Antitumor effects of interferon

Type I IFN family members: similarity, differences and interaction

Interferons (IFN) are key cytokines with multifaceted antiviral and cell-modulatory properties. Three distinct types of IFN are recognized (I-III) based on structural features, receptor usage, cellular source and biological activities. The action of IFNs is mediated by a complex, partially overlapping, transcriptional program initiated by the interaction with specific receptors. Genetic diversity, with polymorphisms and mutations, can modulate the extent of IFN responses and the susceptibility to infections. Almost all viruses developed mechanisms to subvert the IFN response, involving both IFN induction and effector mechanisms. Interactions between IFN types may occur, for both antiviral and cell-modulatory effects, in a complex interplay, involving both synergistic and antagonistic effects. Interferon-associated diseases, not related to virus infections may occur, some of them frequently observed in IFN-treated patients. On the whole, IFNs are pleiotropic biologic response modifiers, that, upon activation of thousands genes, induce a broad spectrum of activities, regulating cell cycle, differentiation, plasma membrane molecules, release of mediators, etc., that can be relevant for cell proliferation, innate and adaptive immunity, hematopoiesis, angiogenesis and other body functions.

The molecular biology of soft-tissue sarcomas and current trends in therapy

Basic research in sarcoma models has been fundamental in the discovery of scientific milestones leading to a better understanding of the molecular biology of cancer. Yet, clinical research in sarcoma has lagged behind other cancers because of the multiple clinical and pathological entities that characterize sarcomas and their rarity. Sarcomas encompass a very heterogeneous group of tumors with diverse pathological and clinical overlapping characteristics. Molecular testing has been fundamental in the identification and better definition of more specific entities among this vast array of malignancies. A group of sarcomas are distinguished by specific molecular aberrations such as somatic mutations, intergene deletions, gene amplifications, reciprocal translocations, and complex karyotypes. These and other discoveries have led to a better understanding of the growth signals and the molecular pathways involved in the development of these tumors. These findings are leading to treatment strategies currently under intense investigation. Disruption of the growth signals is being targeted with antagonistic antibodies, tyrosine kinase inhibitors, and inhibitors of several downstream molecules in diverse molecular pathways. Preliminary clinical trials, supported by solid basic research and strong preclinical evidence, promises a new era in the clinical management of these broad spectrum of malignant tumors.

Translating molecular insights in autoimmunity into effective therapy

Autoimmunity and the pathogenesis of autoimmune diseases were a major focus of the Walter and Eliza Hall Institute, where I started my research career. After my initial studies on immune cell culture and immune regulation, I returned to an analysis of the pathogenesis of human autoimmunity in London. Linking upregulated antigen presentation to autoimmunity led to an investigation of the role of cytokines in rheumatoid arthritis (RA), in collaboration with Ravinder Maini. These experiments defined the concept of a TNF-dependent cytokine cascade driving the manifestations of RA, which led to successful clinical trials of anti-TNF monoclonal antibody in RA patients, heralding a major change in medical practice. This success was made possible by enthusiastic support from many laboratory and clinical colleagues and taught us that cytokines are important rate-limiting steps and hence good therapeutic targets. My current scientific challenge is exploring the hypothesis of whether all major medical needs can be approached via cytokine blockade.

Interferon therapy in Hodgkin's disease. A case report

The treatment of a case of Hodgkin's disease (lymphocyte predominance, stage IV B) with exogenous i.m. interferon therapy is described. B symptoms disappeared, diseased nodes and pulmonary infiltrations decreased in size, and laboratory values normalized. Clinical improvement was associated with increased mitogenic responsiveness of the patient's lymphocytes towards various stimuli in vitro. After almost half a year's treatment tumour progression and a decreased mitogenic response were again observed. Interferon treatment was then abandoned and combined cytostatic courses were instituted. Partial remission was achieved after 6 months of cytostatic therapy, i.e. 1 year after the start of treatment.

Interferon therapy in neoplastic disease. A preliminary report

The treatment of 10 patients having neoplastic disease with exogenous i.m. interferon therapy is described. The interferon given is partially purified interferon produced from human leukocytes. Sendai virus is used as interferon inductor. The patients reported in this paper have been on treatment for periods of 2-28 months. Apart from initial periods of fever, no side-effects have been recorded. Patients suffering from bladder papillomas have shown partial regression after a few months of therapy. The other cases treated are too few to warrant any conclusions, but the therapy does seem to have been beneficial.

