Anti-tumour activity of interferon-alpha in multiple myeloma: role of interleukin 6 and tumor cell differentiation

LncRNA TP53TG1 plays an anti-oncogenic role in cervical cancer by synthetically regulating transcriptome profile in HeLa cells

Long non-coding RNAs (lncRNAs) have been extensively studied as important regulators of tumor development in various cancers. Tumor protein 53 target gene 1 (TP53TG1) is a newly identified lncRNA in recent years, and several studies have shown that TP53TG1 may play oncogenic or anti-oncogenic roles in different cancers. Nevertheless, the role of TP53TG1 in the development of cervical cancer is unclear. In our study, pan-cancer analysis showed that high expression of TP53TG1 was significantly associated with a better prognosis. We then constructed a TP53TG1 overexpression model in HeLa cell line to explore its functions and molecular targets. We found that TP53TG1 overexpression significantly inhibited cell proliferation and induced apoptosis, demonstrating that TP53TG1 may be a novel anti-oncogenic factor in cervical cancer. Furthermore, overexpression of TP53TG1 could activate type I interferon signaling pathways and inhibit the expression of genes involved in DNA damage responses. Meanwhile, TP53TG1 could affect alternative splicing of genes involved in cell proliferation or apoptosis by regulating the expression of many RNA-binding protein genes. Competing endogenous RNA (ceRNA) network analysis demonstrated that TP53TG1 could act as the sponge of several miRNAs to regulate the expression level of target genes. In conclusion, our study highlights the essential role of lncRNA TP53TG1 in the development of cervical cancer and suggests the potential regulatory mechanisms.

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.

Effects of Interferon-α-2a on Th3 Cytokine Response in Multiple Myeloma Patients

Aims and background

Multiple myeloma cells increase Th3 cytokine response by secreting TGF-β, which causes defective Th1 and Th2 cytokine responses. Therefore, a significant suppression of the immune system is seen in multiple myeloma. Interferon-α (IFN-α) is used in the treatment of multiple myeloma due to its immunomodulatory and anti-tumoral effects. We attempted to define the characteristics of immune cytokine responses and the effects of IFN-α-2a on the immune response in multiple myeloma.

Methods

Fifteen patients with multiple myeloma and 15 healthy controls were enrolled. IFN-α-2a, 3 million units/day x 3 times/week, was administered subcutaneously to the patients for 2 weeks. Cytokines (TGF-β, IL-1, IL-2, IL-4, IL-10, IFN-γ) were assessed by the ELISA method in sera of the patients in pretreatment and posttreatment periods and in the sera of the controls.

Results

IL-2 and IL-4 levels in patients, before IFN-α-2a, were lower than the controls, whereas TGF-β levels were higher than the controls. In other words, Th3 cytokine response was increased and Th1 and Th2 cytokine responses were decreased in patients. A short course of IFN-α-2a increased IL-2 levels.

Conclusions

These findings suggest IFN-α-2a may enhance nonTh3 cytokine responses in multiple myeloma patients.

Differentiation therapy in poor risk myeloid malignancies: Results of companion phase II studies

Pre-clinical data in non-M3 AML supports the use of differentiation therapy, but clinical activity has been limited. Myeloid growth factors can enhance anti-leukemic activity of differentiating agents in vitro. We conducted companion phase II trials investigating sargramostim (GM-CSF) 125μg/m(2)/day plus 1) bexarotene (BEX) 300mg/m(2)/day or 2) entinostat (ENT) 4-8mg/m(2)/week in patients with MDS or relapsed/refractory AML. Primary endpoints were response after at least two treatment cycles and toxicity. 26 patients enrolled on the BEX trial had a median of 2 prior treatments and 24 enrolled on the ENT trial had a median of 1. Of 13 response-evaluable patients treated with BEX, the best response noted was hematologic improvement in neutrophils (HI-N) seen in 4 (31%) patients; none achieved complete (CR) or partial remission (PR). Of 10 treated with ENT, there was 1 (10%) partial remission (PR) and 2 (20%) with HI-N. The secondary endpoint responses of HI-N with each combination were accompanied by a numerical increase in ANC (BEX: 524 to 931 cells/mm(3), p=0.096; ENT: 578 to 1 137 cells/mm(3), p=0.15) without increasing marrow blasts. Shared grade 3-4 non-hematologic toxicities included febrile neutropenia, bone pain, fatigue, and dyspnea. GM-CSF plus either BEX or ENT are well tolerated in resistant and refractory MDS and AML and showed modest clinical and biologic activity, most commonly HI-N.

