Interferons: biological and clinical effects

Biologic activity of polyethylene glycol12000-interferon-alpha2b compared with interferon-alpha2b: gene modulatory and antigrowth effects in tumor cells

The relative activities of interferon-alpha2b (IFN-alpha2b) and polyethylene glycol(12000)-IFN-alpha2b (PEG-IFN-alpha2b) were assessed in cell culture studies using WM9 melanoma or ACHN renal cell carcinoma cell lines. Interferon-alpha2b and PEG-IFN-alpha2b had identical antiproliferative activities when tested in cell proliferation studies conducted with equivalent antiviral units of each IFN preparation. Neither IFN formulation was effective in inducing apoptosis in WM9 melanoma cells, but both increased slightly the percentage of ACHN cells undergoing apoptosis as assessed by Annexin V staining. Interferon-alpha2b and PEG-IFN-alpha2b both activated signal transducer and activator of transcription complexes, and the duration of complex activation was similar for both IFN formulations. Induction of different IFN-stimulated genes was assessed by Northern blotting and the quantitative real-time reverse transcription-coupled polymerase chain reaction (RT-PCR) in WM9 melanoma, ACHN renal cell carcinoma, U937 lymphoma, and MOLT-4 and Mono Mac 6 leukemia cell lines. Interferon-alpha2b and PEG-IFN-alpha2b had equivalent gene-modulatory activities within each of these tumor cell lines, although cell line-specific induction patterns were observed. When compared with the antiviral 50% inhibitory concentration (IC(50)) values, the dose-dependent gene expression data correlated with cell sensitivity to IFN treatment. Together, the drug comparability and cell sensitivity data suggest a predictive relation between dose, time, antiviral activity, and gene transcription effects. Therefore, although the specific activity of IFN-alpha2b is approximately three times greater than PEG-IFN-alpha2b, the two preparations have identical in vitro biologic activities when applied to cells at equivalent antiviral units.

Significant antitumor effects obtained by autologous tumor cell vaccine engineered to secrete interleukin (IL)-12 and IL-18 by means of the EBV/lipoplex

The EBV/lipoplex is a nonviral gene delivery system composed of a cationic lipid and Epstein-Barr virus (EBV)-based plasmid vector that carries the EBV oriP and EBV nuclear antigen 1 (EBNA1) gene. Because the EBNA1 supports retention, nuclear localization, and transcriptional upregulation of the oriP-bearing plasmid, cells transfected with the EBV/lipoplex express the transgene at a very high level. We hypothesized that tumor cells genetically manipulated with the EBV/lipoplex may be used as a tumor vaccine without drug selection, strongly contributing to immunotherapy of patients with malignancies. The cytokines interleukin (IL)-12 and IL-18 exert a variety of immune-regulatory functions including interferon (IFN)-gamma production and cytotoxic T lymphocyte (CTL) and natural killer (NK) activation. Here, we investigated the possible therapeutic effects of an autologous tumor cell vaccine in the B16 melanoma model. The vaccine was engineered to secrete IL-12 and IL-18 by means of the EBV/lipoplex. B16 cells were subcutaneously implanted into syngenic mice followed by repetitive immunization with irradiated B16 cells that had been transfected 3 days earlier by TFL2-3, a novel cationic lipid, with EBV-plasmid vectors encoding IL-12 and/or IL-18 genes (B16/mIL-12, B16/mIL-18, and B16/mIL-12+mIL-18). The mice vaccinated with B16/mIL-12 underwent strong tumor suppression accompanied by a high IFN-gamma production. Both CTL and NK activities were significantly elevated in these mice. When the tumor cell vaccine was prepared by means of conventional (non-EBV) plasmid vectors combined with the same cationic lipid, the therapeutic outcome was not as good, suggesting the superiority of the EBV-based plasmid in engineering these types of tumor vaccines. Vaccination with B16/mIL-18 was not effective in suppressing tumors, whereas B16/mIL-12+mIL-18 showed comparable antitumor therapeutic validity as B16/mIL-12 did. When IFN-gamma mutant (IFN-gamma(-/-) mice were treated, B16/mIL-12 vaccine did not show any therapeutic activity, suggesting the necessity of IFN-gamma in the anti-melanoma immune responses. In contrast, the antitumor effect was not affected by NK depletion in mice that received repetitive injections with anti-asialo GM1 antibody. Furthermore, vaccination with B16/mIL-12 significantly suppressed pulmonary metastases in mice that had been intravenously injected with parental B16. Our results suggest that the EBV/lipoplex is quite useful in generating an autologous tumor cell vaccine and that IL-12 is an important component of the vaccine.

