Effect of cimetidine on survival after gastric cancer

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.

Cancer Metabolism as a Therapeutic Target and Review of Interventions

Cancer is amenable to low-cost treatments, given that it has a significant metabolic component, which can be affected through diet and lifestyle change at minimal cost. The Warburg hypothesis states that cancer cells have an altered cell metabolism towards anaerobic glycolysis. Given this metabolic reprogramming in cancer cells, it is possible to target cancers metabolically by depriving them of glucose. In addition to dietary and lifestyle modifications which work on tumors metabolically, there are a panoply of nutritional supplements and repurposed drugs associated with cancer prevention and better treatment outcomes. These interventions and their evidentiary basis are covered in the latter half of this review to guide future cancer treatment.

Cimetidine-Based Cationic Amphiphiles for In Vitro Gene Delivery Targetable to Colon Cancer

Cimetidine, a histamine-2 (H2) receptor antagonist, has been found to have anticancer properties against a number of cancer-type cells. In this report, we have demonstrated that cimetidine can acts as a hydrophilic domain in cationic lipids and targetable to the gastric system by carrying reporter genes and therapeutic genes through in vitro transfection. Two lipids, namely, Toc-Cim and Chol-Cim consisting cimetidine as the main head group and hydrophobic moieties as alpha-tocopherol or cholesterol, respectively, were designed and synthesized. 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is a well-known co-lipid employed to produce liposomes as uniform vesicles. The liposomes and lipoplexes were structurally and functionally evaluated for global surface charges and hydrodynamic diameters, and results found that both liposome and lipoplex size and surface charges are optimal to screen the transfection potentials. DNA-binding studies were analyzed as complete binding at all formulated N/P ratios. The liposomes and lipoplexes of both the lipids Toc-Cim and Chol-Cim show minimal cytotoxicity even though at higher concentrations. The results of the transfection experiments revealed that tocopherol-based cationic lipids (Toc-Cim) show finer transfection efficacy with optimized N/P ratios (2:1 and 4:1) in the colon cancer cell line. Toc-Cim lipoplexes show higher cellular uptake compare to Chol-Cim in the colon cancer cell line at 2:1 and 4:1 N/P ratios. Toc-Cim and Chol-Cim lipids showed highly compatible serum, examined up to 50% of the serum concentration. To evaluate the apoptotic cell death in CT-26 cells, exposed to Toc-Cim:p53 and Chol-Cim:p53 lipoplexes at 2:1 N/P ratios, superior results showed with Toc-Cim:p53. An effect of TP53 protein expression in CT-26 cell lines assayed by western blot, transfected with Toc-Cim:p53 and Chol-Cim:p53 lipoplexes, demonstrated the superior efficacy of Toc-Cim. All of the findings suggest that Toc-Cim lipid is relatively secure and is an effective transfection agent to colon cancer gene delivery.

Histamine in cancer immunology and immunotherapy. Current status and new perspectives

Cancer is the second leading cause of death globally and its incidence and mortality are rapidly increasing worldwide. The dynamic interaction of immune cells and tumor cells determines the clinical outcome of cancer. Immunotherapy comes to the forefront of cancer treatments, resulting in impressive and durable responses but only in a fraction of patients. Thus, understanding the characteristics and profiles of immune cells in the tumor microenvironment (TME) is a necessary step to move forward in the design of new immunomodulatory strategies that can boost the immune system to fight cancer. Histamine produces a complex and fine-tuned regulation of the phenotype and functions of the different immune cells, participating in multiple regulatory responses of the innate and adaptive immunity. Considering the important actions of histamine-producing immune cells in the TME, in this review we first address the most important immunomodulatory roles of histamine and histamine receptors in the context of cancer development and progression. In addition, this review highlights the current progress and foundational developments in the field of cancer immunotherapy in combination with histamine and pharmacological compounds targeting histamine receptors.

Cimetidine promotes STUB1-mediated degradation of tumoral FOXP3 by activating PI3K-Akt pathway in gastric cancer

Background

Previous studies have confirmed the antitumor effects of cimetidine, while the therapeutic targets and the mechanisms are not yet fully understood. We previously reported the protumoral role of endogenous FOXP3 in gastric cancer (GC), but whether cimetidine plays an antitumor role by targeting FOXP3 is still unknown.

Methods

A series of assays were used to examine the role of cimetidine on the malignant behaviors and the expression of endogenous FOXP3 in GC cells. The role of cimetidine on ligase E3-STUB1and the role of STUB1 on FOXP3 level were examined, with the signaling pathway involved in these processes also being explored.

Results

Cimetidine inhibited the malignant behaviors of GC cells, and led to the ubiquitination/degradation of FOXP3. Moreover, cimetidine promoted STUB1 expression, STUB1 knockdown rescued the decline of FOXP3 in cimetidine-treated GC cells, and reduced the turnover effect of cimetidine on GC cells, but had minimal effect in untreated cells. Immunoprecipitation (IP) assay confirmed the formation of the STUB1-FOXP3 complex in cimetidine-treated GC cells. Furthermore, Cimetidine promoted STUB1 expression by activating PI3K/Akt pathway, and the inhibition of PI3K/Akt pathway rescued the decline of FOXP3 by suppressing the upregulation of STUB1.

Conclusions

Cimetidine suppressed GC development by promoting STUB1-mediated ubiquitination/degradation of endogenous FOXP3 through the activation of the PI3K/Akt pathway.

Drug repurposing in oncology: Compounds, pathways, phenotypes and computational approaches for colorectal cancer

The strategy of using existing drugs originally developed for one disease to treat other indications has found success across medical fields. Such drug repurposing promises faster access of drugs to patients while reducing costs in the long and difficult process of drug development. However, the number of existing drugs and diseases, together with the heterogeneity of patients and diseases, notably including cancers, can make repurposing time consuming and inefficient. The key question we address is how to efficiently repurpose an existing drug to treat a given indication. As drug efficacy remains the main bottleneck for overall success, we discuss the need for machine-learning computational methods in combination with specific phenotypic studies along with mechanistic studies, chemical genetics and omics assays to successfully predict disease-drug pairs. Such a pipeline could be particularly important to cancer patients who face heterogeneous, recurrent and metastatic disease and need fast and personalized treatments. Here we focus on drug repurposing for colorectal cancer and describe selected therapeutics already repositioned for its prevention and/or treatment as well as potential candidates. We consider this review as a selective compilation of approaches and methodologies, and argue how, taken together, they could bring drug repurposing to the next level.

