Interleukin-33, a Potential Cytokine Expressed in the Tumor Microenvironment Is Involved in Antitumor Immunotherapy Through Facilitating CD8+ T Cells

The Interleukin-33/ST2 Axis Enhances Lung-Resident CD14+ Monocyte Function in Patients with Non-Small Cell Lung Cancer

Interleukin-33 (IL-33) binds to its cognate receptor suppression of tumorigenicity 2 (ST2), leading to critical modulatory roles in immune responses during inflammation and cancers. The aim of this study was to investigate the role of IL-33/ST2 signaling in monocyte function in non-small cell lung cancer (NSCLC). Sixty-two NSCLC patients and nineteen controls were enrolled. IL-33 levels and ST2 expression were measured in peripheral blood and bronchoalveolar lavage fluid (BALF) by ELISA and flow cytometry. HLA-DR expression by CD14+ monocytes, granzyme B and proinflammatory cytokine secretion were also investigated in lipopolysaccharide-stimulated cells. CD14+ monocytes purified from BALF in the tumor site were stimulated with IL-33 in vitro, and co-cultured with a lung cancer cell line A549 cells. The cytotoxicity of monocytes with IL-33 stimulation was then assessed. IL-33 levels were lower in the peripheral blood and tumor microenvironment of NSCLC patients. There was no significant difference in peripheral ST2 expression between NSCLC patients and controls. Soluble ST2 levels were increased but membrane-bound ST2 expression in CD14+ monocytes was decreased in tumor microenvironment of NSCLC patients. There were no remarkable differences in either HLA-DR expression or proinflammatory cytokine secretion by circulating CD14+ monocytes between NSCLC patients and controls. CD14+ monocytes in the tumor microenvironment revealed a dysfunctional phenotype, which presented as lower HLA-DR expression and reduced granzyme B and proinflammatory cytokines. A higher concentration of IL-33 stimulation promoted tumor-resident CD14+ monocyte-induced target cell death. The present study indicates that IL-33/ST2 signaling pathway might enhance the activity of tumor-resident CD14+ monocytes in NSCLC.

PD-1 blockade combined with IL-33 enhances the antitumor immune response in a type-1 lymphocyte-mediated manner

PD-1 immune checkpoint blockade and cytokine IL-33 have shown significant therapeutic effects in tumor immunotherapy. These therapies promote CD8⁺ T cell activation, proliferation, and effector functions. However, there were few research about the combined therapy efficacy. In this study, we established B16-empty vector and B16-IL33 melanoma mouse models and treated with PD-1 monoclonal antibody. We reported that PD-1 blockade combined with cytokine IL-33 further inhibited tumor progression and prolonged the survival of tumor-bearing mice. Mechanistically, the combination therapy was found to further facilitate CD4⁺ and CD8⁺ T lymphocytes accumulation, and enhance the antitumor effects of CD4⁺or CD8⁺tumor-infiltrating lymphocytes by promoting type-1 immune response within the tumor microenvironment using flow cytometry and quantitative real time polymerase chain reaction. Thus, PD-1 blockade combined with IL-33 has application potential in tumor immunotherapy. Further, this study provides a new promising strategy and theoretical basis for tumor combination immunotherapy.

Interleukin-33 pretreatment promotes metastatic growth of murine melanoma by reducing the cytotoxic capacity of CD8+ T cells and enhancing regulatory T cells

