Protective antitumor activity through dendritic cell immunization is mediated by NK cell as well as CTL activation

Low-dose total body irradiation enhances systemic anti-tumor immunity induced by local cryotherapy

BACKGROUND

Strategies that restore the immune system's ability to recognize malignant cells have yielded clinical benefits but only in some patients. Tumor cells survive cryotherapy and produce a vast amount of antigens to trigger innate and adaptive responses. However, because tumor cells have developed immune escape mechanisms, cryotherapy alone may not be enough to induce a significant immune response.

METHODS

The mice were randomly divided into four groups: Group A: low-dose total body irradiation combined with cryotherapy (L-TBI+cryo); Group B: cryotherapy (cryo); Group C: low-dose total body irradiation(L-TBI); Group D: control group (Control). The tumor growth, recurrence, and survival time of mice in each group were compared and the effects of different treatments on systemic anti-tumor immunity were explored.

RESULTS

L-TBI in conjunction with cryotherapy can effectively control tumor regrowth, inhibit tumor lung metastasis, extend the survival time of mice, and stimulate a long-term protective anti-tumor immune response to resist the re-challenge of tumor cells. The anti-tumor mechanism of this combination therapy may be related to the stimulation of inflammatory factors IFN-γ and IL-2, as well as an increase in immune effector cells (CD8+ T cells) and a decrease in immunosuppressive cells (MDSC, Treg cells) in the spleen or tumor tissue.

CONCLUSIONS

We present unique treatment options for enhancing the immune response caused by cryotherapy, pointing to the way forward for cancer treatment.

Endometrial Tumor Microenvironment Alters Human NK Cell Recruitment, and Resident NK Cell Phenotype and Function

Endometrial Cancer is the most common cancer in the female genital tract in developed countries, and with its increasing incidence due to risk factors such as aging and obesity tends to become a public health issue. However, its immune environment has been less characterized than in other tumors such as breast cancers. NK cells are cytotoxic innate lymphoid cells that are considered as a major anti-tumoral effector cell type which function is drastically altered in tumors which participates to tumor progression. Here we characterize tumor NK cells both phenotypically and functionally in the tumor microenvironment of endometrial cancer. For that, we gathered endometrial tumors, tumor adjacent healthy tissue, blood from matching patients and healthy donor blood to perform comparative analysis of NK cells. First we found that NK cells were impoverished in the tumor infiltrate. We then compared the phenotype of NK cells in the tumor and found that tumor resident CD103⁺ NK cells exhibited more co-inhibitory molecules such as Tigit, and TIM-3 compared to recruited CD103⁻ NK cells and that the expression of these molecules increased with the severity of the disease. We showed that both chemokines (CXCL12, IP-10, and CCL27) and cytokines profiles (IL-1β and IL-6) were altered in the tumor microenvironment and might reduce NK cell function and recruitment to the tumor site. This led to hypothesize that the tumor microenvironment reduces resident NK cells cytotoxicity which we confirmed by measuring cytotoxic effector production and degranulation. Taken together, our results show that the tumor microenvironment reshapes NK cell phenotype and function to promote tumor progression.

NK cells: key to success of DC-based cancer vaccines?

The cytotoxic and regulatory antitumor functions of natural killer (NK) cells have become attractive targets for immunotherapy. Manipulation of specific NK cell functions and their reciprocal interactions with dendritic cells (DCs) might hold therapeutic promise. In this review, we focus on the engagement of NK cells in DC-based cancer vaccination strategies, providing a comprehensive overview of current in vivo experimental and clinical DC vaccination studies encompassing the monitoring of NK cells. From these studies, it is clear that NK cells play a key regulatory role in the generation of DC-induced antitumor immunity, favoring the concept that targeting both innate and adaptive immune mechanisms may synergistically promote clinical outcome. However, to date, DC vaccination trials are only infrequently accompanied by NK cell monitoring. Here, we discuss different strategies to improve DC vaccine preparations via exploitation of NK cells and provide a summary of relevant NK cell parameters for immune monitoring. We underscore that the design of DC-based cancer vaccines should include the evaluation of their NK cell stimulating potency both in the preclinical phase and in clinical trials.

A study of dendritic and endothelial cell interactions in colon cancer in a cell line and small mammal model

AIM

Historically, cancer therapy directly targeting tumor cells have yielded suboptimal clinical results, and therefore anti-angiogenic therapy that targets tumor cells indirectly through impairing tumor vasculature is now considered to be one of the novel approaches potentially effective against various types of cancer. In this study, we evaluated whether lysates of endothelium could be effectively pulsed in dendritic cells (DCs), to enhance their anti-tumor effects.

METHODS

For this purpose, we prepared DCs of BALB/c mouse, incubated them with lysates of autologous or xenogeneic endothelium, and tested their anti-tumor effects in two syngeneic models of colon cancer.