Preclinical evaluation of recombinant human IFNα2b-containing magnetoliposomes for treating hepatocellular carcinoma

Magnetoliposomes are phospholipid vesicles encapsulating magnetic nanoparticles that can be used to encapsulate therapeutic drugs for delivery into specific organs. Herein, we developed magnetoliposomes containing recombinant human IFNα2b, designated as MIL, and evaluated this combination's biological safety and therapeutic effect on both cellular and animal hepatocellular carcinoma models. Our data showed that MIL neither hemolyzed erythrocytes nor affected platelet-aggregation rates in blood. Nitroblue tetrazolium-reducing testing showed that MIL did not change the absolute numbers or phagocytic activities of leukocytes. Acute-toxicity testing also showed that MIL had no devastating effect on mice behaviors. All the results indicated that the nanoparticles could be a safe biomaterial. Pharmacokinetic analysis and tissue-distribution studies showed that MIL maintained stable and sustained drug concentrations in target organs under a magnetic field, helped to increase bioavailability, and reduced administration time. MIL also dramatically inhibited the growth of hepatoma cells. Targeting of MIL in the livers of nude mice bearing human hepatocellular carcinoma showed that MIL significantly reduced the tumor size to 38% of that of the control group. Further studies proved that growth inhibition of cells or tumors was due to apoptosis-signaling pathway activation by human IFNα2b.

Growth differentiating factor 15 enhances the tumor-initiating and self-renewal potential of multiple myeloma cells

Disease relapse remains a major factor limiting the survival of cancer patients. In the plasma cell malignancy multiple myeloma (MM), nearly all patients ultimately succumb to disease relapse and progression despite new therapies that have improved remission rates. Tumor regrowth indicates that clonogenic growth potential is continually maintained, but the determinants of self-renewal in MM are not well understood. Normal stem cells are regulated by extrinsic niche factors, and the tumor microenvironment (TME) may similarly influence tumor cell clonogenic growth and self-renewal. Growth differentiation factor 15 (GDF15) is aberrantly secreted by bone marrow stromal cells (BMSCs) in MM. We found that GDF15 is produced by BMSCs after direct contact with plasma cells and enhances the tumor-initiating potential and self-renewal of MM cells in a protein kinase B- and SRY (sex-determining region Y)-box-dependent manner. Moreover, GDF15 induces the expansion of MM tumor-initiating cells (TICs), and changes in the serum levels of GDF15 were associated with changes in the frequency of clonogenic MM cells and the progression-free survival of MM patients. These findings demonstrate that GDF15 plays a critical role in mediating the interaction among mature tumor cells, the TME, and TICs, and strategies targeting GDF15 may affect long-term clinical outcomes in MM.

Concise review: Emerging concepts in clinical targeting of cancer stem cells

Cancer stem cells (CSCs) are functionally defined by their ability to self-renew and recapitulate tumors in the ectopic setting. They have been identified in a growing number of human malignancies and their association with poor clinical outcomes has suggested that they are the major factors in dictating clinical outcomes. Moreover, recent studies have demonstrated that CSCs may display other functional attributes, such as drug resistance and invasion and migration, that implicate a broad role in clinical oncology spanning initial tumor formation, relapse following treatment, and disease progression. Although our knowledge regarding the basic biology of CSCs continues to improve, proof that they are clinically relevant is still lacking, and translation of the CSC hypothesis from the laboratory to the clinic is of paramount importance. We will review current evidence supporting the role of CSCs in clinical oncology and discuss potential barriers and strategies in designing trials examining CSC-targeting agents.

