Expression of interferon regulatory factor (IRF) genes and response to interferon-alpha in chronic myeloid leukaemia

Expression of interferon regulatory factor family and its prognostic value in acute myeloid leukemia

Aim: To elucidate the clinicopathological and prognostic values of interferon regulatory factor (IRF) family genes in acute myeloid leukemia (AML). Patients & methods: Differential expression analysis and survival analysis from several reliable databases were conducted and further validated using patients with AML. Results: The expression level of IRF1/2/4/5/7/8/9 in patients with AML was upregulated, while IRF3/6 expression was downregulated. High IRF1/7/9 expression indicated a worse overall survival rate. Conclusion: Overexpression of IRF1/7/9 may be associated with poor survival in patients with AML, suggesting that the IRF family may be a promising therapeutic target.

Chronic myeloid leukemia-from the Philadelphia chromosome to specific target drugs: A literature review

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm and was the first neoplastic disease associated with a well-defined genotypic anomaly - the presence of the Philadelphia chromosome. The advances in cytogenetic and molecular assays are of great importance to the diagnosis, prognosis, treatment, and monitoring of CML. The discovery of the breakpoint cluster region (BCR)-Abelson murine leukemia (ABL) 1 fusion oncogene has revolutionized the treatment of CML patients by allowing the development of targeted drugs that inhibit the tyrosine kinase activity of the BCR-ABL oncoprotein. Tyrosine kinase inhibitors (known as TKIs) are the standard therapy for CML and greatly increase the survival rates, despite adverse effects and the odds of residual disease after discontinuation of treatment. As therapeutic alternatives, the subsequent TKIs lead to faster and deeper molecular remissions; however, with the emergence of resistance to these drugs, immunotherapy appears as an alternative, which may have a cure potential in these patients. Against this background, this article aims at providing an overview on CML clinical management and a summary on the main targeted drugs available in that context.

Functional Analysis of IRF1 Reveals its Role in the Activation of the Type I IFN Pathway in Golden Pompano, Trachinotus ovatus (Linnaeus 1758)

Interferon (IFN) regulatory factor 1 (IRF1), a transcription factor with a novel helix–turn–helix DNA-binding domain, plays a crucial role in innate immunity by regulating the type I IFN signaling pathway. However, the regulatory mechanism through which IRF1 regulates type I IFN in fish is not yet elucidated. In the present study, IRF1 was characterized from golden pompano, Trachinotus ovatus (designated ToIRF1), and its immune function was identified to elucidate the transcriptional regulatory mechanism of ToIFNa3. The full-length complementary DNA (cDNA) of IRF1 is 1763 bp, including a 900-bp open reading frame (ORF) encoding a 299-amino-acid polypeptide. The putative protein sequence has 42.7–71.7% identity to fish IRF1 and possesses a representative conserved domain (a DNA-binding domain (DBD) at the N-terminus). The genomic DNA sequence of ToIRF1 consists of eight exons and seven introns. Moreover, ToIRF1 is constitutively expressed in all examined tissues, with higher levels being observed in immune-relevant tissues (whole blood, gill, and skin). Additionally, Cryptocaryon irritans challenge in vivo increases ToIRF1 expression in the skin as determined by Western blotting (WB); however, protein levels of ToIRF1 in the gill did not change significantly. The subcellular localization indicates that ToIRF1 is localized in the nucleus and cytoplasm with or without polyinosinic/polycytidylic acid (poly (I:C)) induction. Furthermore, overexpression of ToIRF1 or ToIFNa3 shows that ToIRF1 can notably activate ToIFNa3 and interferon signaling molecule expression. Promoter sequence analysis finds that several interferon stimulating response element (ISRE) binding sites are present in the promoter of ToIFNa3. Additionally, truncation, point mutation, and electrophoretic mobile shift (EMSA) assays confirmed that ToIRF1 M5 ISRE binding sites are functionally important for ToIFNa3 transcription. These results may help to illuminate the roles of teleost IRF1 in the transcriptional mechanisms of type I IFN in the immune process.

Interferon regulatory factor 2 plays a positive role in interferon gamma expression in golden pompano, Trachinotus ovatus (Linnaeus 1758)

In fish, interferon (IFN) regulatory factor 2 (IRF2) is a regulator of the type I IFN-dependent immune response, thereby playing a crucial role in innate immunity. However, the specific mechanism by which IRF2 regulates type II IFN in fish remains unclear. In the present study, first, to analyse the potential role of golden pompano (Trachinotus ovatus) IRF2 (ToIRF2) in the immune response, the mRNA level of ToIRF2 was detected by quantitative real-time polymerase chain reaction (qRT-PCR) after parasite infection. ToIRF2 was upregulated at early time points in both local infection sites (skin and gill) and system immune tissues (liver, spleen, and head-kidney) after stimulation with Cryptocaryon irritans. Second, to investigate the modulation effect of ToIRF2 on type II IFN (interferon gamma, IFNγ) expression, a promoter analysis was performed using progressive deletion mutations of ToIFNγ. The expression level of IFNγ-5 was highest among the five truncated mutants in response to ToIRF2, indicating that the core promoter region was located from -189 bp to +120 bp, which included the IRF2 binding sites. Mutation analyses showed that the activity of the ToIFNγ promoter dramatically decreased after the targeted mutation of the M1, M2 or M3 binding sites. Additionally, electrophoretic mobile shift assay (EMSA) confirmed that IRF2 interacted with the M1 binding site in the ToIFNγ promoter region to dominate ToIFNγ expression. Finally, overexpressing ToIRF2 in vitro notably increased ToIFNγ and the transcription of several type II IFN/IRF-based signalling pathway genes. These results suggested that ToIRF2 might be involved in the host defence against C. irritans infection and contribute to a better understanding of the transcriptional mechanisms by which ToIRF2 regulates type II IFN in fish.

