Immune cells as anti-cancer therapeutic targets and tools

Chronic inflammation is a contributing factor to overall cancer risk as well as cancer promotion and progression; however, pathways regulating onset of cancer-promoting inflammatory responses are still poorly understood. Clinical data suggest that deficient anti-tumor cell-mediated immunity, in combination with enhanced pro-tumor humoral and/or innate immunity (inflammation), are significant factors influencing malignant outcome. Here, we discuss therapeutic implications from clinical data and experimental studies using de novo immune-competent mouse models of cancer development that together are revealing molecular and cellular mechanisms underlying interactions between immune cells and evolving neoplastic cells that regulate cancer outcome. Understanding the functionally significant links between adaptive and innate immunity that regulate cancer development will open new therapeutic opportunities to manipulate aspects of immunobiology and minimize lethal effects of cancer development.     

Lymphocytes in cancer development: Polarization towards pro-tumor immunity

The classic view that the role of immune cells in cancer is primarily one of tumor rejection has been supplanted by a more complex view of leukocytes having both pro- and anti-tumor properties. This shift is due to the now well recognized capabilities of several myeloid cell types that foster pro-tumor programming of premalignant tissue, as well as the discovery that subsets of leukocytes also suppress development and effector functions of lymphocytes important for mediating anti-tumor immunity. In this review, we focus on the underappreciated role that T lymphocytes play in promoting tumor development. This includes, in addition to the role of T regulatory cells, a role for natural killer T cells and CD4⁺ T helper cells in suppressing anti-tumor immunity and promoting cancer growth and metastasis.     

Vaccination with TCL plus MHSP65 induces anti-lung cancer immunity in mice

To develop effective anti-lung cancer vaccines, we directly mixed mycobacterial heat shock protein 65 (MHSP65) and tumor cell lysate (TCL) from Lewis lung cancer cells in vitro and tested its efficacy on stimulating anti-tumor immunity. Our results showed that MHSP65–TCL immunization significantly inhibited the growth of lung cancer in mice and prolonged the survival of lung cancer bearing mice. In vivo and in vitro data suggest that MHSP65–TCL could induce specific CTL responses and non-specific immunity, both of which could contribute to the tumor inhibition. Thus, this report provides an easy approach to prepare an efficient TCL based tumor vaccine.     

Acetate decreases PVR/CD155 expression via PI3K/AKT pathway in cancer cells

In recent years, restoring anti-tumor immunity has garnered a growing interest in cancer treatment. As potential therapeutics, immune checkpoint inhibitors have demonstrated benefits in many clinical studies. Although various methods have been applied to suppress immune checkpoints to boost anti-tumor immunity, including the use of immune checkpoint inhibitors, there are still unmet clinical needs to improve the response rate of cancer treatment. Here, we show that acetate can suppress the expression of poliovirus receptor (PVR/CD155), a ligand for immune checkpoint, in colon cancer cells. We demonstrated that acetate treatment could enhance effector responses of CD8⁺ T cells by decreasing the expression of PVR/CD155 in cancer cells. We also found that acetate could reduce the expression of PVR/CD155 by deactivating the PI3K/AKT pathway. These results demonstrate that acetate-mediated expression of PVR/CD155 in cancer cells might potentiate the anti-tumor immunity in the microenvironment of cancer. Our findings indicate that maintaining particular acetate concentrations could be a complementary strategy in current cancer treatment.     

Vaccine-induced ErbB (EGFR/HER2)-specific immunity in spontaneous canine cancer

Epidermal Growth Factor Receptor (EGFR) is overexpressed on a number of human cancers, and often is indicative of a poor outcome. Treatment of EGFR/HER2 overexpressing cancers includes monoclonal antibody therapy (cetuximab/trastuzumab) either alone or in conjunction with other standard cancer therapies. While monoclonal antibody therapy has been proven to be efficacious in the treatment of EGFR/HER2 overexpressing tumors, drawbacks include the lack of long-lasting immunity and acquired resistance to monoclonal therapy. An alternative approach is to induce a polyclonal anti-EGFR/HER2 tumor antigen response by vaccine therapy. In this phase I/II open-label study, we examined anti-tumor immunity in companion dogs with spontaneous EGFR expressing tumors. Canine cancers represent an outbred population in which the initiation, progression of disease, mutations and growth factors closely resemble that of human cancers. Dogs with EGFR expressing tumors were immunized with a short peptide of the EGFR extracellular domain with sequence homology to HER2. Serial serum analyses demonstrated high titers of EGFR/HER2 binding antibodies with biological activity similar to that of cetuximab and trastuzumab. Canine antibodies bound both canine and human EGFR on tumor cell lines and tumor tissue. CD8 T cells and IgG deposition were evident in tumors from immunized dogs. The antibodies inhibited EGFR intracellular signaling and inhibited tumor growth in vitro. Additionally, we illustrate objective responses in reducing tumors at metastatic sites in host animals. The data support the approach of amplifying anti-tumor immunity that may be relevant in combination with other immune modifying therapies such as checkpoint inhibitors.     