Repurposing cimetidine for cholangiocarcinoma: Antitumor effects in vitro and in vivo

Cimetidine is a histamine type-2 (H₂) receptor antagonist that has been demonstrated to have antitumor effects on various types of malignancy. However, its effect on cholangiocarcinoma (CCA), a chemotherapy-resistant bile duct tumor, has yet to be investigated. In the present study, the antitumor activity of cimetidine in vitro and in vivo was evaluated. A methylthiotetrazole assay revealed that the proliferation of certain CCA cell lines was inhibited by cimetidine, which induced the caspase-dependent apoptosis of CCA cells via suppression of the protein kinase B signaling pathway. Suppression of Akt phosphorylation, caspase-3, -8 and -9 activation, phosphotidylserine exposure determined by Annexin V binding assay and the presence of a sub-G1 population were demonstrated by western blotting and flow cytometry analysis. In a CCA xenograft mouse model cimetidine inhibited the growth of CCA cells without observable adverse effects. These results suggest that cimetidine has the potential to be an effective antitumor agent for the treatment of CCA.

Ranitidine modifies myeloid cell populations and inhibits breast tumor development and spread in mice

Histamine receptor 2 (H2) antagonists are widely used clinically for the control of gastrointestinal symptoms, but also impact immune function. They have been reported to reduce tumor growth in established colon and lung cancer models. Histamine has also been reported to modify populations of myeloid-derived suppressor cells (MDSCs). We have examined the impact of the widely used H2 antagonist ranitidine, on both myeloid cell populations and tumor development and spread, in three distinct models of breast cancer that highlight different stages of cancer progression. Oral ranitidine treatment significantly decreased the monocytic MDSC population in the spleen and bone marrow both alone and in the context of an orthotopic breast tumor model. H2 antagonists ranitidine and famotidine, but not H1 or H4 antagonists, significantly inhibited lung metastasis in the 4T1 model. In the E0771 model, ranitidine decreased primary tumor growth while omeprazole treatment had no impact on tumor development. Gemcitabine treatment prevented the tumor growth inhibition associated with ranitidine treatment. In keeping with ranitidine-induced changes in myeloid cell populations in non-tumor-bearing mice, ranitidine also delayed the onset of spontaneous tumor development, and decreased the number of tumors that developed in LKB1^−/−/NIC mice. These results indicate that ranitidine alters monocyte populations associated with MDSC activity, and subsequently impacts breast tumor development and outcome. Ranitidine has potential as an adjuvant therapy or preventative agent in breast cancer and provides a novel and safe approach to the long-term reduction of tumor-associated immune suppression.

Histamine type 2 receptor expression on peripheral blood regulatory lymphocytes in patients with allergic rhinitis treated with specific immunotherapy

BACKGROUND

Both histamine H1- and H2-receptors (H2R) were found on regulatory T (Treg) cells; however, there is a paucity of information regarding the role of H2R in Treg function. This study aimed to investigate the effects of natural allergen stimulation and specific immunotherapy (SIT) on H2R expression in Treg cells in patients with allergic rhinitis (AR).

METHODS

In this prospective, double-blind, placebo-controlled study 41 patients with AR were screened for 1 year and treated with SIT (n = 21) or placebo (n = 20) for the next 2 years. Fifteen healthy subjects were included as a control. Subsets of Treg cells that expressed H2R were assessed annually in the blood by flow cytometry: before, at the height of the pollen season, and after, at the end of the pollen season. In addition, total nasal symptom score, the use of rescue medication, and nasal eosinophilia were evaluated.

RESULTS

Treg cells of AR patients slightly up-regulate H2R out of the pollen season. Natural allergen stimulation results in prompt up-regulation of H2R within these cells. SIT significantly decreased the number of Treg cells with increased expression of H2R in the blood exclusively at the height of pollen season, which, however, had no impact on the expression of H2R in Treg cells. SIT improved significantly the symptom score, rescue medication use, and decreased nasal eosinophilia.

CONCLUSION

Natural pollen exposure results in up-regulation of H2R in Treg cells. Immunotherapy might transiently decrease the number of Treg-H2R(+) cells in the blood, which may be associated with their migration to the peripheral tissues. This study was part of the clinical trial registered in www.clinicaltrials.gov.

In silico modeling of the molecular interactions of antacid medication with the endothelium: novel therapeutic implications in head and neck carcinomas

Pathological acid reflux is a common event in patients afflicted with head and neck squamous cell carcinomas (HNSCCs), known to play a role in HNSCC etiology and contribute to complications after surgery or during radiation and chemotherapy. Antacid medications are commonly prescribed in HNSCC patients as part of their cancer treatment, and consist of two classes: histamine 2 receptor antagonist class (H2RA, with cimetidine as its prototypical drug) and proton pump inhibitors class (PPI, with omeprazole as its prototypical drug). Clinical evidence revealed a significant survival benefit of antacid usage in a large cohort of HNSCC patients treated in our Otolaryngology Department, with a median follow-up of over 5 years. Therefore, we postulate that one mechanism by which antacid intake enhances patient survival could involve modulation of tumor cell adhesion to endothelium, critical in the initiation of the metastatic dissemination. This study investigates the potential physical interactions between cimetidine and omeprazole with the endothelial E-selection (E-sel) and its ligand sialyl Lewis X (sLe(x)) using a molecular visualization energy-based program (AutoDock). Docking results were further analyzed with the PyMOL program, which allowed for measurements of the distances between the drugs and the closest interacting atoms or residues on E-sel and sLe(x) molecules. Our model predicts that omeprazole displays a stronger interaction with E-sel than cimetidine, as extrapolated from the calculated overall binding energies. However, the shorter distances existing between interacting atoms in the proposed E-sel/cimetidine complex are suggestive of more stable interactions. Neither antacid/E-sel complex overcame the stronger Autodock-calculated sLe(x)/E-sel interaction, suggesting competitive inhibition was not involved. This study provides the first in silico evidence of omeprazole and cimetidine ability to bind to adhesion molecules involved in tumor dissemination, underlining their therapeutic potential in the HNSCC clinical management.

