The role of interferon regulatory factor-1 and interferon regulatory factor-2 in IFN-gamma growth inhibition of human breast carcinoma cell lines

Molecular mechanisms of microRNA-301a during tumor progression and metastasis

Cancer is known as one of the leading causes of human deaths globally. Late diagnosis is considered as one of the main reasons for the high mortality rate among cancer patients. Therefore, the introduction of early diagnostic tumor markers can improve the efficiency of therapeutic modalities. MicroRNAs (miRNAs) have a key role in regulation of cell proliferation and apoptosis. MiRNAs deregulation has been frequently reported during tumor progressions. Since, miRNAs have a high stability in body fluids; they can be used as the reliable non-invasive tumor markers. Here, we discussed the role of miR-301a during tumor progressions. MiR-301a mainly functions as an oncogene via the modulation of transcription factors, autophagy, epithelial-mesenchymal transition (EMT), and signaling pathways. This review paves the way to suggest miR-301a as a non-invasive marker for the early tumor diagnosis. MiR-301a can also be suggested as an effective target in cancer therapy.

MicroRNA-301a (miR-301a) is induced in hepatocellular carcinoma (HCC) and down- regulates the expression of interferon regulatory factor-1

Hepatocellular carcinoma (HCC) tumors evade death in part by downregulating expression of the tumor suppressor gene Interferon regulatory factor-1 (IRF-1). However, the molecular mechanisms accounting for IRF-1 suppression in HCC have not been well described. In this study, we identified a novel microRNA-301a (miR-301a) binding site in the 3'-untranslated region (3'- UTR) of the human IRF-1 gene and hypothesized a functional role for miR-301a in regulating HCC growth. We show that miR-301a is markedly upregulated in primary HCC tumors and HCC cell lines, while IRF-1 is down-regulated in a post-transcriptional manner. MiR-301a regulates basal and inducible IRF-1 expression in HCC cells with an inverse relationship between miR-301a and IRF-1 expression in HCC cells. Chronic hypoxia induces miR-301a in HCC in vitro and decreases IRF-1 expression. Finally, miR-301a inhibition increases apoptosis and decreases HCC cell proliferation. These findings suggest that targeting of IRF-1 by miR-301a contributes to the molecular basis for IRF-1 downregulation in HCC and provides new insight into the regulation of HCC by miRNAs.

MIR17HG-miR-18a/19a axis, regulated by interferon regulatory factor-1, promotes gastric cancer metastasis via Wnt/β-catenin signalling

MIR17HG, located on chromosome 13, is a class of Pri-miRNAs that generates six miRNAs: miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1 and miR-92-1. These miRNAs are ubiquitously overexpressed in diverse tumour types and exhibit complex biological links to tumour metastasis. We demonstrated that MIR17HG-derived miR-18a and miR-19a coordinately mediate gastric cancer cell metastasis by directly inhibiting SMAD2 expression and upregulating Wnt/β-catenin signalling. Based on previous studies, we hypothesised that an investigation of MIR17HG inhibition would be beneficial to clinical gastric cancer treatment, and systematically coupled bioinformatics analyses brought interferon regulatory factor-1 (IRF-1) to our attention. We then established stable clones in gastric cancer cells containing a doxycycline-inducible IRF-1 expression system and found that the expression of IRF-1 downregulates the embedded miRNAs of MIR17HG in gastric cancer cells and inhibits gastric cancer cell metastasis by attenuating Wnt/β-catenin signalling. Further rescue assays confirmed the crucial roles of miR-18a and miR-19a in the IRF-1-mediated inhibition of Wnt/β-catenin signalling. We also demonstrated that IRF-1 binds to the transcriptional site in the MIR17HG promoter and inhibits MIR17HG expression. Moreover, IFN-γ induced the IRF-1-mediated downregulation of MIR17HG in gastric cancer cells. Our hypothesis was supported by the results of immunohistochemistry analyses of clinical gastric cancer samples, and we also demonstrated the role of IRF-1 in inhibiting MIR17HG expression and tumour metastasis in vivo. We conclude that IRF-1 inhibits gastric cancer metastasis by downregulating MIR17HG-miR-18a/miR-19a axis expression and attenuating Wnt/β-catenin signalling.

Interferon regulatory factor 1 inactivation in human cancer

Interferon regulatory factors (IRFs) are a group of closely related proteins collectively referred to as the IRF family. Members of this family were originally recognized for their roles in inflammatory responses; however, recent research has suggested that they are also involved in tumor biology. This review focusses on current knowledge of the roles of IRF-1 and IRF-2 in human cancer, with particular attention paid to the impact of IRF-1 inactivation. The different mechanisms underlying IRF-1 inactivation and their implications for human cancers and the potential importance of IRF-1 in immunotherapy are also summarized.

Interferon regulatory factor 1 and a variant of heterogeneous nuclear ribonucleoprotein L coordinately silence the gene for adhesion protein CEACAM1

The adhesion protein carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is widely expressed in epithelial cells as a short cytoplasmic isoform (S-iso) and in leukocytes as a long cytoplasmic isoform (L-iso) and is frequently silenced in cancer by unknown mechanisms. Previously, we reported that interferon response factor 1 (IRF1) biases alternative splicing (AS) to include the variable exon 7 (E7) in CEACAM1, generating long cytoplasmic isoforms. We now show that IRF1 and a variant of heterogeneous nuclear ribonucleoprotein L (Lv1) coordinately silence the CEACAM1 gene. RNAi-mediated Lv1 depletion in IRF1-treated HeLa and melanoma cells induced significant CEACAM1 protein expression, reversed by ectopic Lv1 expression. The Lv1-mediated CEACAM1 repression resided in residues Gly⁷¹-Gly⁸⁹ and Ala³⁸-Gly⁸⁹ in Lv1's N-terminal extension. ChIP analysis of IRF1- and FLAG-tagged Lv1-treated HeLa cells and global treatment with the global epigenetic modifiers 5-aza-2'-deoxycytidine and trichostatin A indicated that IRF1 and Lv1 together induce chromatin remodeling, restricting IRF1 access to the CEACAM1 promoter. In interferon γ-treated HeLa cells, the transcription factor SP1 did not associate with the CEACAM1 promoter, but binding by upstream transcription factor 1 (USF1), a known CEACAM1 regulator, was greatly enhanced. ChIP-sequencing revealed that Lv1 overexpression in IRF1-treated cells induces transcriptional silencing across many genes, including DCC (deleted in colorectal carcinoma), associated with CEACAM5 in colon cancer. Notably, IRF1, but not IRF3 and IRF7, affected CEACAM1 expression via translational repression. We conclude that IRF1 and Lv1 coordinately regulate CEACAM1 transcription, alternative splicing, and translation and may significantly contribute to CEACAM1 silencing in cancer.

