Human myeloma cell apoptosis induced by interferon-alpha

Type I interferon and cancer

Type I interferon (IFN) is a class of proinflammatory cytokines with a dual role on malignant transformation, tumor progression, and response to therapy. On the one hand, robust, acute, and resolving type I IFN responses have been shown to mediate prominent anticancer effects, reflecting not only their direct cytostatic/cytotoxic activity on (at least some) malignant cells, but also their pronounced immunostimulatory functions. In line with this notion, type I IFN signaling has been implicated in the antineoplastic effects of various immunogenic therapeutics, including (but not limited to) immunogenic cell death (ICD)-inducing agents and immune checkpoint inhibitors (ICIs). On the other hand, weak, indolent, and non-resolving type I IFN responses have been demonstrated to support tumor progression and resistance to therapy, reflecting the ability of suboptimal type I IFN signaling to mediate cytoprotective activity, promote stemness, favor tolerance to chromosomal instability, and facilitate the establishment of an immunologically exhausted tumor microenvironment. Here, we review fundamental aspects of type I IFN signaling and their context-dependent impact on malignant transformation, tumor progression, and response to therapy.

Dual EZH2 and G9a inhibition suppresses multiple myeloma cell proliferation by regulating the interferon signal and IRF4-MYC axis

Epigenetic mechanisms such as histone modification play key roles in the pathogenesis of multiple myeloma (MM). We previously showed that EZH2, a histone H3 lysine 27 (H3K27) methyltransferase, and G9, a H3K9 methyltransferase, are potential therapeutic targets in MM. Moreover, recent studies suggest EZH2 and G9a cooperate to regulate gene expression. We therefore evaluated the antitumor effect of dual EZH2 and G9a inhibition in MM. A combination of an EZH2 inhibitor and a G9a inhibitor strongly suppressed MM cell proliferation in vitro by inducing cell cycle arrest and apoptosis. Dual EZH2/G9a inhibition also suppressed xenograft formation by MM cells in vivo. In datasets from the Gene Expression Omnibus, higher EZH2 and EHMT2 (encoding G9a) expression was significantly associated with poorer prognoses in MM patients. Microarray analysis revealed that EZH2/G9a inhibition significantly upregulated interferon (IFN)-stimulated genes and suppressed IRF4-MYC axis genes in MM cells. Notably, dual EZH2/G9a inhibition reduced H3K27/H3K9 methylation levels in MM cells and increased expression of endogenous retrovirus (ERV) genes, which suggests that activation of ERV genes may induce the IFN response. These results suggest that dual targeting of EZH2 and G9a may be an effective therapeutic strategy for MM.

Targeted Therapy With Immunoconjugates for Multiple Myeloma

The introduction of proteasome inhibitors (PI) and immunomodulatory drugs (IMiD) has markedly increased the survival of multiple myeloma (MM) patients. Also, the unconjugated monoclonal antibodies (mAb) daratumumab (anti-CD38) and elotuzumab (anti-SLAMF7) have revolutionized MM treatment given their clinical efficacy and safety, illustrating the potential of targeted immunotherapy as a powerful treatment strategy for MM. Nonetheless, most patients eventually develop PI-, IMiD-, and mAb-refractory disease because of the selection of resistant MM clones, which associates with a poor prognosis. Accordingly, these patients remain in urgent need of new therapies with novel mechanisms of action. In this respect, mAbs or mAb fragments can also be utilized as carriers of potent effector moieties to specifically target surface antigens on cells of interest. Such immunoconjugates have the potential to exert anti-MM activity in heavily pretreated patients due to their distinct and pleiotropic mechanisms of action. In addition, the fusion of highly cytotoxic compounds to mAbs decreases the off-target toxicity, thereby improving the therapeutic window. According to the effector moiety, immunoconjugates are classified into antibody-drug conjugates, immunotoxins, immunocytokines, or radioimmunoconjugates. This review will focus on the mechanisms of action, safety and efficacy of several promising immunoconjugates that are under investigation in preclinical and/or clinical MM studies. We will also include a discussion on combination therapy with immunoconjugates, resistance mechanisms, and future developments.

General mechanism of JQ1 in inhibiting various types of cancer

Bromodomain-containing 4 (BRD4) is a histone modification reader and transcriptional regulator that has been reported to interact with acetylated lysine histone motifs transcription factors (TFs), transcription co-activators and RNA polymerase II. The selective small molecule inhibitor JQ1, which binds competitively to bromodomains, has been reported to exhibit anti-proliferative effects in various types of cancer. Previous studies on the mechanism of action of JQ1 mostly focused on a specific tumor type or disease; however, the general mechanism through which JQ1 affects various tumors remains to be determined. In the present study, chromatin immunoprecipitation sequencing data for BRD4 and its expression profiles in six cancer cell lines were integrated and analyzed systematically. The results indicated that BRD4 binds to enhancers with histone H3 acetylated at lysine 27 (H3K27Ac) and mediator complex subunit 1 in a cell type-specific manner, as well as binds to promoter regions with the oncogenic TFs MYC and E2F1 in a cell type-common manner. The cell type-common sites across the six cell types investigated were found to be functionally important for tumorigenesis, whereas the cell type-specific sites were functionally enriched with the cell identity, all of which were sensitive to JQ1 treatment. Furthermore, a core set of JQ1-regulated BRD4 binding genes were obtained, which were significantly inhibited by JQ1 in various cancer cell lines and contributed to hallmarks of cancer. These results implied a common mechanism underlying the therapeutic effects of JQ1 and suggested its potential suitability as an anti-cancer drug targeting BRD4-mediated transcriptional regulation.