KSHV infects a subset of human tonsillar B cells, driving proliferation and plasmablast differentiation

Kaposi sarcoma-associated herpesvirus (KSHV; also known as HHV8) is the causative agent of two B cell tumors, multicentric Castleman disease (MCD) and primary effusion lymphoma (PEL). However, little is known about the nature of the specific B cell subtype(s) most susceptible to infection. Identifying these cells would provide direct insight into KSHV transmission and virus-induced transformation. To identify this subset and to determine whether infection alters its cellular phenotype, we exposed human tonsillar cells to KSHV and characterized infected cells using high-throughput multispectral imaging flow cytometry (MIFC). Stable expression of the virally encoded latency-associated nuclear antigen (LANA), a marker of latent KSHV infection, was observed predominantly in cells expressing the l light chain of the B cell receptor. These LANA+ B cells proliferated and exhibited similarities to the cells characteristic of MCD (IgMl-expressing plasmablasts), including blasting morphology with elevated expression of Ki67, variable expression of CD27, and high levels of IgM and IL-6 receptor. Furthermore, the proportion of infected cells showing a blasting phenotype increased upon addition of exogenous IL-6. Our data lead us to propose that oral transmission of KSHV involves the latent infection of a subset of tonsillar IgMl-expressing B cells, which then proliferate as they acquire the plasmablast phenotype characteristic of MCD.

Multiple myeloma: a paradigm for translation of the cancer stem cell hypothesis

Despite recent advances in drug development, multiple myeloma (MM) remains incurable for the majority of patients due to relapse and disease progression. The cancer stem cell (CSC) hypothesis may provide an explanation for these clinical findings. It suggests that the long-term proliferative potential responsible for disease initiation, maintenance, and relapse is contained within specific subpopulations of biologically distinct tumor cells. Data in MM suggest that CSCs represent a rare cell population phenotypically resembling normal memory B cells. Compared to MM plasma cells, MM CSCs also appear to be relatively resistant to a wide variety of standard anti-cancer agents suggesting they may persist following treatment and mediate tumor re-growth and relapse. A unique property CSCs share with their normal counterparts is the potential for self-renewal that likely maintains the malignant clone over time. The development of therapeutic strategies targeting the signaling elements contributing to cancer cell self-renewal has been limited primarily because the cellular processes involved are poorly understood. However, it is common that the signaling pathway components regulating normal stem cell self-renewal are aberrantly activated in human cancers and may serve as potential therapeutic targets. One class of shared regulatory pathways are those active during normal embryonic patterning and organ formation such as Hedgehog (Hh), Notch and Wingless (Wnt), and emerging data suggest that these may play a role in CSCs. Here we review the identification and characterization of MM CSCs, the role of Hh in MM, and issues to be considered during the early clinical testing of CSC targeting agents.

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.

Induction of acute lymphocytic leukemia differentiation by maintenance therapy

Despite extensive study in many malignancies, maintenance therapy has clinically benefited only two diseases: acute lymphocytic leukemia (ALL) and acute promyelocytic leukemia (APL). ALL maintenance therapy utilizes low-dose 6-mercaptopurine (6MP) and methotrexate (MTX), while maintenance in APL primarily consists of all-trans-retinoic acid (ATRA). 6MP and MTX as used in ALL are also now usually added to maintenance ATRA for APL, based on data suggesting an improved disease-free survival. Although the mechanism of action of MTX and 6MP as maintenance is unknown, low-dose cytotoxic agents are potent inducers of differentiation in vitro. Thus, we studied whether maintenance therapy in ALL, like ATRA in APL, may be inducing terminal differentiation of ALL progenitors. The APL cell line NB4, the ALL cell lines REH and RS4;11, and patients' ALL blasts were incubated with ATRA, 6MP, and MTX in vitro. All three drugs inhibited the clonogenic growth of the APL and ALL cell lines without inducing immediate apoptosis, but associated with induction of phenotypic differentiation. The three drugs similarly upregulated lymphoid antigen expression, while decreasing CD34 expression, on patients' ALL blasts. These data suggest that induction of leukemia progenitor differentiation plays an important role in the mechanism of action of maintenance therapy in ALL.

Complete remission of multiple myeloma after autoimmune hemolytic anemia: possible association with interferon-alpha

A patient with multiple myeloma (MM) was being maintained on human recombinant interferon-alpha (INF-alpha) after VAD and autologous bone marrow transplantation (pretreated with melphalan). An episode of immune thrombocytopenia and (Coombs positive) autoimmune hemolytic anemia (AIHA) was noted while on maintenance INF-alpha, which remitted when it was withdrawn. Following this event, he achieved a state of stable disease that persists (more than 3 years) with no specific myeloma treatment. This sequence of events suggests a relationship between an immunological reaction induced by INF-alpha and the prolonged phase of stable disease.

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.