Functional characterization of IRF8 regulation of type II IFN in golden pompano (Trachinotus ovatus)

Interferon regulatory factor 8 (IRF8) increases type I IFN transcription levels by binding to IFN promoters, thereby playing a role in innate immunity. Nevertheless, the detailed mechanism through which IRF8 regulates type II IFN in fish remains ambiguous. In the present study, two genes from the golden pompano (Trachinotus ovatus), IRF8 (ToIRF8) and IFN gamma (ToIFNγ), were identified in the IFN/IRF-based signalling pathway. The full-length ToIRF8 cDNA was composed of 2,141 bp and encoded a 421 amino acid polypeptide; the genomic DNA was 2,917 bp in length and consisted of 8 exons and 7 introns. The putative protein showed the highest sequence identity (90-92%) with fish IRF8 and possessed a DNA-binding domain (DBD), an IRF-association domain (IAD) and a nuclear localization signal (NLS) motif consistent with those of IRF8 in other vertebrates. Furthermore, the ToIRF8 transcripts were expressed in all examined tissues of healthy fish, with higher levels observed in the central nervous and immune relevant tissues. They were upregulated by polyinosinic acid: polycytidylic acid [poly (I: C)], lipopolysaccharide (LPS) and flagellin treatments in the blood, liver, intestine and kidney. The results from assays of subcellular localization showed that ToIRF8 was localized to the cytoplasm. Moreover, to investigate whether ToIRF8 was a regulator of ToIFNγ, a promoter analysis was performed using progressive deletion mutations of ToIFNγ. The results indicated that the region from -601 bp to -468 bp includes the core promoter. Mutation analyses indicated that the activity of the ToIFNγ promoter significantly decreased after the targeted mutation of the M1-M3 binding sites. Additionally, overexpressed ToIRF8 in vitro notably increased the expression of several IFN/IRF-based signalling pathway genes. These results suggest that IRF8 is vital in the defence of T. ovatus against bacterial infection and contributes to a better understanding of the transcriptional mechanisms of ToIRF8 on type II IFN in fish.

Functional characterization of interferon regulatory factor 2 and its role in the transcription of interferon a3 in golden pompano Trachinotus ovatus (Linnaeus 1758)

Similar to mammals, fish possess interferon (IFN) regulatory factor 2 (IRF2)-dependent type I IFN responses. Nevertheless, the detailed mechanism through which IRF2 regulates type I IFNa3 remains largely unknown. In the present study, we first identified two genes from golden pompano (Trachinotus ovatus), IRF2 (ToIRF2) and IFNa3 (ToIFNa3), in the IFN/IRF-based signalling pathway. The open reading frame (ORF) sequence of ToIRF2 encoded 335 amino acids possessing four typical characteristic domains, including a conserved DNA-binding domain (DBD), an interferon association domain 2 (IAD2), a transcriptional activation domain (TAD), and a transcriptional repression domain (TRD). Furthermore, transcripts of ToIRF2 were significantly upregulated after stimulation by polyinosinic: polycytidylic acid [poly (I:C)], lipopolysaccharide (LPS) and flagellin in immune-related tissues (blood, liver, and head-kidney). Moreover, to investigate whether ToIRF2 was a regulator of ToIFNa3, promoter analysis was performed. The results showed that the region from -896 bp to -200 bp is defined as the core promoter using progressive deletion mutations of IFNa3. Additionally, ToIRF2 overexpression led to a clear time-dependent enhancement of ToIFNa3 promoter expression in HEK293T cells. Mutation analyses indicated that the activity of the ToIFNa3 promoter significantly decreased after targeted mutation of M4/5 binding sites. Electrophoretic mobile shift assays (EMSAs) verified that IRF2 interacted with the binding site of the ToIFNa3 promoter region to regulate ToIFNa3 transcription. Last, the promoter activity of ToIFNa3-2 was more responsive to treatment with poly (I:C) than LPS and flagellin. Furthermore, overexpression of ToIRF2 in vitro obviously increased the expression of several IFN/IRF-based signalling pathway genes after poly (I:C) abduction. In conclusion, the present study provides the first evidence of the positive regulation of ToIFNa3 transcription by ToIRF2 and contributes to a better understanding of the transcriptional mechanisms of ToIRF2 in fish.

The IRF9-SIRT1-P53 axis is involved in the growth of human acute myeloid leukemia

Acute myeloid leukemia (AML) is a highly heterogeneous disease, with biologically and prognostically different subtypes. Although a growing number of distinct AML subsets have been increasingly characterized, patient management has remained disappointingly uniform. The molecular mechanism underlying AML needs to be further investigated. Here we identify IRF9 as a negative regulator of human AML. We show that IRF9 mRNA and protein levels are down-regulated in human AML samples compared with samples from healthy donors. IRF9 knockdown promotes proliferation, colony formation and survival of OCI/AML-2 and OCI/AML-3 cells, whereas IRF9 overexpression obtains oppose results. Mechanism analysis shows that IRF9 binds SIRT1 promoter and represses SIRT1 expression in OCI/AML-2 and OCI/AML-3 cells. In AML samples, the expression of SIRT1 is up-regulated and negatively correlated with IRF9 level. IRF9 also increases the acetylation of p53, a deacetylation substrate of SIRT1, and promotes the expression of p53 target genes. Knockdown of p53 blocks the effects of IRF9 on cell survival and growth in vitro. These findings provide evidence that IRF9 serves as an important regulator in human AML by repressing SIRT1-p53 pathway and that IRF9 may be a potential target for AML treatment.

