Therapeutic potential of interleukin-27 against cancers in preclinical mouse models

Abstract

Since we first reported the antitumor efficacy of IL-27 in 2004, accumulating evidence obtained by several groups using a variety of preclinical mouse models indicates that IL-27 possesses potent antitumor activity against various types of tumors through multiple mechanisms depending on the characteristics of individual tumors without apparent adverse effects.

Abbreviations

ADCC

antibody-dependent cell-mediated cytotoxicity

COX-2

cyclooxygenase-2

DC

dendritic cell

EBI3

Epstein–Barr virus-induced gene 3

EMT

epithelial–mesenchymal transition

gp

glycoprotein

IL

interleukin

IRF

interferon regulatory factor

MHC

major histocompatibility complex

MMP

matrix metalloproteinase

NK

natural killer

PD-L1

programmed death-ligand 1

PGE₂

prostaglandin E₂

poly(I:C)

polyinosinic-polycytidylic acid

STAT

signal transducer and activator of transcription

Tim-3

T-cell immunoglobulin and mucin domain-3

TLR

Toll-like receptor

Tr1

IL-10-producing regulatory T

TRAIL

tumor necrosis factor-related apoptosis-inducing ligand

Treg

regulatory T

VEGF

vascular endothelial growth factor.

Cancer immunotherapy has become one of the most promising new treatments that harnesses powers of the immune system to control cancer and achieve long-term cure. This strategy includes therapeutic vaccines, T-cell checkpoint inhibitors, adoptive therapy of genetically modified immune cells, elimination of immunosuppressive cells such as regulatory T (Treg) cells, and new cytokines. Interleukin (IL)-27 is one of the IL-12 family cytokines, which play critical roles in the regulation of differentiation into respective helper T (Th) cells and their functions.¹ IL-27 consists of p28, which is also called IL-30, and Epstein–Barr virus-induced gene 3 (EBI3), and its receptor (R) is composed of IL-27Rα (WSX-1) and glycoprotein (gp)130, a common receptor subunit for the IL-6 family cytokines.¹ IL-27 possesses both pro-inflammatory and anti-inflammatory properties; it promotes the early induction of Th1 differentiation and generation of cytotoxic T lymphocytes (CTLs), but it inhibits the differentiation of naive CD4⁺ T cells into Th2, Th9, and Th17 cells and suppresses the production of pro-inflammatory cytokines through activation of both signal transducer and activator of transcription (STAT)1 and STAT3.¹

Antitumor effect of IL-27 was first demonstrated in 2004 using mouse colon carcinoma Colon 26 transfected with IL-27 expression vector, which greatly reduced tumor growth through mainly CD8⁺ T cells.² Since then accumulating evidence by several groups has revealed that IL-27 possesses potent antitumor activity against a variety of tumor models, ranging from a transplanted mouse tumor genetically engineered to secret IL-27 before transplantation to a human therapeutic model by injection of IL-27 protein into immunodeficient mice after transplantation of human tumor as preclinical tumor models.^2-7 Molecular mechanisms of the antitumor activity were demonstrated to be mediated in multiple ways by CD8⁺ T cells,² natural killer (NK) cells,³ and macrophages,⁴ antibody-dependent cell-mediated cytotoxicity (ADCC), anti-angiogenesis,^5,6 direct antiproliferative effects,⁷ inhibition of expression of cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂), and suppression of epithelial–mesenchymal transition (EMT),⁴ depending on the characteristics of individual tumors (Fig. 1). Since several tumors were revealed to express both IL-27R subunits on the cell surface, IL-27 elicited direct antiproliferative effects via WSX-1/STAT1 signaling, presumably, by its cytostatic effects rather than by cytotoxic effects.¹ Recently, we have further elucidated a novel antitumor mechanism that IL-27 augments the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and Toll-like receptor 3 (TLR3) in human melanoma cell lines, SK-MEL-13, 28, and 37, and that IL-27 inhibits the tumor growth in cooperation with a TRL3 agonist, polyinosinic-polycytidylic acid [poly(I:C)], partly in a TRAIL-dependent manner.⁷ Moreover, repeated injections of IL-27 protein and poly(I:C) cooperatively suppressed in vivo tumor growth of human melanoma in immunodeficient non-obese diabetic/severe combined mice.⁷ Similar therapeutic effects by repeated injections of IL-27 protein were also demonstrated against various types of human tumors transplanted in immunodeficient mice.^4,6 The human tumors so far revealed to be susceptible to the treatment by IL-27 are not only melanoma⁷ but also multiple myeloma,⁶ B-acute lymphoblastic leukemia, follicular lymphoma, diffuse large B-cell lymphoma, acute myeloid leukemia, prostate cancer, and non-small cell lung cancer.⁴ IL-27 strongly inhibited their tumor growth in vivo mainly due to suppression of pro-angiogenesis-related molecules such as vascular endothelial growth factors, angiopoietins, and matrix metalloproteinases, and also due to inverse augmentation of anti-angiogenesis-related molecules such as tissue inhibitor of metalloproteinase.^5,6