Interferons and osteosarcoma

In 1970, we initiated studies at the Karolinska hospital to find out whether biologically meaningful doses of interferon (IFN) alpha preparations could be administered systemically to patients with viral and tumour diseases without causing unacceptable side effects. Antiviral and antitumour efficiency was demonstrated. Only a limited number of patients were injected due to shortage of high dose IFN preparations. Osteosarcoma patients participated in these early attempts. Due to clinical observations on one patient and due to lack of meaningful systemic standard treatment for osteosarcoma at the time, we decided to continue to give adjuvant IFN treatment to a consecutive series of osteosarcoma patients attending our hospital . We were encouraged by the preliminary follow up results of the series and continued to use this therapeutic principle up to 1990. The clinical results achieved are briefly summarized in this mini-review as are the results obtained in simultaneously ongoing model experiments in vitro and in vivo. A randomized large scale ongoing trial, involving the use of adjuvant IFN treatment of osteosarcoma patients, has been initiated by the European and American osteosarcoma study group 35 years after the first osteosarcoma patient received IFN. The trial is briefly outlined in this article.

Preliminary individual adjuvant therapy for gliomas based on the results of molecular biological analyses for drug-resistance genes

New adjuvant therapy individualized by the results of reverse transcription-polymerase chain reaction (RT-PCR) for drug-resistance genes has been used to treat malignant gliomas. Protocol studies for malignant gliomas were not so encouraging in their therapeutic results because of heterogeneity and the various drug-sensitivities of the tumors. Individualization of glioma therapy is recommended. Drug-resistance genes messenger ribonucleic acid (mRNA) expressions were investigated in drug-resistant human glioma cell lines derived from U87MG and 46 frozen samples of retrospectively examined neuroepithelial tumors (12 low grade neuroepithelial tumors, 16 Grade III gliomas, 11 glioblastomas, and 7 other malignant neuroepithelial tumors such as medulloblastomas and primitive neuroectodermal tumors) by RT-PCR with the specific primers for O6-methylguanine DNA methyltransferase (MGMT), multidrug-resistance gene 1 (MDR1), multidrug-resistance-associated protein (MRP), and glutathione-S-transferase-pi (GST-pi). Thirty-seven preliminary individual adjuvant therapies (IAT) based on RT-PCR results, mainly in MGMT expression, were performed on 30 consecutive patients with neuroepithelial tumors. In the retrospectively examined series, the initial response to 1-(4-amino-2-methyl-5-pyrimidynyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) was correlated most significantly to the MGMT mRNA expression among 11 independent prognostic factors (p = 0.0037) in multivariate logistic regression analysis. In the preliminary IAT, 17 of 32 evaluable therapies had a partial or complete response (53.1% response rate). Our IAT based on RT-PCR seemed to be more effective than conventional therapies for malignant gliomas.

Type I interferons

Type I interferons (IFNs) constitute a family of structurally related proteins that are all derived from the same ancestral gene and act on a common cell-surface receptor. Contrary to many other cytokines, the production of type I IFNs is not a specialized function, and all cells in the organism can produce them, usually as a result of induction by viruses, via the formation of double-stranded RNA. Type I IFNs are indeed responsible for the first line of defense during virus infection and act through the induction of a great number of proteins. Of these, at least thirty have been characterized, and there are probably many more. In addition to their direct antiviral effect, type I IFNs exert a wide variety of other activities, such as for example the induction of various cytokines and the stimulation of different effector cells of the immune system. Due to these pleiotropic effects, recombinant interferons are used in the clinic to treat a variety of diseases, among which cancer, viral hepatitis and multiple sclerosis.

Growth suppression and astrocytic differentiation of glioma cells by interleukin-1