The implication of cancer progenitor cells and the role of epigenetics in the development of novel therapeutic strategies for chronic myeloid leukemia

SIGNIFICANCE

Chronic myeloid leukemia (CML) involves the malignant transformation of hematopoietic stem cells, defined largely by the Philadelphia chromosome and expression of the breakpoint cluster region-Abelson (BCR-ABL) oncoprotein. Pharmacological tyrosine kinase inhibitors (TKIs), including imatinib mesylate, have overcome limitations in conventional treatment for the improved clinical management of CML.

RECENT ADVANCES

Accumulated evidence has led to the identification of a subpopulation of quiescent leukemia progenitor cells with stem-like self renewal properties that may initiate leukemogenesis, which are also shown to be present in residual disease due to their insensitivity to tyrosine kinase inhibition.

CRITICAL ISSUES

The characterization of quiescent leukemia progenitor cells as a unique cell population in CML pathogenesis has become critical with the complete elucidation of mechanisms involved in their survival independent of BCR-ABL that is important in the development of novel anticancer strategies. Understanding of these functional pathways in CML progenitor cells will allow for their selective therapeutic targeting. In addition, disease pathogenesis and drug responsiveness is also thought to be modulated by epigenetic regulatory mechanisms such as DNA methylation, histone acetylation, and microRNA expression, with a capacity to control CML-associated gene transcription.

FUTURE DIRECTIONS

A number of compounds in combination with TKIs are under preclinical and clinical investigation to assess their synergistic potential in targeting leukemic progenitor cells and/or the epigenome in CML. Despite the collective promise, further research is required in order to refine understanding, and, ultimately, advance antileukemic therapeutic strategies.

The interferon-alpha revival in CML

Interferon-alpha (IFNα) was once the standard of frontline treatment for chronic myeloid leukemia (CML). Its pleiotropic mechanism of action in CML includes immune activation and specific targeting of CML stem cells. Early studies of IFNα in CML demonstrated that patients in chronic phase could attain extremely stable remissions, which correlated with long-term survival. Some patients even sustained their remission after discontinuing therapy, but the mechanism underlying this phenomenon is not well understood. Today, BCR-ABL tyrosine kinase inhibitors (TKIs), such as imatinib, induce remarkable responses in CML patients and have become the mainstay of CML therapy. Although TKIs target the pathogenic BCR-ABL protein in CML, they cannot fully eradicate CML stem cells. Some of the clinical trials testing IFNα plus imatinib combination therapy suggest that addition of IFNα increases the speed and rate of responses with imatinib therapy. However, the undesirable side effects of IFNα can make this therapy difficult to deliver, and the optimal therapeutic window for using IFNα in combination therapy is unknown. Further studies are needed to clarify the best niche for IFNα use in CML.

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.

Biological therapy and the immune system in patients with chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of hematopoietic stem cells that has been recognized as a disease responsive to immunotherapy. Despite the huge success of the tyrosine kinase inhibitors (TKIs), CML remains for the most part incurable, probably due to treatment resistance of leukemic stem cells, which are responsible for rapid disease relapse after discontinuation of therapy. Only allogeneic stem cell transplantation enables disease eradication. In addition to the Bcr-Abl1 oncoprotein, TKIs also inhibit off-target kinases (e.g. c-kit, Src, Tec), some of them having physiological functions in immune responses. In vitro studies have implied immunomodulatory effects of TKIs and interferon-alpha (IFN-α), but comprehensive information from in vivo analyses is missing. This review summarizes the recent advances in the field of immunology of CML, including basic information about leukemia-associated antigens and peptide vaccines, that could lead to the incorporation of TKIs and IFN-α in future therapeutic, potentially curative, interventions for CML.

Drug-resistance gene expression and progression of astrocytic tumors

To clarify the influence of biochemotherapy on the progression of astrocytic tumors, the expression of O6-methylguanine DNA-methyltransferase (MGMT) mRNA, as well as of other drug-resistance- and drug-sensitivity-related genes such as multidrug resistance gene 1, multidrug resistance-associated protein, glutathione S-transferase-pi, DNA topoisomerase II, and interferon receptor mRNA, and the interferon regulatory factor (IRF)-1 and -2 ratios in gliomas were investigated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). The mean MGMT/beta2-microglobulin (beta2-MG) ratio for 130 neuroepithelial tumors was 8.2 +/- 17.8. The mean ratio of 45 glioblastomas was significantly higher than that for the other 85 tumors. In contrast, the mean of 26 low-grade gliomas was significantly lower than that of other tumors. The mean IRF-1/IRF-2 ratio of 16 other brain tumors that mainly consisted of medulloblastomas was significantly greater than that of the other 114 tumors. Almost no significant differences were observed between primary and recurrent tumors in the expression of any gene, and before and after therapy with corresponding drugs. The mean MGMT/beta2-MG ratio in primary glioblastomas was significantly higher than that in secondary tumors. These findings suggest that native drug resistance is more important than acquired resistance when glioma therapy is considered.

