Abstract
Aim
Glucans are glucose polymers that constitute a structural part of fungal cell wall. They can stimulate the innate immunity by activation of monocytes/macrophages. In human studies it has been shown that beta glucan has an immunomodulatory effect and can increase the efficacy of the biological therapies in cancer patients. In this prospective clinical trial we assessed in vivo effects of short term oral beta glucan administration on peripheral blood monocytes and their expression of activation markers in patients with advanced breast cancer.
Methods
23 female patients with advanced breast cancer were included in the study. Median age of the patients was 52 years. Sixteen healthy females with a median age of 48 years served as the control group for comparing the initial blood samples. Peripheral blood samples were drawn on day zero and patients started receiving oral 1–3, 1–6, D-beta glucan daily. Blood samples were recollected on the 15th day. In the initial samples mean lymphocyte count was significantly lower in the patients with breast cancer (1281 ± 306/mm3 versus 1930 ± 573/mm3, p = 0.04). In the patients with breast cancer, mean monocyte count which was 326 + 124/mm3 at the beginning, was increased to 496 + 194/mm3 at the 15th day (p = 0.015). Expression of CD95 (Apo1/Fas) on CD14 positive monocytes was 48.17% at the beginning, which was increased to 69.23 % at the 15th day (p = 0.002). Expression of CD45RA on CD14 positive monocytes was 49.9% at the beginning; it was increased significantly to 61.52% on day 15 (p = 0.001).
Conclusion
Oral beta glucan administration seems to stimulate proliferation and activation of peripheral blood monocytes in vivo in patients with advanced breast cancer.
Introduction
Glucans are glucose polymers, constituting a major component of fungal and bacterial cell wall [1]. They are well known biological response modifiers which have been used in cancer patients, particularly in Japan, but in most studies clinical responses were unpredictable [2]. The anti-infective and anti-tumorigenic effects of beta glucans are based on their ability to activate leukocytes by stimulating their phagocytic activity and production of inflammatory cytokines like TNF alpha [3].
Bacterial or fungal products can initiate the immune response mostly by binding to the innate immune receptors like lectin receptors (mannose receptor, Dectin-1), Scavenger receptors, and Toll-like receptors on the leukocytes [4]. Recently, Brown et al. showed that beta glucan interacts on cell surface with dectin-1 receptors for its biological effects. Dectin-1 receptors are expressed mainly on macrophages, neutrophils, dendritic cells, and a subpopulation of T-lymphocytes [5]. Underhill and co-workers showed that activation of Dectin-1 receptors by beta glucan on a subset of macrophages induce intracellular signaling pathway by Syk tyrosine kinase [4].
Another important mechanism for the immune effects of beta glucan is regulation of complement dependent cytotoxicity (CDC). In vitro studies demonstrated that beta glucan plays an important role by complement receptor type 3 (CR3)-dependent phagocytosis and degranulation. Beta glucan binds to the lectin domain of CD11b subunit of CR3 of circulating leukocytes, and this binding serves to prime the receptor for triggering cytotoxic degranulation in response to iC3b-coated cells. C3 deposition on tumor cells was shown to be primarily regulated by anti tumor antibodies [6], [7]. This very interesting effect of beta glucan could be used to augment the clinical effects of monoclonal antibody based cancer therapies like rituximab (anti CD20 MoAb for B-cell NHL), trastuzumab (anti-Her2 for Her-2 positive breast cancer) and cetuximab (anti EGFR for colorectal cancer). Modak et al. showed that the efficacy of rituximab therapy can be increased by co-administration of oral beta glucan in CD20 positive lymphoma xenografts in mice [8].
There is very limited clinical data about oral beta glucan application in humans but until now no serious toxicity was reported.
Monocytes/macrophages are the major effectors of innate immunity, functioning as the first barrier of our natural defense. Beta glucan can stimulate macrophages, neutrophils, and NK cells. Some data suggested that beta glucan could promote T cell specific responses by induction of cytokines like IFN-gamma, IL-6, IL-8, and IL-12 from macrophages, neutrophils and NK cells [1], [3].
Several surface molecules associated with macrophage activation have been defined. Fas/APO-1 (CD95) is a cell surface molecule that can transduce apoptotic signals into cells, regulating immune responses through the induction of cell death. Activated immune cells express both Fas and Fas-L [9]. It has been shown that Fas molecule on peritoneal macrophages was upregulated by application of various cytokines, and interestingly, CD4 positive helper lymphocytes kill macrophages through a Fas mediated pathway after antigen presentation [10].
In humans most of the naïve cells express a 200-kD isoform of a surface molecule called CD45 that contains a segment encoded by an exon designated A. This CD45 isoform named CD45RA. This molecule is also expressed on monocytes, and is regarded as an activation marker [11].
CD4 is an important cell surface molecule for lymphocytes and regulates the function of T-lymphocytes as helper/inducer. CD4 has a function in antigen presentation and expressed also on dendritic cells. The role of CD4 molecule on monocytes is not defined; however, the upregulation of this molecule with GM-CSF application suggests that CD4 could possibly have a role in monocyte activation [12], [13].
In this prospective clinical trial we assessed in vivo effects of short term oral beta glucan administration on peripheral blood monocytes and their surface markers in patients with advanced breast cancer.
Section snippets
Patients and methods
Twenty-three female patients were included in the study with newly diagnosed or relapsed metastatic breast cancer after giving written informed consent. All patients had histological confirmation of disease. Fifteen patients had invasive ductal carcinoma, and 8 patients had invasive lobular carcinoma. Seventeen patients had estrogen receptor (ER) and progesterone receptor (PR) positive tumor. Five patients had Her-2 (c Erb-B2) amplification. Ten patients had prior breast surgery adjuvant
Results
The results are summarized on Table 1. The initial absolute numbers of leukocytes, erythrocytes, and platelets were not significantly different in the control group compared to the initial values of patients with breast cancer. Initial lymphocyte count was significantly lower in breast cancer patients than healthy controls (1281 ± 306/mm3 versus 1930 ± 573/mm3, p = 0.04).
In the basal flow cytometry analysis, a significant difference was observed in the expression of CD95 (Fas, Apo-1) on monocytes of
Discussion
The low lymphocyte counts observed in our patients with advanced breast cancer as compared to the healthy control group is subject to discussion. Ten patients had prior cancer treatment as chemotherapy or radiotherapy but the long term lymphopenic affects of chemotherapy or radiotherapy is not well defined. Seven patients were still receiving tamoxifen just before the study entry but tamoxifen is not known to have any lymphopenic effect. Cancer-induced immunosuppresion as a well known
References