Chromatin Stability as a Target for Cancer Treatment

In this essay, I propose that DNA-binding anti-cancer drugs work more via chromatin disruption than DNA damage. Success of long-awaited drugs targeting cancer-specific drivers is limited by the heterogeneity of tumors. Therefore, chemotherapy acting via universal targets (e.g., DNA) is still the mainstream treatment for cancer. Nevertheless, the problem with targeting DNA is insufficient efficacy due to high toxicity. I propose that this problem stems from the presumption that DNA damage is critical for the anti-cancer activity of these drugs. DNA in cells exists as chromatin, and many DNA-targeting drugs alter chromatin structure by destabilizing nucleosomes and inducing histone eviction from chromatin. This effect has been largely ignored because DNA damage is seen as the major reason for anti-cancer activity. I discuss how DNA-binding molecules destabilize chromatin, why this effect is more toxic to tumoral than normal cells, and why cells die as a result of chromatin destabilization.

Cervical Cancer HeLa Cell Autocrine Apoptosis Induced by Coimmobilized IFN-γ plus TNF-α Biomaterials

Using external methods to induce the death of cancer cells is recognized as one of the main strategies for cancer treatment. Research indicated that TNF-α is frequently used in tumor biotherapy while IFN-γ can directly inhibit tumor cell proliferation. In our study, TNF-α and IFN-γ were coimmobilized on polystyrene material (PSt) or Fe₃O₄-oleic acid nanoparticles (NPs). Then the structural change of these two proteins can be observed. Meanwhile, the expressions of both TNF-α and IFN-α increased significantly, as determined by gene microarray analysis; however, in the presence of TNF-α plus IFN-α inhibitors, TNF-α and IFN-α did not increase in HeLa cells induced by coimmobilized IFN-γ plus TNF-α. Our results indicate that such change can stimilate HeLa cells to secrete more TNF-α and IFN-α, by which the apoptosis of HeLa cells could be further induced. This study is the first report of autocrine-induced apoptosis of HeLa cells. In addition, we performed ELISA, RT-PCR, flow cytometry, and Western blot analyses, as well as a series of analytical tests at the animal level. our data also indicate that the PSt-coimmobilized IFN-γ plus TNF-α has apparent effects for cancer treatment in vivo, which is of great significance for translation into clinical medicine.

Disappearance of Gadolinium Enhancement in a Chemoresistant Astrocytoma of the Tectum after High-Dose Interferon Beta

Interferon beta 6 million units per week was administered to a patient with an aggressive astrocytoma in the tectum that was resistant to cisplatin, etoposide, vinblastine, and the oral alkylating agent temozolomide. The tumor was immunopositive for O6-methylguanine-DNA methyltransferase (MGMT). Interferon beta caused the disappearance of the gadolinium-enhanced lesion in the tectum. Interferons have apoptotic and antiangiogenic effects on tumor cells, and the lesion's disappearance may have been induced by complexes of these effects. Administration of interferon beta might have a favorable effect on tectal gliomas that are immunopositive for MGMT and resistant to chemoradiotherapy including temozolomide.

The mitochondrial pathway and reactive oxygen species are critical contributors to interferon-α/β-mediated apoptosis in Ubp43-deficient hematopoietic cells

UBP43 (also known as USP18) plays a role in the negative regulation of interferon-α/β signaling, and bone marrow cells in Ubp43-deficient mice exhibited hypersensitivity to interferon-α/β-mediated apoptosis. Here, we show that the mitochondrial apoptotic pathway and reactive oxygen species are major contributors to the elevated interferon-α/β-mediated apoptosis in Ubp43-deficient mouse bone marrow cells and in UBP43-knockdown THP-1 cells. Furthermore, TRAIL and FASL, which were proposed as apoptosis inducers upon interferon-α/β treatment in UBP43-knockdown adherent cancer cells, did not cause apoptosis in these hematopoietic cells. Therefore, although UBP43 depletion can cause hypersensitivity to interferon-α/β-mediated apoptosis in a broad range of cell types, the downstream pathway may vary depending on the cell type.

Type I-IFNs control GVHD and GVL responses after transplantation

Although the effects of type II-IFN (IFN-γ) on GVHD and leukemia relapse are well studied, the effects of type I-interferon (type I-IFN, IFN-α/β) remain unclear. We investigated this using type I-IFN receptor-deficient mice and exogenous IFN-α administration in established models of GVHD and GVL. Type I-IFN signaling in host tissue prevented severe colon-targeted GVHD in CD4-dependent models of GVHD directed toward either major histocompatibility antigens or multiple minor histocompatibility antigens. This protection was the result of suppression of donor CD4+ T-cell proliferation and differentiation. Studies in chimeric recipients demonstrated this was due to type I-IFN signaling in hematopoietic tissue. Consistent with this finding, administration of IFN-α during conditioning inhibited donor CD4+ proliferation and differentiation. In contrast, CD8-dependent GVHD and GVL effects were enhanced when type I-IFN signaling was intact in the host or donor, respectively. This finding reflected the ability of type I-IFN to both sensitize host target tissue/leukemia to cell-mediated cytotoxicity and augment donor CTL function. These data confirm that type I-IFN plays an important role in defining the balance of GVHD and GVL responses and suggests that administration of the cytokine after BM transplantation could be studied prospectively in patients at high risk of relapse.

Emerging roles of FAM14 family members (G1P3/ISG 6-16 and ISG12/IFI27) in innate immunity and cancer

Interferons (IFNs) manifest their cellular functions by regulating expression of target genes known collectively as IFN-stimulated genes (ISGs). The repertoires of ISGs vary slightly between cell types, but routinely include a core of common ISGs robustly upregulated in most IFN-treated cells. Here, we review the regulation and cellular functions of 2 related ISGs, ISG12 (IFI27) and G1P3 (ISG 6-16), that are commonly induced by IFNs in most, if not all, IFN-responsive cells. On the basis of sequence similarity, they are grouped together within the newly defined FAM14 family. Emerging data on ISG12 and G1P3 suggest that both are mitochondrial proteins with opposing activities on apoptosis that may influence the innate immune responses of IFNs. The G1P3 gene encodes a low molecular weight mitochondrial protein that may stabilize mitochondrial function and oppose apoptosis. In contrast, ISG12 expression may sensitize cells to apoptotic stimuli via mitochondrial membrane destabilization. On the basis of these results and differences in induction kinetics between ISG12 and G1P3, we have proposed a model for the role of these genes in mediating cellular activity of IFNs.