Chronic myeloid leukemia patients in prolonged remission following interferon-α monotherapy have distinct cytokine and oligoclonal lymphocyte profile

Before the era of tyrosine kinase inhibitors (TKIs), interferon-alpha (IFN-α) was the treatment of choice in chronic myeloid leukemia (CML). Curiously, some IFN-α treated patients were able to discontinue therapy without disease progression. The aim of this project was to study the immunomodulatory effects of IFN-α in CML patients in prolonged remission and isolate biological markers predicting response. Due to rarity of patients on IFN-α monotherapy, a relatively small cohort of patients still on treatment (IFN-ON, n = 10, median therapy duration 11.8 years) or had discontinued IFN-α therapy but remained in remission for >2 years (IFN-OFF, n = 9) were studied. The lymphocyte immunophenotype was analyzed with a comprehensive flow cytometry panel and plasma cytokine levels were measured with multiplex bead-based assay. In addition, the clonality status of different lymphocyte subpopulations was analyzed by TCR γ/δ rearrangement assay. Median NK-cell absolute number and proportion from lymphocytes in blood was higher in IFN-OFF patients as compared to IFN-ON patients or controls (0.42, 0.19, 0.21×10⁹/L; 26%, 12%, 11%, respectively, p<0.001). The proportion of CD8+ T-cells was significantly increased in both patient groups and a larger proportion of T-cells expressed CD45RO. Most (95%) patients had significant numbers of oligoclonal lymphocytes characterized by T-cell receptor γ/δ rearrangements. Strikingly, in the majority of patients (79%) a distinct clonal Vγ9 gene rearrangement was observed residing in γδ⁺ T-cell population. Similar unique clonality pattern was not observed in TKI treated CML patients. Plasma eotaxin and MCP-1 cytokines were significantly increased in IFN-OFF patients. Despite the limited number of patients, our data indicates that IFN-α treated CML patients in remission have increased numbers of NK-cells and clonal γδ⁺ T-cells and a unique plasma cytokine profile. These factors may relate to anti-leukemic effects of IFN-α in this specific group of patients and account for prolonged therapy responses even after drug discontinuation.

Immune modulation of minimal residual disease in early chronic phase chronic myelogenous leukemia: a randomized trial of frontline high-dose imatinib mesylate with or without pegylated interferon alpha-2b and granulocyte-macrophage colony-stimulating factor

BACKGROUND

Most patients with chronic myelogenous leukemia (CML) harbor residual disease, as evidenced by molecular techniques even after treatment with high-dose imatinib (ie, 800 mg/d). Interferon alpha (IFN α) is efficacious in CML likely due to its immunomodulatory properties, and is synergistic in vitro with imatinib and granulocyte macrophage-colony stimulating factor (GM-CSF).

METHODS

A study was undertaken to determine whether adding pegylated (PEG) IFN α-2b and GM-CSF to high-dose imatinib may improve the complete molecular response rate in patients with CML in chronic phase. Ninety-four patients were treated with imatinib 800 mg/d for the first 6 months, then randomly assigned to continue high-dose imatinib alone (n = 49) or in combination with PEG IFN α-2b 0.5 μg/kg/wk and GM-CSF 125 mg/m² 3× weekly (n = 45).

RESULTS

The median follow-up for all patients was 54 months (range, 7-70 months). There were no differences in the rates of complete cytogenetic response (87% vs 90%; P = 1.0), or of major (77% vs 77%; P = 1.0) or complete (11% vs 13%; P = 1.0) molecular response (on the international scale) at 12 months between the 2 arms, or at any time during the study. Adverse events led to PEG IFN α-2b discontinuation in all patients.

CONCLUSIONS

The addition of PEG IFN α-2b and GM-CSF to high-dose imatinib therapy does not improve significantly the cytogenetic or molecular response rates compared with high-dose imatinib alone. The high dropout rate in the PEG IFN α-2b arm may have compromised its potential immunomodulatory benefit.

The response to imatinib and interferon-alpha is more rapid than the response to imatinib alone: a retrospective analysis of 495 Philadelphia-positive chronic myeloid leukemia patients in early chronic phase

Before the introduction of imatinib, interferon alpha-based regimens were the gold standard for treatment of early chronic phase chronic myeloid leukemia patients. The combination of IFN-alpha with imatinib is currently being investigated in at least two large clinical trials, the German CML Study IV and the French SPIRIT trial. We reviewed the cytogenetic and molecular responses of 76 early chronic phase chronic myeloid leukemia patients who were treated with imatinib and interferon-alpha and of 419 early chronic phase chronic myeloid leukemia patients treated with imatinib alone front-line. The complete cytogenetic response rate was higher in the IM+IFN-alpha group than in the imatinib group at six months (60% vs. 42%; P=0.003), but not at 48 months (88% vs. 88%). The durability of the complete cytogenetic response was similar in the two groups with 94% and 91% of complete cytogenetic responders in continuous complete cytogenetic response at 48 months (P=0.56). The major molecular response rate was higher in the IM+IFN-alpha group at six months (58% vs. 34%; P=0.0001) and 12 months (67% vs. 47%; P=0.001) but not later on (65% vs. 57% at 48 months; P=0.25). Overall and progression free survival were comparable in the two groups; a significant trend to a better event free survival was observed in patients treated with PegIFNalpha (91% vs. 78%; P=0.02). These data suggest that the response to the combination treatment is more rapid. It is not yet known how much a rapid reduction will influence the longer-term overall and progression free survival, and the cure rate.

