Proteomic analysis uncovers common effects of IFN-γ and IL-27 on the HLA class I antigen presentation machinery in human cancer cells

Abstract

IL-27, a member of the IL-12-family of cytokines, has shown anti-tumor activity in several pre-clinical models due to anti-proliferative, anti-angiogenic and immune-enhancing effects. On the other hand, IL-27 demonstrated immune regulatory activities and inhibition of auto-immunity in mouse models. Also, we reported that IL-27, similar to IFN-γ, induces the expression of IL-18BP, IDO and PD-L1 immune regulatory molecules in human cancer cells. Here, a proteomic analysis reveals that IL-27 and IFN-γ display a broad overlap of functions on human ovarian cancer cells. Indeed, among 990 proteins modulated by either cytokine treatment in SKOV3 cells, 814 showed a concordant modulation by both cytokines, while a smaller number (176) were differentially modulated. The most up-regulated proteins were common to both IFN-γ and IL-27. In addition, functional analysis of IL-27-regulated protein networks highlighted pathways of interferon signaling and regulation, antigen presentation, protection from natural killer cell-mediated cytotoxicity, regulation of protein polyubiquitination and proteasome, aminoacid catabolism and regulation of viral protein levels.Importantly, we found that IL-27 induced HLA class I molecule expression in human cancer cells of different histotypes, including tumor cells showing very low expression. IL-27 failed only in a cancer cell line bearing a homozygous deletion in the B2M gene. Altogether, these data point out to a broad set of activities shared by IL-27 and IFN-γ, which are dependent on the common activation of the STAT1 pathway. These data add further explanation to the anti-tumor activity of IL-27 and also to its dual role in immune regulation.

IL-27 mediates HLA class I up-regulation, which can be inhibited by the IL-6 pathway, in HLA-deficient Small Cell Lung Cancer cells

“…In view of the defective expression of HLA class I molecules in SCLC [9], we tested whether IL-27 could up-regulate membrane HLA, as recently reported in other tumor cell types [18]. To this end, we cultured a panel of 5 SCLC cell lines for 48 h with IL-27 or IFN-γ, a known inducer of HLA expression, as control.…”

“…Although IL-27 also activates STAT3 phosphorylation, the STAT1-dependent, IFN-like effects prevail, in different cellular models [18, 29]. We then analyzed the effects of sIL-6R/IL-6 on IL-27-mediated STAT signaling.…”

“…Indeed, recent studies by proteomics [18] or gene expression profiling [29] in different cell types showed a broad overlap between IFN-γ and IL-27 effects, including the induction of several components of the HLA class I antigen presentation machinery. However, the NCI-H146 cell line was completely unresponsive to IL-27 both in terms of HLA class I induction and STAT1/3 signaling, suggesting heterogeneity in the response to IL-27 in different SCLC.…”

“…We recently reported that IL-27, a heterodimer cytokine related to both IL-6 and IL-12 cytokine families [16, 17], has several functional activities in common with IFN-γ, in different cancer cells [18]. Indeed, IL-27 up-regulates multiple components of the HLA class I antigen presentation machinery in human cancer cells, thus facilitating Cytotoxic T Lymphocyte (CTL) recognition.…”

“…On the other hand, IL-27 induces the expression of immune-regulatory molecules such as the IL-18 natural inhibitor, IL-18BP [26], the tryptophan catabolic enzyme IDO and PD-L1 [27], in neoplastic cells. Therefore, IL-27 may have a dual role in anti-tumor immunity [28] and shares several immune-regulatory functions with IFN-γ, in relationship to the common usage of the STAT1 intracellular signaling pathway [18, 19, 23, 29]. …”