Interleukin-12 in anti-tumor immunity and immunotherapy

Interleukin-12 (IL-12) has an essential role in the interaction between the innate and adaptive arms of immunity by regulating inflammatory responses, innate resistance to infection, and adaptive immunity. Endogenous IL-12 is required for resistance to many pathogens and to transplantable and chemically induced tumors. In experimental tumor models, recombinant IL-12 treatment has a dramatic anti-tumor effect on transplantable tumors, on chemically induced tumors, and in tumors arising spontaneously in genetically modified mice. IL-12 utilizes effector mechanisms of both innate resistance and adaptive immunity to mediate anti-tumor resistance. IFN-gamma and a cascade of other secondary and tertiary pro-inflammatory cytokines induced by IL-12 have a direct toxic effect on the tumor cells or may activate potent anti-angiogenic mechanisms. The stimulating activity of IL-12 on antigen-specific immunity relies mostly on its ability to determine or augment Th1 and cytotoxic T lymphocyte responses. Because of this ability, IL-12 has a potent adjuvant activity in cancer and other vaccines. The promising data obtained in the pre-clinical models of anti-tumor immunotherapy have raised much hope that IL-12 could be a powerful therapeutic agent against cancer. However, excessive clinical toxicity and modest clinical response observed in the clinical trials point to the necessity to plan protocols that minimize toxicity without affecting the anti-tumor effect of IL-12.     

The pros and cons of interferons for oncolytic virotherapy

Interferons (IFN) are potent immune stimulators that play key roles in both innate and adaptive immune responses. They are considered the first line of defense against viral pathogens and can even be used as treatments to boost the immune system. While viruses are usually seen as a threat to the host, an emerging class of cancer therapeutics exploits the natural capacity of some viruses to directly infect and kill cancer cells. The cancer-specificity of these bio-therapeutics, called oncolytic viruses (OVs), often relies on defective IFN responses that are frequently observed in cancer cells, therefore increasing their vulnerability to viruses compared to healthy cells. To ensure the safety of the therapy, many OVs have been engineered to further activate the IFN response. As a consequence of this IFN over-stimulation, the virus is cleared faster by the immune system, which limits direct oncolysis. Importantly, the therapeutic activity of OVs also relies on their capacity to trigger anti-tumor immunity and IFNs are key players in this aspect. Here, we review the complex cancer–virus–anti-tumor immunity interplay and discuss the diverse functions of IFNs for each of these processes.     

槐生拜尔孔菌(槐耳)的化学成分及其抗肿瘤活性研究进展

槐生拜尔孔菌(槐耳)是我国重要的药用真菌之一,其化学成分主要含有多糖类、甾体类和生物碱类.槐耳被广泛应用于乳腺癌、肝癌、肺癌、胃癌等多种恶性肿瘤的辅助治疗,其作用机制包括抑制肿瘤细胞生长与增殖、侵袭与转移、血管新生、诱导肿瘤细胞发生凋亡、提高机体免疫力等.本文对槐耳的化学成分及其抗肿瘤活性研究进展进行了归纳和总结,为这...     

A New Strategy Using ALDHhigh-CD8+T Cells to Inhibit Tumorigenesis

Background

Currently, many studies suggest that cancer stem cells (CSCs) are responsible for tumor initiation, tumorigenesis, metastasis and recurrence. CSCs have been identified from various human and murine tumors. The identification of CSCs allows us to develop strategies to target the CSCs.