Suppression of interferon (IFN)-inducible genes and IFN-mediated functional responses in BCR-ABL-expressing cells

The interferons (IFNs) are cytokines that play key roles in host defense against viral infections and immune surveillance against cancer. We report that BCR-ABL transformation of hematopoietic cells results in suppression of IFN-dependent responses, including transcription of IFN-inducible genes and generation of IFN-mediated antiviral effects. BCR-ABL transformation suppresses expression of several IFN-regulated genes containing IFN-sensitive response element (ISRE) or GAS elements in their promoters, including Isg15, Irf1, Irf9, and Ifit2 (interferon-induced protein with tetratricopeptide repeats 2). Suppression of transcription of ISRE-containing genes is also seen in cells expressing various BCR-ABL kinase domain mutants, including T315I, H396P, Y253F, and E255K, but not kinase-defective BCR-ABL. Such effects are associated with impaired IFN-dependent phosphorylation of Stat1 on Tyr(701) and Stat3 on Tyr(705) and defective binding of Stat complexes to ISRE or GAS elements. Beyond suppression of Stat activities, BCR-ABL inhibits IFN-inducible phosphorylation/activation of the p38 MAPK, suggesting a dual mechanism by which this abnormal fusion protein blocks IFN transcriptional responses. The inhibitory activities of BCR-ABL ultimately result in impaired IFNalpha-mediated protection against encephalomyocarditis virus infection and reversal of IFN-dependent growth suppression. Altogether, our data provide evidence for a novel mechanism by which BCR-ABL impairs host defenses and promotes malignant transformation, involving dual suppression of IFN-activated signaling pathways.

Therapeutic Implications of Interferon Regulatory Factor (IRF)-1 and IRF-2 in Diffusely Infiltrating Astrocytomas (DIA): Response to Interferon (IFN)-β in Glioblastoma Cells and Prognostic Value for DIA

The precise mechanisms governing the direct effect of IFN-beta, including apoptosis induction, are not yet fully understood. To gain a better insight into these mechanisms, we investigated the signaling pathways focusing particularly on interferon regulatory factor 1 (IRF-1) and IRF-2 in glioblastoma cell lines. Furthermore, we attempted to determine whether or not IRF-1 and IRF-2 act as additional prognostic indicators in diffusely infiltrating astrocytomas (DIA). We first assessed the cytotoxic effects of IFN-beta based on a cell growth study and modified MTT assay, and then quantified the apoptosis using a sandwich enzyme immunoassay following IFN-beta treatment in the cell lines, U-87MG, T98G, and A-172. Subsequently, we carried out an analysis of apoptosis-related molecules as evaluated by densitometric analysis of Western blots, focusing on IRF-1 and IRF-2, and two major initiator caspases, caspase-8 and caspase-9. Furthermore, we assessed the expression of type I IFN receptor, IRF-1, and IRF-2 using immunohistochemical techniques in 63 DIA (15 of WHO grade II, 18 of grade III, and 30 of grade IV), and analyzed their impact on prognosis. An increase in apoptosis was apparent after 48 h of IFN-beta treatment (1 x 10(4) IU/ml) in T98G but not in U-87MG or A-172. IFN-beta treatment for 6 h significantly enhanced the expression of IRF-1 in all three cell lines. However, an enhanced expression of IRF-2 was observed only in the not-most-sensitive, non-apoptosis-induced U-87MG and A-172. While minimal processing of caspase-8 was noted in the three cell lines throughout the experiment, caspase-9 activation was observed in the apoptosis-detected T98G after 48 h of treatment, as indicated by a 1.33-fold increase (P=0.037). On the other hand, the IRF-1 LI and IRF-1/IRF-2 LI ratio were greater in low-grade DAI, and were negatively correlated with the histopathological grade in DIA (P=0.017 and P=0.001, respectively). Furthermore, the IRF-1/IRF-2 LI ratio was negatively correlated with the MIB-1 LI in DIA (P=0.004), and represented an independent and most powerful determinant of overall survival compared to other conventional prognostic factors (P=0.018). However, the relation was not statistically significant when only patients with high-grade DIA were assessed. Our findings suggest that up-regulation of IRF-1 and IRF-2 might be an important determinant of susceptibility to IFN-beta mediated cytotoxicity including apoptosis. Furthermore, the IRF-1/IRF-2 LI ratio may reflect the proliferative state of DIA and constitute an important prognostic marker in DIA. Thus, IRF-1 and IRF-2 could represent one of the therapeutic target sites for the regulation of cell growth in DIA.

Interferon alpha and T-cell responses in chronic myeloid leukemia

Chronic myelogenous leukemia (CML) was the first human malignancy where a consistent chromosomal abnormality, the BCR-ABL translocation, was identified as the causative genetic aberration. There is a mounting body of evidence suggesting that CML cells are particularly good targets for immunological surveillance mechanisms, the most intriguing being the curative effect of allogeneic donor lymphocyte infusion given in relapsed disease after allogeneic bone marrow transplantation. Likewise, interferon alpha (IFN alpha), which has long been considered as the standard conservative therapy in CML, may exert its life-prolonging effect by activating immunological effector functions. This review will focus on the recent advances in the understanding of the contribution of IFN alpha in eliciting T-cell responses against self-antigens in CML.