CpG DNA activation and plasma-cell differentiation of CD27- naive human B cells

Unmethylated CpG DNA activation of naive CD27- B cells has been reported to require B-cell-receptor (BCR) cross-linking. We describe a culture system using CpG DNA with sequential steps for T-cell-independent activation of naive CD19+CD27- human peripheral blood B cells that induces efficient CD138+ plasma-cell differentiation. CD27+ and CD27- B cells were cultured in a 3-step system: (1) days 0 to 4: CpG, IL-2/10/15; (2) days 4 to 7: IL-2/6/10/15 and anti-CD40L; (3) days 7 to 10: IL-6/15, IFN-alpha, hepatocyte growth factor, and hyaluronic acid. Both CD27+ and CD27- B cells up-regulated intracytoplasmic TLR-9 following CpG DNA activation. CD27- B-cell activation required cell-cell contact. Both naive and memory B cells progressed to a plasma-cell phenotype: CD19lowCD20lowCD27+CD38+HLA-DRlow. Seventy percent of the CD27--derived CD138+ cells demonstrated productive V chain rearrangements without somatic mutations, confirming their origin from naive precursors. Plasma cells derived from CD27+ B cells were primarily IgG+, while those from CD27- B cells were IgM+. Our results indicate that under certain conditions, naive B cells increase TLR-9 expression and proliferate to CpG DNA stimulation without BCR signaling. In addition to its immunologic significance, this system should be a valuable method to interrogate the antigenic specificity of naive B cells.

Stat3 cleavage by caspases: impact on full-length Stat3 expression, fragment formation, and transcriptional activity

Stat3 and its isoforms belong to a family of cytoplasmic transcription factors that affect the synthesis of various proteins. Caspases are cysteinyl-aspartate proteases that function under apoptotic and non-apoptotic conditions. We now report that, in addition to transcriptional splicing, Stat3 fragmentation can be mediated by caspases. Caspase activation in DU145 cells was achieved by staurosporine (STS) exposure, and Western analysis revealed a reduction in full-length Stat3 (fl-Stat3) expression that was caspase-mediated. This proteolytic relationship was further studied by exposing purified Stat3 protein to a mixture of active caspases under cell-free conditions. This demonstrated that caspases directly cleaved Stat3 and Stat3 cleavage was accompanied by the apparent formation of cleavage fragment(s). Stat3 cleavage fragments, reflecting multiple caspase cleavage sites, also were observed in vitro following STS exposure in DU145 cells and in HEK293T cells transfected to express Stat3 truncation mutants. The impact of cleavage on Stat3 transcriptional activity next was assessed and revealed that cleavage of fl-Stat3 was accompanied by reductions in Stat3-DNA binding, Stat3-driven reporter protein (luciferase) activity, and the expression of selected Stat3-dependent genes. Further, reduced Stat3 expression correlated with increased sensitivity to apoptotic stimuli. In concomitant experiments, reporter activity was assessed in Stat3 truncation mutant-expressing HEK293T cells and revealed that, under non-apoptotic conditions, expression of different Stat3 fragments induced differential effects on Stat3-driven luciferase activity. These findings demonstrate that fl-Stat3 undergoes proteolytic processing by caspases that reduces its expression and leads to the formation of cleavage fragments that may modulate Stat3 transcriptional activity.

Novel therapy in multiple myeloma

Treatment in patients with multiple myeloma remain to be defined. Younger patients (defined as a cut-off level < 65 years old) will be treated with chemotherapy and transplant procedures. However, most patients > 65 years old are not candidates for this therapeutic approach and the use of intensive chemotherapy could be associated to severe toxicity. We developed an new, not-cytotoxic regimen with dexamethasone 30 mg/m(2), iv, days 1 to 4, all trans retinoic acid 45 mg/m(2), po, days 5 to 14 and interferon alfa 2a 4.5 MU, sc, daily, days 5 to 14 (DAI regimen) administered every 28 days in number of 6 cycles, at this point patients were restaging, if they showed complete response, objective response or partial response they were conducted to received thalidomide 100-200 mg po, daily and dexamethasone 10 mg/2, po days 1 to 4 at monthly intervals, for 18 months. Forty one patients were enrolled in an Phase II study. In an intent to treat analysis all patients were evaluable. Complete response was observed in 18 cases (43%), objective response in 10 patients (24%) and partial response in 5 patients (12%), overall response rate was 80%. Eight patients were considered failures. At an median of 36 months, no relapse of progression disease has been observed, thus actuarial curves at 3-years showed that event free survival is 100% and overall survival is 91%. Toxicity was mild, all patients received the planned dose in time. This regimen appear to be useful in older patients with multiple myeloma, the response rate is higher and toxicity was mild. Controlled clinical trials comparing with conventional chemotherapy will be conducted to define the role of this therapeutic approach.