The effect of recombinant human interleukin-1 (rHuIL-1) derivatives on human glioma cell lines was examined in vitro. Five glioma cell lines, U-251 MG, U-373 MG, U-87 MG, A-172, and T98G, were incubated in medium containing 1% fetal calf serum and various concentrations of different type of rHuIL-1: OCT-43 (rHuIL-1 beta), OCT-7000 (rHuIL-1 alpha), and OCT-8000 (rHuIL-1 alpha). The high-affinity IL-1 receptors were expressed in the U-251 MG and U-373 MG cell lines, and rHuIL-1 was found to suppress cell growth and to induce morphological differentiation of these cell lines. Growth inhibition occurred in a dose-dependent manner in concentrations or rHuIL-1 ranging between 1 and 100 ng/ml. Interestingly, rHuIL-1 induced a transient growth of glioma cells shortly after administration, then suppressed cell growth with accompanying elongation of cytoplasmic processes. This unique process of transient growth stimulation followed by growth suppression was parallel to the efficacy of bromodeoxyuridine uptake in the rHuIL-1-treated cells. Concomitantly, accumulation of glial fibrillary acidic protein and cyclic adenosine monophosphate contents was observed in four glioma cell lines. Continuous rHuIL-1 treatment for longer than 30 days elicited irreversible astrocytic terminal differentiation. These results indicate that IL-1 is an effector on the growth regulation of glioma cells, resulting in astrocytic differentiation in vitro.

Enhancement of anticancer agent activity by selective inhibition of rapidly proliferating tissues of the host

Most cytotoxic drugs used in cancer therapy do not discriminate between neoplastic and normal proliferating cells. To avoid irreversible damage to vital host tissues, such as bone marrow and intestine, drugs must be administered at dosages which usually prove insufficient to eradicate all of the neoplastic cells present. This review focuses on an approach to improve cancer chemotherapy by selectively protecting normal, proliferating cells during treatment, thereby permitting the administration of otherwise lethal doses of drug. Preclinical in vivo studies of cytokinetic modulation with interferon, or L-histidinol, as well as recent clinical studies of interferon modulation of the activity of 5-fluorouracil are reviewed.

Intratumoural and intraventricular human lymphoblastoid alpha interferon (HLBI) for treatment of glioblastoma multiforme

A series of ten patients with glioblastoma multiforme were treated with human lymphoblastoid alpha interferon (HLBI) as a single therapy after partial surgical resection (5 cases) or stereotactic biopsy (5 cases). Treatment consisted of intratumoural administration of HLBI (15 x 16(6) IU) every month (8 cases) or in the continuous intraventricular infusion of HLBI (1.8 x 10(6) IU daily) in 15-day cycles (2 cases) until rapid growing of the tumour and important neurological deterioration. The treatments were well tolerated. As judged from data from control groups, the patients demonstrated no improvement in mean survival time and follow-up CT-scan showed rapid progression of the tumour in all cases.

Effects of scheduling and ascites-associated macrophages on combined antiproliferative activity of alpha-2b interferon and gamma-interferon in a clonogenic assay

Effects of combination treatment with human recombinant alpha-2b interferon (IFN-alpha 2b) and gamma interferon (IFN-gamma) and sequencing of the combination on colony formation of human tumor cells were studied in a human tumor clonogenic assay (HTCA) with or without ascites-associated macrophages (AAM). Five different human tumor cell lines were studied. Three of the five cell lines (ovarian cancer cell line BG-1, cervical cancer cell line ME-180, and melanoma cell line SK-MEL 28) were sensitive to both IFNs. Cervical cancer cell line CaSki was sensitive to IFN-alpha 2b but resistant to IFN-gamma. Endometrial cancer cell line HEC-1A was resistant to both IFNs. Synergistic interaction was observed in BG-1 and SK-MEL 28 with a combination of the IFNs. ME-180 did not exhibit a positive interaction, in spite of its sensitivity to each IFN. CaSki and HEC-1A also did not exhibit a positive combined interaction at clinically achievable concentrations. One sequential combination method (method 1: IFN-alpha 2b----IFN gamma with a 24-h interval) resulted in a similar antitumor effect as the simultaneous combination. A reversed sequential method (method 2: IFN-gamma----IFN-alpha 2b with a 24-h interval) was less effective in three of the five cell lines. In BG-1, AAM enclosed in the lower layer markedly enhanced the antitumor effect of combined IFNs as well as each IFN alone. The antitumor effect with method 1 was significantly greater than that achieved with simultaneous combination or combination according to method 2 in the presence of AAM (P less than 0.01). These results suggest that (1) a synergistic antitumor effect of IFN-alpha 2b and IFN gamma is demonstrable in selected types of tumors, depending upon the sensitivity of each tumor cell line to both IFNs; (2) optimal scheduling for the direct antitumor effect of combined IFNs seems to be long-term exposure of cells to the IFN, the cells being treated with both IFNs either simultaneously or sequentially (IFN-alpha 2b preceding IFN-gamma); and (3) AAM potentiate the antitumor effect of IFNs either alone or in combination. Finally, IFN-alpha 2b may have some priming effects for the indirect effect of IFN gamma mediated through AAM in certain tumor cells.

