Continuous delivery of human type I interferons (α/β) has significant activity against acute myeloid leukemia cells in vitro and in a xenograft model

Type I interferon signaling in malignant blasts contributes to treatment efficacy in AML patients

While type I interferon (IFN) is best known for its key role against viral infection, accumulating preclinical and clinical data indicate that robust type I IFN production in the tumor microenvironment promotes cancer immunosurveillance and contributes to the efficacy of various antineoplastic agents, notably immunogenic cell death inducers. Here, we report that malignant blasts from patients with acute myeloid leukemia (AML) release type I IFN via a Toll-like receptor 3 (TLR3)-dependent mechanism that is not driven by treatment. While in these patients the ability of type I IFN to stimulate anticancer immune responses was abolished by immunosuppressive mechanisms elicited by malignant blasts, type I IFN turned out to exert direct cytostatic, cytotoxic and chemosensitizing activity in primary AML blasts, leukemic stem cells from AML patients and AML xenograft models. Finally, a genetic signature of type I IFN signaling was found to have independent prognostic value on relapse-free survival and overall survival in a cohort of 132 AML patients. These findings delineate a clinically relevant, therapeutically actionable and prognostically informative mechanism through which type I IFN mediates beneficial effects in patients with AML.

Megakaryopoiesis impairment through acute innate immune signaling activation by azacitidine

Thrombocytopenia, prevalent in the majority of patients with myeloid malignancies, such as myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML), is an independent adverse prognostic factor. Azacitidine (AZA), a mainstay therapeutic agent for stem cell transplant-ineligible patients with MDS/AML, often transiently induces or further aggravates disease-associated thrombocytopenia by an unknown mechanism. Here, we uncover the critical role of an acute type-I interferon (IFN-I) signaling activation in suppressing megakaryopoiesis in AZA-mediated thrombocytopenia. We demonstrate that megakaryocytic lineage-primed progenitors present IFN-I receptors and, upon AZA exposure, engage STAT1/SOCS1-dependent downstream signaling prematurely attenuating thrombopoietin receptor (TPO-R) signaling and constraining megakaryocytic progenitor cell growth and differentiation following TPO-R stimulation. Our findings directly implicate RNA demethylation and IFN-I signal activation as a root cause for AZA-mediated thrombocytopenia and suggest mitigation of TPO-R inhibitory innate immune signaling as a suitable therapeutic strategy to support platelet production, particularly during the early phases of AZA therapy.

Immunomodulatory and Direct Activities of Ropeginterferon Alfa-2b on Cancer Cells in Mouse Models of Leukemia

Although ropeginterferon alfa‐2b has recently been clinically applied to myeloproliferative neoplasms with promising results, its antitumor mechanism has not been thoroughly investigated. Using a leukemia model developed in immunocompetent mice, we evaluated the direct cytotoxic effects and indirect effects induced by ropeginterferon alfa‐2b in tumor cells. Ropeginterferon alfa‐2b therapy significantly prolonged the survival of mice bearing leukemia cells and led to long‐term remission in some mice. Alternatively, conventional interferon‐alpha treatment slightly extended the survival and all mice died. When ropeginterferon alfa‐2b was administered to interferon‐alpha receptor 1–knockout mice after the development of leukemia to verify the direct effect on the tumor, the survival of these mice was slightly prolonged; nevertheless, all of them died. In vivo CD4⁺ or CD8⁺ T‐cell depletion resulted in a significant loss of therapeutic efficacy in mice. These results indicate that the host adoptive immunostimulatory effect of ropeginterferon alfa‐2b is the dominant mechanism through which tumor cells are suppressed. Moreover, mice in long‐term remission did not develop leukemia, even after tumor rechallenge. Rejection of rechallenge tumors was canceled only when both CD4⁺ and CD8⁺ T cells were removed in vivo, which indicates that each T‐cell group functions independently in immunological memory. We show that ropeginterferon alfa‐2b induces excellent antitumor immunomodulation in hosts. Our finding serves in devising therapeutic strategies with ropeginterferon alfa‐2b.