Repurposing drugs in oncology (ReDO)-cimetidine as an anti-cancer agent

Cimetidine, the first H₂ receptor antagonist in widespread clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical and clinical studies for a number of different cancer types. These data are summarised and discussed in relation to a number of distinct mechanisms of action. Based on the evidence presented, it is proposed that cimetidine would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of cimetidine as an anti-cancer therapeutic is warranted. Furthermore, there is compelling evidence that cimetidine administration during the peri-operative period may provide a survival benefit in some cancers. A number of possible combinations with other drugs are discussed in the supplementary material accompanying this paper.

Prognostic molecular markers in head and neck squamous cell carcinoma in a New Zealand population: matrix metalloproteinase-2 and sialyl Lewis x antigen

OBJECTIVE

The survival rate for head and neck squamous cell carcinoma (HNSCC) is among the lowest of the major cancers and has not substantially improved in the past two decades. Tumours with similar histological features may have widely differing clinical outcomes and thus identification of prognostic and predictive biomarkers may be valuable for determining appropriate clinical management strategies. The objective of this study was to establish the prognostic significance of six molecular markers in HNSCC in a New Zealand population: matrix metalloproteinases 2 and 9 (MMP-2, MMP-9), tissue inhibitor of matrix metalloproteinase-1, sialyl Lewis antigens a and x (sLe(a) , sLe(x) ) and alpha B-crystallin.

METHODS

Retrospective review of 145 sequential HNSCC patients from a tertiary centre with minimum 3 years surveillance. Sections from formalin-fixed paraffin-embedded tumour blocks were immunostained for the molecular markers and scored. Cox regression modelling was used to adjust for potential confounding variables impacting on cancer survival.

RESULTS

Multivariate analysis for individual biomarkers, controlling for age, sex, tumour grade, N-stage, T-stage, tumour site, smoking history and alcohol use, revealed poorer survival with tumour expression of MMP-2 (hazard ratio = 1.98, 95% confidence interval: 1.11-3.52, P = 0.021) and sLe(x) (hazard ratio = 3.22, 95% confidence interval: 1.33-7.80, P = 0.010). A stepwise analysis showed that MMP-2 and sLe(x) were independently prognostic after covariate adjustment.

CONCLUSIONS

MMP-2 and sLe(x) were negative prognostic markers for survival in these HNSCC patients. This offers opportunities for clinical trials to reduce the risk of nodal and distant metastases through blocking tumour cell adhesion to endothelium.

Association between common genetic variant of HRH2 and gastric cancer risk

Histamine plays important physiological roles in the upper gastrointestinal tract and acts via the H2 receptor. The -1018 G>A (rs2067474) in an enhancer element of the promoter and non-synonymous rs79385261 (Asn46Thr) were identified in HRH2. We attempted to clarify the associations of these polymorphisms with gastric carcinogenesis. The study was performed in 321 patients with gastric cancer and 599 subjects with no evidence of gastric malignancies on upper gastroduodenal endoscopy. The genotypes were determined using a one-tube multiplex PCR-SSCP method. The degree of gastritis was assessed in 496 subjects and serum pepsinogen (PG) I/II levels were measured in 124 subjects without gastric cancer. The minor allele of Asn46Thr could not be detected. The frequencies of the -1018 A allele in the non-GC and GC groups were 13.5% and 8.26%, respectively (p=0.00077). Overall, -1018 GG homozygotes had an increased risk for developing gastric cancer (OR 1.68; 95% CI 1.17-2.42; p=0.0052), especially intestinal type cancer (OR 1.94; 95% CI 1.23-3.08; p=0.0047). In subjects aged >60 years, the adjusted risk for gastric cancer among individuals who were -1018 GG homozygotes was 1.87 (range 1.19-2.93; p=0.0065) compared with A carriers. In the gastric cancer cases located in the antrum and at comparative advanced stage, -1018 GG homozygosity was a significantly increased risk factor. In subjects >60 years, the metaplasia score was significantly higher in -1018 GG homozygotes than A carriers. Both atrophy and metaplasia scores were significantly increased with age only in -1018 GG homozygotes. The PG I/II ratio was significantly decreased in H. pylori positive GG homozygotes than negative GG homozygotes and positive A carriers. Our results suggest that -1018 GG homozygosity of HRH2 may be associated with the severity of gastric mucosal atrophy. This genotype has an increased risk for the subsequent development of gastric cancer, especially intestinal type, at advanced age.

Safety of the long-term use of proton pump inhibitors

The proton pump inhibitors (PPIs) as a class are remarkably safe and effective for persons with peptic ulcer disorders. Serious adverse events are extremely rare for PPIs, with case reports of interstitial nephritis with omeprazole, hepatitis with omeprazole and lansoprazole, and disputed visual disturbances with pantoprazole and omeprazole. PPI use is associated with the development of fundic gland polyps (FGP); stopping PPIs is associated with regression of FGP. In the absence of Helicobacter pylori infection, the long-term use of PPIs has not been convincingly proven to cause or be associated with the progression of pre-existing chronic gastritis or gastric atrophy or intestinal metaplasia. Mild/modest hypergastrinemia is a physiological response to the reduction in gastric acid secretion due to any cause. The long-term use of PPIs has not been convincingly proven to cause enterochromaffin-like cell hyperplasia or carcinoid tumors. PPIs increase the risk of community acquired pneumonia, but not of hospital acquired (nosocomial) pneumonia. There is no data to support particular care in prescribing PPI therapy due to concerns about risk of hip fracture with the long-term use of PPIs. Long-term use of PPIs does not lead to vitamin B12 deficiencies, except possibly in the elderly, or in persons with Zollinger-Ellison Syndrome who are on high doses of PPI for prolonged periods of time. There is no convincingly proven data that PPIs increase the risk of Clostridium difficile-associated diarrhea in persons in the community. The discontinuation of PPIs may result in rebound symptoms requiring further and even continuous PPI use for suppression of symptoms. As with all medications, the key is to use PPIs only when clearly indicated, and to reassess continued use so that long-term therapy is used judiciously. Thus, in summary, the PPIs are a safe class of medications to use long-term in persons in whom there is a clear need for the maintenance of extensive acid inhibition.