MicroRNA-23a downregulates the expression of interferon regulatory factor-1 in hepatocellular carcinoma cells

Interferon regulatory factor-1 (IRF-1) is a tumor-suppressor gene induced by interferon-γ (IFNγ) and plays an important role in the cell death of hepatocellular carcinoma (HCC). HCC tumors evade death in part by downregulating IRF-1 expression, yet the molecular mechanisms accounting for IRF-1 suppression in HCC have not yet been characterized. Previous studies have shown that microRNA-23a (miR-23a) can suppress apoptosis by targeting IRF-1. Therefore, we hypothesized that miR-23a promotes HCC growth by downregulating IRF-1. For the in vivo studies, 7 cases of resected HCC and adjacent liver samples were analyzed. For the in vitro studies, IRF-1 mRNA and protein were examined in HepG2 and Huh-7 HCC cells after IFNγ stimulation by real-time PCR and western blotting, respectively. To determine the role of miR-23a in regulating IRF-1, HepG2 cells were transfected with an miR-23a mimic or inhibitor, and IRF-1 expression was examined. Binding of miR-23a was assessed by cloning the 528-bp human IRF-1 3'-untranslated region (3'UTR) into luciferase reporter plasmid pMIR-IRF-1-3'UTR. The results showed that IRF-1 mRNA expression was downregulated in the human HCC tumor tissues compared to that in the adjacent background liver tissues. IFNγ-induced IRF-1 protein was less in the HepG2 tumor cells compared to that in the primary human hepatocytes. miR-23a expression was inversely correlated with IRF-1, and addition of the miR-23a inhibitor increased basal IRF-1 mRNA and protein. Likewise, the miR-23a mimic downregulated IFNγ-induced IRF-1 protein expression, while the miR-23a inhibitor increased IRF-1. Furthermore, the miR-23a mimic repressed IRF-1-3'UTR reporter activity, while the miR-23a inhibitor increased the reporter activity. These results demonstrated that IRF-1 expression is downregulated in human HCC tumors compared to that noted in the background liver. miR-23a downregulates the expression of IRF-1 in HCC cells, and the IRF-1 3'UTR has an miR‑23a binding site that binds miR-23a and decreases reporter activity. These findings suggest that the targeting of IRF-1 by miR-23a may be the molecular basis for IRF-1 downregulation in HCC and provide new insight into the regulation of HCC by miRNAs.

RelA-Induced Interferon Response Negatively Regulates Proliferation

Both oncogenic and tumor-suppressor activities are attributed to the Nuclear Factor kappa B (NF-kB) pathway. Moreover, NF-kB may positively or negatively regulate proliferation. The molecular determinants of these opposing roles of NF-kB are unclear. Using primary human mammary epithelial cells (HMEC) as a model, we show that increased RelA levels and consequent increase in basal transcriptional activity of RelA induces IRF1, a target gene. Induced IRF1 upregulates STAT1 and IRF7, and in consort, these factors induce the expression of interferon response genes. Activation of the interferon pathway down-regulates CDK4 and up-regulates p27 resulting in Rb hypo-phosphorylation and cell cycle arrest. Stimulation of HMEC with IFN-γ elicits similar phenotypic and molecular changes suggesting that basal activity of RelA and IFN-γ converge on IRF1 to regulate proliferation. The anti-proliferative RelA-IRF1-CDK4 signaling axis is retained in ER+/HER2- breast tumors analyzed by The Cancer Genome Atlas (TCGA). Using immuno-histochemical analysis of breast tumors, we confirm the negative correlation between RelA levels and proliferation rate in ER+/HER2- breast tumors. These findings attribute an anti-proliferative tumor-suppressor role to basal RelA activity. Inactivation of Rb, down-regulation of RelA or IRF1, or upregulation of CDK4 or IRF2 rescues the RelA-IRF1-CDK4 induced proliferation arrest in HMEC and are points of disruption in aggressive tumors. Activity of the RelA-IRF1-CDK4 axis may explain favorable response to CDK4/6 inhibition observed in patients with ER+ Rb competent tumors.

Regulatory systemic effect of postsurgical polychromatic light (480-3400 nm) irradiation of breast cancer patients on the proliferation of tumor and normal cells in vitro

OBJECTIVE

The aim of this work was to study the effect of phototherapy (PT) with percutaneous exposures to polychromatic visible and IR light (pVIS + pIR) on breast cancer (BC) patients at the early postmastectomy period, on the growth-promoting (GP) properties of their blood serum, by evaluating its capability to support proliferation of normal and tumor human cells in vitro.

MATERIAL AND METHODS

After mastectomy, one group of patients was treated daily for 1 week on the sacral area with pVIS + pIR light (480-3400 nm, 40 mW/cm(2), 95% polarization, 24 J/cm(2)). The second group used as a control was sham irradiated. Blood serum samples collected before surgery, and 1 and 8 days after surgery, were added (2.5%) into nutrition media for cells instead of 10% of fetal calf serum. Cell targets were cultures of human fibroblasts (FBs), keratinocytes (KCs), three lines of the human BC cells (BT-474, HBL-100, Hs 578T) and cells of human epidermoid carcinoma (A-431). Cell number was evaluated by staining cell nuclei with crystal violet and a spectrometric assay of the extracted dye.