Blocking UBE2N abrogates oncogenic immune signaling in acute myeloid leukemia

Dysregulation of innate immune signaling pathways is implicated in various hematologic malignancies. However, these pathways have not been systematically examined in acute myeloid leukemia (AML). We report that AML hematopoietic stem and progenitor cells (HSPCs) exhibit a high frequency of dysregulated innate immune-related and inflammatory pathways, referred to as oncogenic immune signaling states. Through gene expression analyses and functional studies in human AML cell lines and patient-derived samples, we found that the ubiquitin-conjugating enzyme UBE2N is required for leukemic cell function in vitro and in vivo by maintaining oncogenic immune signaling states. It is known that the enzyme function of UBE2N can be inhibited by interfering with thioester formation between ubiquitin and the active site. We performed in silico structure-based and cellular-based screens and identified two related small-molecule inhibitors UC-764864/65 that targeted UBE2N at its active site. Using these small-molecule inhibitors as chemical probes, we further revealed the therapeutic efficacy of interfering with UBE2N function. This resulted in the blocking of ubiquitination of innate immune- and inflammatory-related substrates in human AML cell lines. Inhibition of UBE2N function disrupted oncogenic immune signaling by promoting cell death of leukemic HSPCs while sparing normal HSPCs in vitro. Moreover, baseline oncogenic immune signaling states in leukemic cells derived from discrete subsets of patients with AML exhibited a selective dependency on UBE2N function in vitro and in vivo. Our study reveals that interfering with UBE2N abrogates leukemic HSPC function and underscores the dependency of AML cells on UBE2N-dependent oncogenic immune signaling states.

Interferon-α as maintenance therapy can significantly reduce relapse in patients with favorable-risk acute myeloid leukemia

To evaluate the efficacy of interferon-α (IFN-α) as maintenance therapy in patients with favorable-risk acute myeloid leukemia (AML), this retrospective study enrolled 84 patients with favorable-risk AML: 42 patients who received IFN-α maintenance therapy and 42 patients who did not (control). The median follow-up time and duration of IFN-α treatment was 26 (6-54) months and 18 (2-24) months, respectively. The 4-year estimated relapse-free survival (RFS) after the last consolidation chemotherapy was 86.8% (95% confidence interval (CI), 75.8-97.8%) in the IFN-α group and 55.7% (95% CI, 37.2-74.3%) in the control group (p=.007). The 4-year estimated overall survival was 94.4% (95% CI, 86.8-102%) and 76.4% (95% CI, 61.9-90.9%) in IFN-α and control groups, respectively (p=.040). The Cox regression analysis showed that IFN-α treatment was the only independent factor affecting RFS (p=.004). Maintenance therapy with IFN-α may prevent relapse in favorable-risk AML after consolidation chemotherapy.

Activation of plasmacytoid dendritic cells promotes AML-cell fratricide

Acute myeloid leukemia (AML) is characterized by the proliferation of immature myeloid blasts and a suppressed immune state. Interferons have been previously shown to aid in the clearance of AML cells. Type I interferons are produced primarily by plasmacytoid dendritic cells (pDCs). However, these cells exist in a quiescent state in AML. Because pDCs express TLR 7–9, we hypothesized that the TLR7/8 agonist R848 would be able to reprogram them toward a more active, IFN-producing phenotype. Consistent with this notion, we found that R848-treated pDCs from patients produced significantly elevated levels of IFNβ. In addition, they showed increased expression of the immune-stimulatory receptor CD40. We next tested whether IFNβ would influence antibody-mediated fratricide among AML cells, as our recent work showed that AML cells could undergo cell-to cell killing in the presence of the CD38 antibody daratumumab. We found that IFNβ treatment led to a significant, IRF9-dependent increase in CD38 expression and a subsequent increase in daratumumab-mediated cytotoxicity and decreased colony formation. These findings suggest that the tolerogenic phenotype of pDCs in AML can be reversed, and also demonstrate a possible means of enhancing endogenous Type I IFN production that would promote daratumumab-mediated clearance of AML cells.