Antitumor effect of recombinant murine interferon-beta against mouse malignant glioma

A study was made on the antitumor effect of recombinant murine interferon-beta (rMuIFN-beta) against virus-induced mouse malignant glioma. In in vitro experiments, a dose-dependent and a time-dependent manner were observed for 24 h in the antiproliferative activity of rMuIFN-beta. In in vitro experiments, the growth of subcutaneously transplanted gliomas in mice treated with intraperitoneal administration of rMuIFN-beta was inhibited slightly, whereas, with intratumoral administration, it was inhibited more effectively. In immunological studies, natural killer (NK) cell and cytotoxic T-lymphocyte activities of spleen cells were enhanced with intraperitoneal administration of rMuIFN-beta. The analysis of IFN-induced change in a subpopulation of peripheral blood lymphocytes revealed a decrease of Thy.1,2-positive cells and an increase in the ratio of Lyt.1/Lyt.2-positive cells. But these immunological effects of rMuIFN-beta declined on the 7th day with daily administration. Such hyporeactivity may be noteworthy for the clinical application of IFN.

Alpha interferon in the treatment of hematologic malignancies

The interferons are an important first member of a family of biologic response-modifiers used in treating human malignancies. Activities associated with the interferons include inhibition of viral replication, influence on cellular protein production, direct antiproliferative effects, and a variety of modulatory effects on the immune response. These regulatory functions of interferon underlie the interest in its use as an anticancer agent. Alpha interferon is the most extensively studied interferon species. Although antitumor activity has been seen both in vitro and in vivo in some solid malignancies, the most impressive responses have occurred in the hematologic malignancies. More than 90 percent of patients with hairy cell leukemia have a sustained recovery of their peripheral blood cell counts with alpha interferon therapy. Approximately 50 percent of patients with low-grade non-Hodgkin's lymphoma and cutaneous T cell lymphoma demonstrate a response to alpha interferon. More than 80 percent of patients with chronic myelogenous leukemia have a response to alpha interferon, and in one study, nearly half of the patients with response had complete suppression of the Philadelphia chromosome clone on at least one examination. Ongoing clinical trials are addressing such issues as optimal dosage, duration of alpha interferon therapy, and combinations of alpha interferon with other biologic agents, chemotherapy drugs, and radiation.

The myelosuppressive effect of recombinant interferon gamma in short-term and long-term marrow cultures

The effect of a highly purified human gamma IFN (r-gamma-IFN) on the growth of haemopoietic progenitors was examined in soft agar assays and in long-term bone marrow cultures. r-gamma-IFN reduced colony formation by progenitor cells of the granulocyte/macrophage lineage (GM-CFC), the erythroid lineage (BFU-E) and multipotent cells (GEMM-CFC), and suppressed haemopoiesis in long-term culture in a dose-related fashion. At high doses (1000 units/ml) r-gamma-IFN appeared to be toxic to the stromal cells of the bone marrow.

Phase II trial of interferon-beta for treatment of recurrent glioblastoma multiforme

Twelve patients were admitted to a Phase II study on the treatment of recurrent glioblastoma multiforme with interferon-beta (IFN-beta). All patients had previously undergone craniotomy and received a standard course of radiation therapy. Recurrence was inferred from enlargement of the lesion on computerized tomography (CT) scanning and in each case was confirmed by CT-guided stereotaxic biopsy. Treatment consisted of combined intravenous (10 X 10(6) IU/day) and intratumoral (1 X 10(6) IU every other day) administration of IFN-beta over three 10-day cycles. This regimen was well tolerated, with toxicity requiring temporary dose modifications in five patients. As judged from data from historical cases, however, the patients admitted to this study demonstrated no clear improvement in mean survival time. The findings of this study also emphasize the importance of distinguishing between radiation necrosis and tumor recurrence.