RESULTS

The day after mastectomy there were no significant changes in the GP activity of sera. After a 7-day PT course, an increase of this activity was recorded for normal FBs and KCs by 18% and 24%, respectively, in comparison with presurgical levels. GP activity of the same patients' sera for all tumor cells, BT-474, HBL-100, Hs 578T and A-431, decreased by 32%, 17%, 11%, and 7% respectively. As a result, enhancement of proliferation of KCs and FBs and inhibition of proliferation of tumor cells was seen.

CONCLUSIONS

The results suggest an effect at the systemic level where pVIS + pIR light may stimulate growth of human skin cells and simultaneously downregulate the proliferation of tumor cells, including BC cells. This argues in favor of the oncological safety of PT for BC patients postsurgically.

Interferon regulatory factor-1 signaling regulates the switch between autophagy and apoptosis to determine breast cancer cell fate

Interferon regulatory factor-1 (IRF1) is a tumor suppressor that regulates cell fate in several cell types. Here, we report an inverse correlation in expression of nuclear IRF1 and the autophagy regulator ATG7 in human breast cancer cells that directly affects their cell fate. In mice harboring mutant Atg7, nuclear IRF1 was increased in mammary tumors, spleen, and kidney. Mechanistic investigations identified ATG7 and the cell death modulator beclin-1 (BECN1) as negative regulators of IRF1. Silencing ATG7 or BECN1 caused estrogen receptor-α to exit the nucleus at the time when IRF1 nuclear localization occurred. Conversely, silencing IRF1 promoted autophagy by increasing BECN1 and blunting IGF1 receptor and mTOR survival signaling. Loss of IRF1 promoted resistance to antiestrogens, whereas combined silencing of ATG7 and IRF1 restored sensitivity to these agents. Using a mathematical model to prompt signaling hypotheses, we developed evidence that ATG7 silencing could resensitize IRF1-attenuated cells to apoptosis through mechanisms that involve other estrogen-regulated genes. Overall, our work shows how inhibiting the autophagy proteins ATG7 and BECN1 can regulate IRF1-dependent and -independent signaling pathways in ways that engender a new therapeutic strategy to attack breast cancer.

IFN-γ mediates graft-versus-breast cancer effects via enhancing cytotoxic T lymphocyte activity

Previous studies have demonstrated the beneficial effect of graft-versus-tumor (GVT) following hematopoietic stem cell transplantation (HSCT) on the incidence of leukemia relapse and the overall survival rate of patients with leukemia; however, detailed mechanisms underlying the effects GVT exhibits on solid tumors following allogeneic HSCT are yet to be elucidated. The aim of the present study was to investigate the immune mechanism underlying the effect of interferon (IFN)-γ on GVT following allogeneic HSCT in breast cancer therapy. An in situ breast cancer mouse model was established by injecting 5×10⁴ 4T1 cells into the mammary fat pads of BALB/c mice. The 4T1 cells were transfected with the firefly luciferase reporter gene in order to monitor the tumor progression in real time. An allogeneic HSCT model was then established by transplanting bone marrow mononuclear cells from C57BL/6 mice to the BALB/c mice. To investigate the influence of T lymphocyte proliferation following allogeneic bone marrow transplantation, the levels of CD3⁺CD8⁺ cytotoxic T lymphocytes (CTLs) and CD4⁺CD25⁺ regulatory T cells were determined. In addition, IFN-γ and granzyme B expression levels in splenic lymphocytes were analyzed using flow cytometry. Allogeneic HSCT was found to significantly promote the proliferation and cytotoxicity of CTLs and suppress the growth of breast cancer. Furthermore, the secretory levels of IFN-γ and granzyme B by T cells were elevated following allogeneic HSCT. These results indicated that alloreactive T cells increased the secretion of IFN-γ, which promoted the alloresponse of donor CTLs. In addition, the CTLs produced granzyme B, which exerted a tumor suppressive effect.

Survival in patients with high-risk prostate cancer is predicted by miR-221, which regulates proliferation, apoptosis, and invasion of prostate cancer cells by inhibiting IRF2 and SOCS3

A lack of reliably informative biomarkers to distinguish indolent and lethal prostate cancer is one reason this disease is overtreated. miR-221 has been suggested as a biomarker in high-risk prostate cancer, but there is insufficient evidence of its potential utility. Here we report that miR-221 is an independent predictor for cancer-related death, extending and validating earlier findings. By mechanistic investigations we showed that miR-221 regulates cell growth, invasiveness, and apoptosis in prostate cancer at least partially via STAT1/STAT3-mediated activation of the JAK/STAT signaling pathway. miR-221 directly inhibits the expression of SOCS3 and IRF2, two oncogenes that negatively regulate this signaling pathway. miR-221 expression sensitized prostate cancer cells for IFN-γ-mediated growth inhibition. Our findings suggest that miR-221 offers a novel prognostic biomarker and therapeutic target in high-risk prostate cancer.

Adaptive immune responses associated with breast cancer relapse

The generation, survival, and differentiation of breast cancer stem cells (BCSC) in immunocompetent hosts remain elusive. Some investigators have shown that BCSC can be induced from epithelial tumor cells by the pathologic epithelial to mesenchymal transition (EMT). Emerging evidence suggests that the induction of EMT among epithelial tumor cells originates from signals produced by the non-tumor cells that constitute the tumor microenvironment, including the immune effectors that infiltrate the tumors. Thus, this suggests that the immune system not only has anti-tumor function, but also paradoxically immunoedits tumors, facilitating tumor escape and progression. Indeed, many studies in human breast cancers show both positive and negative associations between the infiltration of various immune effectors (e.g., CD4 and CD8 T cells) and the propensity to relapse with metastatic disease. These observations suggest that distinct types of immune effector cells may induce or inhibit tumor relapse. This review focuses on recent advances in identifying components of the immune system that may directly induce tumor escape and relapse. We propose that levels of interferon (IFN)-γ production or levels of the expression of IFN-γ receptor α on tumor cells may determine whether tumor inhibitory or relapse-promoting effect of IFN-γ may prevail.