Interleukin-33 (IL-33) regulates innate and acquired immune response to pathogens, self-antigens and tumors. IL-33 effects on tumors depend on the dose and mode of administration along with the type of malignancy. We studied the effects of IL-33 on the development of primary and metastatic melanoma induced by B16-F1 cell line in C57BL/6 mice. Intraperitoneally applied IL-33 restricts primary tumor growth. When administered intranasally 3 days prior to the intravenous injection of the tumor cells, IL-33 promoted growth of B16-F1 melanoma metastases, while B16-F10 gave massive metastases independently of IL-33. To mimic natural dissemination, we next used a limited number (5 × 10⁴) of B16-F1 cells intravenously followed by application of IL-33 intraperitoneally. IL-33 increased the size of metastases (10.96 ± 3.96 mm²) when compared to the control group (0.86 ± 0.39 mm²), without changing incidence and number of metastases. IL-33 increased expression of ST2 on both tumor and immune cells in metastases. Also, IL-33 enhanced eosinophils and anti-tumor NK cells in the lung. The striking finding was reduced cytotoxicity of CD8⁺ T cells derived from metastatic lung of IL-33 injected mice. IL-33 reduced the percentage of TNF-α⁺ and IFN-γ⁺ CD8⁺ T cells while increasing the frequency of CD8⁺ T cells that express inhibitory molecules (PD-1, KLRG-1 and CTLA-4). There was a significant accumulation of CD11b⁺Gr-1⁺ myeloid suppressor cells and FoxP3⁺, IL-10⁺ and CTLA-4⁺ regulatory T cells in the metastatic lung of IL-33 injected mice. The relevance of IL-33 for melanoma metastases was also documented in a significantly increased level of serum IL-33 in stage III melanoma patients.

Association between interleukin-36γ and tumor progression in non-small cell lung cancer

Immunotherapy is effective in improving the survival and prognosis of patients with non-small cell lung cancer (NSCLC), and identifying effective immunomarkers is important for immunotherapy. Interleukin (IL)-36γ is a novel immunomarker that has an important function in the antitumor immune response. The present study investigated the association between IL-36γ and NSCLC to provide novel insight into immunotherapy for patients with NSCLC. Tissue microarrays of lung adenocarcinoma and squamous cell carcinoma were purchased for immunohistochemical analysis of IL-36γ expression levels and clinical parameters. In addition, fresh clinical NSCLC and adjacent normal tissue samples were collected to analyze IL-36γ mRNA expression levels using quantitative PCR. IL-36γ protein was primarily located in the cytoplasm, with a small quantity in the nucleus, and IL-36γ mRNA and protein expression levels in lung cancer tissues were significantly higher compared with those in adjacent normal tissues. Elevated IL-36γ protein expression levels were significantly associated with a higher tumor grade of lung adenocarcinoma; however, IL-36γ mRNA expression levels were inversely associated with the clinical Tumor-Node-Metastasis stage in patients with lung squamous cell carcinoma. In addition, patients with adenocarcinoma with high IL-36γ protein expression levels tended to longer post-operative survival times. These findings indicate that IL-36γ may have potential as an immunomarker for prediction of tumor progression and survival in patients with NSCLC.

Characterization of peripheral blood mononuclear cells isolated using two kinds of leukocyte filters

OBJECTIVE

The objective of this study was to compare the activity and biological function of leukocytes isolated using apheresis platelet leukoreduction system chambers (LRSC), whole blood leukoreduction filters (LRF), and leukocytes in unfiltered peripheral whole blood (WB).

METHODS

Peripheral blood mononuclear cells (PBMCs) and granulocytes were obtained by density gradient centrifugation using recovery filters and WB. Flow cytometry was used to detect the activity, phenotype, and apoptosis ratio of each cell subtype.

RESULTS

The proportion of lymphocytes obtained from PBMCs was similar when using the two different filters as compared to traditional isolation; however, there were significant differences between the monocytes and granulocytes. The phenotypic frequency of lymphocytes was similar, but the apoptosis rate of lymphocytes from the two filters was slightly higher. Additionally, monocytes isolated via the three sources were able to be induced into dendritic cells expressing specific molecules; Granulocytes isolated from the LRF showed a lower purity and a higher level of apoptosis than granulocytes isolated from the WB.

CONCLUSION

Compared with WB, the PBMCs isolated from the filters used in our blood center had no statistical difference in their activity and biological function, but they did differ in the proportion and quantity of monocytes and granulocytes. Our results show that the two filters can be used as an alternative method to collect leukocytes, which solves the problem of an insufficient blood supply for clinical and basic science research. Thus, these filters have significant value beyond their practical use in clinics.