In vitro response of cells from three patients with hairy cell leukemia to a recombinant leukocyte interferon

Mononuclear cells from the peripheral blood of two patients and from the spleen of one patient, all of whom had hairy cell leukemia, were cultured with a recombinant human leukocyte interferon (RD alpha 2-IFN). The IFN was added at concentrations of 10, 100, 1,000, and 10,000 IU/ml, and the cells were cultured for 1, 3, and 7 days. A cytocidal effect of IFN was observed only on cultured cells from the spleen at day 7. Electron-microscopic observations demonstrated that RD alpha 2-IFN induced the formation of tubuloreticular structures (TRSs) and annulate lamellae (ALs) in hairy cells, as well as in co-isolated non-leukemic cells, from all three patients. Ultrastructural examination revealed a close proximity between ALs and TRSs in co-isolated non-leukemic cells. A variability with respect to the induction of TRSs in hairy cells was observed among the three patients. In two of the three patients, the percentage of hairy cells with TRSs increased with the duration of incubation and with the dose of IFN. In the third patient, few hairy cells showed TRSs after 7 days of incubation with IFN. Our findings indicate that leukemic hairy cells may be heterogenous in their response to IFN.

Clinical results of leukocyte interferon-induced tumor regression in resistant human metastatic cancer resistant to chemotherapy and/or radiotherapy-pulse therapy schedule

The efficacy of Human 6 IFN (HLIFN) given in a pulse fashion was determined in a phase II study. Ninety-one cancer patients were evaluated (9 myeloma, 12 breast, 14 prostate, 9 melanoma, 4 renal, 6 astrocytoma, 7 ovarian, 9 large bowel, 7 gastric, 14 head and neck). They all had advanced progressive cancer that was resistant to chemotherapy and/or radiotherapy. Patients were treated by intramuscular injection of 6 X 10(2) I.U./m2 for three consecutive days every four weeks. 84 patients were evaluable. Complete clinical response was obtained in 23 patients (4 myeloma, 2 breast, 5 prostate, 1 melanoma, 1 renal, 2 astrocytoma, 2 ovarian, 2 large bowel, 1 gastric, 3 head and neck). Partial responses were observed in 35 patients (3 myeloma, 7 breast, 6 prostate, 4 melanoma, 1 renal, 2 astrocytoma, 3 ovarian, 4 head and neck). Objective responses were related (P less than 0.01) to serum IFN level, with complete and partial responses (P less than 0.01) more commonly seen in those patients whose serum IFN levels at two hours were in the range of 1000 to 1650 I.U./ml. Side effects resulting from pulse IFN were acceptable for this group of patients and consisted of fever, transient chills, malaise and asthenia, and transient thrombocytopenia and leukocytopenia. The extent of fever was directly related (P less than 0.01) to response, and was most elevated in patients who achieved objective responses. IFN administered in a pulse fashion appears to be more effective than daily IFN and merits further evaluation.

Single agent therapy of interferon for brain tumours: correlation between natural killer activity and clinical course

The anti-tumour effect of mouse interferon (IFN) on an intracranially transplanted 203-glioma in C 57BL mice and the natural killer (NK) activity of spleen cells were studied. As a clinical trial, five patients with glioblastomas were treated with human fibroblast IFN and the anti-tumour effect of IFN and the NK activity of peripheral blood lymphocytes were also studied. The NK activity increased after the beginning of IFN therapy but there was no remarkable anti-tumour effect of IFN in both mouse and human studies. There was no marked correlation between the increased NK activity and the anti-tumour effect of IFN in this study.

Clinical effect of interferon in malignant brain tumours

Phase I and phase II clinical studies of interferon (IFN) were conducted in malignant brain tumours (47 cases of glioblastoma, medulloblastoma and others) using three preparations of the drug. The drug was administered daily in doses 3.0 - 9.0 X 10(6) I.U. locally or intravenously (beta-type) or intramuscularly (alpha-type). The administration was continued as many days as possible, eight weeks being the shortest period. The efficacy of the therapy was assessed mainly by the CT findings (computed volume of the tumour). As for efficacy against glioblastomas, the highest effectiveness rate (40%) was obtained with Human Fibroblast IFN (HFIF) (beta-type) (Toray) (one case of complete remission and seven cases of partial remission out of 20 cases) as compared to Human Lymphoblastoid IFN (HLBI) (alpha a-type) (Wellcome) (one case of partial remission out of three cases) and recombinant IFN (rIFN-alpha A) (alpha-type) (Roche) (two cases of partial remission out of nine cases). The high rate of responsiveness of HFIF seems to be largely attributable to the local, rather than systemic, administration of the drug. Our pharmacokinetic study revealed that, by means of intrathecal administration a much higher IFN titre was detected in the cerebrospinal fluid, while by intravenous or intramuscular route, the IFN titre in the CSF was undetectably low. The generally lower incidence of side-effects with HFIF compared to other preparations was also largely ascribable to the route of administration. IFN therapy in combination with radiotherapy and/or chemotherapy should also be investigated.