Interferon regulatory factor (IRF)-1 and IRF-2 are associated with prognosis and tumor invasion in HCC

BACKGROUND

Interferon regulatory factor (IRF)-1 and IRF-2 are transcriptional factors that mediate interferons functions; the loss of IRF-1 expression and gain of IRF-2 expression were associated with malignant phenotype in multiple cancers. However, their roles in the progression of hepatocellular carcinoma (HCC) remain poorly described.

METHODS

Immunohistochemistry was used to analyze the nuclear expression of IRF-1/2 in a cohort of 332 HCC patients. The expression of IRF-1/2 in HCC cell lines with stepwise metastasis potential was determined by immunoblotting. Downregulation of IRF-1 or IRF-2 expression was mediated by shRNAs; a series of experiments were conducted to determine the changes of invasion ability and downstream molecular events.

RESULTS

High expression of IRF-1 was associated with good outcome (p<.001 for OS/TTR), while high expression of IRF-2 was relevant to increased recurrence probability (p=.049) in HCC patients. The combination of the 2 IRFs showed better predictive power than either factor alone. Immunoblotting analysis revealed that IRF-2/IRF-1 ratio was positively correlated with the metastatic potential in human HCC cell lines. Downregulation of IRF-2 led to sharply attenuated invasion ability, paralleled with a decreased expression of STAT3, p-STAT3(Ser727), and MMP9. While downregulation of IRF-1 caused a concurrent decrease in IRF-2, little or no change was displayed in IRF-2/IRF-1 ratio, invasion ability, and MMP9 expression.

CONCLUSIONS

IRF-1 and IRF-2 expression were associated with prognosis of HCC patients with opposite predictive power. IRF-2/IRF-1 ratio was associated with tumor invasion, probably through modulation of MMP9 expression mediated by STAT3.

Interferon-γ induces autophagy with growth inhibition and cell death in human hepatocellular carcinoma (HCC) cells through interferon-regulatory factor-1 (IRF-1)

Interferon-gamma (IFN-γ) is a pleiotropic cytokine with immunomodulatory, anti-viral, and anti-proliferative effects. In this study, we examined the effects of IFN-γ on autophagy and cell growth in human hepatocellular carcinoma (HCC) cells. IFN-γ inhibited cell growth of Huh7 cells with non-apoptotic cell death. IFN-γ induced autophagosome formation and conversion/turnover of microtubule associated protein 1 light chain 3 (LC3) protein. Furthermore, overexpression of IRF-1 also induced autophagy in Huh7 cells. Silencing IRF-1 expression with target small hairpin RNA blocked autophagy induced by IFN-γ. Silencing of the autophagy signals Beclin-1 or Atg5 attenuated the inhibitory effect of IFN-γ on Huh7 cells with decreased cell death. Additionally, IFN-γ activated autophagy in freshly cultured human HCC cells. Together, these findings show that IFN-γ induces autophagy through IRF-1 signaling pathway and the induction of autophagy contributes to the growth-inhibitory effect of IFN-γ with cell death in human liver cancer cells.

Loss of interferon regulatory factor 5 (IRF5) expression in human ductal carcinoma correlates with disease stage and contributes to metastasis

INTRODUCTION

New signaling pathways of the interleukin (IL) family, interferons (IFN) and interferon regulatory factors (IRF) have recently been found within tumor microenvironments and in metastatic sites. Some of these cytokines stimulate while others inhibit breast cancer proliferation and/or invasion. IRFs, a family of nine mammalian transcription factors, have multiple biologic functions that when dysregulated may contribute to tumorigenesis; most well-known are their roles in regulating/initiating host immunity. Some IRF family members have been implicated in tumorigenesis yet little is still known of their expression in primary human tumors or their role(s) in disease development/progression. IRF5 is one of the newer family members to be studied and has been shown to be a critical mediator of host immunity and the cellular response to DNA damage. Here, we examined the expression of IRF5 in primary breast tissue and determined how loss of expression may contribute to breast cancer development and/or progression.

METHODS

Formalin-fixed paraffin-embedded archival breast tissue specimens from patients with atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) were examined for their expression of IRF1 and IRF5. Knockdown or overexpression of IRF5 in MCF-10A, MCF-7 and MDA-MB-231 mammary epithelial cell lines was used to examine the role of IRF5 in growth inhibition, invasion and tumorigenesis.

RESULTS

Analysis of IRF expression in human breast tissues revealed the unique down-regulation of IRF5 in patients with different grades of DCIS and IDC as compared to IRF1; loss of IRF5 preceded that of IRF1 and correlated with increased invasiveness. Overexpression of IRF5 in breast cancer cells inhibited in vitro and in vivo cell growth and sensitized them to DNA damage. Complementary experiments with IRF5 siRNAs made normal mammary epithelial cells resistant to DNA damage. By 3-D culture, IRF5 overexpression reverted MDA-MB-231 to normal acini-like structures; cells overexpressing IRF5 had decreased CXCR4 expression and were insensitive to SDF-1/CXCL12-induced migration. These findings were confirmed by CXCR4 promoter reporter assays.

CONCLUSIONS

IRF5 is an important tumor suppressor that regulates multiple cellular processes involved in the conversion of normal mammary epithelial cells to tumor epithelial cells with metastatic potential.

The Role of Interferon Regulatory Factor-1 (IRF1) in Overcoming Antiestrogen Resistance in the Treatment of Breast Cancer

Resistance to endocrine therapy is common among breast cancer patients with estrogen receptor alpha-positive (ER+) tumors and limits the success of this therapeutic strategy. While the mechanisms that regulate endocrine responsiveness and cell fate are not fully understood, interferon regulatory factor-1 (IRF1) is strongly implicated as a key regulatory node in the underlying signaling network. IRF1 is a tumor suppressor that mediates cell fate by facilitating apoptosis and can do so with or without functional p53. Expression of IRF1 is downregulated in endocrine-resistant breast cancer cells, protecting these cells from IRF1-induced inhibition of proliferation and/or induction of cell death. Nonetheless, when IRF1 expression is induced following IFNγ treatment, antiestrogen sensitivity is restored by a process that includes the inhibition of prosurvival BCL2 family members and caspase activation. These data suggest that a combination of endocrine therapy and compounds that effectively induce IRF1 expression may be useful for the treatment of many ER+ breast cancers. By understanding IRF1 signaling in the context of endocrine responsiveness, we may be able to develop novel therapeutic strategies and better predict how patients will respond to endocrine therapy.