Figure 1.

Potent antitumor activity of IL-27 through multiple mechanisms, which are mediated by CD8⁺ T cells, NK cells, macrophages, macrophages, ADCC, anti-angiogenesis, direct anti-proliferative effect, inhibition of COX-2 and PGE₂ expression, and suppression of EMT, depending on the characteristics of individual tumors. Abbreviations: ADCC, antibody-dependent cell-mediated cytotoxicity; COX-2, cyclooxygenase-2; DC, dendritic cell; EBI3, Epstein–Barr virus-induced gene 3; EMT, epithelial–mesenchymal transition; gp, glycoprotein; IL, interleukin; IRF, interferon regulatory factor; MHC, major histocompatibility complex; MMP, matrix metalloproteinase; NK, natural killer; PD-L1, programmed death-ligand 1; PGE₂, prostaglandin E₂; poly(I:C), polyinosinic-polycytidylic acid; STAT, signal transducer and activator of transcription; Tim-3, T-cell immunoglobulin and mucin domain-3; TLR, Toll-like receptor; Tr1, IL-10-producing regulatory T; TRAIL, tumor necrosis factor-related apoptosis-inducing ligand; Treg, regulatory T; VEGF, vascular endothelial growth factor.

Since IL-27 possesses both pro-inflammatory and anti-inflammatory activities,¹ some of them such as IL-27-mediated augmentation of IL-10 production and up-regulation of programmed death-ligand 1 (PD-L1) may function against its antitumor effects, although the role of IL-27 in the induction of Treg cells is still controversial.^8,9 Therefore, it is reasonable to consider that the potent antitumor activity of IL-27 is the sum of these positive and negative effects on the immune responses to tumors. Although the role of IL-10 in induction of antitumor immune responses is often controversial, recent evidence supports a positive role for IL-10 in the induction of antitumor CTL responses, which were demonstrated in IL-10-deficeient mice and IL-10-transgenic mice. Indeed, IL-10 production by IL-27-induced CTLs was recently demonstrated to contribute to the generation of memory precursor-like effector CTLs to augment antitumor immunity.¹⁰ Moreover, IL-27 was recently shown to induce the expression of PD-L1 in T cells, a major mediator of T-cell exhaustion, which hampers the induction of antitumor immune responses.¹ However, since antibody drugs have currently become very popular as one of the most promising cancer immunotherapies, IL-27 injection could augment antitumor immune responses in synergy with antibodies against immune checkpoints such as PD-L1, whose possibility remains to be clarified. On the other hand, IL-27 was initially demonstrated to inhibit the differentiation of naive CD4⁺ T cells to Treg cells,¹ whereas recent reports oppositely revealed that IL-27 does not inhibit the generation of Treg cells but rather promotes it; IL-27 produced a distinct Treg cell population which expresses T-cell-specific T-box transcription factor T-bet and CXCR3, to control Th1-mediated immunity.¹ Similar paradoxical roles of IL-27 in the tumor microenvironment were also reported.^8,9 Thus, the effects of IL-27 on Treg cells may depend on the context. However, so far there is no report showing that injection of IL-27 protein or tumor cells transfected with IL-27 expression vector would augment the number of Treg cells in mice bearing tumors, although transgenic mice over-expressing IL-27 were previously demonstrated to decrease the number of Treg cells,¹ which could presumably result in enhancement of antitumor immune responses. Besides, since IL-27 was shown to have lower toxicity in mouse models,^2,3 collectively, IL-27 may have great potential as one of the most promising therapeutic cytokines against cancer.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.