Imatinib and pegylated human recombinant interferon-α2b in early chronic-phase chronic myeloid leukemia

Since interferon-α and imatinib (IM; STI571, Glivec, Gleevec) are effective for the treatment of chronic myeloid leukemia (CML), and their mechanisms of action are different, we designed an exploratory study investigating the effects of a standard IM dose (400 mg/d) and a variable pegylated interferon-α (PegIFN) dose (50 μg/wk, 100 μg/wk, and 150 μg/wk). The criteria for dose adjustment were designed so as to ensure the delivery of the IM dose and to protect life quality. There were 76 patients with previously untreated Philadelphia (Ph)–positive CML enrolled in the study. There were 3 patients who discontinued IM and 45 patients who discontinued PegIFN. The severity of adverse events increased with increasing PegIFN dose. The IM dose could be administered to the patients who were assigned to receive 50 μg/wk or 100 μg/wk PegIFN but not to those who were assigned to receive 150 μg/wk. The median administered dose of PegIFN ranged between 32 μg/wk and 36 μg/wk. The cytogenetic response was 70% complete (Ph-neg 100%) and 83% major (Ph-neg &gt; 65%). The BCR/ABL transcript was reduced by at least 3 logs in 68% of complete cytogenetic responders. These data of toxicity, compliance, and efficacy may assist in the design and preparation of prospective studies.

Initial expression of interferon alpha receptor 2 (IFNAR2) on CD34-positive cells and its down-regulation correlate with clinical response to interferon therapy in chronic myelogenous leukemia

In order to investigate the mechanism of interferon-alpha (IFNalpha) action in the treatment of chronic myelogenous leukemia (CML), we examined surface expressions of both type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) subunits on CD34-positive cells in bone marrow (BM) in a total of 57 CML patients. Initial cell-surface IFNAR2 expression at diagnosis assessed by flow cytometry widely distributed but showed overall significantly higher expression in CML patients when compared with normal controls. In 15 fresh patients who subsequently received IFNalpha therapy, IFNAR2 expression at diagnosis was significantly higher in cytogenetic good responders than in poor responders. Down-regulation of IFNAR2 expression during IFNalpha therapy was observed only in good responders but not in poor responders. In addition to protein level, both initial high IFNAR2c mRNA expression level and its down-regulation during IFNalpha therapy, in purified CD34-positive cells, were also observed only in good responders. In contrast to IFNAR2, cell-surface IFNAR1 expression was generally lower than IFNAR2, and correlation between either the pretreatment level or down-regulation of IFNAR1 and clinical response was not evident. With in vitro IFNalpha stimulation, CD34-positive cells showed down-regulations of cell-surface IFNAR2, and IFNAR1 to a lesser extent, in one good-responder patient, but not in one poor-responder patient. Serum soluble interferon receptor (sIFNR) was higher in untreated CML patients than in normal controls, without any correlation with clinical response to IFNalpha. Thus, the pretreatment protein and mRNA expression levels of IFNAR2 and their down-regulations during IFNalpha therapy correlate well with IFNalpha response in CML patients.

Low expression of interferon regulatory factor-1 and identification of novel exons skipping in patients with chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is a malignant clonal disorder of the haematopoietic stem cell. Treatment of CML patients with interferon alpha (IFN-alpha) has induced haematological and cytogenetic remission. Interferons transcriptionally activate target genes through the JAK-STAT and interferon regulated factors (IRFs) family pathways. Interferon regulated factor-1 (IRF-1) is a transcriptional activator of genes critical for cell growth, differentiation and apoptosis. The skipping of exons 2 or 2 and 3 of IRF-1 in patients with myelodysplastic syndromes and acute myelogenous leukaemia suggests that this factor may have a critical role in leukaemogenesis. The role of IRF-1 in CML is currently unknown. Therefore, mutational analysis of IRF-1 was performed and its expression pattern was also studied in CML patients. We studied IRF-1 in peripheral blood mononuclear cells of 21 patients in chronic phase CML. No point mutations were identified at the cDNA level. Surprisingly, fourfold reduction of full-length IRF-1 mRNA expression was established in 17/21 patients compared with normal individuals. Low expression of full-length IRF-1 was observed in conjunction with high levels of aberrantly spliced mRNAs, reported for the first time. In three patients who were also analysed during blastic transformation, further reduction of full-length IRF-1 mRNA was observed. These findings demonstrate that, in CML patients, IRF-1 can produce high levels of aberrant spliced mRNAs with subsequent reduction in the levels of full-length IRF-1 mRNA. This observation is consistent with the notion that exon skipping may constitute another mechanism of tumour suppressor gene inactivation in this disease.

Alterations in IRF1/IRF2 expression in acute myelogenous leukemia

The interferon response genes 1 and 2 have been shown to be involved in the regulation of differentiation and proliferation of cells of the myeloid series, with the former functioning as an anti-oncogene and the latter as an oncogene. In the study described here, the levels of expression of these two genes and the ratio of their expression were compared in AML and normal marrow. The ratio of gene expression was significantly less in AML marrow cells as compared to normal marrow cells [med ratio = 1.33 vs. 2.97, P = 0.003]. While the expression ratio was unaffected by the presence or absence of either ras or fms mutations, p53 mutations were associated with higher IRF1:IRF2 expression ratios that wt p53 genes [med = 1.701 vs. 1.135, P = 0.014]. Given the functional characteristics and the competitive nature of these two genes, it is possible that leukemic transformation is associated with a fall in IRF1:IRF2 ratios. Finally, the administration of IL4 can result in the normalization of the IRF1:IRF2 ratio in the marrow cells of some patients with AML.