The interferon-gamma-induced GTPase, mGBP-2, inhibits tumor necrosis factor alpha (TNF-alpha) induction of matrix metalloproteinase-9 (MMP-9) by inhibiting NF-kappaB and Rac protein

Matrix metalloproteinase-9 (MMP-9) is important in numerous normal and pathological processes, including the angiogenic switch during tumor development and tumor metastasis. Whereas TNF-α and other cytokines up-regulate MMP-9 expression, interferons (IFNs) inhibit MMP-9 expression. We found that IFN-γ treatment or forced expression of the IFN-induced GTPase, mGBP-2, inhibit TNF-α-induced MMP-9 expression in NIH 3T3 fibroblasts, by inhibiting MMP-9 transcription. The NF-κB transcription factor is required for full induction of MMP-9 by TNF-α. Both IFN-γ and mGBP-2 inhibit the transcription of a NF-κB-dependent reporter construct, suggesting that mGBP-2 inhibits MMP-9 induction via inhibition of NF-κB-mediated transcription. Interestingly, mGBP-2 does not inhibit TNF-α-induced degradation of IκBα or p65/RelA translocation into the nucleus. However, mGBP-2 inhibits p65 binding to a κB oligonucleotide probe in gel shift assays and to the MMP-9 promoter in chromatin immunoprecipitation assays. In addition, TNF-α activation of NF-κB in NIH 3T3 cells is dependent on Rac activation, as evidenced by the inhibition of TNF-α induction of NF-κB-mediated transcription by a dominant inhibitory form of Rac1. A role for Rac in the inhibitory action of mGBP-2 on NF-κB is further shown by the findings that mGBP-2 inhibits TNF-α activation of endogenous Rac and constitutively activate Rac can restore NF-κB transcription in the presence of mGBP-2. This is a novel mechanism by which IFNs can inhibit the cytokine induction of MMP-9 expression.

IRF-1 transcriptionally upregulates PUMA, which mediates the mitochondrial apoptotic pathway in IRF-1-induced apoptosis in cancer cells

Interferon Regulatory Factor-1 (IRF-1) is a transcription factor which acts as a tumor suppressor and causes apoptosis in cancer cells. We evaluated IRF-1 induced apoptosis in gastric cancer cell lines. We established stable clones in AGS cells that have a tetracycline inducible IRF-1 expression system. We used these clones and recombinant adenovirus expressing IRF-1 to explore the mechanism of IRF-1 induced apoptosis in gastric cancer. Expression of IRF-1 causes apoptosis in gastric cancer cell lines as demonstrated by phosphatidylserine exposure and cleavage of caspase-8, caspase-3, and Bid with mitochondrial release of cytochrome c. However, inhibition of caspase-8 and Bid did not inhibit apoptosis and did not decrease cleaved caspase-9 or mitochondrial release of cytochrome c. We then demonstrate that IRF-1 up-regulates PUMA (p53 up-regulated modulator of apoptosis), that is known to activate apoptosis by the intrinsic pathway; this can be p53 independent. IRF-1 binds to distinct sites in the promoter of PUMA and activates PUMA transcription. Moreover, molecular markers of mitochondrial apoptosis are eliminated in PUMA knockout and knockdown cells and phospatidylserine exposure is decreased dramatically. Finally, we demonstrate that IFN-γ induces IRF-1 mediated up-regulation of PUMA in cancer cells. We conclude that IRF-1 can induce apoptosis by the intrinsic pathway independent of the extrinsic pathway by up-regulation of PUMA.

Gene network signaling in hormone responsiveness modifies apoptosis and autophagy in breast cancer cells

Resistance to endocrine therapies, whether de novo or acquired, remains a major limitation in the ability to cure many tumors that express detectable levels of the estrogen receptor alpha protein (ER). While several resistance phenotypes have been described, endocrine unresponsiveness in the context of therapy-induced tumor growth appears to be the most prevalent. The signaling that regulates endocrine resistant phenotypes is poorly understood but it involves a complex signaling network with a topology that includes redundant and degenerative features. To be relevant to clinical outcomes, the most pertinent features of this network are those that ultimately affect the endocrine-regulated components of the cell fate and cell proliferation machineries. We show that autophagy, as supported by the endocrine regulation of monodansylcadaverine staining, increased LC3 cleavage, and reduced expression of p62/SQSTM1, plays an important role in breast cancer cells responding to endocrine therapy. We further show that the cell fate machinery includes both apoptotic and autophagic functions that are potentially regulated through integrated signaling that flows through key members of the BCL2 gene family and beclin-1 (BECN1). This signaling links cellular functions in mitochondria and endoplasmic reticulum, the latter as a consequence of induction of the unfolded protein response. We have taken a seed-gene approach to begin extracting critical nodes and edges that represent central signaling events in the endocrine regulation of apoptosis and autophagy. Three seed nodes were identified from global gene or protein expression analyses and supported by subsequent functional studies that established their abilities to affect cell fate. The seed nodes of nuclear factor kappa B (NFkappaB), interferon regulatory factor-1 (IRF1), and X-box binding protein-1 (XBP1)are linked by directional edges that support signal flow through a preliminary network that is grown to include key regulators of their individual function: NEMO/IKKgamma, nucleophosmin and ER respectively. Signaling proceeds through BCL2 gene family members and BECN1 ultimately to regulate cell fate.

The IRF family transcription factors in immunity and oncogenesis

The interferon regulatory factor (IRF) family, consisting of nine members in mammals, was identified in the late 1980s in the context of research into the type I interferon system. Subsequent studies over the past two decades have revealed the versatile and critical functions performed by this transcription factor family. Indeed, many IRF members play central roles in the cellular differentiation of hematopoietic cells and in the regulation of gene expression in response to pathogen-derived danger signals. In particular, the advances made in understanding the immunobiology of Toll-like and other pattern-recognition receptors have recently generated new momentum for the study of IRFs. Moreover, the role of several IRF family members in the regulation of the cell cycle and apoptosis has important implications for understanding susceptibility to and progression of several cancers.