Ductal Access for Prevention and Therapy of Mammary Tumors

In cancer patients and in those at high risk, systemic exposure to agents for therapy or prevention is accompanied by undesirable side effects. We hypothesized that it is possible to prevent and treat breast cancer by introducing anticancer agents into the mammary ductal network. Here, we show the efficacy of intraductally administered anticancer agents 4-hydroxytamoxifen and pegylated liposomal doxorubicin (PLD) in the prevention and treatment of breast cancer using the rat N-methyl-N'-nitrosourea-induced and spontaneous HER-2/neu transgenic mouse (neu-N) models of breast cancer. Intraductal administration of PLD to neu-N mice caused regression of established tumors and prevented tumor development more effectively than i.v. injection (P < 0.0001). Intraductal administration resulted in lower circulating levels of PLD compared with i.v. administration, with no evidence of systemic toxicity or long-term histopathologic changes in the mammary gland. Compared with systemic administration, intraductal injection provides direct access to breast lesions with higher local and lower systemic drug exposure. These studies suggest that this approach has potential for application to prevention and neoadjuvant therapy of early breast cancer.

Apoptosis and complement-mediated lysis of myeloma cells by polyclonal rabbit antithymocyte globulin

Current monoclonal antibody therapies for multiple myeloma have had limited success, perhaps due to narrow target specificity. We have previously described the ability of polyclonal rabbit antithymocyte globulin (rATG) to induce caspase- and cathepsin-mediated apoptosis in human B and plasma cells. We now extend this observation to myeloma cells. Complement independent cell death was measured after addition of rATG (1-1000 microg/mL) to cultures of myeloma cell lines or primary CD138+ isolates from patient bone marrow aspirates. rATG induced significant levels of apoptosis in myeloma cells as assayed by caspase induction, annexin V binding, subdiploid DNA fragmentation, plasma-membrane permeability, and loss of mitochondrial-membrane potential. Addition of complement greatly augmented myeloma-cell death. Binding of rATG to individual myeloma cell-surface proteins, primarily CD38, CD52, CD126, and CD138, was demonstrated by competitive inhibition experiments with targeted monoclonal antibodies. Three pathways of cell death were identified involving caspase activation, cathepsin D, and the genistein sensitive tyrosine kinase pathway. Fab'2 fragments of rATG had reduced proapoptotic activity, which was restored by coincubation with Fc fragments, and anti-CD32 or anti-CD64 antibodies. We conclude that rATG is an effective agent for in vitro induction of apoptosis in multiple myeloma, and that exploratory clinical trials may be warranted.

Effects of imatinib and interferon on primitive chronic myeloid leukaemia progenitors

Imatinib has impressive activity against chronic myeloid leukaemia (CML), but does not appear to completely eradicate the disease. Although responses to interferon-alpha (IFN) are slower and less dramatic than those to imatinib, they can be durable even after discontinuation of the drug. Unlike imatinib, the specific mechanisms responsible for IFN's clinical activity in CML are unknown. We found that IFN induced a G1 cell cycle arrest, as well as terminal differentiation, of the CML cell line KT-1 and CML CD34+ cells from clinical specimens. Myeloid growth factors augmented the antileukaemic activity of IFN, and neutralising antibodies directed against myeloid growth factors inhibited IFN's antileukaemic activity. We next directly compared the effects of imatinib and IFN against differentiated and primitive CML progenitors from newly-diagnosed patients. Although less active against CML granulocyte-macrophage colony forming units than imatinib, IFN was significantly more toxic to primitive CML progenitors responsible for the maintenance of long-term cultures. Imatinib and IFN appear to have divergent effects on CML progenitors at different stages of maturation, with imatinib more active against differentiated CML progenitors and IFN more active against primitive CML progenitors. The different target cells for these agents may explain the disparities in the kinetics and durability of their clinical responses. At least part of the clinical effect of IFN in CML appears to result from its ability to differentiate primitive CML progenitors.