Analysis of apoptosis of memory T cells and dendritic cells during the early stages of viral infection or exposure to toll-like receptor agonists

Profound type I interferon (IFN-I)-dependent attrition of memory CD8 and CD4 T cells occurs early during many infections. It is dramatic at 2 to 4 days following lymphocytic choriomeningitis virus (LCMV) infection of mice and can be elicited by the IFN-inducing Toll receptor agonist poly(I:C). We show that this attrition occurs in many organs, indicating that it is due to T cell loss rather than redistribution. This loss correlated with elevated intracellular staining of T cells ex vivo for activated caspases but with only low levels of ex vivo staining with annexin V, probably due to the rapid clearance of apoptotic cells in vivo. Instead, a high frequency of annexin V-reactive CD8alpha(+) dendritic cells (DCs), which are known to be highly phagocytic, accumulated in the spleen as the memory T cell populations disappeared. After short in vitro incubation, memory phenotype T cells isolated from LCMV-infected mice (day 3) or mice treated with poly(I:C) (12 h) displayed substantial DNA fragmentation, as detected by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay, compared to T cells isolated from uninfected mice, indicating a role for apoptosis in the memory T cell attrition. This apoptosis of memory CD8 T cells early during LCMV infection was reduced in mice lacking the proapoptotic molecule Bim. Evidence is presented showing that high levels of T cell attrition, as found in young mice, correlate with reduced immunodomination by cross-reactive memory cells.

Regulation of apoptosis by type III interferons

OBJECTIVE

Two types of interferons (IFNs), type I (IFN-alpha/beta) and type III (IFN-lambdas), utilize distinct receptor complexes to induce similar signalling and biological activities, including recently demonstrated for IFN-lambdas antitumour activity. However, ability of type III IFNs to regulate cell population growth remains largely uncharacterized.

MATERIALS AND METHODS

Intact and modified human colorectal adenocarcinoma HT29 cells were used to study regulation of apoptosis by IFN-lambdas.

RESULTS AND CONCLUSIONS

We report that the IFN-lambdaR1 chain of the type III IFN receptor complex possesses an intrinsic ability to trigger apoptosis in cells. Signalling induced through the intracellular domain of IFN-lambdaR1 resulted in G(1)/G(0) phase cell cycle arrest, phosphatidylserine surfacing and chromosomal DNA fragmentation. Caspase-3, caspase-8 and caspase-9 were activated; however, pancaspase inhibitor Z-VAD-FMK did not prevent apoptosis. In addition, the extent of apoptosis correlated with the level of receptor expression and was associated with prolonged IFN-lambda signalling. We also demonstrated that the ability to trigger apoptosis is a unique intrinsic function of all IFN receptors. However, more robust apoptosis was induced by signalling through type III IFN receptor than through type I or type II (IFN-gamma) receptors, suggesting higher cytotoxic potential of type III IFNs. In addition, we observed that IFN-gamma treatment sensitized HT29 cells to IFN-lambda-mediated apoptosis. These results provide evidence that type III IFNs, alone or in combination with other stimuli, have the potential to induce apoptosis.

Adjuvant immunotherapy of feline fibrosarcoma with recombinant feline interferon-omega

BACKGROUND

Recombinant feline interferon-omega (rFeIFN-omega) was tested as a treatment option for cats with fibrosarcoma to assess safety and feasibility.

HYPOTHESIS

Treatment with rFeIFN-omega in cats with fibrosarcoma is safe and feasible.

ANIMALS

Twenty domestic cats.

METHODS

In an open-labeled uncontrolled clinical trial 12 injections of 1 x 10(6) U/kg rFeIFN-omega were administered over a 5-week period: the 1st through 4th injections were given intratumorally, and the 5th through 12th injections were administered subcutaneously at the tumor excision site. Wide surgical excision of the tumors was carried out after the 4th injection and before the 5th injection of rFeIFN-omega. A Common Terminology Criteria for Adverse Events (CTCAE) analysis was conducted. Flow cytometry of fibrosarcoma cells after incubation with rFeIFN-omega and recombinant feline interferon-gamma was performed to assess the biological effect of rFeIFN-omega.

RESULTS

Changes in blood cell count, increases in serum aspartate-amino-transferase activity, serum bilirubin concentration, serum creatinine and serum electrolyte concentrations, weight loss, anorexia, increased body temperature, and reduced general condition were observed but were mostly minor (grade 1 and 2) and self limiting. Eosinophilia (P = .025), neutropenia (P = .021), and weight loss (P < .001) were statistically correlated with rFeIFN-omega-treatment (analysis of parameters before treatment and after 3 injections of rFeIFN-omega). Flow cytometry of 5 unrelated feline fibrosarcoma cell lines showed increased expression of major histocompatibility complex (MHC) class I molecules (P = .026) in response to in vitro incubation with rFeIFN-omega, whereas expression of MHC class II molecules was not affected significantly.

CONCLUSIONS AND CLINICAL IMPORTANCE

RFeIFN-omega for the treatment of feline fibrosarcoma is safe, well tolerated, and can be easily performed in practice. To assess the efficacy of the treatment, it should be tested in a placebo-controlled trial.

Adjuvant immunotherapy of feline fibrosarcoma with recombinant feline interferon-omega

BACKGROUND

Recombinant feline interferon-omega (rFeIFN-omega) was tested as a treatment option for cats with fibrosarcoma to assess safety and feasibility.

HYPOTHESIS

Treatment with rFeIFN-omega in cats with fibrosarcoma is safe and feasible.

ANIMALS

Twenty domestic cats.

METHODS

In an open-labeled uncontrolled clinical trial 12 injections of 1 x 10(6) U/kg rFeIFN-omega were administered over a 5-week period: the 1st through 4th injections were given intratumorally, and the 5th through 12th injections were administered subcutaneously at the tumor excision site. Wide surgical excision of the tumors was carried out after the 4th injection and before the 5th injection of rFeIFN-omega. A Common Terminology Criteria for Adverse Events (CTCAE) analysis was conducted. Flow cytometry of fibrosarcoma cells after incubation with rFeIFN-omega and recombinant feline interferon-gamma was performed to assess the biological effect of rFeIFN-omega.

