IFN-ß activates cytotoxic function of human natural killer cells toward IL-27 and poly(I:C) stimulated PC3 and DU145 cells.

Natural killer (NK) cell phenotype and function are altered in patients with prostate cancer, and increased NK cell activity is associated with a better prognosis in patients with disease. For patients with advanced stage prostate cancer, immunotherapies are a promising approach when standard treatment options have been exhausted. With the rapid emergence of NK cell-based therapies, it is important to understand the mechanisms by which NK cells can be triggered to kill cancer cells that have developed immune-evasive strategies. Altering the cytokine profiles of advanced prostate cancer cells may be an area to explore when considering ways in which NK cell activation can be modulated. We have previously demonstrated that combining the cytokine, IL-27, with TLR3 agonist, poly(I:C), changes cytokine secretion in the advanced prostate cancer models, PC3 and DU145 cells. Herein, we extend our previous work to study the effect of primary human NK cells on prostate cancer cell death in an in vitro co-culture model. Stimulating PC3 and DU145 cells with IL-27 and poly(I:C) induced IFN-ß secretion, which was required for activation of primary human NK cells to kill these stimulated prostate cancer cells. PC3 cells were more sensitized to NK cell-mediated killing when compared to DU145 cells, which was attributed to differential levels of IFN-ß produced in response to stimulation with IL-27 and poly(I:C). IFN-ß increased granzyme B secretion and membrane-bound TRAIL expression by co-cultured NK cells. We further demonstrated that these NK cells killed PC3 cells in a partially TRAIL-dependent manner. This work provides mechanistic insight into how the cytotoxic function of NK cells can be improved to target cancer cells.

Antiviral Activities of Interleukin-27: A Partner for Interferons?

Emergence of new, pandemic-level viral threats has brought to the forefront the importance of viral immunology and continued improvement of antiviral therapies. Interleukin-27 (IL-27) is a pleiotropic cytokine that regulates both innate and adaptive immune responses. Accumulating evidence has revealed potent antiviral activities of IL-27 against numerous viruses, including HIV, influenza, HBV and more. IL-27 contributes to the immune response against viruses indirectly by increasing production of interferons (IFNs) which have various antiviral effects. Additionally, IL-27 can directly interfere with viral infection both by acting similarly to an IFN itself and by modulating the differentiation and function of various immune cells. This review discusses the IFN-dependent and IFN-independent antiviral mechanisms of IL-27 and highlights the potential of IL-27 as a therapeutic cytokine for viral infection.

IL-27 Improves Prophylactic Protection Provided by a Dead Tumor Cell Vaccine in a Mouse Melanoma Model.

The protocol used to induce cell death for generating vaccines from whole tumor cells is a critical consideration that impacts vaccine efficacy. Here we compared how different protocols used to induce cell death impacted protection provided by a prophylactic whole tumor cell vaccine in a mouse melanoma model. We found that melanoma cells exposed to γ-irradiation or lysis combined with UV-irradiation (LyUV) provided better protection against tumor challenge than lysis only or cells exposed to UV-irradiation. Furthermore, we found that the immunoregulatory cytokine, IL-27 enhanced protection against tumor growth in a dose-dependent manner when combined with either LyUV or γ-irradiated whole tumor cell vaccine preparations. Taken together, this data supports the use of LyUV as a potential protocol for developing whole tumor cell prophylactic cancer vaccines. We also showed that IL-27 can be used at low doses as a potent adjuvant in combination with LyUV or γ-irradiation treated cancer cells to improve the protection provided by a prophylactic cancer vaccine in a mouse melanoma model.

TLR7 Ligation Inhibits TLR8 Responsiveness in IL-27-Primed Human THP-1 Monocytes and Macrophages.

Regulation of proinflammatory cytokine expression is critical in the face of single-stranded RNA (ssRNA) virus infections. Many viruses, including coronavirus and influenza virus, wreak havoc on the control of cytokine expression, leading to the formation of detrimental cytokine storms. Understanding the regulation and interplay between inflammatory cytokines is critical to the identification of targets involved in controlling the induction of cytokine expression. In this study, we focused on how the antiviral cytokine interleukin-27 (IL-27) regulates signal transduction downstream of Toll-like receptor 7 (TLR7) and TLR8 ligation, which recognize endosomal single-stranded RNA. Given that IL-27 alters bacterial-sensing TLR expression on myeloid cells and can inhibit replication of single-stranded RNA viruses, we investigated whether IL-27 affects expression and function of TLR7 and TLR8. Analysis of IL-27-treated THP-1 monocytic cells and THP-1-derived macrophages revealed changes in mRNA and protein expression of TLR7 and TLR8. Although treatment with IL-27 enhanced TLR7 expression, only TLR8-mediated cytokine secretion was amplified. Furthermore, we demonstrated that imiquimod, a TLR7 agonist, inhibited cytokine and chemokine production induced by a TLR8 agonist, TL8-506. Delineating the immunomodulatory role of IL-27 on TLR7 and TLR8 responses provides insight into how myeloid cell TLR-mediated responses are regulated during virus infection.

IL-27, IL-30, and IL-35: A Cytokine Triumvirate in Cancer.

The role of the immune system in anti-tumor immunity cannot be overstated, as it holds the potential to promote tumor eradication or prevent tumor cell escape. Cytokines are critical to influencing the immune responses and interactions with non-immune cells. Recently, the IL-12 and IL-6 family of cytokines have accumulated newly defined members each with specific immune functions related to various cancers and tumorigenesis. There is a need to better understand how cytokines like IL-27, IL-30, and IL-35 interact with one another, and how a developing tumor can exploit these interactions to enhance immune suppression. Current cytokine-based immunotherapies are associated with cytotoxic side effects which limits the success of treatment. In addition to this toxicity, understanding the complex interactions between immune and cancer cells may be one of the greatest challenges to developing a successful immunotherapy. In this review, we bring forth IL-27, IL-30, and IL-35, "sister cytokines," along with more recent additions to the IL-12 family, which serve distinct purposes despite sharing structural similarities. We highlight how these cytokines function in the tumor microenvironment by examining their direct effects on cancer cells as well their indirect actions via regulatory functions of immune cells that act to either instigate or inhibit tumor progression. Understanding the context dependent immunomodulatory outcomes of these sister cytokines, as well as their regulation within the tumor microenvironment, may shed light onto novel cancer therapeutic treatments or targets.

Poly(I:C)-Mediated Death of Human Prostate Cancer Cell Lines Is Induced by Interleukin-27 Treatment.

Interleukin (IL)-27 is a promising anti-cancer cytokine with therapeutic potential. Exhibiting overlapping properties with type I and II interferons (IFNs), IL-27 impacts cancer cell viability and immune cell activity. Known to modulate toll-like receptor (TLR) expression, we investigated whether IL-27 affected TLR-mediated death in cancer cells. Using DU145 and PC3 cell lines as models of prostate cancer, we investigated whether IL-27 and IFN-γ affect TLR3-mediated cell death. Our results demonstrate that when IL-27 or IFN-γ is added with polyinosinic-polycytidylic acid [poly(I:C)], type I IFN (IFN-I) expression increases concurrently with cell death. IL-27 and IFN-γ enhanced TLR3 expression, suggesting a mechanism for sensitization to cell death. Further, PC3 cells were more sensitive to IL-27/poly(I:C)-induced cell death compared with DU145 cells. This correlated with higher production of IFN-ß and inducible protein-10 versus IL-6 in response to treatment of PC3 cells compared with DU145. Taken together, this study demonstrates a potential role for IL-27 in the treatment of prostate cancer.