody. The specificity of anti-HDC antibody was confirmed by inhibition of HDC translation (i.e., immunopositivity) in melanoma cells by HDC-specific antisense oligonucleotide. Moreover, the decrease in proliferation caused by HDC antisense oligonucleotides indicates considerable functional relevance of histamine synthesis in melanoma growth and suggests a possible in situ application of specific antisense oligonucleotides for HDC in melanoma therapy.

Inhibition of effects of endogenously synthesized histamine disturbs in vitro human dendritic cell differentiation

Histamine, a principal mediator in various physiological and pathological cell functions is synthesized from L-histidine exclusively by histidine decarboxylase, an enzyme, which is expressed in many tissues of mammalian organism. Histamine plays a role in various cellular functions, including cell differentiation. The aim of this study was to determine the presence and to characterize the role of the endogenously produced histamine during in vitro dendritic cell (DC) differentiation induced by interleukin-4 (IL-4) and granulocyte-monocyte colony stimulating factor (GM-CSF). The changes in intracellular histamine content, biosynthesis and gene expression of histidine decarboxylase were investigated during this process. One also studied how histamine receptor antagonists and a histamine synthesis blocker influence the expression of differentiation antigens on the DC during in vitro maturation. During in vitro differentiation parallel culture incubations were performed by adding H1 receptor antagonist triprolidine, H2 receptor antagonist tiotidine, the tamoxifene derivate DPPE which blocks the intracellular binding of histamine, and an irreversible blocker of histidine decarboxylase, alpha-fluoromethyl histamine (alpha-FMH). The results show simultaneous increase in both histidine decarboxylase level and histamine content during differentiation of elutriated monocytes toward DC. Both blockade of de novo histamine production (by alpha-FMH) and inhibition of histamine binding (by H1 and H2 receptor antagonists, triprolidine and tiotidine, respectively) markedly decreased CD40 expression and that of CD45 from the 3rd day of treatment. DPPE by disturbing intracellular interaction of histamine with cytochrome P-450 moieties was able to decrease the expression of CD45, CD86, HLA-DR, CD33, CD40 and CD11c. Based on the data it is suggested that endogenous histamine is actively synthesized during cytokine-induced in vitro DC differentiation. The functional relevance and autocrine and paracrine action of endogenously produced histamine is supported by the data showing that inhibition of histamine synthesis by HDC, blocking of histamine binding by both 'extracellular' histamine receptors (by specific antagonists, triprolidine and tiotidine) and 'intracellular' antagonists (DPPE) disturb the differentiation of DC. This conclusion is supported by the fact, that by the inhibition of histamine acting in an autocrine/paracrine way, the expression pattern of differentiation markers on DC is markedly changed.

Biosynthesis of interleukin-6, an autocrine growth factor for melanoma, is regulated by melanoma-derived histamine

Interleukin-6 is an autocrine growth factor in advanced stage melanoma and biosynthesis of IL-6 is increased by histamine in various cell lines. In our study we analysed the direct relation of histamine and IL-6 synthesis in human melanoma cell lines. All melanoma cells contained IL-6 mRNA, but only metastatic melanoma cells secreted the IL-6 protein. The H1 histamine receptor antagonist triprolidine decreased gene expression and biosynthesis of IL-6, while other histamine receptor antagonists had no effect. These data indicate that endogenous histamine has a definite role in the regulation of local IL-6, suggesting that histamine and IL-6 could be part of autocrine growth regulation of the tumor.