RESULTS

Changes in blood cell count, increases in serum aspartate-amino-transferase activity, serum bilirubin concentration, serum creatinine and serum electrolyte concentrations, weight loss, anorexia, increased body temperature, and reduced general condition were observed but were mostly minor (grade 1 and 2) and self limiting. Eosinophilia (P = .025), neutropenia (P = .021), and weight loss (P < .001) were statistically correlated with rFeIFN-omega-treatment (analysis of parameters before treatment and after 3 injections of rFeIFN-omega). Flow cytometry of 5 unrelated feline fibrosarcoma cell lines showed increased expression of major histocompatibility complex (MHC) class I molecules (P = .026) in response to in vitro incubation with rFeIFN-omega, whereas expression of MHC class II molecules was not affected significantly.

CONCLUSIONS AND CLINICAL IMPORTANCE

RFeIFN-omega for the treatment of feline fibrosarcoma is safe, well tolerated, and can be easily performed in practice. To assess the efficacy of the treatment, it should be tested in a placebo-controlled trial.

G1P3, an IFN-induced survival factor, antagonizes TRAIL-induced apoptosis in human myeloma cells

The effectiveness of IFN-alpha2b for human multiple myeloma has been variable. TRAIL has been proposed to mediate IFN-alpha2b apoptosis in myeloma. In this study we assessed the effects of IFN-alpha2b signaling on the apoptotic activity of TRAIL and human myeloma cell survival. While TRAIL was one of the most potently induced proapoptotic genes in myeloma cells following IFN-alpha2b treatment, less than 20% of myeloma cells underwent apoptosis. Thus, we hypothesized that an IFN-stimulated gene (ISG) with prosurvival activity might suppress TRAIL-mediated apoptosis. Consistent with this, IFN-alpha2b stabilized mitochondria and inhibited caspase-3 activation, which antagonized TRAIL-mediated apoptosis and cytotoxicity after 24 hours of cotreatment in cell lines and in fresh myeloma cells, an effect not evident after 72 hours. Induced expression of G1P3, an ISG with largely unknown function, was correlated with the antiapoptotic activity of IFN-alpha2b. Ectopically expressed G1P3 localized to mitochondria and antagonized TRAIL-mediated mitochondrial potential loss, cytochrome c release, and apoptosis, suggesting specificity of G1P3 for the intrinsic apoptosis pathway. Furthermore, RNAi-mediated downregulation of G1P3 restored IFN-alpha2b-induced apoptosis. Our data identify the direct role of a mitochondria-localized prosurvival ISG in antagonizing the effect of TRAIL. Curtailing G1P3-mediated antiapoptotic signals could improve therapies for myeloma or other malignancies.

Interferon alpha induces cell death through interference with interleukin 6 signaling and inhibition of STAT3 activity

In multiple myeloma, which commonly depends on interleukin 6, IL-6, survival signaling induced by this cytokine is largely mediated by activation of STAT3. Interferon alpha (IFNalpha) treatment of cell lines derived from multiple myeloma or of myeloma tumor cells ex vivo leads to apoptosis. In this study we demonstrate that IFNalpha treatment of the two myeloma cell lines, U266-1984 and U-1958, results in the decrease of STAT3 activity as demonstrated by a diminished STAT3/3 DNA-binding activity and the shift from STAT3/3 towards STAT1/1 and STAT3/1 complexes in EMSA, leading to the down-regulation of known STAT3 target genes such as Bcl-X(L), Mcl-1 and survivin. Ectopic expression of a form of STAT3, STAT3C, rescued U266-1984 cells from IFNalpha-induced apoptosis. IFNalpha promoted sustained accumulation of tyrosine phosphorylated STAT3C in the nucleus and a prolonged DNA binding of the STAT3/3 homodimers in EMSA. The shift towards a sustained STAT3 response in IFNalpha-treated STAT3C-transfected cells led to a hyper-induction of Bcl-2 and Mcl-1 proteins. Thus our data demonstrated that IFNalpha is able to interfere with IL-6 signaling by inhibiting STAT3 activity and that the abrogation of STAT3 activity accounts for the ability of IFNalpha to induce apoptosis in myeloma cells.

Leptin restores plasma cholesterol, glucose and weight loss induced by IFNalpha treatment

Leptin, an adipokine, a major regulator of food intake, was recently suggested to play a role in immune response. We previously showed that weight reduction following IFNalpha therapy is due, at least in part, to direct induction of adipose tissue apoptosis. We now studied the effect of leptin on IFNalpha treated adipocytes in vitro and in vivo. Diet induced obese C57/B6 mice were treated continually with recombinant (r) IFNalphaA/D + leptin (100 U/g body weight + 10 microg/day, respectably) or leptin (10 microg/day) alone for 8 days. Co-administration of IFNalphaA/D + leptin significantly reduced plasma cholesterol (P<0.001), glucose (P<0.007) and pro-apoptotic protein levels (P<0.05). Additionally, co-administration prevented loss of body weight due to adipocyte apoptosis. Thus, leptin co-administration with IFNalphaA/D decreases some of the side effects of IFNalpha administration such as weight loss, cholesterol and glucose levels.

