"Immunoregulatory effects of cimetidine: inhibition of suppressor cell effector function in vivo"

Pathophysiological Roles of Histamine Receptors in Cancer Progression: Implications and Perspectives as Potential Molecular Targets

High levels of histamine and histamine receptors (HRs), including H1R~H4R, are found in many different types of tumor cells and cells in the tumor microenvironment, suggesting their involvement in tumor progression. This review summarizes the latest evidence demonstrating the pathophysiological roles of histamine and its cognate receptors in cancer biology. We also discuss the novel therapeutic approaches of selective HR ligands and their potential prognostic values in cancer treatment. Briefly, histamine is highly implicated in cancer development, growth, and metastasis through interactions with distinct HRs. It also regulates the infiltration of immune cells into the tumor sites, exerting an immunomodulatory function. Moreover, the effects of various HR ligands, including H1R antagonists, H2R antagonists, and H4R agonists, on tumor progression in many different cancer types are described. Interestingly, the expression levels of HR subtypes may serve as prognostic biomarkers in several cancers. Taken together, HRs are promising targets for cancer treatment, and HR ligands may offer novel therapeutic potential, alone or in combination with conventional therapy. However, due to the complexity of the pathophysiological roles of histamine and HRs in cancer biology, further studies are warranted before HR ligands can be introduced into clinical settings.

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.

Immunomodulatory properties of cimetidine: Its therapeutic potentials for treatment of immune-related diseases

Histamine exerts potent modulatory impacts on the cells of innate- [including neutrophils, monocytes, macrophages, dendritic cells (DCs), natural killer (NK) cells and NKT cells] and adaptive immunity (such as Th1-, Th2-, Th17-, regulatory T-, CD8⁺ cytotoxic T cells, and B cells) through binding to histamine receptor 2 (H2R). Cimetidine, as an H2R antagonist, reverses the histamine-mediated immunosuppression, as it has powerful stimulatory effects on the effector functions of neutrophils, monocytes, macrophages, DCs, NK cells, NKT cells, Th1-, Th2-, Th17-, and CD8⁺ cytotoxic T cells. However, cimetidine reduces the regulatory/suppressor T cell-mediated immunosuppression. Experimentally, cimetidine potentiate some immunologic activities in vitro and in vivo. The therapeutic potentials of cimetidine as an immunomodulatory agent were also investigated in a number of human diseases (such as cancers, viral warts, allergic disorders, burn, and bone resorption) and vaccination. This review aimed to provide a concise summary regarding the impacts of cimetidine on the immune system and highlight the cellular mechanisms of action and the immunomodulatory effects of this drug in various diseases to give novel insights regarding the therapeutic potentials of this drug for treatment of immune-related disorders. The review encourages more investigations to consider the immunomodulatory characteristic of cimetidine for managing of immune-related disorders.

The Effect of Perioperative Cimetidine Administration on Time to Colorectal Cancer Recurrence

BACKGROUND

Studies have reported that the perioperative use of cimetidine, a histamine type 2 receptor antagonist, in addition to chemotherapy in patients with lymph node-positive colorectal cancer (CRC) improves the survival.

STUDY QUESTION

To determine if time to CRC recurrence could be prolonged with cimetidine.

STUDY DESIGN

Cimetidine was prescribed to American Joint on Cancer Committee (AJCC) stage III CRC patients perioperatively. Tumor recurrence was defined as the time (in days) between tumor resection and CRC recurrence. Medical charts of patients diagnosed with CRC between 1996 and 2006 were reviewed. Inclusion criteria were patients with (a) AJCC stage III CRC, (b) who had undergone surgical resection of the tumor, and (c) who received chemotherapy (5-fluorouracil).

MEASURES AND OUTCOMES

AJCC stage III CRC patients who did and did not receive cimetidine as part of the treatment regimen were compared with respect to their clinical outcomes using univariate analysis and Kaplan-Meier modeling.