Methods and Results

In this study, we used ALDEFLUOR as a single marker to isolate the CSCs from the human lung cancer cell line H460. We then characterized the CSCs by testing their sphere formation ability and tumorigenicity. Furthermore, we used CSC lysate-pulsed dendritic cells to stimulate CD8+T cells as a treatment strategy. Our study demonstrated that ALDEFLUOR could be used as a single marker to identify CSCs from the human lung cancer cell line H460. The ALDH^high cells could form more spheres and were more tumorigenic than the ALDH^low cells. Further study demonstrated that ALDH^high-CD8+T cells conferred more significant antitumor effects, resulting in the inhibition of tumor growth and prolonged survival. And the ALDH^high-CD8+T cells-mediated anti-tumor immunity might be due to the directly targeting against ALDH^high cancer stem cells (CSCs).

Conclusions

This study shows that ALDH^high-CD8+T cells mediate anti-tumor immunity by selectively targeting cancer stem cells, which result in inhibiting tumor growth and prolonging the survival of tumor-bearing mice, which provides a new strategy using ALDH^high-CD8+T cells to treat tumors.     

Antigenic Differences Between Normal and Malignant Cells as a Basis for Treatment of Intracerebral Neoplasms Using a DNA-Based Vaccine

Antigenic differences between normal and malignant cells of the cancer patient form the rationale for clinical immunotherapeutic strategies. Because the antigenic phenotype of neoplastic cells varies widely among different cells within the same malignant cell-population, immunization with a vaccine that stimulates immunity to the broad array of tumor antigens expressed by the cancer cells is likely to be more efficacious than immunization with a vaccine for a single antigen. A vaccine prepared by transfer of DNA from the tumor into a highly immunogenic cell line can encompass the array of tumor antigens that characterize the patient's neoplasm. Poorly immunogenic tumor antigens, characteristic of malignant cells, can become strongly antigenic if they are expressed by highly immunogenic cells. A DNA-based vaccine was prepared by transfer of genomic DNA from a breast cancer that arose spontaneously in a C3H/He mouse into a highly immunogenic mouse fibroblast cell line, where genes specifying tumor-antigens were expressed. The fibroblasts were modified in advance of DNA-transfer to secrete an immune augmenting cytokine and to express allogeneic MHC class I-determinants. In an animal model of breast cancer metastatic to the brain, introduction of the vaccine directly into the tumor bed stimulated a systemic cellular anti-tumor immune response measured by two independent in vitro assays and prolonged the lives of the tumor-bearing mice. Furthermore, using antibodies against the various T-cell subsets, it was determined that the systemic cellular anti-tumor immunity was mediated by CD8(+), CD4(+) and NK/LAK cells. The application of DNA-based genomic vaccines for the treatment of a variety of brain tumors is being explored.     

Human Survivin and Trypanosoma cruzi Calreticulin Act in Synergy against a Murine Melanoma In Vivo

Immune-based anti-tumor or anti-angiogenic therapies hold considerable promise for the treatment of cancer. The first approach seeks to activate tumor antigen-specific T lymphocytes while, the second, delays tumor growth by interfering with blood supply. Tumor Associated Antigens are often employed to target tumors with therapeutic drugs, but some are also essential for tumor viability. Survivin (Surv) is a member of the inhibitor of apoptosis protein family that is considered a Tumor Associated Antigen important for cancer cell viability and proliferation. On the other hand, Trypanosoma cruzi (the agent of Chagas’ disease) calreticulin (TcCRT) displays remarkable anti-angiogenic properties. Because these molecules are associated with different tumor targets, we reasoned that immunization with a Surv-encoding plasmid (pSurv) and concomitant TcCRT administration should generate a stronger anti-tumor response than application of either treatment separately. To evaluate this possibility, C57BL/6 mice were immunized with pSurv and challenged with an isogenic melanoma cell line that had been pre-incubated with recombinant TcCRT (rTcCRT). Following tumor cell inoculation, mice were injected with additional doses of rTcCRT. For the combined regimen we observed in mice that: i). Tumor growth was impaired, ii). Humoral anti-rTcCRT immunity was induced and, iii). In vitro rTcCRT bound to melanocytes, thereby promoting the incorporation of human C1q and subsequent macrophage phagocytosis of tumor cells. These observations are interpreted to reflect the consequence of the following sequence of events: rTcCRT anti-angiogenic activity leads to stress in tumor cells. Murine CRT is then translocated to the external membrane where, together with rTcCRT, complement C1 is captured, thus promoting tumor phagocytosis. Presentation of the Tumor Associated Antigen Surv induces the adaptive anti-tumor immunity and, independently, mediates anti-endothelial cell immunity leading to an important delay in tumor growth.     