Cimetidine inhibits salivary gland tumor cell adhesion to neural cells and induces apoptosis by blocking NCAM expression

Background

Cimetidine, a histamine type-2 receptor antagonist, has been reported to inhibit the growth of glandular tumors such as colorectal cancer, however the mechanism of action underlying this effect is unknown. Adenoid cystic carcinoma is well known as a malignant salivary gland tumor which preferentially invades neural tissues. We demonstrated previously that human salivary gland tumor (HSG) cells spontaneously express neural cell adhesion molecule (NCAM), that HSG cell proliferation may be controlled via a homophilic (NCAM-NCAM) binding mechanism and that NCAM may be associated with perineural invasion by malignant salivary gland tumors. We further demonstrated that cimetidine inhibited NCAM expression and induced apoptosis in HSG cells. Here, we investigated the effects of cimetidine on growth and perineural/neural invasion of salivary gland tumor cells.

Methods

In this study, we have examined the effect of cimetidine on cancer cell adhesion to neural cells in vitro, one of the critical steps of cancer invasion and metastasis. We have also used an in vivo carcinogenesis model to confirm the effect of cimetidine.

Results

We have demonstrated for the first time that cimetidine can block the adhesion of HSG cells to neural cell monolayers and that it can also induce significant apoptosis in the tumor mass in a nude mouse model. We also demonstrated that these apoptotic effects of cimetidine might occur through down-regulation of the cell surface expression of NCAM on HSG cells. Cimetidine-mediated down-regulation of NCAM involved suppression of the nuclear translocation of NF-κB, a transcriptional activator of NCAM gene expression.

Conclusion

These findings suggest that growth and perineural/neural invasion of salivary gland tumors can be blocked by administration of cimetidine via induction of apoptosis and in which NCAM plays a role.

Histamine metabolism influences blood vessel branching in zebrafish reg6 mutants

Background

Vascular branching morphogenesis is responsible for the extension of blood vessels into growing tissues, a process crucial for organogenesis. However, the genetic mechanism for vessel branching is largely unknown. Zebrafish reg6 is a temperature-sensitive mutation exhibiting defects in blood vessel branching which results in the formation of swollen vessel lumina during capillary plexus formation.

Results

We performed a screening for chemical suppressors of reg6 and identified SKF91488, an inhibitor of histamine methyltransferase (HMT), that can rescue the reg6 vessel branching defects in a dose-dependent manner. Inhibition of HMT by SKF91488 presumably blocks histamine degradation, thus causing histamine accumulation. Consistent with this idea, we found that a high level of histamine also showed significant suppression of reg6 vessel phenotypes. Interestingly, when reg6 adults that had already developed swollen vessel lumina in regenerating fins were treated with histamine or SKF91488, either treatment significantly reduced the number of swollen vessels within 12 h, suggesting a rapid and constant influence of histamine on blood vessel branching. Furthermore, the expression of HMT was significantly elevated in reg6 regenerating fins. Conversely, lowering histamine by administering urocanic acid, a histidine decarboxylase inhibitor, enhanced the reg6 phenotypes. Finally, we identified that the transcription factor, egr-1 (early growth response factor 1), was closely associated with the reg6 phenotype and chemical treatments.

Conclusion

Taken together, our results suggest that blood vessel branching is influenced by histamine metabolism, possibly through regulating the expression of the egr-1 transcription factor.

Effect of cimetidine on the proliferation and apoptosis of human gastric cancer cell line SGC-7901

AIM: To investigate the effect of cimetidine on the proliferation and apoptosis of human gastric cancer cell line SGC-7901 and its related mechanism.

METHODS: Human gastric cancer cell SGC-7901 was cultivated by routine method, then treated with different concentrations of cimetidine. The proliferation of SGC-7901 cells was examined by MTT assay, and the cell cycle and apoptosis were detected by flow cytometry. After Hoechst33258 staining, the morphologic changes of SGC-7901 cells were observed under fluorescence microscope, and the ultrastructure of the cells was investigated by transmission electron microscopy. The levels of Bcl-2 and Bax protein expression were detected by Western blot analysis.

RESULTS: After dealing with cimetidine (0.5, 1, 2.5, 5, 10 mmol/L) for 24 and 48 hours, we found that cimetidine significantly inhibited the proliferation of SGC-7901 cells in a time- and concentration-dependent manner (24 h: 0.705 ± 0.018, 0.560 ± 0.038, 0.408 ± 0.029, 0.276 ± 0.042, 0.205 ± 0.031 vs 0.803 ± 0.012, P < 0.05; 48 h: 0.902 ± 0.024, 0.671 ± 0.015, 0.420 ± 0.030, 0.180 ± 0.037, 0.117 ± 0.021 vs 1.079 ± 0.040, P < 0.05), whereas there was no significant cytotoxic effect as the concentration was below 0.25 mmol/L. cimetidine at the concentrations of 0.5, 1, 2.5, 5, and 10 mmol/L induced typical apoptosis of SGC-7901 cells, and flow cytometry showed an apoptosis peak. The percentage of G0/G1-phase cells was significantly increased (60.83% ± 2.27%, 67.21% ± 1.18%, 75.15% ± 4.01%, 81.88% ± 3.10%, 86.99% ± 1.43% vs 50.28% ± 1.97%, P < 0.05). The expression of Bcl-2 protein was decreased while that of Bax protein was increased following cimetidine treatment.

CONCLUSION: Cimetidine may inhibit the proliferation of SGC-7901 cells through inducing cell apoptosis and cell cycle arrest.

Effect of Pre-Operative Short Course Famotidine on Tumor Infiltrating Lymphocytes in Colorectal Cancer: A Double Blind, Placebo Controlled, Prospective Randomized Study

BACKGROUND

Pilot studies have shown that histamine H2 receptor antagonists augment the natural immunity against cancer in colorectal and gastric cancer by enhancing lymphocytic infiltration in the tumors. However, a study of adjuvant ranitidine failed to show a significant benefit in colorectal cancer, possibly because of the immunosuppression exerted by blood transfusion and post-operative infections. The pre-operative use of H2 receptor antagonists may therefore be of greater benefit. Except for a pilot study using cimetidine, there are no trials that have evaluated the effect of pre-operative H2 receptor antagonists on tumor infiltrating lymphocytes in colorectal cancer.

OBJECTIVE

To evaluate the efficacy of famotidine in augmenting tumor infiltrating lymphocytes in colorectal cancer.

STUDY DESIGN

Double blind, placebo controlled, prospective randomized study.

METHODS

Twenty-three patients with resectable colorectal cancer were randomized to receive famotidine (n = 11) or placebo (n = 12). Famotidine was given for 1 week pre-operatively in a dose of 40 mg per day p.o. After resection, the specimens were analyzed histologically for lymphocytic infiltration by a pathologist blinded to the two groups. Lymphocytic infiltration more than 50 cells per high power field, involving more than 50% of the tumor-normal tissue interface was considered significant.