RESULTS

Between 1996 and 2006, 38 patients met our inclusion criteria. Twenty-six percent (10/38) received perioperative cimetidine (mean daily dose, 750 mg; mean duration, 369 days; mean total cumulative cimetidine dose, 274,070 mg/d) in addition to chemotherapy. Time to recurrence and cancer deaths were prolonged in the chemotherapy plus cimetidine group compared with the group that received chemotherapy alone (mean ± SD: 1078 ± 290 vs. 446 ± 62; P = 0.03). In addition, we found a significant positive relationship between the duration of cimetidine therapy (days) and survival duration (correlation coefficient = 0.94, P = 0.02) and time until cancer recurrence (correlation coefficient = 0.99, P = 0.04). Moreover, there was a significant positive relationship between the total cumulative cimetidine dose and survival duration (correlation coefficient = 0.92, P = 0.03).

CONCLUSIONS

Prolonged duration of cimetidine may be superior to shorter courses in prolonging recurrence of CRC and thus survival.

Cimetidine down-regulates stability of Foxp3 protein via Stub1 in Treg cells

Foxp3-expressing Treg cells have been well documented to provide immune regulation by promoting immune tolerance and suppressing immune over-reaction. Cimetidine (CIM), used to inhibit stomach acid secretion, has been reported to promote immune responses and suppress Treg cell function in several studies. However, the underlying mechanism is unknown. To investigate CIM effects on the suppressive function of Treg and Foxp3, here we used CIM to stimulate human CD4⁺CD25⁺ Treg cells and Jurkat T cells and evaluated changes of Foxp3 expression and stability. Our data showed that CIM leads to a reduction of Foxp3 via E3 ligase Stub1-mediated proteosomal degradation, which is dependent on an activated PI3K-AKT-mTOR pathway. Thus, CIM affects the suppressive function of Treg cells by destabilizing their Foxp3 expression.

Pilot study--cimetidine enhances lymphocyte infiltration of human colorectal carcinoma: results of a small randomized control trial

BACKGROUND

Cimetidine preserves postoperative immune function and inhibits the growth of some cancers. In this study, the effect of cimetidine on the local immune response to colorectal carcinoma was investigated.

METHODS

Forty-two patients scheduled for elective resection of colorectal carcinoma were randomized either to receive cimetidine for 1 week perioperatively or to act as controls. A lymphocyte density of 50 cells per high-power field (approximately 50% of the tumor/tissue interface) was considered a positive response. Patient survival was determined by Kaplan-Meier life table analysis. The effects of histamine and cimetidine on normal subject lymphocyte function was determined in a mitogen-stimulated proliferation assay.

RESULTS

A positive lymphocyte response was observed in 5 of 24 control carcinoma patients (21%) and 10 of 18 cimetidine-treated carcinoma patients (56%) (P = 0.03). The presence of a lymphocyte response correlated with a better survival (P = 0.02). Histamine had an inhibitory effect on lymphocyte proliferation with a median effective dose of 5 x 10(-7) M. Cimetidine antagonized this effect with a negative logarithm of the cimetidine molar concentration required to reduce the effect of histamine in half of 6.55.

CONCLUSIONS

Histamine inhibits normal lymphocyte function, antagonized by cimetidine at a histamine type 2 receptor. Cimetidine increases lymphocyte infiltration of primary colorectal carcinoma, possibly by overcoming the immunosuppressive effects of high local histamine concentrations. The presence of a local lymphocyte response correlates with an improved 3-year survival.

Case report: successful treatment with cimetidine and zinc sulphate in chronic mucocutaneous candidiasis

The authors evaluated the clinical efficacy of a treatment with cimetidine and zinc sulphate in a patient with chronic mucocutaneous candidiasis. Cimetidine was given at a dose of 400 mg three times daily; zinc sulphate at a dose of 200 mg daily, then adjusted to maintain blood zinc levels at the upper normal range. This treatment lasted 16 months. An impressive and significant reduction of the infectious events and an increased CD4 (helper/inducer) cell counts were observed. The authors conclude that this combined immunopotentiating treatment is safe and inexpensive to treat immunodeficiency disorders.

Cimetidine preserves non-specific immune function after colonic resection for cancer

Fifty consecutive patients undergoing resection of colorectal cancer were randomized to either receive cimetidine at a dose of 400 mg bd for a minimum of 5 pre-operative days, then intravenously for 2 postoperative days, or to act as controls. Baseline immune function was determined in all patients by in vitro testing of lymphocyte proliferation (LP) in response to mitogen, skin testing for cell mediated immunity (CMI) and measurement of lymphocyte subsets. Immune function was retested in both groups on the second postoperative day. In control patients the mean postoperative LP value was 41% of pre-operative levels (P < 0.0001) and the mean CMI reduced to 29% (P < 0.0001). Patients treated with cimetidine had no significant fall in these parameters. Numbers of T and natural killer (NK) cells fell after surgery in both groups, and B cell numbers were maintained in the cimetidine group. It is concluded that cimetidine reduces the immunosuppression that follows colonic resection.

