Protein-bound polysaccharide K augments IL-2 production from murine mesenteric lymph node CD4+ T cells by modulating T cell receptor signaling

The use of Hericium erinaceus and Trametes versicolor extracts in supportive treatment in oncology

Substances available in nature with potential therapeutic effects are the subject of research that raises tremendous hopes for new challenges in medicine. Fungi are the most common organisms in the ecosystem and the most interesting in this respect. This review discusses two species of edible fungi, used for centuries in Eastern natural medicine, with the best-documented effect - Hericium erinaceus (He) and Trametes versicolor (Tv). The results of in vivo and in vitro studies conducted on mice and human cell lines demonstrate immunomodulatory, potentially, anticancer, anti-inflammatory and neuroregenerative effects of substances isolated from these fungi. The substances contained in the extracts of He and Tv seem to have immunomodulatory effects that may support chemotherapy. The use of these extracts is justified stronger than the other supportive treat ments based on supplements.

Anti-tumor activity and immunogenicity of a succinoglycan riclin

Natural polysaccharides have attracted considerable interests due to diverse biological activities. Succinoglycan is an extracellular polysaccharide produced by most Agrobacterium strains. Here, we confirmed riclin was a typical succinoglycan by NMR and methylation analysis, and investigated the antitumor effects of riclin in sarcoma 180 tumor-bearing mice. The results showed that riclin inhibited the tumor growth significantly as well as cyclophosphamide (CTX). While CTX caused serious damage to spleen structure, riclin increased the spleen index and promoted lymphocytes proliferation in peripheral blood, spleen and lymph nodes. Riclin decreased splenocytes apoptosis as evidenced by alterations of B-cell lymphoma-2 family proteins and Cleaved Caspase-3 protein. Moreover, ¹H nuclear magnetic resonance (NMR)-based metabolomics analysis revealed that riclin partially altered the metabolic profiles of splenocytes. In conclusion, riclin is a succinoglycan that performed strong immunogenicity and suppressed sarcoma growth in mice. Succinoglycan riclin could be a potential antitumor agent for functional food and pharmaceutical purpose.

Clinical efficacy of protein-bound polysaccharide K in patients with gastric cancer undergoing chemotherapy with an oral fluoropyrimidine (S-1)

BACKGROUND

The aim of the present study was to evaluate the clinical significance of protein-bound polysaccharide K (PSK) in patients with primary gastric cancer who were being treated with an oral fluoropyrimidine (S-1).

METHODS

Clinical reports of 190 gastric cancer patients treated with S-1 chemotherapy, with or without PSK, at Kochi Medical School between 2007 and 2012 were investigated retrospectively to analyze survival. The neutrophil:lymphocyte ratio (NLR) was also evaluated as indicator of the immunoenhancing effect of PSK.

RESULTS

Overall survival was significantly longer in patients treated with S-1 + PSK than in those given S-1 alone (hazard ratio for death, 0.608; 95% confidence interval 0.375-0.985; P = 0.041). Furthermore, there was a tendency for changes in the NLR during chemotherapy to be lower in the S-1 + PSK group than in the S-1 group, but the difference did not reach statistical significance (P = 0.054). When patients were divided into groups based on preoperative NLR (i.e. <2.5 and ≥2.5), the mean (±SEM) NLR 1 month after the beginning of chemotherapy in the NLR ≥2.5 subgroup was significantly lower in patients treated with S-1 + PSK rather than S-1 alone (1.7 ± 0.7 vs. 3.3 ± 4.1, respectively; P = 0.043).

CONCLUSIONS

Immunochemotherapy using PSK improves the survival of patients with advanced gastric cancer. The NLR may be a useful biomarker for evaluating prognosis in these patients.

Polysaccharide K and Coriolus versicolor extracts for lung cancer: a systematic review

BACKGROUND

Polysaccharide K, also known as PSK or Krestin, is derived from the Coriolus versicolor mushroom and is widely used in Japan as an adjuvant immunotherapy for a variety of cancer including lung cancer. Despite reported benefits, there has been no English language synthesis of PSK for lung cancer. To address this knowledge gap, we conducted a systematic review of PSK for the treatment of lung cancer.