CD154 tone sets the signaling pathways and transcriptome generated in model CD40-pluricompetent L3055 Burkitt's lymphoma cells

Activated B cells reacting to small amounts of CD40L (CD154) maintain homeostasis by suppressing default apoptosis. Additional outcomes, particularly differentiation, demand higher CD40 occupancy. Here, focusing on survival, we compared changes in the transcriptome of pleiotropically competent, early passage L3055 Burkitt's lymphoma cells confronted with low (picomolar) and high (nanomolar) concentrations of CD154 to gain insight into how a single receptor sets these distinct phenotypes. Of 267 genes altering transcriptional activity in response to strong CD154 tone, only 25 changed coordinately on low receptor occupancy. Seven of the top nine common up-regulated genes were targets of NF-kappaB. Direct measurement and functional inhibition of the NF-kappaB pathway revealed it to be central to a CD40-dependent survival signature. Although the canonical NF-kappaB axis was engaged by both signaling strengths equally, robust alternative pathway activation was a feature selective to a strong CD40 signal. Discriminatory exploitation of the two separate arms of NF-kappaB activation may indicate a principle whereby a cell senses and reacts differentially to shifting ligand availability. Identifying components selectively coupling CD40 to each axis could indicate targets for disruption in B cell pathologies underpinned by ectopic and/or hyper-CD154 activity such as neoplasia and some autoimmunities.

Interferon regulatory factor-1-induced apoptosis mediated by a ligand-independent fas-associated death domain pathway in breast cancer cells

Interferon (IFN) regulatory factor-1 (IRF-1) is a transcription factor that has apoptotic anti-tumor activity. In breast cancer cell types, IRF-1 is implicated in mediating apoptosis by both novel and established anti-tumor agents, including the anti-estrogens tamoxifen and faslodex. Here we demonstrate that in MDA468 breast cancer cells, apoptosis by IFN-gamma is mediated by IRF-1 and IFN-gamma, and IRF-1-induced apoptosis is caspase-mediated. IRF-1 induction results in cleavage of caspase-8, -3 and -7, and application of caspase inhibitors attenuate activated cleavage products. IRF-1-induced apoptosis involves caspase-8 since apoptosis is significantly decreased by the caspase-8-specific inhibitor IETD, c-FLIP expression and in caspase-8-deficient cancer cells. Furthermore, we demonstrate that IRF-1-induced apoptosis requires fas-associated death domain (FADD) since dominant-negative FADD expressing cells resist IRF-1-induced apoptosis and activated downstream products. Immunofluorescent studies demonstrate perinuclear colocalization of FADD and caspase-8. Despite the known role of FADD in mediating death-ligand induced apoptosis, neutralizing antibodies against classical death receptors do not inhibit IRF-1 induced apoptosis, and no secreted ligand appears to be involved since MDA468 coincubated with IRF-1 transfected cells do not apoptose. Therefore, we demonstrate that IRF-1 induces a ligand-independent FADD/caspase-8-mediated apoptosis in breast cancer cells.

Involvement of IFN regulatory factor (IRF)-1 and IRF-2 in the formation and progression of human esophageal cancers

IFN regulatory factor (IRF)-1 and IRF-2 are generally regarded as a tumor suppressor and an oncoprotein, respectively. However, little is known about their expression and function in esophageal squamous cell carcinomas (ESCC). In our present work, IRF-1 expression was decreased and IRF-2 expression was increased in ESCCs compared with matched normal esophageal tissues. Moreover, statistical data indicated that IRF-2 expression was tightly correlated with progression of ESCCs. As expected, overexpression of either IRF-1 or IRF-2 in an ESCC cell line resulted in either suppression or enhancement of cell growth, respectively. Also, proliferation- and apoptosis-related molecules (p21(WAF1/CIP1), cyclin-D1, Bcl-2, and histone H4) were regulated by IRF-1 and IRF-2. Additionally, high levels of IRF-2 blocked the function of IRF-1 by preventing the latter from translocating into the nucleus; in contrast, knock down of IRF-2 by small interfering RNA permitted nuclear localization and activity of IRF-1. In vivo assay using nude mice indicated that the tumorigenicity of ESCC cells was enhanced with IRF-2 overexpression but dramatically attenuated after forced expression of IRF-1. In conclusion, IRF-1 and IRF-2 are able to regulate tumorigenicity of ESCC cells as antioncoprotein and oncoprotein, respectively. Relative amounts of IRF-1 to IRF-2 are functionally very important for the development and progression of ESCCs, and reduction of the ratio of IRF-1/IRF-2 may lead to the enhancement of tumorigenicity of ESCC cells. Therefore, levels of IRF-1 and IRF-2 are useful indicators in diagnosis and prognosis for ESCCs, and these molecules are potential drug targets for ESCC therapy.

HER-2/neu raises SHP-2, stops IFN-γ anti-proliferation in bladder cancer

Gene amplification or HER-2/neu protein overexpression signals a poor outcome for bladder cancer patients. We investigated the anti-proliferative effect of IFN-gamma in HER-2/neu-transfected human bladder cancer cells (TCC-N5 and TCC-N10). The cells continued growing after IFN-gamma stimulation but did not activate the Janus kinase (Jak)/Stat pathway. We found Jak/Stat protein phosphatase in TCC-N5 and TCC-N10 cells with upregulated Src homology 2-containing protein tyrosine phosphatase-2 (SHP-2). After the cells had been treated with AG825, a HER-2/neu-specific inhibitor, SHP-2 expression declined, and Jak2/Stat1 reactivated. Similar results were reported in a mouse bladder cancer cell line, MBT2, with constitutive HER-2/neu overexpression. Further, AG825 pretreatment restored the anti-proliferation activity of IFN-gamma in TCC-N5 and TCC-N10 cells. Therefore, the suppression of IFN-gamma signaling in HER-2/neu-overexpressing bladder cancer cells might be due to SHP-2 upregulation. The regulation of SHP-2 by HER-2/neu provides a new target for blocking the HER-2/neu oncogenic pathway.