RESULTS

The two groups were comparable for age, gender, pre-operative carcino embryonic antigen (CEA) levels and pathological stage. Significant lymphocytic infiltration was seen in 63.6% (7 of 11) patients in the study group compared to only 8.5% (1 of 12) patients in the placebo group (P = 0.005). Despite fewer recurrences and a longer survival in the study group, the difference was not significant.

CONCLUSION

This study shows that pre-operative famotidine may significantly enhance lymphocytic infiltration in colorectal cancer and may have potential for use as an anticancer agent in colorectal cancer.

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.

Synergistic inhibitory effects of gastrin and histamine receptor antagonists on Helicobacter-induced gastric cancer

BACKGROUND & AIMS

Apart from its importance as an acid secretogogue, the role of histamine as a downstream target of gastrin has not been fully explored. Previous studies have shown that the combination of hypergastrinemia and Helicobacter infection resulted in accelerated gastric cancer in mice. We used this model to examine the role of cholecystokinin 2 (CCK2)/gastrin receptor and histamine H2-receptor signaling in the development of gastric atrophy and cancer.

METHODS

Male hypergastrinemic mice (INS-GAS mice) were infected with Helicobacter felis and given the CCK2/gastrin receptor antagonist YF476 and/or the histamine H2-receptor antagonist loxtidine for 3 or 6 months. In addition, mice were treated with omeprazole alone or in combination with either YF476 or loxtidine for 3 months.

RESULTS

Mice treated with YF476 or loxtidine alone showed partial suppression of both gastric acid secretion and progression to neoplasia. The combination of YF476 plus loxtidine treatment resulted in nearly complete inhibition of both parameters. YF476 and/or loxtidine treatment did not alter the overall level of H. felis colonization but did result in significant down-regulation of the growth factors regenerating gene I and amphiregulin. Loxtidine treatment, with or without YF476, induced a mild shift in T-helper cell polarization. In contrast, omeprazole treatment resulted in mild progression of gastric hyperplasia/dysplasia, which was ameliorated by the addition of YF476 or loxtidine.

CONCLUSIONS

The combination of CCK2/gastrin- and histamine H2-receptor antagonists has synergistic inhibitory effects on development of gastric atrophy and cancer in H. felis/INS-GAS mice, while the proton pump inhibitor showed no such effects. These results support an important role for the gastrin-histamine axis in Helicobacter-induced gastric carcinogenesis.

Cimetidine inhibits angiogenesis and suppresses tumor growth

Cimetidine, a histamine type-2 receptor antagonist, has been reported to improve survival of patients with cancers. However, the exact mechanisms by which cimetidine suppresses development of cancers remain to be elucidated. Solid tumors require neovascularization for their growth. Here, we investigated the effects of cimetidine on tumor growth and angiogenesis. Syngeneic colon cancer cells, CMT93 cells, were inoculated into the subcutaneous space of C57BL/6 mice. Mice were treated with either saline or cimetidine. Tumor size was measured everyday and angiogenesis was evaluated histologically. Cimetidine markedly suppressed tumor growth with reduced neovascularization in the tumor. Cimetidine had no effect on proliferation of CMT93 cells in vitro. Vascular endothelial growth factor production by cancer cells was not affected by cimetidine, while vascular-like tube formation by endothelial cells in vitro was significantly impaired in the presence of cimetidine. Our findings suggest that cimetidine suppresses tumor growth, at least in part, by inhibiting tumor-associated angiogenesis.

Roxatidine- and cimetidine-induced angiogenesis inhibition suppresses growth of colon cancer implants in syngeneic mice

Cimetidine is known to suppress the growth of several tumors, including gastrointestinal cancer, in humans and animals. Nonetheless, whether other histamine H(2)-receptor antagonists exert such tumor suppressive effects remains unclear. The effect of roxatidine acetate hydrochloride (roxatidine), an H(2)-receptor antagonist, on the growth of colon cancer implanted in mice was examined and compared with that of cimetidine. Drugs were orally delivered for 26 - 29 days beginning before or after implantation of syngeneic colon cancer (Colon 38) in C57BL/6 mice. Tumor volume was determined throughout and histochemical analysis was also performed. Tumor tissue and serum vascular endothelial growth factor (VEGF) levels were measured. In vitro cell growth was assessed by the MTT assay. Both roxatidine and cimetidine significantly suppressed the growth of Colon 38 tumor implants. Histologic analysis revealed that such antagonists markedly increased necrotic areas and decreased the density of microvessels in tumor tissue. Both H(2)-receptor antagonists suppressed VEGF levels in tumor tissue and significantly decreased serum VEGF levels in Colon 38-bearing mice. Such drugs, however, failed to suppress in vitro growth of the cell line. In conclusion, both roxatidine and cimetidine were found to exert suppressive effects on the growth of colon cancer implants in mice by inhibiting angiogenesis via reducing VEGF expression.

The histamine H2-receptor antagonist, cimetidine, inhibits the articular osteopenia in rats with adjuvant-induced arthritis by suppressing the osteoclast differentiation induced by histamine

The effects of cimetidine on rat adjuvant arthritis (AA) and rat osteoclast differentiation were studied. For the in vivo experiments, AA was induced by injections of Mycobacterium tuberculosis H37RA either subcutaneously into the base of the tail or into the right hind paw. The osteoclast differentiation was assessed by estimating the number of tartrate-resistant acid phosphatase-positive multinuclear cells in the bone marrow culture. Cimetidine, at the dose of 25 mg/kg body weight, reduced the paw swelling by 70% (P<0.01). Cimetidine, at 10 microM concentration, inhibited 1,25-dihydroxyvitamin D(3) (1,25[OH](2)D(3)) and histamine mediated osteoclast differentiations by 40% (P<0.01) and 60% (P<0.001), respectively. Dimaprit, at 0.3 microM, stimulated the cell differentiation by 100% (P<0.01). Mepyramine reduced osteoclast differentiation, but the reduction was not statistically significant. Measurements of bone mineral density of the femur indicated that 5 mg/kg of cimetidine treated animals had 30% (P<0.01) higher mineral density in comparison with that of the AA control group that received no cimetidine. These results suggest that histamine is a potent inducer of osteoclast differentiation, at least in part, through the histamine H(2)-receptor, and cimetidine has a preventive effect on articular destruction and accompanying inflammation in arthritic rats. These observations may provide critical insights into the pathogenesis of the bone pathology seen in patients with RA.