Alpha interferon combined with ribavirin potentiates proliferative suppression but not cytokine production in mitogenically stimulated human lymphocytes

The improved clinical outcome observed among patients with hepatitis C treated with the combination of alpha interferon (IFN) and ribavirin (RBV) is presumed to result from immunomodulation and viral inhibition. However, the impact of the drug combination upon lymphocyte activity is unknown. The present study evaluated the effects of IFN and RBV, singly and in combination, upon proliferation, cell cycle sensitivity and cytokine elaboration following PHA stimulation of lymphocytes. Two formulations of IFN, interferon-a-2b (IFN-2b) and interferon-a-con-1 (CIFN), were included. Titration of each drug over a wide range of concentrations showed dose dependent proliferative suppression without cytotoxicity. Proliferation was suppressed 57-99% (P<0.001) by IFN-2b (10(5)-10(7) IU/ml), 41-74% (P<0.001) by CIFN (1.5-150 ng/ml), and 10-94% (P<0.001) by RBV (0.5-50 microg/ml). Isobologram analysis showed that the interaction between IFN-2b and RBV on proliferative suppression was additive. In contrast, the interaction between CIFN and RBV was weakly antagonistic. Proliferative suppression by both the IFNs was cell cycle restricted. IFN-2b and CIFN added at the onset of PHA stimulation (G0/G1) versus 24 h later (S phase) inhibited proliferation by 50 versus 5%, respectively (P<0.05). The onset of IFN resistance correlated with a 50% reduction (P<0.05) in IFN receptors on the cell surface. In contrast, RBV caused equivalent proliferative suppression (P=NS) when added at any time during PHA activation. Cytokine secretion after 24 h of PHA stimulation showed that IFN-2b versus CIFN increased the secretion of IL2, TNF and gamma IFN by 4.5-, 4.1- and 8.3-fold (P<0.005) versus 1-, 1.9- and 1.9-fold (P<0.05), respectively, above control levels. Neither IFN affected IL10 secretion. RBV, singly and in combination with IFN, had no impact on cytokine expression (P=NS). This study identifies several potential mechanisms by which the combination of IFN and RBV may exert a more potent effect upon cellular immunity than either agent alone and shows that different formulations of IFN may have non-identical effects upon lymphocyte responses.

Formation of the early-region-2 transcription-factor-1-retinoblastoma-protein (E2F-1-RB) transrepressor and release of the retinoblastoma protein from nuclear complexes containing cyclin A is induced by interferon alpha in U937V cells but not in interferon-alpha-resistant U937VR cells

We have analysed the different regulation of cell-cycle-relevant proteins by interferon alpha (IFN alpha) in IFN alpha-sensitive and resistant U937 leukemic cell lines. In contrast to the INF alpha-sensitive U937 variant cell line U937V, the IFN alpha-resistant derivative (U937VR) is insensitive to the antiproliferative activity of IFN alpha. As we found no differences between these cell lines concerning the induction by IFN alpha of the pathway involving tyrosine-protein kinases and the signal transducer and activator of transcription (Jak-Stat), we examined whether cell-cycle-regulating proteins are differently affected by IFN alpha in U937VR and U937VR cells. In U937V cells IFN alpha induced the formation of the complex between early-region-2 transcription factor 1 (E2F-1) and retinoblastoma protein (RB) which is known to repress transcription of E2F-1-inducible genes, necessary for cell cycle progression. Formation of this complex was not inducible by IFN alpha in U937VR cells, although the suitable binding partners (E2F-1 and under-phosphorylated RB) were present. Interestingly, treatment of nuclear extracts from logarithmically growing U937V and U937VR cells with an antiserum against cyclin A that disrupts cyclin-A-containing complexes, led to the formation of the E2F-1-RB complex, suggesting the presence of under-phosphorylated (active) RB, trapped in nuclear complexes that contain cyclin A. This suggestion was supported by combined immunoprecipitation/western blot experiments that revealed a physical interaction between phosphorylated as well as under-phosphorylated forms of RB and cyclin A complex(es) in U937V and U937VR cells. RB, especially the under-phosphorylated form, was released by treatment with IFN alpha from this complex(es) in the case of U937V cells but not U937VR cells. We conclude that the missing induction of the E2F-1-RB transrepressor by IFN alpha and the failure to release RB from cyclin-A-containing complexes might contribute to the resistance of U937VR cells to the antiproliferative effects of IFN alpha.