Quantitation of interferon regulatory factor transcripts in patients with acute myeloid leukemia

Interferon regulatory factors IRF-1 and IRF-2, the two mutually antagonistic factors, fluctuate during the cell cycle and play an important role in normal and neoplastic growth processes. The relative levels of these two transcripts were analyzed in 5 normal and 43 acute myeloid leukemia (AML) bone marrow (BM) specimens by a semiquantitative RT-PCR method. IRF-1 and IRF-2 cDNA sequences were coamplified using primers that were designed to span regions of high homology between the genes. Each primer can anneal equally to both IRF-1 and IRF-2 sequences. Hence, the relative amount of amplified products from each cDNA species provides an estimation of proportional concentration of the RNA transcripts in the test sample. Results indicate expression of both the transcripts on all the leukemia and lymphoma cell lines tested, normal and AML BM. Significantly higher IRF-1:IRF-2 ratio was observed in normal as compared to AML BM (p = 0.007). There was no correlation with clinical factors such as FAB subtype. A single dose of amifostine or three daily doses of recombinant IL-4 were administered to 5 and 8 AML patients, respectively. The changes in the expression of these transcripts were studied prior to administration of the agent (d0) and after 3 days (d3). IL-4 treatment showed significant increase in the IRF-1:IRF-2 ratio in 4 of 8 patients (p = 0.05); amifostine treatment did not show any appreciable change.

Expression of nuclear transcription factor interferon consensus sequence binding protein in chronic myeloid leukemia correlates with pretreatment risk features and cytogenetic response to interferon-α

Recently, it was shown that interferon consensus sequence binding protein (ICSBP), a member of the interferon regulatory factor (IRF) family, has a potential role in chronic myeloid leukemia (CML). Deletion of ICSBP gene in mice leads to a CML-like syndrome and samples from CML patients exhibited impaired ICSBP expression. The present study found that ICSBP expression correlated with risk features determined by Sokal score in untreated CML (P = .007 for high versus low risk). In addition, analyzing ICSBP expression during interferon-α (IFN-α) therapy in “good” (n = 27) versus “poor” (n = 15) cytogenetic responders, high ICSBP levels were only observed in “good” responders (P = .0002). Together, these data suggest that ICSBP levels are related to initial presentation of CML and the therapeutic response of CML to IFN-α, indicating an important role of ICSBP in CML.

Philadelphia-positive chronic myelogenous leukemia with a 5q-- abnormality in a patient following interferon-alpha therapy

In this report, we describe a rare 5q--/CML association in a patient with Ph-positive chronic myelogenous leukemia (CML) who achieved complete cytogenetic response on interferon-alpha (IFN-alpha) treatment, but who developed a new clone in the blastic crisis. The patient was treated with interferon-alpha beginning in 1996 and a serial chromosome and molecular study was performed over the clinical course of the disease. The patient remained in complete hematologic and cytogenetic remission until November 1998, when a reverse transcriptase PCR study performed on the bone marrow and peripheral blood cells was negative for chimeric BCR/ABL mRNA. The treatment was discontinued until April 1999, when the patient developed acute transformation of the disease. In June 1999, cytogenetic examination showed the development of a new clone, consisting of the deletion of the long arm of chromosome 5 in addition to the standard Ph translocation. The unusual association of a Ph with an abnormality usually observed in a secondary myeloproliferative disease raises the question of whether the new finding is treatment-induced or part of the disease process and casually related to the acute transformation.

Expression of interferon-α (IFN-α) receptor 2c at diagnosis is associated with cytogenetic response in IFN-α–treated chronic myeloid leukemia

For the management of chronic myeloid leukemia (CML), prediction or early determination of the response to interferon-alpha (IFN-α) treatment is important for identifying nonresponder patients to whom alternative therapy may be proposed. In this study, the levels of expression of both BCR-ABL and subunit 2c of IFN-α receptor (IFN-αR2c) genes were analyzed at diagnosis in 74 patients with chronic phase CML treated with an IFN-α monotherapy. By using blood samples, real-time quantitative polymerase chain reaction was performed to quantify BCR-ABL, IFN-αR2c, and G6PDH mRNA as external control. The results were compared with hematologic and cytogenetic responses to IFN-α. A wide variation in the BCR-ABL/G6PDH ratio was observed at diagnosis (median, 6.68%; range, 0.18%-41.31%), but no significant association with response to IFN-α was observed. In contrast, the variation of IFN-αR2c/G6PDH ratio at diagnosis was significantly associated with the achievement of major cytogenetic response (MCR; 34% or lower Ph+metaphases). Median values of IFN-αR2c/G6PDH ratio for patients achieving MCR and for those who did not achieve it were 110.75% (range, 9.47%-612.30%) and 64.42% (range, 5.96%-425.40%), respectively (P = .037). In addition, this novel molecular factor, combined with the achievement of complete hematologic response at 3 months, makes it possible to predict MCR achievement with high probability by Kaplan-Meier analysis (91% ± 17% at 24 months; P = .0001).

Expression of interferon regulatory factor 4 in chronic myeloid leukemia: correlation with response to interferon alfa therapy

PURPOSE

Mice experiments have established an important role for interferon regulatory factor (IRF) family members in hematopoiesis. We wanted to study the expression of interferon regulatory factor 4 (IRF4) in various hematologic disorders, especially chronic myeloid leukemia (CML), and its association with response to interferon alfa (IFN-alpha) treatment in CML.

MATERIALS AND METHODS

Blood samples from various hematopoietic cell lines, different leukemia patients (70 CML, 29 acute myeloid leukemia [AML], 10 chronic myelomonocytic leukemia [CMMoL], 10 acute lymphoblastic leukemia, and 10 chronic lymphoid leukemia patients), and 33 healthy volunteers were monitored for IRF4 expression by reverse transcriptase polymerase chain reaction. Then, with a focus on CML, the IRF4 level was determined in sorted cell subpopulations from CML patients and healthy volunteers and in in vitro-stimulated CML cells. Furthermore, IRF4 expression was compared in the CML samples taken before IFN-alpha therapy and in 47 additional CML samples taken during IFN-alpha therapy. IRF4 expression was then correlated with cytogenetic response to IFN-alpha.