Cimetidine inhibits in vivo growth of human colon cancer and reverses histamine stimulated in vitro and in vivo growth

The effect of histamine and cimetidine on the growth of four human colon cancer cell lines was studied. Histamine significantly stimulated the uptake of tritiated thymidine in vitro in a dose dependent manner, to a maximum of 120% and 116% of controls for C170 and LIM2412, respectively. This effect was antagonised by cimetidine, but not diphenhydramine. Histamine also stimulated a dose dependent increase in cyclic adenosine monophosphate accumulation in C170 cells, antagonised by cimetidine. When grown as subcutaneous xenografts in Balb/c nu/nu mice, cimetidine had a significant inhibitory effect on the same two cell lines. The final volume of C170 tumours in animals given cimetidine was 44% of controls. This response was dose dependent, plateauing at a cimetidine dose of 50 mg/kg/day. The final volume of LIM2412 tumours in animals given cimetidine was 60% of controls. Histamine administered locally by a mini-osmotic pump stimulated C170 tumour growth to 164% of controls, was antagonised by cimetidine at a dose of 200 mg/kg/day, but not by lower concentrations. Histamine has a trophic effect on at least two colorectal cancer cell lines in vivo and in vitro. As this effect is antagonised by cimetidine, it may be mediated via tumour histamine type 2 receptors.

The effect of cimetidine on lymphocyte subpopulations in vivo in experimental mice

The effects of cimetidine, an H2 receptor antagonist, on subpopulation of splenic lymphocytes were studied in mice. Cimetidine (50 mg/kg) was given to groups of mice by intraperitoneal injection. The splenic mononuclear cells from treated and control animals were evaluated for relative number of lymphocyte subpopulations (i.e. LYT1, LYT2, L3T4 and GAM cells) by flow cytometry. The percentages of LYT2 cells (suppressor equivalent) were significantly lower (5.5 vs 12.0%) in mice who were treated with cimetidine vs control animals. The percentages of L3T4 (helper equivalent) were not statistically different in any of the experimental groups.

Does H2-receptor antagonist alter the renal function of cyclosporine-treated kidney grafts?

Histamine-type 2 antagonists (H2-blockers) as represented by cimetidine have been shown to adversely affect renal allograft function, particularly when coadministered with cyclosporine, currently a major immunosuppressant. To determine whether or not a newer and more powerful H2-blocker, famotidine, would produce similar adverse effects, we assessed seven cyclosporine-treated renal allograft recipients with regard to changes in their renal function on or off the H2-blocker over a one-week period. Neither the administration nor withdrawal of famotidine (20-40 mg/day) resulted in any significant changes in serum creatine, BUN, urine output or cyclosporine trough levels, suggesting that famotidine can be safely administered as an H2-blocker to cyclosporine-treated renal allograft recipients.

Cimetidine: an immunomodulator

Suppressor T lymphocytes possess histamine2 (H2) receptors and contribute significantly to the function of the immune system. Experimentally, cimetidine, an H2-receptor antagonist, has been shown to enhance a variety of immunologic functions both in vivo and in vitro because of its inhibitory effects on suppressor-cell function. Successful tumor immunotherapy, as well as some protection from infection, has been reported in experimental animals. Patients receiving cimetidine have been shown to exhibit enhanced cell-mediated immunity as evaluated by increased response to skin-test antigens, restoration of sensitivity following development of acquired tolerance, and increased responses of lymphocytes to mitogen stimulation. Preliminary reports also indicate that cimetidine may offer therapeutic benefits for patients with Varicella zoster and Herpes simplex infections, as well as those suffering from mucocutaneous candidiasis and common variable hypogammaglobulinemia. These immunoregulatory effects are dose-related but are not always consistent. Because of its inhibitory effect on suppressor function, cimetidine treatment may be deleterious in patients with organ transplant and autoimmune disorders. Cimetidine should be used as an immunomodulator on an experimental basis only.