Location First: Targeting Acute Myeloid Leukemia Within Its Niche

Despite extensive research and development of new treatments, acute myeloid leukemia (AML)-backbone therapy has remained essentially unchanged over the last decades and is frequently associated with poor outcomes. Eradicating the leukemic stem cells (LSCs) is the ultimate challenge in the treatment of AML. Emerging evidence suggests that AML remodels the bone marrow (BM) niche into a leukemia-permissive microenvironment while suppressing normal hematopoiesis. The mechanism of stromal-mediated protection of leukemic cells in the BM is complex and involves many adhesion molecules, chemokines, and cytokines. Targeting these factors may represent a valuable approach to complement existing therapies and overcome microenvironment-mediated drug resistance. Some strategies for dislodging LSCs and leukemic blasts from their protective niche have already been tested in patients and are in different phases of the process of clinical development. Other strategies, such as targeting the stromal cells remodeling processes, remain at pre-clinical stages. Development of humanized xenograft mouse models, which overcome the mismatch between human leukemia cells and the mouse BM niche, is required to generate physiologically relevant, patient-specific human niches in mice that can be used to unravel the role of human AML microenvironment and to carry out preclinical studies for the development of new targeted therapies.

Towards a Better Understanding of Cohesin Mutations in AML

Classical driver mutations in acute myeloid leukemia (AML) typically affect regulators of cell proliferation, differentiation, and survival. The selective advantage of increased proliferation, improved survival, and reduced differentiation on leukemia progression is immediately obvious. Recent large-scale sequencing efforts have uncovered numerous novel AML-associated mutations. Interestingly, a substantial fraction of the most frequently mutated genes encode general regulators of transcription and chromatin state. Understanding the selective advantage conferred by these mutations remains a major challenge. A striking example are mutations in genes of the cohesin complex, a major regulator of three-dimensional genome organization. Several landmark studies have shown that cohesin mutations perturb the balance between self-renewal and differentiation of hematopoietic stem and progenitor cells (HSPC). Emerging data now begin to uncover the molecular mechanisms that underpin this phenotype. Among these mechanisms is a role for cohesin in the control of inflammatory responses in HSPCs and myeloid cells. Inflammatory signals limit HSPC self-renewal and drive HSPC differentiation. Consistent with this, cohesin mutations promote resistance to inflammatory signals, and may provide a selective advantage for AML progression. In this review, we discuss recent progress in understanding cohesin mutations in AML, and speculate whether vulnerabilities associated with these mutations could be exploited therapeutically.

Effects of preemptive interferon-α monotherapy in acute leukemia patients with relapse tendency after allogeneic hematopoietic stem cell transplantation: a case-control study

Interferon-α (IFN-α) inhibits tumor growth and mimics graft-versus-leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the current case-control study, we compared treatment responses in acute leukemia patients with relapse tendency post-allo-HSCT receiving preemptive IFN-α after withdrawal of immunosuppressants (n = 31) vs. receiving no IFN-α (n = 67). In the IFN-α group, 25 patients responded to the treatment without progressing to hematological relapse. In the non-IFN-α group, only 22 patients responded to the treatment. The response rate differed significantly (80.6 vs. 32.8%, P < 0.001). The 2-year cumulative incidence of relapse was 31.6 and 61.2% in the IFN-α and the non-IFN groups, respectively (P = 0.006). The 2-year leukemia-free survival and overall survival rate was 57.4 vs. 28.4% (P < 0.001) and 67.6 vs. 32.9% (P = 0.001), respectively. Among the 31 patients in the IFN-α group, 18 patients (58.1%) developed graft-versus-host disease (GVHD): 6 acute and 12 limited chronic GVHD. Patients who developed GVHD had higher treatment response rate than patients without GVHD (88.9 vs. 53.8%, P = 0.022). In conclusion, preemptive IFN-α therapy is a safe and effective treatment to prevent disease progression in high-risk patients with relapse tendency post-allo-HSCT.