Mechanism of apoptosis induced by IFN-alpha in human myeloma cells: role of Jak1 and Bim and potentiation by rapamycin

Interferon-alpha (IFN-alpha) has been used for the last 20 years in the maintenance therapy of multiple myeloma (MM), though it is only effective in some patients. Congruent with this, IFN-alpha induces apoptosis in some MM cell lines. Understanding the mechanism of IFN-alpha-induced apoptosis could be useful in establishing criteria of eligibility for therapy. Here we show that IFN-alpha-induced apoptosis in the MM cell lines U266 and H929 was completely blocked by a specific inhibitor of Jak1. The mTOR inhibitor rapamycin mitigated apoptosis in U266 but potentiated it in H929 cells. IFN-alpha induced PS exposure, DeltaPsi(m) loss and pro-apoptotic conformational changes of Bak, but not of Bax, and was fully prevented by Mcl-1 overexpression in U266 cells. IFN-alpha treatment caused the release of cytochrome c from mitochondria to cytosol and consequently, a limited proteolytic processing of caspases. Apoptosis induced by IFN-alpha was only slightly prevented by caspase inhibitors. Levels of the BH3-only proteins PUMA and Bim increased during IFN-alpha treatment. Bim increase and apoptosis was prevented by transfection with the siRNA for Bim. PUMA-siRNA transfection reduced electroporation-induced apoptosis but had no effect on apoptosis triggered by IFN-alpha. The potentiating effect of rapamycin on apoptosis in H929 cells was associated to an increase in basal and IFN-alpha-induced Bim levels. Our results indicate that IFN-alpha causes apoptosis in myeloma cells through a moderate triggering of the mitochondrial route initiated by Bim and that mTOR inhibitors may be useful in IFN-alpha maintenance therapy of certain MM patients.

Novel interferon-lambdas induce antiproliferative effects in neuroendocrine tumor cells

Interferon-alpha (IFN-alpha) is used for biotherapy of neuroendocrine carcinomas. The interferon-lambdas (IL-28A/B and IL-29) are a novel group of interferons. In this study, we investigated the effects of the IFN-lambdas IL-28A and IL-29 on human neuroendocrine BON1 tumor cells. Similar to IFN-alpha, incubation of BON1 cells with IL-28A (10 ng/ml) and IL-29 (10 ng/ml) induced phosphorylation of STAT1, STAT2, and STAT3, significantly decreased cell numbers in a proliferation assay, and induced apoptosis as demonstrated by poly(ADP-ribose) polymerase (PARP)-cleavage, caspase-3-cleavage, and DNA-fragmentation. Stable overexpression of suppressor of cytokine signaling proteins (SOCS1 and SOCS3) completely abolished the aforementioned effects indicating that SOCS proteins act as negative regulators of IFN-lambda signaling in BON1 cells. In conclusion, the novel IFN-lambdas IL-28A and IL-29 potently induce STAT signaling and antiproliferative effects in neuroendocrine BON1 tumor cells. Thus, IFN-lambdas may hint a promising new approach in the antiproliferative therapy of neuroendocrine tumors.

IFN-alpha induces apoptosis of adipose tissue cells

Interferon alpha (IFN-alpha) is produced in response to viral infections and used clinically in the therapy of a variety of cancers and viral infections. IFN-alpha treatment is often associated with severe weight reduction. To elucidate the mechanism of IFN-associated weight loss, we studied its effect on adipocytes in vitro and in vivo. Diet-induced obese (DIO) C57BL/6 mice were treated continuously for 8 days with human IFN-alpha A/D (100 U/g body weight) or with vehicle alone. The body weight and adipose cell size of IFN-alpha A/D-treated DIO mice were significantly lower (P<0.05 and P<0.001, respectively) as compared with those of control DIO mice. PI3K and Bcl-2 were down-regulated whereas Bax expression was elevated in adipose tissue following IFN treatment as compared to adipose tissue of control DIO mice. Treatment of differentiated 3T3-F442A adipocytes with IFN-alpha A/D (250 U/ml, 36 h) significantly increased the number of apoptotic cells from 15.8% in control cells to 56+/-6%. In conclusion, weight loss following IFN-alpha therapy is due at least in part to increased apoptosis of adipocytes.

Alternative signaling pathways regulating type I interferon-induced apoptosis

Type I interferons (IFNs) are pleiotropic cytokines that exert multiple effects on normal and tumor cells. These effects are supposedly mediated through the stimulation of several signal transduction pathways by type I IFNs. These include the well-studied canonical Jak-Stat pathway, largely responsible for the antiviral and growth-inhibitory activities of IFNs, as well as the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways, whose importance in IFN-induced biologic outcomes has not been precisely established. One of the effects of type I IFNs on tumor cells is the induction of programmed cell death, apoptosis, which has been studied extensively over the last decade and has been suggested to be an important effector mechanism for IFN's antitumor effects in the treatment of cancer. The aim of this review is to summarize and discuss the recent data in the field of type I IFN-induced apoptosis, with special emphasis on the molecular mechanisms of apoptosis and on the role of alternative noncanonical signaling pathways stimulated by type I IFNs in this process.

Detection, epitope-mapping and function of anti-Fas autoantibody in patients with silicosis

Dysregulation of apoptosis through the Fas-Fas ligand pathway is associated with the onset of autoimmune disease. Since autoantibodies directed against unknown antigens are present in the sera of these patients, sera samples were examined for the presence of autoantibodies directed against the Fas molecule. Using Western blotting and a ProteinChip analysis, autoantibodies against Fas were detected in patients with silicosis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), and weakly detected in healthy individuals. Using epitope mapping employing 12-amino-acid polypeptides with the SPOTs system, a minimum of four epitopes and a maximum of 10 epitopes were found. Several amino acid residues involved in binding FasL, such as C66, R87, L90, E93 and H126, were presented within the epitopes. Serum containing a large amount of anti-Fas autoantibody from silicosis patients inhibited the growth of a Fas-expressing human cell line, but did not inhibit the growth of a low Fas-expresser nor a Fas-expresser in which the Fas gene had been silenced by small interference RNA. All epitopes in the intracellular region of Fas were located in the death domain. The possible roles of anti-Fas autoantibody detected in healthy volunteers and patients with silicosis or autoimmune diseases are discussed here.