Biological modifiers as cytoreductive therapy before stem cell transplant in previously untreated patients with multiple myeloma

BACKGROUND

High dose chemotherapy with supporting autologous stem cell transplantation is now considered the treatment of choice in patients with multiple myeloma <65 years old. The best regimen appears to be VAD (vincristine, doxorubicin and dexamethasone), but acute and late toxicity can limit the use of this combination. The use of biological modifiers has not been considered in this situation. We developed a new cytoreductive regimen, in an attempt to retain clinical efficacy but reduce toxicity.

PATIENTS AND METHODS

Thirty-six patients, previously untreated with diagnosis of multiple myeloma were enrolled to received the DAI regimen (dexamethasone 30 mg/m(2), i.v., days 1-4, all-trans-retinoic acid 45 mg/m(2), p.o., days 5-14 and interferon alpha 2a, 4.5 MU s.c., days 5-14) administered every 28 days for six cycles before high-dose chemotherapy (melphalan 200 g/m(2)) and autologous stem cell transplantation.

RESULTS

Overall response was observed in 29 cases (80%), complete response in 19 and partial response in 10 patients. Five patients were >65 years old and were treated with dexamethasone/thalidomide. Twenty-four patients underwent transplants. At a median follow-up of 31.6 months, no relapse or disease progression was observed, thus actuarial curves at 3-years showed that event-free survival was 86% and overall survival was 94%. Toxicity was mild.

CONCLUSIONS

This regimen appears to be an excellent alternative as cytoreductive treatment before high-dose chemotherapy and autologous stem cell transplantation with excellent overall response and minimal toxicity. Controlled clinical trials are warranted to define the role of this new therapeutic approach.

Requirement for myeloid growth factors in the differentiation of acute promyelocytic leukaemia

It is well known that the differentiation of acute promyelocytic leukaemia (APL) cells by all-trans-retinoic acid (ATRA) may be enhanced by myeloid growth factors, but the requirement for growth factors in this process is unclear. Our previous studies in multiple myeloma and non-APL acute myeloid leukaemia demonstrated that lineage-specific growth factors are required for the maximal activity of many pharmacologic differentiating agents in vitro. Thus, we studied whether the differentiation of APL is similarly dependent on growth factors. We found that the myeloid growth factors granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor markedly increased the differentiation of NB4 cells or APL blasts from clinical samples treated with ATRA, arsenic trioxide (ATO), or bryostatin-1 as evidenced by the enhanced expression of myeloid surface antigens and the inhibition of clonogenic growth. Furthermore, myeloid growth factors were necessary for the differentiation of APL cells since the activity of each pharmacologic agent could be blocked by specific growth factor-neutralizing antibodies. Each differentiating agent was active only at concentrations that inhibited cell cycling, suggesting that this property is also required for differentiation. These data demonstrate that both pharmacologic differentiating agents and myeloid growth factors are required, but neither sufficient, for the differentiation of APL cells. The combined use of pharmacologic differentiating agents and growth factors may improve the clinical efficacy of differentiation therapy in APL.

Alpha-interferon and its effects on signal transduction pathways

Interferon-alpha (IFNalpha) is a recombinant protein widely used in the therapy of several neoplasms such as myeloma, renal cell carcinoma, epidermoid cervical and head and neck tumors, and melanoma. IFNalpha, the first cytokine to be produced by recombinant DNA technology, has emerged as an important regulator of cancer cell growth and differentiation, affecting cellular communication and signal transduction pathways. However, the way by which tumor cell growth is directly suppressed by IFNalpha is not well known. Wide evidence exists on the possibility that cancer cells undergo apoptosis after the exposure to the cytokine. Here we will review the consolidate signal transducer and activator of transcription (STAT)-dependent mechanism of action of IFNalpha. We will discuss data obtained by us and others on the triggering of the stress-dependent kinase pathway induced by IFNalpha and its correlations with the apoptotic process. The regulation of the expression of proteins involved in apoptosis occurrence will be also described. In this regard, IFNalpha is emerging as a post-translational controller of the intracellular levels of the apoptosis-related protein tissue transglutaminase (tTG). This new way of regulation of tTG occurs through the modulation of their proteasome-dependent degradation induced by the cytokine. Until today, inconsistent data have been obtained regarding the clinical effectiveness of IFNalpha in the therapy of solid tumors. In fact, the benefit of IFNalpha treatment is limited to some neoplasms while others are completely or partially resistant. The mechanisms of tumor resistance to IFNalpha have been studied in vitro. The alteration of JAK-STAT components of the IFNalpha-induced signaling, can be indeed a mechanism of resistance to IFN. However, we have recently described a reactive mechanism of protection of tumor cells from the apoptosis induced by IFNalpha dependent on the epidermal growth factor (EGF)-mediated Ras/extracellular signal regulated kinase (Erk) signaling. The involvement of the Ras-->Erk pathway in the protection of tumor cells from the apoptosis induced by IFNalpha is further demonstrated by both Ras inactivation by RASN17 transfection and mitogen extracellular signal regulated kinase 1 (Mek-1) inhibition by exposure to PD098059. These data strongly suggest that the specific disruption of the latter could be a useful approach to potentiate the antitumour activity of IFNalpha against human tumors based on the new mechanistic insights achieved in the last years.