Immunological and chemotherapeutic prevention and control of oncogenic viruses

Computed tomographic (CT) and surgical findings were correlated retrospectively in 51 patients with preoperative diagnoses of prolactin-secreting pituitary microadenomas. Twenty-four had microadenomas at surgery. Twenty-eight had identifiable discrete lesions. Of these, 18 had microadenomas and 10 did not; these two groups could not be distinguished reliably. Six patients with proven microadenomas had normal CT scans. Focal hypodense lesions, sellar floor erosion, infundibulum displacement, gland height greater than 8 mm, and an abnormal diaphragma sellae configuration are neither sensitive nor specific findings of microadenoma. A significant number of patients with proven microadenomas had few or none of these abnormalities. Thus, recognition of prolactin microadenoma is seldom possible by CT alone, even with high-resolution direct coronal imaging.

Interferons: several questions and few answers

Interferons, which have been studied for many years as antiviral agents, are now receiving considerable attention as antitumor and immunomodulatory agents. The data to date are sufficiently interesting to warrant further studies on several fronts. Clearly, the results that have been obtained so far tend to pose more questions than they answer.

In vitro inhibition of allogeneic CTL generation and interferon gamma production by the cells of a chemically induced fibrosarcoma

We have previously shown that a highly tumorigeneic 3-methylcholanthrene transformed clone (MCA-C3H CL 15) of C3H10T1/2 fibroblasts and a normal nontransformed clone (C3H10 1/2 CL 8) from the same parental stock fail to stimulate the generation of syngeneic cytolytic effector cells. In attempting to further dissect and understand the immune response to these cells, we have extended our studies to examine their ability to stimulate the in vitro generation of allogeneic cytolytic effector cells. This model is unique in that studies of immune responses to tumor cells rarely have or utilize appropriate normal cell counterparts. The normal fibroblasts stimulated both the generation of allogeneic cytolytic T lymphocytes (CTL) and the production of immune interferon (IFN-gamma), whereas the tumor fibroblasts did not. The normal fibroblasts were negative for mycoplasma, indicating that these organisms did not account for the observed IFN-gamma induction. When added as third-party cells to cultures containing allogeneic responders and normal fibroblast stimulators, the tumor fibroblasts inhibited the generation of CTL as well as the production of IFN-gamma. The absence of IFN-gamma was not the result of the tumor fibroblasts absorbing or inactivating IFN-gamma, since culturing the tumor cells in IFN-gamma of predetermined activity did not appreciably alter that activity.

Interferon potentiates cytotoxic effects of 5-fluorouracil on cell proliferation of established human cell lines originating from neoplastic tissues

A potentiation of the cytotoxic effects of 5-fluorouracil (5-FU) on human tumor cells by interferon was examined. The human neoplastic cell lines used were HeLa (uterine cervical cancer), MCF-7 (mammary cancer), WI-38 CT-1 (embryonic lung fibroblasts transformed in culture by Co-60 gamma-ray irradiation), KMM-1 (myeloma) and Raji (Burkitt's lymphoma). The normal human cell strain used was WI-38 (normal human lung fibroblasts). The cytotoxic effects were determined by colony formation for HeLa, MCF-7, WI-38 CT-1 and WI-38 cells, and by cell growth for KMM-1 and Raji cells. Each cell line was different in sensitivity to interferon or 5-FU. Interferon potentiated synergistically the cytotoxic effects of 5-FU on HeLa, WI-38 CT-1 and KMM-1 cells. In the case of Raji cells, the cytotoxic effects of the combination of interferon and 5-FU were additive. Neither synergistic nor additive lethal effects of the combination of the 2 agents were observed in MCF-7 and WI-38 cells. The present results indicate a possibility that interferon and 5-FU can mutally reduce the amount of the other needed to treat cancer patients.