Apo2L/TRAIL is an indirect mediator of apoptosis induced by interferon-alpha in human myeloma cells

Interferon-alpha (IFN-alpha) is currently used for the therapy of multiple myeloma (MM) though it is only effective in some patients. IFN-alpha induces apoptosis in some MM cell lines and it has been proposed to occur through an autocrine loop involving Apo2L/TRAIL. We have analysed the sensitivity to IFN-alpha and Apo2L/TRAIL of five MM cell lines and found no correlation between the apoptosis inducing ability of both cytokines. IFN-alpha-induced apoptosis in MM cells was not prevented by a caspase-8 selective inhibitor (Z-IETD-fmk) or blocking Apo2L/TRAIL. However, human monocytes treated with IFN-alpha release bioactive Apo2L/TRAIL to culture media which was cytotoxic for MM cells resistant to IFN-alpha. We propose that Apo2L/TRAIL released from IFN-alpha-stimulated blood monocytes would be a major mediator of the anti-myeloma effect of IFN-alpha in vivo.

Interferon α-induced Apoptosis in Tumor Cells Is Mediated through the Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Signaling Pathway

Interferon (IFN) alpha induces a caspase-dependent apoptosis that is associated with activation of the proapoptotic Bak and Bax, loss of mitochondrial membrane potential, and release of cytochrome c. In addition to the onset of the classical Jak-STAT pathway, IFNalpha also induced phosphoinositide 3-kinase (PI3K) activity. Pharmacological inhibition of PI3K activity by Ly294002 disrupted IFN-induced apoptosis upstream of mitochondria. Inhibition of mTOR by rapamycin or by overexpression of a kinase dead mutant of mTOR, efficiently blocked IFNalpha-induced apoptosis. A PI3K and mTOR-dependent phosphorylation of p70S6 kinase and 4E-BP1 repressor was induced by IFNalpha treatment of cells and was strongly inhibited by Ly294002 or rapamycin. The activation of Jak-STAT signaling upon IFNalpha stimulation was not affected by abrogating PI3K/mTOR pathway. Neither was the expression of several IFNalpha target genes affected, nor the ability of IFNalpha to protect against virus-induced cell death affected by inhibition of the PI3K/mTOR pathway. These data demonstrate that an intact PI3K/mTOR pathway is necessary for the ability of IFNalpha to induce apoptosis, whereas activation of the Jak-STAT pathway alone appears to be insufficient for this specific IFNalpha-induced effect.

Study of the effects of interferon a on several human hepatoma cell lines: analysis of the signalling pathway of the cytokine and of its effects on apoptosis and cell proliferation

BACKGROUND

Interferon alpha (IFNalpha), currently used for the treatment of chronic viral hepatitis, is also known to prevent the development of hepatocellular carcinoma (HCC), the mechanism of this action being still debatable.

AIMS

To study thoroughly in human hepatoma cell lines (HHL)--Hep3B, HepG2, HuH7, SKHep1, and Chang-Liver--submitted to rhIFNalpha, the signalling pathway of IFNalpha, the binding activity of the cytokine on specific gamma-activated sequence (GAS) and interferon-stimulated regulatory element (ISRE) nuclear sequences, and its effects on apoptosis and cell proliferation.

METHODS

The behaviour of signal transducer and activator of transcription (STAT)1, STAT2, p48(IRF9) and the binding of nuclear proteins were investigated by immunoblot and electro-mobility shift assay. Expression of some IFNalpha-dependent proteins--p21/(WAF1), inducible nitric oxide synthase, IRF1 and 2--were studied by immunoblot. Apoptosis and the cell cycle were studied by morphological and biochemical methods.

RESULTS

Transduction of INFalpha was unaltered, although there were some variations in the different HHL. Nuclear protein binding to GAS or ISRE showed that ISRE was mainly involved. Apoptosis did not occur. The cell cycle was slightly modified in HuH7. Three GAS- and/or ISRE-dependent proteins increased, suggesting that IFNalpha may have some biological effects on HHL.

CONCLUSIONS

The IFNalpha signalling pathway is functional in several HHL, but the cytokine has no apoptotic effect and a moderate anti-proliferative effect. This suggests that the preventive role of IFNalpha on HCC cannot be explained by an apoptotic and/or an anti-proliferative effect, but possibly by its action on several specific nuclear sequences that protect liver cells from transformation.

Interferons: mechanisms of action and clinical applications

PURPOSE OF REVIEW

Interferons are pleiotropic cytokines that exhibit important biologic activities, including antiviral, antitumor, and immunomodulatory effects. These cytokines have found important applications in clinical medicine, including the treatment of certain malignancies. The purpose of this review is to provide an update on basic and clinical research in the interferon field.

RECENT FINDINGS

Significant advances have recently occurred in the field of type I interferon signal transduction. It is well known that the interferons transduce signals via activation of multiple signaling cascades, involving Jak kinases, signal transducer and activator of transcription proteins, Map kinases, and IRS and Crk proteins. Recent evidence indicates that the p38 Map kinase pathway plays an important role in type I interferon signaling in malignant cells and that its function is required for type I interferon-dependent gene transcription and generation of the antiproliferative of type I interferons. In clinical oncology, interferon-alpha remains an active and useful agent in the treatment of several malignant disorders, and efforts are underway to improve its efficacy by using different schedules and combinations with other agents.

SUMMARY

This review summarizes the mechanisms of signal transduction of interferons and the emerging new concepts in this area. An update on the clinical applications of interferons in oncology is also provided, and potential translational applications, reflecting recent advances in the field, are discussed.

Receptor synergy of interleukin-6 (IL-6) and insulin-like growth factor-I in myeloma cells that highly express IL-6 receptor alpha [corrected]

Interleukin-6 (IL-6) is a growth and antiapoptotic factor for human myeloma cells. The autocrine loop and increased expression of the growth factor receptors have been postulated as the mechanisms of tumorigenesis. Here we show that IL-6 stimulation induced the phosphorylation of insulin-like growth factor-I (IGF-I) receptors in a human myeloma cell line, NOP2, highly expressing IL-6 receptor alpha (IL-6R alpha) and in the IL-6R alpha-transfected U266 cell line. IL-6-dependent complex formation of IL-6R alpha with IGF-I receptor beta was found in NOP2 where IL-6R alpha colocalized with IGF-I receptors at lipid rafts. Moreover, the IL-6-induced phosphorylation of IGF-I receptor beta was not blocked by a Janus kinase 2 (Jak2) inhibitor. In addition to the activation of the signal transducer and activator of transcription 3 and extracellular signal-regulated kinase 1/2, IL-6 stimulation led to the activation of Akt, presumably following the phosphorylation of IGF-I receptors. Thus, our results suggest that in NOP2, IL-6R alpha and IGF-I receptors exist on the plasma membrane in close proximity, facilitating the efficient assembly of 2 receptors in response to IL-6. The synergistic effects of highly expressed IL-6R alpha on IGF-I receptor-mediated signals provide a novel insight into the Jak-independent IL-6 signaling mechanism of receptor cross-talk in human myeloma cells.