JAK-mediated signaling inhibits Fas ligand-induced apoptosis independent of de novo protein synthesis

There is a growing appreciation for how cells integrate and appropriately respond to competing signals for proliferation and apoptosis. The studies described in this report examined the effects of exposure to the cytokine IFN-alpha (IFN-alpha-2a) on sensitivity of the human cell lines H9 and SKW6.4 to Fas ligand (FasL)-induced apoptosis. In a concentration-dependent manner, FasL induced apoptosis, as shown by Western blot analysis of procaspase 8 and poly(ADP-ribose) polymerase cleavage after 3-h exposure and by cytofluorometric analysis of sub-G(0)-G(1) cellular DNA content after 24-h exposure. H9 and SKW6.4 cell lines responded to 10,000 IU/ml IFN-alpha-2a, as evidenced by decreased cell proliferation and tyrosine phosphorylation of Stat1 and Stat3 proteins without significant cytotoxicity. The effects of cytokine exposure on apoptosis were examined; incubation in medium containing 10,000 IU/ml IFN-alpha-2a for 1 h before FasL treatment significantly reduced all above-mentioned hallmarks of apoptosis. Surprisingly, these antiapoptotic effects of IFN-alpha-2a were independent of de novo protein synthesis, because they occurred in both the absence and the presence of cycloheximide. However, chemical inhibitors of JAK completely abrogated the effects of IFN-alpha-2a on FasL-induced apoptosis, indicating a direct role for JAK-mediated protein phosphorylation in modulating sensitivity to apoptosis. Together, these data suggest a novel mechanism, independent of protein synthesis, by which cytokine signals through JAKs can interact with and attenuate this receptor-mediated apoptotic process.

Myelodysplastic syndrome

The last decade has witnessed a multistep evolution in the understanding of the natural history, clinical manifestations, and some of the molecular mechanisms that underlie the ineffective hematopoiesis and leukemic transformation in the myelodysplastic syndrome (MDS). The international prognostic scoring system, FAB, and WHO classifications have helped define specific subgroups with their characteristic cytogenetic, molecular and immunological abnormalities. Until recently the mainstay of the treatment has been entirely supportive with blood and platelet transfusions. What is increasingly manifest now is the considerable excitement generated by the emergence of novel therapeutic strategies based on painstaking research findings from the laboratories. In Section I, Dr. Alan List reviews the therapeutic strategies with the specific emphasis on the relevance of molecular mechanism of apoptosis and targeted therapies using small molecules. Of particular interest is the excitement surrounding the clinical benefit obtained from potent immunomodulatory derivative (IMiD) of thalidomide CC5013. The review provides an update of the role of small molecule inhibitors of VEGF receptor tyrosine kinase, arsenic trioxide, oral matrix metalloprotease inhibitors, farnesyl transferase inhibitors, and imatinib mesylate in the treatment of MDS subgroups. In Section II, Dr. Steven Gore describes the results of clinical trials of inhibitors of DNA methylation such as 5 azacytidine (5 AC) and 5-aza 2-deoxycytidine (Decitabine). The review also provides an update on the rationale and results obtained from the combination therapy using histone deacetylases (HDAC) and DNA methyltransferase inhibitors in the treatment of MDS. In Section III, Professor Ghulam Mufti and Dr. Aloysius Ho describe the role of bone marrow transplantation with particular emphasis on recent results from reduced-intensity conditioned transplants, exploiting the graft versus leukemia effect without significant early treatment-related mortality. The section provides an update on the results obtained from the manipulation of the host's immune system with immunosuppressive agents such as ALG and/or cyclosporine A.