Iron and neoplasia

Normal and neoplastic cells (like nonpathogenic and pathogenic microorganisms) apparently have similar needs and tolerances for iron, but neoplastic cells (like pathogenic microorganisms) may exhibit altered mechanisms of iron acquisition that permit continued growth in host iron-restricted tissues. Excess iron tends to interfere with host defense against malignant cells (as well as against microbial invaders); severe iron deficiency may likewise be detrimental. Elevated temperature is more toxic towards neoplastic than to normal host cells; it is not yet known whether the site of action of heat might be associated with iron acquisition (as has been demonstrated for gram negative bacteria). Persons or animals with iron overload tend to be at greater risk than normal hosts in the development of neoplasms. Construction of animal models of iron overload, although difficult, is strongly indicated at this time. Based on such models, decisions then can be made about the extent to which (a) nutritional immunity against neoplastic cells is practiced by vertebrate hosts and (b) clinical procedures could be employed to strengthen such immunity as an adjunct to radiotherapy, chemotherapy, and surgery.     

Immunization with heat shock protein 105-pulsed dendritic cells leads to tumor rejection in mice

Recently, we reported that heat shock protein 105 (HSP105) DNA vaccination induced anti-tumor immunity. In this study, we set up a preclinical study to investigate the usefulness of dendritic cells (DCs) pulsed with mouse HSP105 as a whole protein for cancer immunotherapy in vivo. The recombinant HSP105 did not induce DC maturation, and the mice vaccinated with HSP105-pulsed BM-DCs were markedly prevented from the growth of subcutaneous tumors, accompanied with a massive infiltration of both CD4+ T cells and CD8+ T cells into the tumors. In depletion experiments, we proved that both CD4+ T cells and CD8+ T cells play a crucial role in anti-tumor immunity. Both CD4+ T cells and CD8+ T cells specific to HSP105 were induced by stimulation with HSP105-pulsed DCs. As a result, vaccination of mice with BM-DCs pulsed with HSP105 itself could elicit a stronger tumor rejection in comparison to DNA vaccination.     

Antitumor effect of malaria parasite infection in a murine Lewis lung cancer model through induction of innate and adaptive immunity

Background

Lung cancer is the most common malignancy in humans and its high fatality means that no effective treatment is available. Developing new therapeutic strategies for lung cancer is urgently needed. Malaria has been reported to stimulate host immune responses, which are believed to be efficacious for combating some clinical cancers. This study is aimed to provide evidence that malaria parasite infection is therapeutic for lung cancer.

Methodology/Principal Findings

Antitumor effect of malaria infection was examined in both subcutaneously and intravenously implanted murine Lewis lung cancer (LLC) model. The results showed that malaria infection inhibited LLC growth and metastasis and prolonged the survival of tumor-bearing mice. Histological analysis of tumors from mice infected with malaria revealed that angiogenesis was inhibited, which correlated with increased terminal deoxynucleotidyl transferase-mediated (TUNEL) staining and decreased Ki-67 expression in tumors. Through natural killer (NK) cell cytotoxicity activity, cytokine assays, enzyme-linked immunospot assay, lymphocyte proliferation, and flow cytometry, we demonstrated that malaria infection provided anti-tumor effects by inducing both a potent anti-tumor innate immune response, including the secretion of IFN-γ and TNF-α and the activation of NK cells as well as adaptive anti-tumor immunity with increasing tumor-specific T-cell proliferation and cytolytic activity of CD8⁺ T cells. Notably, tumor-bearing mice infected with the parasite developed long-lasting and effective tumor-specific immunity. Consequently, we found that malaria parasite infection could enhance the immune response of lung cancer DNA vaccine pcDNA3.1-hMUC1 and the combination produced a synergistic antitumor effect.

Conclusions/Significance

Malaria infection significantly suppresses LLC growth via induction of innate and adaptive antitumor responses in a mouse model. These data suggest that the malaria parasite may provide a novel strategy or therapeutic vaccine vector for anti-lung cancer immune-based therapy.     