Recombinant IFN-alpha2b treatment activates poly (ADPR) polymerase-1 (PARP-1) in KB cancer cells

In the present paper, we investigated the relationship between the growth inhibitory effects of recombinant interferon-alpha2b (rIFN-alpha2b) and poly (ADPR) polymerase-1 (PARP-1) activity in the human squamous KB cancer cell line. Growth inhibition of the KB cells mediated by 1000 IU/ml of rIFN-alpha2b was accompanied by a transient rise in PARP-1 specific activity 24 h after rIFN-alpha2b treatment, confirmed by both the increase of intracellular poly (ADP-ribose) content and the PARP-1 auto-modification level. At longer times of incubation, the onset of apoptosis accompanied KB cell growth inhibition, as demonstrated by both flow cytometry and western-blotting analysis showing an 89 kDa apoptotic fragment of PARP-1. Moreover, pretreatment of the cells with the PARP-1 inhibitor, 3-aminobenzamide (3-ABA), at non-cytotoxic concentrations (1 mM), reduced the cell-growth inhibition, cell-cycle perturbation and apoptosis caused by rIFN-alpha2b. Taken together, these results strongly suggest that PARP-1 may be directly involved in the effects of rIFN-alpha2b in the KB cancer cell line.

Apo2L/TRAIL: apoptosis signaling, biology, and potential for cancer therapy

Apo2 ligand or tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL) is one of several members of the TNF gene superfamily that induce apoptosis through engagement of death receptors. Apo2L/TRAIL is unusual as compared to any other cytokine as it interacts with a complex system of receptors: two pro-apoptotic death receptors and three anti-apoptotic decoys. This protein has generated tremendous excitement as a potential tumor-specific cancer therapeutic because, as a stable soluble trimer, it selectively induces apoptosis in many transformed cells but not in normal cells. Transcriptional activation of Apo2L/TRAIL by interferons (IFNs) through specific regulatory elements in its promoter, and possibly by a number of other cytokines, reveals its possible involvement in the activation of natural killer cells, cytotoxic T lymphocytes, and dendritic cells. In this review, we focus on the apoptosis signaling pathways stimulated by Apo2L/TRAIL, summarize what is known to date about the physiological role of this ligand and the potential for its application to cancer therapy.

Progesterone-modulated induction of apoptosis by interferon-tau in cultured epithelial cells of bovine endometrium

Interferon-tau (IFN-tau) is produced by the trophoblast prior to implantation in ruminants. It is involved in maternal recognition of pregnancy, and is a pleiotropic molecule that can alter the synthesis of endometrial proteins and inhibit proliferation of some cells. We have observed that IFN-tau reduces the DNA content in cultures of bovine endometrial epithelial cells; therefore, the objective of this study was to determine whether IFN-tau would induce apoptosis in bovine endometrial cells. Epithelial cells were prepared, cultured to confluence, and then incubated for 24 or 48 h in the presence or absence of 10 ng/ml progesterone, 100 ng/ml IFN-tau, or 10 microg/ml cycloheximide (CHX; an apoptosis inducer used as a positive control). Cells undergoing apoptosis exhibit such characteristics as the appearance of apoptotic bodies and DNA fragmentation. The incidence of apoptosis was assessed by using TUNEL, DNA fragmentation analysis, and Western blot analysis of Bax-alpha protein expression. The results showed that IFN-tau and CHX significantly increased the percentage of cells with apoptotic nuclei (33.6% and 44.8%, respectively) compared with controls (11.7%; P < 0.05). Progesterone treatment of the cells significantly inhibited the ability of IFN-tau to induce apoptosis (14.6%) compared with IFN-tau alone (33.6%; P < 0.05). DNA fragmentation analysis showed that INF-tau and CHX treatment resulted in an increase in the appearance of DNA laddering compared with that in untreated control cultures. Western blot analysis showed that IFN-tau and CHX treatment resulted in a greater expression of the proapoptotic protein Bax-alpha compared with that in control cultures. These data demonstrate that IFN-tau can induce apoptosis in bovine uterine epithelial cells and that this effect is modulated by progesterone. We speculate that IFN-tau might play a critical role in the remodeling of the endometrium around the time of implantation.

Synergistic growth inhibition of YM529 with biologic response modifiers (BRMs) in myeloma cells

Bisphosphonates (BPs) are effective in the management of bone disease in patients with multiple myeloma. Recent reports have suggested that they may also have an antitumor activity. YM529 is a new synthetic BP with more than 1000 times the bone resorption inhibitory activity of pamidronate. To clarify the direct effects of YM529 on myeloma cells, the cell proliferation and cell cycle perturbation were analyzed using 12 myeloma cell lines established in our laboratory. The growth inhibition was dose dependent. The cells accumulated in [2n<<4n] of the cell cycle and subsequently formed an apoptotic sub-G1 fraction. Combined treatment with all-trans retinoic acid, thalidomide, or interferon-alpha enhanced the growth inhibitory effects of YM529 on these cells. However, there were no remarkable effects of YM529 on the messenger RNA expression for angiogenic factors, cell cycle regulators, or cytokines related to myeloma cells. These results indicate that YM529 is beneficial not only to bone lesions but also for its direct antitumor effects on myeloma cells.