Ad-IRF-1 induces apoptosis in esophageal adenocarcinoma

The nuclear transcription factor interferon regulatory factor-1 (IRF-1) is a putative tumor suppressor, but the expression and function of IRF-1 in esophageal adenocarcinoma (EA) remain unknown. We hypothesized that IRF-1 expression was reduced or lost in EA and that restoration of IRF-1 would result in the apoptosis of EA cells in vitro and the inhibition of tumor growth in vivo. Three EA cell lines were used to examine IRF-1 expression, IFN-gamma responsiveness, and the effects of IRF-1 overexpression using a recombinant adenoviral vector (Ad-IRF-1). All three EA cell lines produced IRF-1 protein following IFN-gamma stimulation, although IFN-gamma did not induce cell death. In contrast, Ad-IRF-1 infection resulted in high levels of IRF-1 protein and triggered apoptosis in all three EA cell lines. Potential mechanisms for the differential response to IFN-gamma versus Ad-IRF-1--such as modulation of c-Met or extracellular regulated kinase signaling, or altered expression of IRF-2, Fas, or survivin--were investigated, but none of these mechanisms can account for this observation. In vivo administration of IRF-1 in a murine model of EA modestly inhibited tumor growth, but did not lead to tumor regression. Strategies aimed at increasing or restoring IRF-1 expression may have therapeutic benefits in EA.

Interferon Regulatory Factor 1 (IRF-1) and IRF-2 Expression in Breast Cancer Tissue Microarrays

Interferon-gamma (IFN-gamma) is a pleiotropic cytokine with potent antitumor effects, both in vitro and in vivo. The antitumor activity of IFN-gamma is mediated in part through IFN regulatory factor-1 (IRF-1) and may be blocked by IRF-2. To test our hypothesis that some tumors escape the antitumor effects of IFN-gamma by cellular changes reflected in IRF-1 and IRF-2 expression, we examined IRF-1 and IRF-2 expression in tissue microarrays (TMA) containing 187 specimens of clinically defined invasive breast carcinoma. TMAs (Cooperative Breast Cancer Tissue Resource [CBCTR], National Cancer Institute [NCI]) were stained and then scored by three evaluators blinded to the patients' clinical status. After final scoring, the CBCTR provided the available clinical data for each patient. Whether sorted by carcinoma type or for all data together, statistical analysis showed a significant positive correlation between IRF-1 and IRF-2 expression (p = 0.01) and a negative correlation between IRF-1 expression and tumor grade (p = 0.005). IRF-1 expression is consistent with its role as a tumor suppressor; high-grade breast carcinomas were less likely to maintain expression of IRF-1, a finding consistent with a role for IRF-1 as a tumor suppressor. Further, tumors maintained expression of IRF-2 if there was coincident expression of IRF-1. These data support a model in which alterations of the expression of intracellular effectors of IFN-gamma signaling may diminish the immune-mediated tumor control mechanisms of IFN-gamma.

Interferon regulatory factor-1 (IRF-1) exhibits tumor suppressor activities in breast cancer associated with caspase activation and induction of apoptosis

We have directly assessed the ability of interferon regulatory factor-1 (IRF-1) to act as a tumor suppressor gene in human breast cancer cells and explored whether this suppressor function is mechanistically conferred by affecting cell cycle transition, apoptosis and/or caspase activation. We have used a dual approach, measuring whether overexpression of wild-type IRF-1 or a dominant negative IRF-1 (dnIRF-1) produce opposing effects on breast cancer cell proliferation in vitro or tumorigenicity in athymic nude mice. Mechanistic studies determined the effects of blocking endogenous IRF-1 expression on cell cycle transition by flow cytometry, on apoptosis by Annexin V staining, and on caspase activation by fluorescent substrate cleavage. IRF-1 mRNA (P < or = 0.001) and protein (P < or = 0.001) are highly expressed in non-tumorigenic, normal, mammary epithelial cells, with intermediate expression in tumorigenic, but non-metastatic, cells and very low expression in metastatic cell lines. In MCF-7 cells transfected with a wild-type IRF-1 (MCF-7/IRF-1), IRF-1 mRNA expression inversely correlates with the rate of cell proliferation (r = -0.91; P = 0.002). Conversely, expression of dnIRF-1 in both MCF-7 (MCF-7/dnIRF-1; p53 wild-type) and T47D cells (T47D/dnIRF-1; p53 mutant) increases cell proliferation (P < or = 0.001). In athymic nude mice, the incidence of MCF-7/IRF-1 xenografts is reduced (P = 0.045), whereas MCF-7/dnIRF-1 xenografts exhibit a significantly higher tumor incidence (P < or = 0.001). Effects of IRF-1/dnIRF-1 are mediated through changes in the rates of apoptosis and not through cell cycle regulation. MCF-7/dnIRF-1 cells exhibit a 50% decrease in basal apoptosis (P = 0.007) and a significant reduction in caspase 8 activity (P = 0.03); similar effects occur in T47D/dnIRF-1 cells, where the effects on apoptosis appear to be mediated through inhibition of caspases 3/7 (P < 0.001) and caspase 8 (P = 0.03). These data establish a functional role for IRF-1 in the growth suppression of breast cancer cells and strongly implicate IRF-1 as a tumor suppressor gene in breast cancer that acts, independent of p53, to control apoptosis.

Immunotherapy of cancer through targeting of minor histocompatibility antigens

Minor histocompatibility antigens are allogeneic targets of T-cell mediated graft-versus-tumour effects following allogeneic stem cell transplantation. Recent research has identified several minor histocompatibility antigens as tumour proteins and has also disclosed their unique properties in both the induction and the effector phase of graft-versus-tumour effects. Targeting tumour-specific minor histocompatibility antigens by adoptive immunotherapy will battle against tumour tolerance and evoke allo-immune responses, thereby enhancing graft-versus-tumour effects against leukaemia and solid tumours. Recently acquired knowledge of the role of donor immunisation status, new techniques in the generation of minor histocompatibility antigen-specific cytotoxic T lymphocytes in vitro, and innovative principles in vaccination will help to design clinical trials that exploit minor histocompatibility antigens in the immunotherapy of cancer.

