Interferon-γ induces regression of epithelial cell carcinoma: critical roles of IRF-1 and ICSBP transcription factors

Abstract

We have developed an epithelial cell carcinoma model for studying efficacy of IFNc gene therapy and have identified components of IFNc-signaling pathway responsible for its direct anti-tumor actions. The tumor results from ectopic expression of SV40 Large T-Antigen (SV40 T-Ag) oncogene in lens of transgenic mouse (aT3) and complete regression of the tumor is induced by targeting expression of IFNc into malignant lens cells. Inflammatory cells are absent in lens of aT3 or DT (co-expressing IFNc and SV40-T-Antigen) mice and the transformed lens cells are non-immunogenic, suggesting non-involvement of immunologic cells. We show that IFNc has direct growth-inhibitory effects on tumor cells, induces death of tumor cells by apoptosis and that these effects are mediated by two transcription factors, IRF-1 (interferon-regulatory factor-1) and ICSBP (interferon-consensus sequence-binding protein) induced by IFNc. Furthermore, stable transfection with ICSBP or IRF-1 construct inhibits lens carcinoma cell growth by upregulating Caspase-1, p21 WAF1 and p27 expression. In contrast, tumor progression in aT3 lens correlates with inhibition of IRF-1 and ICSBP expression. Our results suggest that IFNc gene therapy maybe effective in malignant diseases for which DNA tumor viruses are etiologic agents and that antitumor actions of IRF-1/ ICSBP can be exploited therapeutically to circumvent adverse clinical effects associated with IFN therapy.

Antiproliferative Activity of IL-27 on Melanoma

“…To next confirm the enhancement, B16F10 transfectants were stimulated with various concentrations of IL-27 for 24 h, and total cell lysate was prepared and subjected to Western blot analysis. Among these enhanced molecules, we focused on two IRF members, IRF-1 and IRF-8, because they were reported to possess a tumor suppressor activity (38,39). Consistent with the microarray data, IL-27 greatly enhanced the expression of both IRF-1 and IRF-8 at protein levels in a dose-dependent manner in B16F10 tranfectant expressing wildtype WSX-1, but not in that expressing vector alone or mutant WSX-1 (Fig.…”

“…IRF-1 is a transcriptional factor originally identified as a regulator of the IFN-␤ gene and initiates the transcription of specific genes including IFN-␣ and ␤, MHC class I and II expression, inducible NO synthase, IL-12, and IL-15 (40). In addition, several studies demonstrated that IRF-1 and IRF-8 function as a tumor suppressor (38,39). For instance, ectopic expression of IRF-1 can revert oncogene-transformed culture cells to a normal phenotype (41), whereas the loss of IRF-1 contributes to tumor development in conjunction with c-Ha-ras in vivo (42).…”

Wilms’ tumor gene 1 protein represses the expression of the tumor suppressor interferon regulatory factor 8 in human hematopoietic progenitors and in leukemic cells

“…In some cases of carcinoma, the tumor suppressor IRF8 is silenced by strong methylation of the promoter, 39,41 leading to perturbed response to INFg. 44 The methylation status of the proximal promoter near the transcription start site of IRF8 was previously investigated in U937 cells.…”

“…[39][40][41] In AML, 7 out of 21 analyzed samples showed signs of promoter methylation. 42 However, high expression of IRF8 in the presence of methylated promoter has been reported for leukemic cell lines.…”

Decreased accumulation of immune regulatory cells is correlated to the antitumor effect of IFN-γ overexpression in the tumor

“…We have also shown that the tumor-induced immuno-suppression observed in these mammary tumor bearers is associated with an accumulation of myeloid-derived suppressor cells in several peripheral organs (10) as well as a decrease in the IFN-γ peripheral circulation and its production by T cells (27). A number of studies have revealed an important role for IFN-γ in tumor immunity (31)(32)(33). It has also been shown that IFN-γ has direct anti-proliferative, apoptotic, and anti-angiogenic effects that could complement its indirect effects on anti-tumor immunity (4).…”