Ranitidine as adjuvant treatment in colorectal cancer

BACKGROUND

Results from short-term studies of histamine type 2 (H2) receptor antagonists on survival of patients with solid tumours are debatable. In this study the efficacy of the H2-receptor antagonist ranitidine on long-term survival of patients with colorectal cancer was evaluated.

METHODS

Patients scheduled for elective resection of primary tumours were consecutively included in a randomized double-blind placebo-controlled clinical study designed to evaluate the effect of ranitidine on survival. Before skin incision ranitidine 100 mg or placebo was given intravenously twice daily followed by oral ranitidine 150 mg or placebo twice daily for 5 years. Adjuvant cytotoxic or radiation therapy was not given. An observer-blinded interim analysis performed after 40 months showed that there was no effect of ranitidine on overall survival, and the study was discontinued in accordance with the protocol. The patient cohort has been followed continuously without loss of any patient, and a final statistical analysis was performed on an intention-to-treat basis after more than 5 years; this included a subgroup analysis of perioperative blood transfusion and postoperative infectious complications.

RESULTS

The median observation period of the 740 patients included was 6.8 (range 5.4-7.9) years. A univariate analysis of all 740 patients and of the subgroup of 560 who underwent curative resection showed no significant effect of ranitidine on survival. Furthermore, ranitidine had no survival benefit in curatively resected patients who received a perioperative blood transfusion (n = 358), but it improved the survival of non-transfused patients (n = 202; hazard ratio (HR) 0.6 (95 per cent confidence interval (c.i.) 0.4 to 0.9), P = 0.02) and of non-transfused patients who did not develop postoperative infectious complications (n = 170; HR 0.6 (95 per cent c.i. 0.4 to 0.9), P = 0.01). In multivariate analysis of patients who had a curative resection, including Dukes' stage, age, gender, tumour location, blood transfusion, postoperative infectious complications and treatment, ranitidine still had an independent, beneficial effect on survival (HR 0.6 (95 per cent c.i. 0.4 to 1.0), P = 0.04) within the subgroup of patients who did not receive perioperative blood transfusion and did not develop postoperative infectious complications.

CONCLUSION

Ranitidine may prolong the survival of patients who undergo curative resection of colorectal cancer and who do not receive perioperative blood transfusion and do not develop postoperative infectious complications.

Pd(II)- and Pt(II)-cimetidine complexes. Crystal structure of trans-[Pt(N,S-cimetidine)(2)]Cl(2)(*)12H(2)O

The influence of cimetidine on patients under cisplatin treatment for cancer is controversial. It has moderate or no effects on several types of cancer and its effects on the nephrotoxicity induced by cisplatin are uncertain. To examine the binding properties and antiproliferative effects of the known anticancer noble metals, cimetidine (cim) was complexed to platinum(II) and palladium(II). The crystal structure of the Pt-cim compound shows two molecules of cimetidine coordinated to the metal through thioether sulfur and imidazolic nitrogen whereas spectroscopic studies in solution for Pd-cim reveal that the ratio of the metal to cimetidine is 1:1 with identical coordination environments. To determine the antitumor activity of the drugs, the interaction of the metallic complexes and free cimetidine with DNA was assessed. Their cytotoxic activity was compared with that of cisplatin.

Cimetidine modulates the antigen presenting capacity of dendritic cells from colorectal cancer patients

Cimetidine, a H(2) receptor antagonist, has been reported to improve survival in gastrointestinal cancer patients. These effects have largely been attributed to the enhancing effects of cimetidine on the host's antitumour cell-mediated immune response, such as inhibition of suppressor T lymphocyte activity, stimulation of natural killer cell activity and increase of interleukin-2 production from helper T lymphocytes. We conducted an in vitro study on the effects of cimetidine on differentiation and antigen presenting capacity of monocyte-derived dendritic cells from advanced colorectal cancer patients and normal controls. As a result, an investigation of expression of surface molecules associated with dendritic cells by flow cytometric analyses showed that cimetidine had no enhancing effect on differentiation of dendritic cells from cancer patients and normal controls. An investigation of [(3)H]thymidine incorporation by allogeneic mixed lymphocyte reactions revealed that cimetidine increased the antigen presenting capacity of dendritic cells from both materials. Moreover, a higher antigen presenting capacity was observed in advanced cancer patients compared to normal controls. These effects might be mediated via specific action of cimetidine and not via H(2) receptors because famotidine did not show similar effects. Our results suggest that cimetidine may enhance the host's antitumour cell-mediated immunity by improving the suppressed dendritic cells function of advanced cancer patients.

A review of epidemiological studies on cancer in relation to the use of anti-ulcer drugs

H2-receptor antagonists have been widely used since the late 1970s for the treatment of gastrointestinal ulcers and other benign conditions of the stomach, oesophagus and duodenum. Several case reports suggested that long-term therapy with H2-receptor antagonists, mainly cimetidine and ranitidine, might increase the risk of gastric cancer. After early case reports, at least six analytical epidemiological studies (two cohort and four case-control) were published, including a total of about 1000 cases of gastric cancer. The relative risks (RR) were systematically and substantially elevated in the first year since starting H2-receptor antagonist use, and levelled off in the following years. Some excess risk was still apparent during the first 5 years of drug use, probably due to incorrect diagnosis and treatment of pre-existing neoplastic gastric lesions, but the estimated RR was not above unity for > or = 10 years since starting drug treatment in the two studies including information on long-term use. The findings of analytical epidemiological studies are thus consistent with the absence of a causal association between H2-receptor antagonist use and gastric cancer risk. Data on oesophageal and colorectal cancer do not support a relevant relation between cimetidine use and the risk of these neoplasms. With reference to total cancer mortality, in a Danish cohort study, for males the RR was 1.9 in the first year, and 1.4 in the first 5 years; corresponding values for females were 1.7 and 1.5. In a British cohort study, the RR was 3.4 in the first year, and 1.3 in the years 2-10. The excess risk in the first year was essentially due to gastric cancer. Post-marketing surveillance data for omeprazole and other proton pump inhibitors are much scantier than for H2-receptor antagonists, particularly on long-term use.