RESULTS

IRF4 expression was significantly impaired in CML, AML, and CMMoL samples. The downregulation of IRF4 in CML samples was predominantly found in T cells. In CML patients during IFN-alpha therapy, a significant increase in IRF4 levels was detected, and this was also observed in sorted T cells from CML patients. The increase seen during IFN-alpha therapy was not due to different blood counts. In regard to the cytogenetic response with IFN-alpha, a good response was associated with high IRF4 expression.

CONCLUSION

IRF4 expression is downregulated in T cells of CML patients, and its increase is associated with a good response to IFN-alpha therapy. These data suggest IRF4 expression as a useful marker to monitor, if not predict, response to IFN-alpha in CML.

Correlation between pretreatment levels of interferon response genes and clinical responses to an immune response modifier (Imiquimod) in genital warts

Imiquimod (IQ) has been successfully used in treatment of genital warts. In clinical settings, patients responded well but wart reduction rates varied. Our aim was to find a correlation between clinical responses and pretreatment (constitutive) levels of genes that might be involved in the molecular action of IQ. Since IQ is a cytokine inducer, we analyzed levels of expression of genes of the JAK/STAT signaling pathway and their inhibitors as well as interferon response factors (IRFs) in pretreatment biopsy specimens from complete responders (99 to 100% wart reduction rate) versus incomplete responders (75 to 92% wart reduction rate) by reverse transcription-PCR. We found that mRNA levels of signal transducer and activator of transcription 1 (STAT1) and IRF1 were higher in complete responders than in incomplete responders. Incomplete responders expressed larger amounts of STAT3, IRF2, and protein inhibitor of activated STAT1 (PIAS1) mRNAs compared to complete responders before IQ treatment. We hypothesize that high-level expression of STAT1 and IRF1 is advantageous for a better IQ response. The observed differences in constitutive mRNA levels of these genes may be the consequence of alterations in cellular differentiation and/or variable expression of endogenous interferons. Previous in vitro studies showed that keratinocyte differentiation coordinates the balance between positive and negative signals along the JAK/STAT pathway by regulating the IRF1:IRF2 and STAT1:PIAS1 ratios and thus affecting induction of IQ-inducible genes. Specifically, differentiation supports constitutive expression of STAT1 and IRF1 mRNAs but not expression of IRF2 and PIAS1. Our data are in good agreement with studies that showed the importance of STAT1 in cytokine induction and activation of interferon-responsive genes by IQ.

Regulation of CD26/DPPIV gene expression by interferons and retinoic acid in tumor B cells

Interferons (IFNs alpha, beta and gamma) and all trans retinoic acid (RA) have the ability to activate genes with GAS sites. We have found that the promoter of CD26/dipeptidylpeptidase IV (DPPIV) contains a consensus GAS site TTCnnnGAA located at bp-35 to -27, and computer analysis confirmed this sequence to be a putative Stat binding site. Consistent with this finding, we show that IFNs and RA rapidly enhanced CD26 gene and protein expression in chronic B lymphocytic leukemia (B-CLL) cells. Immunoblot analyses revealed that unstimulated B-CLL cells expressed detectable levels of serine/tyrosine-phosphorylated Stat1alpha, and RA and IFN-gamma treatment led to increased levels of tyrosine phosphorylation of Stat1alpha and its nuclear accumulation. As shown by electrophoretic mobility shift assay, RA and IFN-gamma increased the binding of a nuclear protein to the GAS-CD26 element. Shift-Western blotting identified Stat1alpha as the GAS-CD26 binding factor. Augmented levels of CD26 protein in malignant B cells cultured with IFNs or RA coincided with the enhancement of DPPIV activity. Taken together, our results are in favor of the IFN-/RA-mediated upregulation of CD26/DPPIV in B-CLL through the signaling pathway involving Stat1alpha and the GAS response element of CD26 promoter.

Interphase cytogenetics and competitive RT-PCR for residual disease monitoring in patients with chronic myeloid leukaemia during interferon-alpha therapy

There is a need for fast and sensitive methods to evaluate the response of patients with chronic myeloid leukaemia (CML) to interferon-alpha (IFN-alpha) therapy to complement cytogenetic analysis of Philadelphia (Ph) chromosome-positive metaphases. We have used interphase FISH (fluorescence in situ hybridization) and competitive RT-PCR (reverse transcriptase-polymerase chain reaction) techniques for detection of BCR-ABL-positive cells to measure suppression of leukaemic clone in a series of 51 follow-up samples from 24 CML patients undergoing IFN-alpha treatment. Interphase FISH analysis of the malignant clone in bone marrow using BCR and ABL probes was found to be highly correlated to conventional G-banding metaphase examination (r = 0.98). RT-PCR quantification of BCR-ABL mRNA transcripts in blood also showed a high degree of concordance with the proportion of Ph-positive metaphases (r = 0.93). In addition, the degree of cytogenetic response did not influence the equivalence between karyotype analysis and molecular methods. We concluded that interphase FISH and competitive RT-PCR provide reliable information on residual tumour burden and response to IFN-alpha in CML patients. These molecular methods may significantly improve the efficiency of residual disease monitoring during IFN-alpha therapy of CML.