Endotoxin induces increased intracellular cathepsin B activity in THP-1 cells

Macrophage cathepsin B (CB) is implicated in tissue injury in inflammatory diseases. Lipopolysaccharide (LPS) is an activator of macrophages whose effect on CB is unknown. This study was undertaken to investigate the potential of macrophages as a source of increased CB and to determine if exposure to LPS might stimulate CB levels. As a model we chose the macrophage-like tumor line, THP-1. Incubation with LPS led to a time and dose-dependent increase in CB activity. LPS potentiated interferon-gamma (IFN-gamma)-induced elevations of CB and led to an additive increase in CB activity. Pretreatment of the cells with LPS not only caused a marked stimulation of CB activity over that seen with IFN-gamma alone, but also decreased the concentration and exposure time to the cytokine necessary to achieve maximum induction of the enzyme. The LPS and IFN-gamma induced CB increases were abolished by cycloheximide or actinomycin D in the cultures, indicating that the increases in CB required increased RNA transcription and de novo protein synthesis. Direct measurement of CB mRNA showed increases. These data indicate that although LPS alone appears to induce the production of CB in THP-1 cells, it augments IFN-gamma induced increases, suggesting that two signals are necessary for maximum CB induction in this system.

Interferon-gamma induced increases in intracellular cathepsin B activity in THP-1 cells are dependent on RNA transcription

Interferon-gamma (IFN-gamma) treatment of human macrophages induces increased intracellular levels of cathepsin B (CB), a lysosomal cysteine proteinase which is implicated in inflammatory tissue injury. To determine the mechanism of the increase, we studied the macrophage-like cell line, THP-1. Dose and time dependent increases in intracellular CB were seen when cells primed with phorbol ester (PMA) were cultured with IFN-gamma. To determine whether protein synthesis was required for the increase, PMA primed cells were cultured in the presence of IFN-gamma and cycloheximide: The expected increase was inhibited. To determine whether RNA synthesis was required for the IFN-gamma induced increases, PMA primed cells were cultured in the presence of IFN-gamma and actinomycin D. Again the expected increases were not seen. Direct measurement of CB mRNA levels showed increases in cells not treated with inhibitors. These results suggest that the IFN-gamma induced increases in THP-1 cell CB are dependent on RNA and protein synthesis.

Biology and therapeutic uses of myeloid hematopoietic growth factors and interferons

Recent advances in basic science and clinical trials have demonstrated that IFNs and myeloid hematopoietins play crucial roles in host defense against pathogens and immune surveillance. Here we have reviewed the biologic functions of GM-CSF, G-CSF, IFN-alpha and IFN-gamma. For patients with neutropenia resulting from cytotoxic chemotherapy, bone marrow transplantation, congenital agranulocytosis and cyclic neutropenia, therapeutic uses of GM-CSF and G-CSF were reviewed. Application of these growth factors to patient management represents a major contribution of biotechnology to a difficult area of therapeutics in febrile, neutropenic patients. Because IFN-alpha plays crucial roles in antiviral responses, its clinical applications in hepatitis B and C, human papilloma virus, HIV infection and malignancy were discussed. The use of IFN-gamma in bacterial prophylaxis in patients with chronic granulomatous disease was also presented. Advances in clinical applications of IFNs and hematopoietic growth factors serve as a paradigm for further development to investigate the use of other important cytokines in modern therapeutics.

The interferons: a biological system with therapeutic potential in viral infections

Successful medical use of interferon for chronic viral infections is increasingly dependent on understanding the biologic and molecular mechanisms of the interferon system. Interferon (IFN) is one of the body's natural defenses. Production of IFN is a defensive response to foreign components of microbes, tumors and antigens. This IFN response begins with the production of the IFN proteins (alpha, beta and gamma) which then induce antiviral, antimicrobial, antitumor, and immunomodulatory actions. Thus, the initial production or administration of IFN(s) does not protect directly but instead reacts with specific receptors on cell surfaces to activate cytoplasmic transduction signals that then enter the nucleus to stimulate cellular genes encoding a number of effector proteins which lead to the defensive actions. The known molecular, humoral and cellular mechanisms by which these effector proteins exert their antiviral activities are presented. In addition, the pathogenesis of chronic infections is overviewed in the context of the interferon defenses.

Therapeutic effect of a vaccinia colon oncolysate prepared with interleukin-2-gene encoded vaccinia virus studied in a syngeneic CC-36 murine colon hepatic metastasis model