橙盖鹅膏多糖(AC-1)体外免疫调节活性、细胞毒性和抗肿瘤活性的研究

为研究橙盖鹅膏多糖的体外免疫调节活性、细胞毒性和抗肿瘤活性,本研究运用细胞学技术探究AC-1对T细胞、B细胞和RAW264.7三种免疫细胞的体外免疫调节活性;研究AC-1对小鼠成纤维细胞(L929)的细胞毒性以及对小鼠胃癌细胞(MFC)、小鼠肉瘤细胞(S180)的体外抗肿瘤活性。结果表明,AC-1能在体外显著刺激三种免疫细胞的增殖及RAW264.7细胞的吞噬,表明AC-1在增强机体免疫方面具有重要作用,进一步研究发现AC-1主要通过显著促进IgE和IgG的分泌来增强体液免疫。在浓度为5~20μg/mL时AC-1对L929细胞无显著的促进及抑制作用,说明AC-1对正常细胞无毒性;在浓度为10~20μg/mL时AC-1能显著抑制小鼠胃癌细胞(MFC)的生长,但对小鼠肉瘤细胞(S180)的抑制效果较弱,说明AC-1在体外能够直接抑制肿瘤细胞的生长,但对不同的肿瘤细胞具有不同的抑制效果。综上所述,橙盖鹅膏多糖(AC-1)在体外具有良好的免疫调节活性、抗肿瘤活性,但对不同的肿瘤细胞具有不同的抑制效果并且对正常细胞无毒性。     

Retracted: Apoptosis of CT26 colorectal cancer cells induced by Clostridium difficile toxin A stimulates potent anti-tumor immunity

Clostridium difficile toxin A (TcdA) is one of the main pathogenic factors released by C. difficile. Due to its potent cytotoxic and proinflammatory activities, we investigated the anti-tumor activity of TcdA. CT26 colorectal cancer cells were challenged with recombinant TcdA, and it was found that TcdA could induce apoptosis of CT26 cells. Calreticulin (CRT) exposure to the cell surface during TcdA-induced apoptosis suggested that this apoptosis may correlate with immunogenicity. Moreover, TcdA-treated apoptotic CT26 cells were highly immunogenic since they could stimulate DC activation, T-cell activation, and anti-tumor activity. Furthermore, the anti-tumor immune response generated was specific and long-term. In summary, these studies demonstrate that C. difficile toxin A can induce apoptotic death of CT26 colorectal cancer cells and stimulate potent anti-tumor immunity.     

DNA fusion vaccines against B-cell tumors

DNA vaccination is currently being explored as a potential strategy for combatting cancer. However, tumor antigens are often weak and the immune system of patients may be compromised. For B-cell tumors, immunoglobulin idiotypic antigens provide defined targets but are poorly immunogenic. Fusion of a sequence derived from tetanus toxin to the genes encoding idiotypic determinants has proved highly effective in activating protective anti-tumor immunity. DNA fusion vaccines containing immuno-enhancing sequences can augment and direct immune attack on a range of target antigens. Gene-based fusion vaccines offer ease of manipulation and flexible design to activate effective attack on cancer.     

Utility of Clostridium difficile Toxin B for Inducing Anti-Tumor Immunity

Clostridium difficile toxin B (TcdB) is a key virulence factor of bacterium and induces intestinal inflammatory disease. Because of its potent cytotoxic and proinflammatory activities, we investigated the utility of TcdB in developing anti-tumor immunity. TcdB induced cell death in mouse colorectal cancer CT26 cells, and the intoxicated cells stimulated the activation of mouse bone marrow-derived dendritic cells and subsequent T cell activation in vitro. Immunization of BALB/c mice with toxin-treated CT26 cells elicited potent anti-tumor immunity that protected mice from a lethal challenge of the same tumor cells and rejected pre-injected tumors. The anti-tumor immunity generated was cell-mediated, long-term, and tumor-specific. Further experiments demonstrated that the intact cell bodies were important for the immunogenicity since lysing the toxin-treated tumor cells reduced their ability to induce antitumor immunity. Finally, we showed that TcdB is able to induce potent anti-tumor immunity in B16-F10 melanoma model. Taken together, these data demonstrate the utility of C. difficile toxin B for developing anti-tumor immunity.