METHODS

We searched PubMed, EMBASE, CINAHL, the Cochrane Library, AltHealth Watch, and the Library of Science and Technology from inception to August 2014 for clinical and preclinical evidence pertaining to the safety and efficacy of PSK or other Coriolus versicolor extracts for lung cancer.

RESULTS

Thirty-one reports of 28 studies were included for full review and analysis. Six studies were randomized controlled trials, 5 were nonrandomized controlled trials, and 17 were preclinical studies. Nine of the reports were Japanese language publications. Fifteen of 17 preclinical studies supported anticancer effects for PSK through immunomodulation and potentiation of immune surveillance, as well as through direct tumor inhibiting actions in vivo that resulted in reduced tumor growth and antimetastatic effects. Nonrandomized controlled trials showed improvement of various survival measures including median survival and 1-, 2-, and 5-year survival. Randomized controlled trials showed benefits on a range of endpoints, including immune parameters and hematological function, performance status and body weight, tumor-related symptoms such as fatigue and anorexia, as well as survival. Although there were conflicting results for impact on some of the tumor-related symptoms and median survival, overall most randomized controlled trials supported a positive impact for PSK on these endpoints. PSK was safely administered following and in conjunction with standard radiation and chemotherapy.

CONCLUSIONS

PSK may improve immune function, reduce tumor-associated symptoms, and extend survival in lung cancer patients. Larger, more rigorous randomized controlled trials for PSK in lung cancer patients are warranted.

Selective targeting of Toll-like receptors and OX40 inhibit regulatory T-cell function in follicular lymphoma

Immunotherapeutic strategies are promising approaches for the treatment of follicular lymphoma (FL). However, their efficacy may be limited by immunosuppressive elements in the immune system and tumor microenvironment. Therefore, strategies to reverse the effects of the immunosuppressive elements are needed. We observed that regulatory T cells (Tregs) were increased in the peripheral blood at diagnosis and persisted in high numbers after induction of clinical remission with a cyclophosphamide and doxorubicin-containing chemotherapy regimen in FL patients. High levels of peripheral blood Tregs prior to therapy were associated with decreased progression-free survival in FL patients treated with either chemotherapy or combination immunotherapy that targeted CD20 and PD-1 with monoclonal antibodies rituximab and pidilizumab, respectively. Intratumoral and peripheral blood Tregs potently suppressed autologous antitumor effector T cells in FL. However, the effects of FL Tregs could be reversed by triggering Toll-like receptors (TLR) with TLR ligands Pam3 CSK4 (TLR 1/2), flagellin (TLR 5), and CpG-B (TLR 9), and/or OX40. The TLR ligands synergized with each other as well as OX40 signaling to inhibit Tregs. Furthermore, they restored the function of FL tumor-specific effector T cells. Our results suggest that a state of tolerance exists in FL patients at diagnosis and after induction of clinical remission, and agents that activate TLRs 1/2, 5, and 9, and OX40 may serve as adjuvants to enhance the efficacy of antitumor immunotherapeutic strategies and preventive vaccines against infectious diseases in these patients.

The expression of integrins is decreased in colon cancer cells treated with polysaccharide K

Polysaccharide K (PSK), a protein-bound polysaccharide used as a non-specific immunotherapeutic agent, is said to improve the prognosis of malignant tumors such as colon cancer, but there have been few in‑depth investigations of its mechanism of action. In the present study, we investigated which genes in colon cancer cells themselves are regulated by PSK and what sort of action it exerts. Colon cancer cells were exposed to PSK in vitro and changes to their morphology and adhesive capacity were investigated, as were the changes in integrin expression that occurred. Exposure to PSK caused colon cancer cells to become spherical in morphology and investigation of their adhesion rate showed that it reduced adhesion to laminin, fibrinogen, collagen IV, collagen I and fibronectin. In terms of changes to molecules on the surface of cancer cells, there was reduced expression of integrin mRNA α and β, which are ligands for the proteins of basement membrane. An investigation of the adhesiveness of PSK-stimulated colon cancer cells to vascular endothelial cells also showed that the adhesion rate decreased significantly compared with cells not exposed to PSK. Suppression of integrin expression on the cell surface and reduced adhesion to vascular endothelial cells were observed as a novel mechanism of action of PSK on colon cancer cells.