Cimetidine increases survival of colorectal cancer patients with high levels of sialyl Lewis-X and sialyl Lewis-A epitope expression on tumour cells

Cimetidine has been shown to have beneficial effects in colorectal cancer patients. In this study, a total of 64 colorectal cancer patients who received curative operation were examined for the effects of cimetidine treatment on survival and recurrence. The cimetidine group was given 800 mg day(-1) of cimetidine orally together with 200 mg day(-1) of 5-fluorouracil, while the control group received 5-fluorouracil alone. The treatment was initiated 2 weeks after the operation and terminated after 1 year. Robust beneficial effects of cimetidine were noted: the 10-year survival rate of the cimetidine group was 84.6% whereas that of control group was 49.8% (P<0.0001). According to our previous observations that cimetidine blocked the expression of E-selectin on vascular endothelium and inhibited the adhesion of cancer cells to the endothelium, we have further stratified the patients according to the expression levels of sialyl Lewis antigens X (sL(x)) and A (sL(a)). We found that cimetidine treatment was particularly effective in patients whose tumour had higher sL(x) and sL(a) antigen levels. For example, the 10-year cumulative survival rate of the cimetidine group with higher CSLEX staining, recognizing sL(x), of tumours was 95.5%, whereas that of control group was 35.1% (P=0.0001). In contrast, in the group of patients with no or low levels CSLEX staining, cimetidine did not show significant beneficial effect (the 10-year survival rate of the cimetidine group was 70.0% and that of control group was 85.7% (P=n.s.)). These results clearly indicate that cimetidine treatment dramatically improved survival in colorectal cancer patients with tumour cells expressing high levels of sL(x) and sL(a).

Cimetidine in colorectal cancer--are the effects immunological or adhesion-mediated?

British Journal of Cancer (2002) 86, 159–160. DOI: 10.1038/sj/bjc/6600097www.bjcancer.com

© 2002 The Cancer Research Campaign

Effect of cimetidine on intratumoral cytokine expression in an experimental tumor

To evaluate the immunomodulatory effects of histamine in vivo, we analyzed an experimental syngenic tumor model using a colon adenocarcinoma cell line, CT-26, in Balb/c mice. In this model, distinct tumor growth was observed around 6 days after inoculation. Daily administration of cimetidine (0.12 mg/kg/day) significantly suppressed the increases in tumor volume and weight. On day 6 and day 7, histidine decarboxylase (HDC) activity was markedly increased. To examine the alterations in the local immune system, the cytokine expressions in the tumor tissue were measured by ribonuclease protection assay. The cytokine expression levels such as lymphotoxin-beta, tumor necrosis factor-alpha, interferon-gamma, interleukin-10, and interleukin-15 were considerably lower in tissues on day 14 than those on day 6. These decreased expressions were all restored by cimetidine. These results indicated that the effects of cimetidine on tumor growth in this model might be mediated by restoration of the decreased local cytokine expression, which exerts antitumoral effects.

Histidine decarboxylase expression in human melanoma

Histamine has been implicated as one of the mediators involved in regulation of proliferation in both normal and neoplastic tissues. Histidine decarboxylase, the only enzyme that catalyzes the formation of histamine from L-histidine, is an essential regulator of histamine levels. In this study, we investigated the gene and protein expression of histidine decarboxylase in melanoma. Reverse transcriptase polymerase chain reaction and in situ hybridization studies of WM-35, WM-983/B, HT-168, and M1 human melanoma cell lines both resulted in positive signals for histidine decarboxylase messenger RNA. A polyclonal chicken antibody was developed against human histidine decarboxylase and protein expression was confirmed by western blot analysis of the cell lysates, revealing a predominant immunoreactive band at approximately 54 kDa corresponding to monomeric histidine decarboxylase. Protein expression of histidine decarboxylase was also shown by flow cytometric analysis and strong punctate cytoplasmic staining of melanoma cell lines. Moreover, both primary and metastatic human melanoma tissues were brightly stained for histidine decarboxylase. When compared with the very weak or no reactions on cultivated human melanocytes both western blot and immunohistochemical studies showed much stronger histidine decarboxylase expression in melanoma cells. These findings suggest that expression of histidine decarboxylase is elevated in human melanoma.

Immunomodulation therapy in colorectal carcinoma

There has been much progress in the understanding of the relationship between the immune system and colorectal cancer. This has led to the use of immunomodulatory therapy in the adjuvant and palliative treatment of the condition. Although attempts at the use of non-specific immunomodulation with agents such as levamisole, cimetidine, alpha interferon and Bacillus Calmette-Guerin (BCG) have not produced significant clinical benefits when tested in randomized trials in both the adjuvant setting and for metastatic disease, promising results are being obtained with more specific therapy. Edrecolomab [corrected], a murine monoclonal antibody targeting the 17-1A antigen on malignant colorectal cells has produced a reduction in relapse and mortality rates when used as adjuvant treatment following surgery for Dukes' C colon cancer. Active specific therapy with autologous tumour vaccine administered with BCG has produced similar benefits in Dukes' B cancer. Both 3H1 anti-idiotypic antibody against carcinoembryonic antigen and 105AD7 antibody to gp72 glycoprotein have demonstrated in-vitro and in-vivo immune activation against tumour. Non-randomized studies postulate prolongation of survival using these antibodies in advanced disease. These agents are all currently being tested in randomized studies powered to detect meaningful survival differences and clinical benefit. Immune therapy offers the potential of low toxicity therapy in colorectal cancer and may have a role as an adjunct to conventional chemotherapy.

H2-antagonists in the treatment of colon and breast cancer

Several clinical trials have now been carried out with histamine type 2 receptor antagonists in cancer patients often as an adjunct to surgical resection of the primary tumour While promising results have been obtained in some groups of patients with gastrointestinal cancer, with increased survival and evidence of increased immunological recognition of tumour, results are less encouraging for breast cancer. This may be due to differences in the levels of histamine or the role of histamine in growth of these different tumour types.

Adjuvant histamine in cancer immunotherapy

Interleukin-2 (IL-2) is an effective activator of lymphocytes with anti-neoplastic properties such as T-cells or natural killer cells, and this property of IL-2 has formed the basis for its widespread used as an immunotherapeutic agent in human neoplastic disease. In recent years, IL-2 therapy for solid neoplastic diseases and hematopoietic cancers has been supplemented with histamine dihydrochloride with the aim of counteracting immunosuppressive signals from monocytes/macrophages. Here we review the preclinical basis for the use of histamine as an adjunct to IL-2 in cancer immunotherapy.