Direct cytolysis by partially-purified preparations of immune interferon

Mouse IFN gamma preparations purified 30-fold were found to have direct cytolytic activity against a number of tumor and normal cells. Cell killing was determined using a sensitive, rapid and accurate assay which employed very low numbers of cells and very small quantities of interferon. The cytolytic activity of IFN gamma on 11 murine tumor cell lines was investigated. A 20-fold difference was found between the most-sensitive cell type, P-388 lymphoma, versus the most resistant cell type, C127v leukemia. A number of normal mouse cells was also found to have low to intermediate sensitivity to the cytolytic action of IFN gamma. Human IFN gamma was also shown to have cytolytic activity which, like mouse IFN gamma, was relatively species-specific. Direct cytolysis was not found to be a characteristic of IFN-alpha/beta. Different mechanisms of action for the antiviral and cytolytic activities of IFN gamma are indicated because the cytolytic titer of IFN gamma did not parallel its antiviral titer on most cell types and increasing the cell number produced a decrease in the cytolytic titer and an increase in the anti-viral titer. High concentrations of IFN gamma (i.e., 2,900 units/ml) resulted in complete lysis of cells within 24 h, while lower concentrations (i.e., 700 units/ml) resulted in a reversible inhibition of cell growth during this time period. Evidence that the cytolytic substance in the IFN gamma preparation was IFN gamma include the following: (1) both antiviral and anticellular activities copurified through a 30-fold purification; and both activities were (2) relatively species-specific; (3) sensitive to heat; (4) inactivated by low pH and (5) neutralized by antibodies to IFN gamma. Therefore, we propose the possibility that direct cytolysis is yet another of IFN gamma's distinctive antivities.

Effect of a simulated weightlessness model on the production of rat interferon

A rat model simulating some aspects of weightlessness was used to determine whether simulated weightlessness might alter interferon production. The optimum time for in-vivo induction of alpha/beta interferon (alpha/beta-IFN) by polyriboinosinic-polyribocytidylic acid was determined to be four hours in normal, mature rats. Rats suspended in the model for two weeks were injected with polyriboinosinic-polyribocytidylic acid and bled four hours later. A dramatic decrease (80%) in alpha/beta-IFN production was observed in those animals exposed to simulated weightlessness as compared to control rats. These data suggest that weightlessness may alter certain immunological functions.

Interferon-mediated inhibition of adenylate cyclase in mouse cells

Adenylate cyclase activity was measured in mouse cell plasma membrane after 30 units/ml of interferon (IFN) treatment. The basal and Gpp(NH)p stimulated enzyme activity in LB cell was inhibited by 20%-40% throughout the time course of treatment (30 min to 18 h). The reduced enzyme activity was not associated with enhanced breakdown of cAMP, but was related to alteration in the catalytic component of the enzyme. Moreover, there was no change in the affinity for guanine-nucleotide regulatory unit and 1 X 10(-7) M Gpp(NH)p was required to obtain half-maximal activation with either type of membrane. Interferon action on adenylate cyclase was biphasic, at 10 u/ml it was stimulatory and between 30 and 1000 u/ml it inhibited the enzyme activity to a great extent; but IFN did not exert its effect directly on the enzyme. The reduction in enzyme activity was comparable to a reduction in the intracellular level of cAMP in most of the interferon-sensitive cell lines studied. We propose, therefore, that the inhibitory effect on adenylate cyclase is related to a step in the development of antiviral activity.

Interferon-inducing activity of an immunotherapeutic anticancer agent, SSM, prepared from Mycobacterium tuberculosis strain Aoyama B

The interferon-inducing capacity of arabinomannan-lipid preparation (SSM) extracted from Mycobacterium tuberculosis Aoyama B in both BCG-sensitized and unsensitized mice was studied in comparison with that of purified protein derivative (PPD) prepared from the same tubercle bacillus. Although it is known that PPD cannot stimulate interferon production in BCG-unsensitized mice, interferon activity was found in sera of both groups of mice after intravenous injection of SSM at a dose of 5 mg/kg. The maximum titer was detected 5 hr after injection. The interferon induced by SSM in both groups of mice shared certain physicochemical properties with the immune interferon induced by PPD in BCG-sensitized mice. In BCG-unsensitized mice, interferon induction by SSM was markedly inhibited by pretreatment with trypan blue and carrageenan, whereas it was not depressed in BCG-sensitized mice given the same treatment or when interferon was induced by PPD. In addition, induction of interferon in BCG-sensitized mice by SSM and PPD and in unsensitized mice by SSM was completely abrogated by pretreatment with hydrocortisone acetate and whole-body x-irradiation (700 R). These results suggest that in BCG-unsensitized mice macrophages, in addition to X-ray or hydrocortisone-sensitive cells, may be required for interferon induction by SSM.