Interleukin 10 abolishes the growth inhibitory effects of all-trans retinoic acid on human myeloma cells

Recently, it was disclosed that all-trans retinoic acid (ATRA) inhibits myeloma cell growth by downregulating the interleukin 6 (IL-6)/IL-6 receptor (IL-6R) auto/paracrine loop, and upregulating p21/Cip1 cyclin-dependent kinase inhibitor (CDK-I), thereby inducing apoptosis with a decrease in Bcl-2 protein expression. To elucidate and generalize the effects of ATRA on the proliferation and cellular biology of myeloma cells, 12 human myeloma cell lines established in our laboratory were utilized. Two out of the 12 lines showed enhanced growth on supplementation of ATRA and were characterized by IL-10 production, downregulation of membrane Fas and reduced upregulation of p21/Cip1 CDK-I message. These characteristics may prove important for the clinical use of ATRA and should be considered before starting ATRA therapy for myeloma.

Cell cycle analysis and expression of cell cycle regulator genes in myeloma cells overexpressing cyclin D1

Among the recently discovered myeloma-specific gene alterations associated with chromosomal translocations, cyclin D1/PRAD1/Bcl-1 overexpression caused by t(11;14)(q13;q32) is considered to be the most frequent in myeloma patients and cell lines, and may be a prognostic factor clinically. To elucidate the cellular biological role of overexpressed cyclin D1 in myeloma cells, we examined the mRNA expression levels of cell cycle regulators including three cyclin Ds, cyclin-dependent kinase inhibitors (CDK-Is) and accelerators. Cyclin D1 overexpression was clearly demonstrated in the lines with abnormal 11q13 and associated with overexpression of S and G2 accelerator genes. The cyclin D1-overexpressing lines tended to have a shortened G1 phase compared with the non-expressing lines. In addition, artificial silencing using antisense oligonucleotides for cyclin D1 suppressed the growth rate of some but not all cyclin D1-overexpressing cells. These results indicate that overexpression of cyclin D1 caused by cytogenetic abnormalities may make cells progress through the cell cycle rapidly, but it seems that other factors such as cyclin D2 and translocation-related genes affect the cell cycle progression in myeloma cells.

A specific isozyme of 2'-5' oligoadenylate synthetase is a dual function proapoptotic protein of the Bcl-2 family

2-5(A) synthetases are a family of interferon-induced enzymes that polymerize ATP into 2'-5' linked oligoadenylates that activate RNase L and cause mRNA degradation. Because they all can synthesize 2-5(A), the reason for the existence of so many synthetase isozymes is unclear. Here we report that the 9-2 isozyme of 2-5(A) synthetase has an additional activity: it promotes apoptosis in mammalian cells. The proapoptotic activity of 9-2 was isozyme-specific and enzyme activity-independent. The 9-2-expressing cells exhibited many properties of cells undergoing apoptosis, such as DNA fragmentation, caspase activation, and poly ADP-ribose polymerase and lamin B cleavage. The isozyme-specific carboxyl-terminal tail of the 9-2 protein was shown, by molecular modeling, to contain a Bcl-2 homology 3 (BH3) domain, suggesting that it may be able to interact with members of the Bcl-2 family that contain BH1 and BH2 domains. Co-immunoprecipitate assays and confocal microscopy showed that 9-2 can indeed interact with the anti-apoptotic proteins Bcl-2 and Bclx(L) in vivo and in vitro. Mutations in the BH3 domain that eliminated the 9-2-Bcl-2 amd 9-2-Bclx(L) interactions also eliminated the apoptotic activity of 9-2. Thus, we have identified an interferon-induced dual function protein of the Bcl-2 family that can synthesize 2-5(A) and promote cellular apoptosis independently. Moreover, the cellular abundance of this protein is regulated by alternative splicing; the other isozymes encoded by the same gene are not proapoptotic.

Anti-HER2 antibody enhances the growth inhibitory effect of anti-oestrogen on breast cancer cells expressing both oestrogen receptors and HER2

Anti-oestrogen is effective for the treatment of oestrogen receptor (ER)-positive breast carcinomas, but most of these tumours become resistant to anti-oestrogen. It has been suggested that anti-oestrogen therapy may induce a HER2 signalling pathway in breast cancer cells and this may cause resistance to anti-oestrogen. Thus, it is conceivable that combined therapy with anti-oestrogen and anti-HER2 antibody might be more effective. In the present study, we investigated the effect of combined treatment with a humanized anti-HER2 monoclonal antibody, rhumAbHER2 (trastuzumab), and an anti-oestrogen, ICI 182,780, on the cell growth of three human breast cancer cell lines which respectively express different levels of ER and HER2. The combined treatment enhanced the growth inhibitory effect on ML-20 cells, which express a high level of ER and a moderate level of HER2, but showed no additive effect on either KPL-4 cells, which express no ER and a moderate level of HER2, or MDA-MB-231 cells, which express no ER and a low level of HER2. It is also suggested that both the antibody and anti-oestrogen induce a G1-S blockade and apoptosis. These findings indicate that combined treatment with anti-HER2 antibody and anti-oestrogen may be useful for the treatment of patients with breast cancer expressing both ER and HER2.

Inhibition of B Cell Receptor-Mediated Apoptosis by IFN

IFNs are a family of cytokines that are involved in the regulation of immune and inflammatory responses. Clinical use of IFN-α/β encompasses treatment for a variety of diseases; however, prolonged exposure to IFN-α/β results in elevated levels of autoreactive Abs. In this study, we investigated the potential of IFNs to modulate apoptotic signals in B cells. We demonstrate that IFN-α or IFN-β inhibit Ag receptor-mediated apoptosis in a dose-dependent manner. Inhibition of phosphatidylinositol 3′ (PI3)-kinase did not abolish the effect of IFN, indicating that the antiapoptotic mechanism is PI3-kinase- and protein kinase B/Akt-independent. Instead, IFN-α and IFN-β, but not IFN-γ, significantly increase the levels of the survival protein Bcl-2, and to a lesser extent, Bcl-xL expression. Thus, IFN-α/β-mediated inhibition of B cell Ag receptor-triggered apoptosis may offer a model for the process that leads to the escape of self-reactive B cells from negative selection and consequently results in autoantibody production.