miR-155 promotes FLT3-ITD-induced myeloproliferative disease through inhibition of the interferon response

FLT3-ITD⁺ acute myeloid leukemia (AML) accounts for ∼25% of all AML cases and is a subtype that carries a poor prognosis. microRNA-155 (miR-155) is specifically overexpressed in FLT3-ITD⁺ AML compared with FLT3 wild-type (FLT3-WT) AML and is critical for the growth of FLT3-ITD⁺ AML cells in vitro. However, miR-155's role in regulating FLT3-ITD-mediated disease in vivo remains unclear. In this study, we used a genetic mouse model to determine whether miR-155 influences the development of FLT3-ITD-induced myeloproliferative disease. Results indicate that miR-155 promotes FLT3-ITD-induced myeloid expansion in the bone marrow, spleen, and peripheral blood. Mechanistically, miR-155 increases proliferation of the hematopoietic stem and progenitor cell compartments by reducing the growth-inhibitory effects of the interferon (IFN) response, and this involves targeting of Cebpb. Consistent with our observations in mice, primary FLT3-ITD⁺ AML clinical samples have significantly higher miR-155 levels and a lower IFN response compared with FLT3-WT AML samples. Further, inhibition of miR-155 in FLT3-ITD⁺ AML cell lines using CRISPR/Cas9, or primary FLT3-ITD⁺ AML samples using locked nucleic acid antisense inhibitors, results in an elevated IFN response and reduces colony formation. Altogether, our data reveal that miR-155 collaborates with FLT3-ITD to promote myeloid cell expansion in vivo and that this involves a multitarget mechanism that includes repression of IFN signaling.

Immunotherapy in acute myeloid leukemia

Despite the remarkable progress made in some leukemias such as CML and CLL, cytotoxic treatment for AML remains essentially unchanged over the last 4 decades. Several lines of evidence, including the graft versus leukemia effect associated with allogeneic hematopoietic stem cell transplantation (HSCT), suggest that immunotherapy is an active modality in AML. Given the lack of progress for chemotherapy in this disease, many novel immunologic treatment approaches have been explored. The goals of non-transplant-based immune approaches have largely consisted of the stimulation or restoration of endogenous immune responses or the targeting of specific tumor antigens by immune cells. These strategies have been associated with less toxicity than allogeneic HSCT but typically have inferior efficacy. Allogeneic HSCT exploits major and minor histocompatibility differences between the donor and recipient in order to recognize and eradicate malignancy. With the recognition that the immune system itself provides a basis for treating AML, immunotherapy continues to be an attractive modality to exploit in the treatment of this disease.

Interferon α may be back on track to treat acute myeloid leukemia

Our own experience and a thorough literature review suggest that interferon α (IFNα) should be reconsidered for the treatment of acute myeloid leukemia patients. Most likely, the success of such treatment depends on the achievement of high serum levels of IFNα for several months, which can be obtained by using pegylated IFNα.

Synergistic interaction of Smac mimetic and IFNα to trigger apoptosis in acute myeloid leukemia cells

Therapeutic targeting of inhibitor of apoptosis (IAP) proteins by small-molecule inhibitors such as Smac mimetic is considered as a promising anticancer strategy to elicit apoptosis. Recent advances have renewed the interest in exploiting the antileukemic activity of interferon (IFN)α for the treatment of acute myeloid leukemia (AML). Here, we identify a novel synergistic interaction of the Smac mimetic BV6 and IFNα to trigger cell death in AML cells. Calculation of combination index (CI) confirms the synergism of BV6 and IFNα. In contrast to AML cells, no synergistic toxicity of BV6 and IFNα at equimolar concentrations is found against normal peripheral blood lymphocytes. BV6 and IFNα act in concert to stimulate expression of tumor necrosis factor (TNF)α and its secretion into the supernatant, thereby initiating an autocrine/paracrine TNFα/TNF receptor 1 (TNFR1) loop that drives cell death by BV6 and IFNα. Consistently, pharmacological inhibition of TNFα by the TNFα-blocking antibody Enbrel or genetic silencing of TNFR1 significantly reduces BV6/IFNα-induced cell death. In addition, BV6/IFNα-induced cell death depends on interferon regulatory factor (IRF)1, since RNA interference-imposed knockdown of IRF1 significantly rescues cell death. In conclusion, the identification of a novel synergistic antileukemic combination of Smac mimetic and IFNα has important implications for the development of innovative treatment strategies in AML.