Vaccinia CC-36 murine colon oncolysate (VCO) prepared with interleukin-2-gene encoded recombinant vaccinia virus (IL-2VCO) was used in the treatment of a syngeneic murine colon adenocarcinoma (CC-36) hepatic metastasis to test the beneficial effect of the interleukin-2-gene encoded vaccinia virus over a control recombinant vaccinia virus in producing a vaccinia oncolysate tumor cell vaccine. Results suggest that the IL-2VCO treatment significantly reduced the hepatic tumor burden in comparison with the controls that received either IL-2-gene-encoded recombinant vaccinia virus or a plain recombinant vaccinia virus or vaccinia oncolysate prepared with the plain recombinant virus. The survival of mice treated with IL-2VCO was also improved in comparison with mice treated with other preparations. The induction of a cytolytic T lymphocyte response was examined to elucidate the mechanism of the induction of antitumor responses in IL-2VCO-treated mice. Fresh peripheral blood lymphocytes (PBL) isolated from IL-2VCO-treated mice showed a higher cytolytic activity against CC-36 tumor cell target when compared to PBL from the mice of other treatment groups, suggesting that the IL-2VCO induced an antitumor cytolytic T lymphocyte response. These results suggest that a vaccinia oncolysate, prepared with recombinant vaccinia virus encoding an immunomodulating cytokine gene will enhance antitumor responses in the host.

Phase II trials of interferons-alpha and -beta in advanced sarcomas

Interferons (IFNs)-alpha and -beta were administered to patients with metastatic sarcomas in two different Eastern Cooperative Oncology Group studies. In one study, patients received IFN-alpha 2b, 20 million units/m2 i.v. 5 days/week x 4, then 10 million units s.c.t.i.w. In the second study, patients received IFN-beta ser 180 million units t.i.w. Of 87 patients evaluable for response, there were three responses in 64 patients (5%) treated with IFN-alpha-2b and no responses in 23 patients treated with IFN-beta ser. Severe or life-threatening fatigue with decline in performance status complicated treatment of 37% of patients receiving IFN-alpha 2b and 17% of patients receiving IFN-beta ser. Further investigation of IFNs in sarcomas should depend on evidence from preclinical studies demonstrating synergistic effects of IFNs combined with a cytoreductive modality which has proven activity in these malignancies.

Dipyridamole enhances an anti-proliferative effect of interferon in various types of human tumor cells

The anti-proliferative activity of human interferon (HuIFN) was enhanced by dipyridamole, 2,6-bis-(diethanolamino)-4,8-dipiperidinopyrimido-[5,4-d]-py rimidine, when tested against various human tumor cell lines, including KT (breast carcinoma), PLC/PRF/5 (hepatoma), MGC-I, U251-SP and T98 (glioma), HAC-2 and SHIN-3 (ovarian carcinoma), and MM-ICB (melanoma). The enhancement occurred irrespective of the kind of HuIFN used (alpha, beta or gamma) and the original degree of susceptibility of the cells to HuIFN. Even low doses down to 0.01 microM of dipyridamole that had no intrinsic anti-proliferative activity could enhance the effect of HuIFN. The enhancement of HuIFN effects seems not to be caused by induction of HuIFN production, because neither anti-viral activity nor HuIFN antigens were detected in culture medium in cells treated with dipyridamole. Mopidamole, a derivative of dipyridamole lacking one piperidine residue, produced little enhancement of the effects of HuIFN. Among ovarian cancer cell lines tested, the enhancement of the activity of HuIFN by dipyridamole for HAC-2 and SHIN-3 cells was equivalent to or greater than that for 3 chemotherapy agents (adriamycin, vincristine, and a camptothecin derivative). However, neither HOC-21 ovarian cancer cells nor HEC-1 endometrial adenocarcinoma cells were susceptible to any combinations. When MGC-1, U251-SP, and HAC-2 cells were injected into nude mice, the growth of tumors was more markedly inhibited by the subcutaneous administration of HuIFN in combination with oral administration of dipyridamole than by the HuIFN alone. Thus, this combination therapy seems to be worth trying for human cancer, although the enhancement of the effects of HuIFN by dipyridamole varied among the cell lines examined.

Interferons: Pleiotropic cellular modulators

Interferons play a key role in host response as pleiotropic modulators of cell function. As induced proteins, interferons contrast with other physiologic regulators such as glucocorticoids which are produced relatively continuously. Antitumor effects have been suggested to be principally the result of two mechanisms: a direct effect on the functional capacity or antigenic composition of tumor cells or an indirect effect on modulation of immunological effector cell populations with tumor specificities. Over the past decade, interferons have been established as therapeutically useful molecules for malignant and viral diseases.

Immunotherapy for malignant melanoma: a review and update

Several different approaches to the application of specific active immunotherapy for the adjuvant therapy of melanoma have developed independently. Specific active immunotherapy refers to autologous or allogenic inoculation or transplantation of tumor cells or cell products into patients with cancer. Several different types of tumor vaccines have been studied and have been combined with different immunotherapeutic modalities. This report will include a review of several of those different techniques and will also review the observed 5-year survival rates for a melanoma tumor homogenate (concentrated) vaccine, developed by L.J. Humphrey and colleagues.