Effect of human leukocyte interferon on the metastatic lung tumor of osteosarcoma: case reports

Three patients with pulmonary metastases of osteosarcoma underwent treatment with intravenous or intramuscular administration of human leukocyte interferon. In 2 cases, the size of the metastasized tumor mass diminished temporarily six or eight months after interferon treatment, and serum alkaline phosphatase levels decreased to normal. In 1 case, the tumor cell from the pleural exudate 1 could be isolated and cultivated in vitro. When 2,000 IU of interferon was added to the tumor cell culture, marked inhibition of tumor cell growth resulted. In the other case, interferon had no effect on the metastasized lung tumor.

Differential effect of interferon on DNA synthesis, 2-deoxyglucose uptake and ornithine decarboxylase activity in 3T3 cells stimulated by polypeptide growth factors and tumor promotors

Quiescent 3T3 cells can be stimulated to enter S by defined factors. When used in combination, three polypeptide hormones (EGF, vasopressin, and insulin), or a tumor promotor and insulin, are very effective in stimulating DNA synthesis. Like serum, the defined factors also stimulate deoxyglucose uptake and induce the synthesis of ornithine decarboxylase during G1. The second stage of deoxyglucose uptake and the induction of ornithine decarboxylase are protein synthesis-dependent events. When added with the growth factors, mouse interferon inhibits the synthesis of DNA and the induction of ornithine decarboxylase but has no effect on the uptake of deoxyglucose. Kinetic experiments comparing the effect of inhibitors of translation or transcription on induction of ornithine decarboxylase with the effect of interferon suggest that interferon may affect the synthesis of enzyme by inhibiting both transcription and translation of message. The findings provide further support for the proposition that interferon exerts a differential effect on mitogen-stimulated events events which are dependent on continuous protein synthesis.

Alterations of a mouse mammary tumor virus glycoprotein with interferon treatment

The effects of exogenous mouse interferon on the MJY-alpha mammary tumor cell line chronically infected with mouse mammary tumor virus (MMTV) were examined. Interferon at concentrations of 25 to 2,000 IU/ml in culture medium did not alter the growth rate or morphology of the cell layers. Electron microscopic examination of interferon-treated cells indicated a decrease in the numbers of A-type and budding B-type particles of MMTV. However, the levels of extracellular MMTV virions in the culture supernatants were not significantly reduced. Profiles of MMTV glycoproteins and nonglycosylated polypeptides obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of virions purified from interferon-treated cultures revealed increases in the relative levels of the 60,000-dalton glycoprotein, gp60.

Studies on Brucella interferon: chromatographic behaviour and purification

Interferon was induced by infecting mice with Brucella suis. Serum containing interferon activity was analyzed by chromatography on Concanavalian A-Sepharose and Phenyl-Sepharose CL-4B columns. Antiviral activity was completely retained by the lectin column indicating that all the interferon molecules are glycosylated. The chromatographic behaviour of Brucella interferon on Phenyl-Sepharose CL-4B shows that, like other interferons, Brucella displays hydrophobic properties. However, the hydrophobicity of the interferon molecule was masked in the crude preparation and was only detectable when purified Brucella interferon was used for chromatography. The antigenic properties of Brucella interferon provided the means for developing an affinity chromatographic method resulting in about 60,000 fold purification. As in the case of viral interferon, treatment of L cells with Brucella interferon induced specific enhanced in vitro phosphorylation of a 67,000 molecular weight protein after incubation of cell extracts with double-stranded RNA and [gamma-32P] ATP.

Effects of tilorone on hemopoietic stem cells and on the development of Friend leukemia

Hematological effects of tilorone, an interferon inducer, on the hematopoietic cell system of normal CBA/Ca mice and on the development of Friend virus (FV-P)-induced polycythemia in DBA/2 mice were studied. In normal mice 80 mg/kg IP had a marked depressive effect on pluripotent (CFU-s), granuloid committed (CFU-C), and erythroid committed (CFU-E) stem cells with regeneration between days 5 and 12. In bone marrow smears only lymphopenia was detected. Treatment of mice before FV-P infection caused a slight retardation in the development of the splenomegaly and the transformation of bone marrow cells to Ep independence. Repeated treatment after FV-P infection also reduced the increase in spleen weight and the development of reticulocytosis, but the Ep independence of bone marrow and spleen cells was not influenced. In vitro exposure of normal cells and cells from FV-P-infected animals to the drug showed the same sensitivity of colony growth in normal as well as in Ep-independent CFU-E. The action of the drug on Friend leukemia is at least in part considered a toxic effect on the hematopoietic stem cell system.