RUNX1-ETO induces a type I interferon response which negatively effects t(8;21)-induced increased self-renewal and leukemia development

The 8;21 translocation is the most common chromosomal aberration occurring in acute myeloid leukemia (AML). This translocation causes expression of the RUNX1-ETO (AML1-ETO) fusion protein, which cooperates with additional mutations in leukemia development. We report here that interferons (IFNs) and IFN-stimulated genes are a group of genes consistently up-regulated by RUNX1-ETO in both human and murine models. RUNX1-ETO-induced up-regulation of IFN-stimulated genes occurs primarily via type I IFN signaling with a requirement for the IFNAR complex. Addition of exogenous IFN in vitro significantly reduces the increase in self-renewal potential induced by both RUNX1-ETO and its leukemogenic splicing isoform RUNX1-ETO9a. Finally, loss of type I IFN signaling via knockout of Ifnar1 significantly accelerates leukemogenesis in a t(8;21) murine model. This demonstrates the role of increased IFN signaling as an important factor inhibiting t(8;21) fusion protein function and leukemia development and supports the use of type I IFNs in the treatment of AML.

Successful attenuation of humoral immunity to viral capsid and transgenic protein following AAV-mediated gene transfer with a non-depleting CD4 antibody and cyclosporine

The ability of transient immunosuppression with a combination of a non-depleting anti-CD4 (NDCD4) antibody and cyclosporine (CyA) to abrogate immune reactivity to both adeno-associated viral vector (AAV) and its transgene product was evaluated. This combination of immunosuppressants resulted in a 20-fold reduction in the resulting anti-AAV8 antibody titres, to levels in naïve mice, following intravenous administration of 2 × 10(12) AAV8 vector particles per kg to immunocompetent mice. This allowed efficient transduction upon secondary challenge with vector pseudotyped with the same capsid. Persistent tolerance did not result, however, as an anti-AAV8 antibody response was elicited upon rechallenge with AAV8 without immunosuppression. The route of vector administration, vector dose, AAV serotype or the concomitant administration of adenoviral vector appeared to have little impact on the ability of the NDCD4 antibody and CyA combination to moderate the primary humoral response to AAV capsid proteins. The combination of NDCD4 and CyA also abrogated the humoral response to the transgene product, that otherwise invariably would occur, following intramuscular injection of AAV5, leading to stable transgene expression. These observations could significantly improve the prospects of using rAAV vectors for chronic disorders by allowing for repeated vector administration and avoiding the development of antibodies to the transgene product.

Interferon-α in acute myeloid leukemia: an old drug revisited

Interferon-α (IFN-α), a type I IFN, is a well-known antitumoral agent. The investigation of its clinical properties in acute myeloid leukemia (AML) has been prompted by its pleiotropic antiproliferative and immune effects. So far, integration of IFN-α in the therapeutic arsenal against AML has been modest in view of the divergent results of clinical trials. Recent insights into the key pharmacokinetic determinants of the clinical efficacy of IFN along with advances in its pharmaceutical formulation, have sparked renewed interest in its use. This paper reviews the possible applicability of IFN-α in the treatment of AML and provides a rational basis to re-explore its efficacy in clinical trials.