Prospective, double-blind, placebo-controlled randomized trial of cimetidine in gastric cancer. British Stomach Cancer Group

Cimetidine is thought to inhibit suppressor T-lymphocyte function and preliminary evidence from a randomized trial indicated that it might prolong survival for patients with operable and inoperable gastric cancer. The British Stomach Cancer Group conducted a randomized, double-blind, placebo-controlled trial examining the effects of cimetidine (400 mg or 800 mg twice a day) on the survival of patients with early (stages I, II and III: n = 229) and advanced (stages IVa and IVb: n = 201) gastric cancer. The primary end point was death. A total of 442 patients were randomized by 59 consultants in 39 hospitals between February 1990 and March 1995. Log-rank survival analysis was used to assess differences between the groups. Three hundred and forty patients died during the study: 166 (49%) in the cimetidine treatment groups and 174 (51%) in the placebo groups. Median survival for patients receiving cimetidine was 13 months (95% confidence interval (CI) 9-16 months) and 11 months in the placebo arm (95% CI 9-14 months). There was no significant difference in survival between the two treatment groups (P = 0.42) or between different doses of cimetidine tablets (P = 0.46). Five-year survival of those patients randomized to cimetidine was 21% compared to 18% for those patients randomized to placebo. Cimetidine at a dose of 400 mg or 800 mg twice a day does not have a significant influence on the survival of patients with gastric cancer compared to placebo.

Cimetidine reduces impairment of cellular immunity after cardiac operations with cardiopulmonary bypass

OBJECTIVE

Depressive effects of cardiopulmonary bypass on cell-mediated immune responses may lead to postoperative infectious complications. We previously reported that cimetidine reduced postbypass depression of the cytotoxic activity of natural killer cells. This study evaluated cimetidine as an agent to preserve cellular immunity after cardiac operations.

METHODS

In a prospective randomized study, 20 patients were divided into two groups of equal size. Cimetidine-group patients received 400 mg of cimetidine intravenously before bypass and a 33 mg/hr intravenous infusion of cimetidine after the operation, continuing until the fifth postoperative day. Control-group patients received conventional perioperative therapy. Lymphocyte subsets, natural killer cell activity, percentage of CD56+CD16+ (percentage of natural killer cells), and percentage of CD11b+CD8+ (percentage of suppressor T lymphocytes) were measured perioperatively.

RESULTS

Although temporary postoperative reductions in percentages of CD3+, CD4+, and CD56+CD16+ cells were observed in both groups, CD8+ percentages on postoperative day 1 and CD11b+CD8+ percentages on postoperative days 1 and 3 in the cimetidine group were significantly lower compared with those in the control group (p = 0.01,p = 0.004, andp = 0.02, respectively). Temporary postoperative reduction of natural killer cell activity was also observed in both groups, but the natural killer cell activity on postoperative day 1 in the cimetidine group (17.1%) was significantly higher (p = 0.02) than that in the control group (8.20%).

CONCLUSIONS

Cimetidine counteracts depressive effects of cardiopulmonary bypass on cell-mediated immunity and may possibly reduce postoperative susceptibility to infection.

Histamine in human breast cancer

BACKGROUND

Histamine inhibits lymphocyte function in vitro at concentrations of greater than 10(-6) mol/l. The aim of this study was to determine whether histamine concentrations in breast cancers were sufficient to produce an immunological effect.

METHODS

Tumour and adjacent normal breast content of histamine was measured using a radioenzymatic assay in 29 patients having surgery for breast cancer.

RESULTS

The median content of histamine in breast cancer tissue was 5.4 (range 0.9-27.3) microg/g (median concentration 4.5 x 10(-5) mol/l), and was significantly greater than that in adjacent breast tissue (P = 0.007).

CONCLUSION

The concentration of histamine in breast cancer was sufficient to inhibit lymphocyte function and could be locally immunosuppressive.

Activation of the human histamine H2 receptor is linked to cell proliferation and c-fos gene transcription

We examined whether histamine could regulate cell proliferation and expression of the early response gene c-fos in HEK-293 cells stably transfected with the human H2 receptor (HEK-H2). Histamine stimulated [3H]thymidine incorporation [50% effective concentration (EC50) = 3.6 x 10(-6) M] in HEK-H2 cells in a cimetidine-sensitive manner and increased c-fos mRNA in a time-dependent fashion, reaching maximal induction after 30 min. Histamine induced luciferase activity in HEK-H2 cells transiently transfected with a construct containing the luciferase reporter gene (Luc) coupled to the serum response element (SRE) of the c-fos gene promoter (EC50 = 1.5 x 10(-6) M) or a plasmid containing the SRE core fragment (bases -320 to -298). The protein kinase C (PKC) inhibitor staurosporine and long-term pretreatment of HEK cells with phorbol ester inhibited the effect of histamine on PKC activation, SRE-Luc activity, and [3H]thymidine incorporation. We have demonstrated that activation of the human H2 receptor can lead to induction of c-fos gene transcription and cell proliferation through a PKC-dependent mechanism.

Novel insights into histamine H2 receptor biology

Histamine exerts multiple biological actions through one of three receptor subtypes (H1, H2, and H3). This review focuses on new developments regarding the structure and function of the H2 receptor. In addition to the important role this receptor plays in stimulating gastric acid secretion, recent studies have demonstrated that it is also involved in regulating gastrointestinal motility and intestinal secretion. The potential role of the H2 receptor in regulating cell growth and differentiation has also been added to the list of actions this biogenic amine may exert in both normal and transformed tissues. Molecular cloning of the gene indicates that it has the structural characteristics of a heptahelical G protein-linked receptor. Site-directed mutagenesis studies of this receptor reveal the presence of key amino acids within the third and fifth transmembrane domains that are critical for ligand recognition. Molecular approaches have also shed light on the structural components of the H2 receptor important in regulating desensitization and internalization. Although the H2 receptor was classically thought to couple to the adenylate cyclase pathway, recent work with the cloned receptor indicates that it can also activate the phosphoinositide signaling cascade through an independent G protein-dependent mechanism. The novel observation that histamine may stimulate c-fos gene expression lends further support to the possible role of this receptor in regulating cell growth and differentiation.