RESULTS

DCs pulsed with the respective endothelium lysates significantly inhibited the growth of subcutaneous tumors as well as pulmonary metastases in mice, and their anti-tumor effect was superior to that of unpulsed DCs. Immunohistopathological analysis showed significant decrease in the mean vascular density of tumors, correlating well with the extent of tumor inhibition. In vitro analysis of splenocytes isolated from immunized mice revealed an induction of cytotoxic T lymphocytes and activation of natural killer cells, with a lytic activity against activated endothelium but not tumor cells. In addition, antibodies reacting with activated endothelium, but not tumor cells, were detected in murine sera by ELISA, and their function was confirmed by complement-dependent cytotoxicity assay.

CONCLUSIONS

Our present results suggest that lysates of endothelium can be effectively pulsed in DCs and enhance their anti-tumor effects through induction of anti-angiogenesis, and therefore should have important clinical implications for adjuvant cancer therapy.

Lymphocyte Subpopulations in Melanoma Patients Treated with Dendritic Cell Vaccines

The main goal of cancer immunotherapy is to induce or boost tumor-specific effector cells able to eliminate or reduce tumor progression. In this study, we characterized lymphocyte phenotypes in melanoma patients receiving dendritic cell (DC)-based vaccinotherapy. We found that several biological markers served as unfavorable prognostic factors for patients' response to therapy. This included decrease of CD4+ and CD8+ lymphocyte levels, 10% and higher increase of CD16+CD3+CD8+ lymphocyte population, and increase of CD16+CD8+perforin+ T lymphocytes, especially in combination with decreased levels of CDI6+CD8(-)perforin+ and CD8+CD16(-)perforin+ cells. Increase in CD8+CD16(-)perforin+ T lymphocytes with normal levels of CD16+CD8(-)perforin+ cells and the absence of CD16+CD8+perforin+ and regulatory lymphocytes were shown to be the positive prognostic markers for patients' response to DC vaccines.

Overexpression of interleukin-12 enables dendritic cells to activate NK cells and confer systemic antitumor immunity

Dendritic cells (DC) are initiators of T cell-mediated immunity. However, less is known about the relationship between DC and natural killer (NK) cells, and direct evidence of their interaction in vivo is scarce. Interleukin (IL)-12 is an activator of both DC and NK cells. We postulated that secretion of IL-12 by DC would enable them to activate NK cells. Bone marrow-derived DC propagated only in granulocyte macrophage colony-stimulating factor did not activate NK cells. In contrast, DC engineered to express IL-12 markedly stimulated NK cells as determined by coculture experiments in vitro, assays of NK cells isolated from treated animals, and survival experiments in a systemic tumor model. Activation depended on both DC-NK cellular interaction and secretion of IL-12. Adoptive transfer of DC expressing IL-12 to mice markedly increased NK cell interferon-gamma production and lytic activity in vivo. Treated mice were also protected against B16 melanoma hepatic metastases. The in vivo effects on NK cells were DC-specific. Administration of IL-12 protein alone or melanoma cells or fibroblasts engineered to secrete IL-12 were only weakly activating. Our findings demonstrate that IL-12 expression by DC enables them to activate NK cells and provide evidence for a substantial DC-NK relationship in vivo.

Dendritic cell-tumor coculturing vaccine can induce antitumor immunity through both NK and CTL interaction

Immunization of dendritic cells (DC) pulsed with tumor antigen can activate tumor-specific cytotoxic T lymphocytes (CTL) that are responsible for protection and regression. We show here that immunization with bone marrow-derived DC cocultured with tumor cells can induce a protective immunity against challenges to viable tumor cells. In this study, we further investigated the mechanism by which the antitumor activity was induced. Immunization of mice with DC cocultured with murine colon carcinoma. CT-26 cells, augmented CTL activity against the tumor cells. Concomitantly, an increase in natural killer (NK) cell activity was also detected in the same mice. When DC were fixed with paraformaldehyde prior to coculturing with tumor cells, most of the CTL and NK cell activity diminished, indicating that DC are involved in the process of presenting the tumor antigen(s) to CTL. NK cell depletion in vivo produced markedly low tumor-specific CTL activity responsible for tumor prevention. In addition, RT-PCR analysis confirmed the high expression of INF-gamma mRNA in splenocytes after vaccination with DC cocultured with tumors, but low expression in splenocytes from NK-depleted mice. Most importantly, the tumor protective effect rendered to DC by the coculturing with CT-26 cells was not observed in NK-depleted mice, which suggests that DC can induce an antitumor immune response by enhancing NK cell-dependent CTL activation. Collectively, our results indicate that NK cells are required during the priming of cytotoxic T-cell response by DC-based tumor vaccine and seem to delineate a mechanism by which DC vaccine can provide the desired immunity.