Ectopic Expression of Interferon Regulatory Factor-1 Promotes Human Breast Cancer Cell Death and Results in Reduced Expression of Survivin

The overexpression of the inhibitor of apoptosis protein, survivin, may provide tumor cells with a distinct survival advantage in situ; hence, therapeutic strategies have been designed to inhibit its expression. In this study, we ectopically expressed the interferon regulatory factor (IRF)-1 protein in the breast carcinoma cell lines MDA-MB-468 and SK-BR-3 using a recombinant adenovirus (Ad-IRF-1). By screening microarray analysis of cDNA from the human breast cancer cell line MDA-MB-468 infected with Ad-IRF-1, we observed a 15-fold down-regulation of the survivin gene when compared with uninfected cells. Consequently, we tested survivin expression in Ad-IRF-1-infected MDA-MB-468 and SK-BR-3 breast cancer cell lines. Immunoblotting analyses supported the contention that ectopic expression of the IRF-1 protein results in down-regulation of survivin protein expression that is independent of p53. In addition, Ad-IRF-1 infection of these human breast cancer cell lines induces the expression of p21. We also report that increased apoptosis is observed in tumor cells infected with Ad-IRF-1 compared with Ad-Psi5 mock-infected cells and that cell death is further augmented when the IRF-1-infected cells are cultured with Adriamycin. Moreover, in a xenogeneic mouse model of breast carcinoma, in vivo treatment of tumor-bearing mice with intratumoral Ad-IRF-1 injections results in tumor growth inhibition. In resected tumors from mice that had been treated with Ad-IRF-1, tumor cells that express the IRF-1 transgene have a predominant IRF-1-positive, survivin-negative phenotype. Collectively, these observations suggest that therapies designed to enhance IRF-1 expression within tumor cells may represent novel treatment strategies for breast cancer.

Expression profiling of sodium butyrate (NaB)-treated cells: identification of regulation of genes related to cytokine signaling and cancer metastasis by NaB

Histone deacetylase (HDAC) inhibitors induce growth arrest and apoptosis in a variety of human cancer cells. Sodium butyrate (NaB), a short chain fatty acid, is a HDAC inhibitor and is produced in the colonic lumen as a consequence of microbial degradation of dietary fibers. In order to dissect out the mechanism of NaB-induced growth inhibition of cancer cells, we carried out expression profiling of a human lung carcinoma cell line (H460) treated with NaB using a cDNA microarray. Of the total 1728 genes analysed, there were 32 genes with a mean expression value of 2.0-fold and higher and 66 genes with a mean expression value 3.0-fold and lower in NaB-treated cells. For a few selected genes, we demonstrate that their expression pattern by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis is matching with the results obtained by microarray analysis. Closer view at the expression profile of NaB-treated cells revealed the downregulation of a total of 16 genes associated with cytokine signaling, in particular, interferon gamma (IFNgamma) pathway. In good correlation, NaB-pretreated cells failed to induce interferon regulatory factor 1, an INFgamma target gene, efficiently upon IFNgamma addition. These results suggest that NaB inhibits proinflammatory cytokine signaling pathway, thus providing proof of mechanism for its anti-inflammatory activity. We also found that NaB induced three genes, which are known metastatic suppressors, and downregulated 11 genes, which have been shown to promote metastasis. Upregulation of metastatic suppressor Kangai 1 (KAI1) by NaB in a time-dependent manner was confirmed by RT-PCR analysis. The differential regulation of metastasis-associated genes by NaB provides explanation for the anti-invasive properties of NaB. Therefore, our study presents new evidence for pathways regulated by NaB, thus providing evidence for the mechanism behind anti-inflammatory and antimetastatic activities of NaB.

A novel approach in the treatment of neuroendocrine gastrointestinal tumors: additive antiproliferative effects of interferon-gamma and meta-iodobenzylguanidine

BACKGROUND

Therapeutic options to effectively inhibit growth and spread of neuroendocrine gastrointestinal tumors are still limited. As both meta-iodobenzylguanidine (MIBG) and interferon-gamma (IFNgamma) cause antineoplastic effects in neuroendocrine gastrointestinal tumor cells, we investigated the antiproliferative effects of the combination of IFNgamma and non-radiolabeled MIBG in neuroendocrine gut STC-1 and pancreatic carcinoid BON tumor cells.

METHODS AND RESULTS

IFNgamma receptors were expressed in both models. IFNgamma dose- and time-dependently inhibited the growth of both STC-1 and of BON tumor cells with IC50-values of 95 +/- 15 U/ml and 135 +/- 10 U/ml, respectively. Above 10 U/ml IFNgamma induced apoptosis-specific caspase-3 activity in a time-dependent manner in either cell line and caused a dose-dependent arrest in the S-phase of the cell cycle. Furthermore, IFNgamma induced cytotoxic effects in NE tumor cells. The NE tumor-targeted drug MIBG is selectively taken up via norepinephrine transporters, thereby specifically inhibiting growth in NE tumor cells. Intriguingly, IFNgamma treatment induced an upregulation of norepinephrine transporter expression in neuroendocrine tumors cells, as determined by semi-quantitative RT-PCR. Co-application of sub-IC50 concentrations of IFNgamma and MIBG led to additive growth inhibitory effects, which were mainly due to increased cytotoxicity and S-phase arrest of the cell cycle.

CONCLUSION

Our data show that IFNgamma exerts antiproliferative effects on neuroendocrine gastrointestinal tumor cells by inducing cell cycle arrest, apoptosis and cytotoxicity. The combination of IFNgamma with the NE tumor-targeted agent MIBG leads to effective growth control at reduced doses of either drug. Thus, the administration of IFNgamma alone and more so, in combination with MIBG, is a promising novel approach in the treatment of neuroendocrine gastrointestinal tumors.