Development of a protein biochip to identify 6 monoclonal antibodies against subtypes of recombinant human interferons

Recombinant human interferons (rhIFNs) are broadly used as effective therapeutic agents with antiviral, antitumor, and immune-modulating properties. Advances in protein biochip technology have benefited the medical community greatly, making true parallelism, miniaturization, and high throughput possible. In this study, 5 rhIFN proteins (IFN-alpha1b, IFN-alpha2a, IFN-alpha2b, IFN-beta, and IFN-gamma) were immobilized onto an N-hydroxysuccinimide (NHS)-modified gold-based biochip. The protein biochip was incubated with 6 specific mouse IgG antibodies (AK1, AK2, AK3, AK4, BK1, and CK1) against the human IFNs and then with Cy3-conjugated goat anti-mouse IgG antibody. The results showed that monoclonal antibody AK1 presented a unique binding characteristic to IFN-alpha1b. AK2 reacted in immunoassays equally with IFN-alpha2a and IFN-alpha2b. AK3 detected IFN-alpha1b, IFN-alpha2a, and IFN-alpha2b. AK4 had positive immunological responses directed to both IFN-alpha1b and IFN-alpha2b. Monoclonal antibodies BK1 and CK1 recognized epitope of IFN-beta and IFN-gamma, specifically. The assay specificity of the biochip was further confirmed by enzyme-linked immunosorbent assay (ELISA) and western blotting. Finally, 88 serum samples from patients treated with rhIFN-alpha2b were simultaneously tested on a single biochip. The result demonstrated that 6.8% (6 of 88 cases) presented positive reactions to anti-IFN-alpha2b antibodies, indicating that the patients under rhIFN-alpha2b therapy produced neutralized antibody against the IFN. The biochip format would offer a competitive alternative tool not only for facilitating characterization of IFN subtypes but also potentially for enabling clinical serum detection of corresponding antibodies directed against IFNs.

Improved intratumoral oxygenation through vascular normalization increases glioma sensitivity to ionizing radiation

PURPOSE

Ionizing radiation, an important component of glioma therapy, is critically dependent on tumor oxygenation. However, gliomas are notable for areas of necrosis and hypoxia, which foster radioresistance. We hypothesized that pharmacologic manipulation of the typically dysfunctional tumor vasculature would improve intratumoral oxygenation and, thus, the antiglioma efficacy of ionizing radiation.

METHODS AND MATERIALS

Orthotopic U87 xenografts were treated with either continuous interferon-beta (IFN-beta) or bevacizumab, alone, or combined with cranial irradiation (RT). Tumor growth was assessed by quantitative bioluminescence imaging; the tumor vasculature using immunohistochemical staining, and tumor oxygenation using hypoxyprobe staining.

RESULTS

Both IFN-beta and bevaziumab profoundly affected the tumor vasculature, albeit with different cellular phenotypes. IFN-beta caused a doubling in the percentage of area of perivascular cell staining, and bevacizumab caused a rapid decrease in the percentage of area of endothelial cell staining. However, both agents increased intratumoral oxygenation, although with bevacizumab, the effect was transient, being lost by 5 days. Administration of IFN-beta or bevacizumab before RT was significantly more effective than any of the three modalities as monotherapy or when RT was administered concomitantly with IFN-beta or bevacizumab or 5 days after bevacizumab.

CONCLUSION

Bevacizumab and continuous delivery of IFN-beta each induced significant changes in glioma vascular physiology, improving intratumoral oxygenation and enhancing the antitumor activity of ionizing radiation. Additional investigation into the use and timing of these and other agents that modify the vascular phenotype, combined with RT, is warranted to optimize cytotoxic activity.

NF-kappaB activation mediates resistance to IFN beta in MLL-rearranged acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) harboring the t(4;11) translocation is associated with a very poor prognosis; innovative treatment strategies are required to improve the current 5-year survival rate of 30-40%. Interferon beta (IFN beta) has shown promise in the treatment of both solid and hematologic malignancies, although the short half-life and toxicity associated with high doses have limited its clinical utility. To overcome these limitations, we investigated the effect of continuous, gene transfer-mediated delivery of IFN beta using adeno-associated virus (AAV)-mediated expression, on ALL cells with the t(4;11) translocation. We found that this method of IFN beta delivery resulted in complete remission of leukemia in a murine model. However, leukemic cells eventually became resistant to IFN beta and relapse was observed. Activation of NF-kappaB was identified as a mechanism for IFN beta resistance, and inhibition of NF-kappaB activity in resistant cells sensitized cells to IFN beta. IFN beta combined with agents that inhibit NF-kappaB could have therapeutic potential in the treatment of children with mixed lineage leukemia subtype ALL.

