Immune enhancement and anti-tumour activity of IL-23

Abstract

Immunotherapy, including the use of cytokines and/or modified tumour cells immune stimulatory cytokines, can enhance the host anti-tumour immune responses. Interleukin-23 (IL-23) is a relative novel cytokine, which consists of a heterodimer of the IL-12p40 subunit and a novel p19 subunit. IL-23 has biological activities similar to but distinct from IL-12. IL-23 can enhance the proliferation of memory T cells and the production of IFN-gamma, IL-12 and TNF-alpha from activated T cells. IL-23 activates macrophages to produce TNF-alpha and nitric oxide. IL-23 can also act directly on dendritic cells and possesses potent anti-tumour and anti-metastatic activity in murine models of cancer. IL-23 can also induce a lower level of IFN-gamma production compared with that induced by IL-12. This may make IL-23 an alternative and safer therapeutic agent for cancer, as IL-12 administration can lead to severe toxic side effects because of the extremely high levels of IFN-gamma it induces.

Fig. 1

Effects of IL-23 on macrophages. Peritoneal cells were collected from mice 5 days after i.p. injection, washed in PBS and plated onto a plastic surface for 1 h in serum-free culture medium. Adherent cells were collected as peritoneal macrophages. a Evaluation of the capacity of peritoneal macrophages to produce NO. Triplicate samples of peritoneal macrophages were cultured in medium alone or medium with LPS (2 × 10⁵ cells/microtiter well). Following a 48 h incubation (in 37°C, 5% CO₂ incubator), NO in culture supernatants was quantified using Griess reagent. b Production of TNF-α of peritoneal macrophages. Triplicate samples of macrophages (2 × 10⁵ cells/well) were cultured in 96-well microtiter plates with or without LPS for 48 h, then culture supernatants were collected and TNF-α levels were assessed by ELISA. c Cytotoxic activity of macrophages in vitro. Colon26 cells in their exponential growth phase were incubated for 24 h with medium containing 1.5 μCi/ml [³H-methyl]thymidine. The macrophages (1 × 10⁵ cells/well) and ³H-labelled Colon26 cells (1 × 10⁴ cells/well) were plated into wells of 96-well microtiter plates. After 48 h incubation, the wells were washed twice with PBS, and adherent viable cells were lysed with 0.1 ml 0.1 N NaOH. The lysates were harvested and [³H-methyl]thymidine levels counted using a liquid scintillation counter. The percentage of cytotoxicity was calculated by formula: cytotoxicity (%) = (A − B)/A × 100, where A is cpm in the culture of target cells alone, and B is the cpm in the test culture

Fig. 2

Production of cytokines by spleen cells. Spleen cells were collected from mice at day 30 after inoculation. The spleen cells (1 × 10⁶ cells/ml) were cultured with mitocycin C-treated Colon26 cells (1 × 10⁵ cells/ml) in culture medium. Culture supernatants were collected 48 h later and the concentration of secreted cytokines examined using standard ELISA assays