Polysaccharide-K (PSK) increases p21(WAF/Cip1) and promotes apoptosis in pancreatic cancer cells

BACKGROUND

Polysaccharide-K (PSK, Krestin(®)) is a natural remedy and one of the most commonly used medicinal mushroom extracts. It has been used as oral adjuvant treatment in cancer therapy in Japan and other Asian countries for more than 40 years. PSK is thought to be an immune modulator, however, its antitumor actions remain undefined. The aim of the present study was to investigate underlying mechanisms by which PSK exerts its antitumor effects on malignant epithelial cells.

METHODS

Antitumor activities of PSK were evaluated on multiple human pancreatic adenocarcinoma cells in vitro. Cell viability, apoptotic pathways, cytokine expression and involvement of TLR2 and TLR4 were monitored by MTT, flow cytometry, Western blotting and protein arrays.

RESULTS

We demonstrate that PSK acts as a growth inhibitor for pancreatic cancer cells, known otherwise to be highly resistant to conventional chemotherapies. Pancreatic cancer cells can be protected against PSK-mediated growth inhibition by neutralizing antibodies against TLR2 and TLR4. The antiproliferative actions were associated with upregulated cell cycle regulatory p21(WAF/Cip1) and pro-apoptotic protein Bax levels, resulting in cell cycle arrest and induction of apoptosis. In addition, a significant growth inhibition and additive effect was observed with PSK and gemcitabine administered as combined treatment.

CONCLUSION

While previous studies have emphasized the potential importance of PSK in immune activation, the present results uncover additional mechanisms on epithelial cells that may contribute to the antitumor effects provided by PSK as suggested by clinical observations.

Biological mechanism and clinical effect of protein-bound polysaccharide K (KRESTIN(®)): review of development and future perspectives

The mechanism of action of protein-bound polysaccharide K (PSK; KRESTIN(®)) involves the following actions: (1) recovery from immunosuppression induced by humoral factors such as transforming growth factor (TGF)-β or as a result of surgery and chemotherapy; (2) activation of antitumor immune responses including maturation of dendritic cells, correction of Th1/Th2 imbalance, and promotion of interleukin-15 production by monocytes; and (3) enhancement of the antitumor effect of chemotherapy by induction of apoptosis and inhibition of metastasis through direct actions on tumor cells. The clinical effectiveness of PSK has been demonstrated for various cancers. In patients with gastric or colorectal cancer, combined use of PSK with postoperative adjuvant chemotherapy prolongs survival, and this effect has been confirmed in multiple meta-analyses. For small-cell lung carcinoma, PSK in conjunction with chemotherapy prolongs the remission period. In addition, PSK has been shown to be effective against various other cancers, reduce the adverse effects of chemotherapy, and improve quality of life. Future studies should examine the effects of PSK under different host immune conditions and tumor properties, elucidate the mechanism of action exhibited in each situation, and identify biomarkers.

Immunotherapy eradicates metastases with reversible defects in MHC class I expression

Tumor or metastatic cells lose MHC class I (MHC-I) expression during cancer progression as an escape mechanism from immune surveillance. These defects in MHC-I may be reversible by cytokines or different agents (soft lesions) or irreversible due to structural defects (hard lesions). The nature of these MHC-I alterations might determine the success or failure of immunotherapy treatments. In this study, we have used an MHC-I-positive murine fibrosarcoma tumor clone, GR9-A7, which generates multiple lung and lymph node metastases with reversible MHC-I alterations after treatment with IFN-γ. Four different antitumor treatments were carried out after primary tumor excision to determine their capacity to inhibit spontaneous metastatic colonization of the GR9-A7 tumor clone. We found that 2 different immunotherapy protocols (CpG plus autologous irradiated-GR9-A7 cells and protein-bound polysaccharide K (PSK) and 1 chemoimmunotherapy (docetaxel plus PSK) induced eradication of metastases. In contrast, chemotherapy with docetaxel alone produced only partial reduction in the number of metastases. Flow cytometric analysis of lymphocyte populations showed an immunosuppression in GR9-A7 tumor-bearing host, which could be reverted by immunotherapy treatments. Our results suggest that irreversible or reversible MHC-I alterations in tumor target cells may determine its progression or regression independently of the type of immunotherapy used.