Suppression of cancer growth in mice by adeno-associated virus vector-mediated IFN-beta expression driven by hTERT promoter

Adeno-associated virus (AAV) has rapidly become a promising gene delivery vehicle for its excellent advantages of non-immunogenic, low pathogenicity and long-term gene expression in vivo. However, a major obstacle in development of effective AAV vector is the lack of tissue specificity, which caused low efficiency of AAV transfer to target cells. The application of human telomerase reverse transcriptase (hTERT) promoter is a prior targeting strategy for AAV in cancer gene therapy as hTERT activity is transcriptionally upregulated in most cancer cells. In the present work, we investigated whether AAV-mediated human interferon beta (IFN-beta) gene driven by hTERT promoter could specifically express in tumor cells and suppress tumor cell growth. Our data demonstrated that hTERT promoter-driven IFN-beta expression was the tumor-specific, decreased the cell viability of tumor cells but not normal cells, and induced tumor cell apoptosis via activation of caspase pathway and release of cytochrome c. AAV-mediated IFN-beta expression driven by hTERT promoter significantly suppressed the growth of colorectal cancer and lung cancer xenograft in mice and resulted in tumor cells death in vivo. These data suggested that AAVs in combination with hTERT-mediated IFN-beta expression could exert potential antitumor activity and provide a novel targeting approach to clinical gene therapy of varieties of cancers.

Types I and II interferons upregulate the costimulatory CD80 molecule in monocytes via interferon regulatory factor-1

CD80/B7.1 expressed on monocytes plays a prominent role in the activation of T cell-mediated immunity and its level is reduced in monocytes from cancer patients. Type I (alpha/beta) and type II (gamma) IFNs are widely administered as adjuvant therapy. We show here that both classes of IFNs upregulate CD80 mRNA and protein in primary monocytes ex vivo. The stimulatory action of IFN-alpha/beta on CD80 is accompanied by the activation of both interferon regulatory factors IRF-1 and IRF-7, whereas IFN-gamma stimulating effect is associated only with IRF-1 induction. IFNs concomitantly upregulate the transcription of CD40 costimulatory molecule whose activation is known to require IRF-1. In monocytic U937 cells, IRF-1 is activated by IFN-gamma but not by IFN-alpha/beta, whereas it is the reverse for IRF-7; in the latter cells, only IFN-gamma is capable of stimulating CD80 transcription emphasizing the essential role of IRF-1. Moreover, siRNA against IRF-1 prevents IFN-gamma-mediated CD80 activation. In AML cells, IFNs upregulate CD40, CD80 and IRF-1 in the FAB-M4/M5 subtypes but not in the less differentiated M1/M2 subtypes. Monitoring the expression of CD80 on AML cells and its modulation by IFNs could help to predict the patients more susceptible to benefit from therapeutic strategies aimed at eliciting specific T cell responses to leukemia-associated antigens.

Successful cell-mediated cytokine-activated immunotherapy for relapsed acute myeloid leukemia after hematopoietic stem cell transplantation

Acute myeloid leukemia (AML) is an extremely aggressive disease with a high relapse rate even after allogeneic hematopoietic stem cell transplantation (HSCT). We report the successful outcome of cell-mediated cytokine-activated immunotherapy in a high-risk pediatric AML patient who relapsed shortly after allogeneic HSCT. Donor lymphocyte infusion along with interferon induced a graft-versus-leukemia effect, presenting as a reversible episode of graft-versus-host disease, which led to stable complete donor chimerism and total eradication of AML for over 24 months, at the time of this report. The curative potential of immunotherapy in hematological malignancies is discussed.