Antitumor effects of interferon

Radioprotective activity of interferon inducers

The radioprotective activity of interferon inducers (tilorone, Acranil, poly I:C and LPS) was investigated against acute X-ray irradiation and prolonged 60Co-gamma rays irradiation. The endogenous spleen colony formation test and percentage of surviving mice 30 days after irradiation were used as indicators. All interferon inducers investigated proved to have radioprotective activity.

Interferon production in leukaemia

Leucocyte interferon production in vitro and circulating interferon levels were studied in healthy subjects and in 80 patients with acute or chronic leukaemia. Circulating interferon was not found in either group. Interferon synthesis in response to a virus was normal in patients with acute leukaemia and appeared to be enhanced in some. In chronic leukaemia reduced levels were common particularly in CLL, in which condition normal results were rarely found; lymphocyte transformation to PHA was also depressed in this group. No clinical or haematological correlation with the interferon levels was found and no consistent effect of treatment was shown. The possible factors which could account for these findings and their significance in relation to pathogenesis and treatment of leukaemia are discussed.

Chemical modifications of tyrosyl residue(s) and action of human-fibroblast interferon

Partially purified and purified human fibroblastoid interferon were iodinated and nitrated under experimental conditions in which the most likely amino acyl residue modified was tyrosine(s). The modification resulted in a loss of human interferon activity suggesting that tyrosyl residue(s) is associated with the antiviral action of human interferon.

Heterocomplexes of human interferon and immunoglobulins: formation and properties

To form heterocomplexes, human diploid fibroblast interferon was reacted with an excess of human immunoglobulin in the presence of an optimal concentration of glutaraldehyde. There was virtually no loss of interferon activity due to this treatment and the resulting heterocomplexes possessed the biological properties of both native interferon and immunoglobulin molecules. The apparent molecular weights determined by gel electrophoresis in the presence of sodium dodecyl sulfate were 20,000 for native interferon and 0.5 to 1 X 10(6) for the heterocomplex. Native interferon injected into mice intramuscularly had a serum half life of about 5 hours. However, serum interferon was not detected in mice receiving a similar dose of the heterocomplex.

Interferon therapy for neoplastic diseases in man in vitro and in vivo studies

With the object of examining the anti-tumour effect of exogenous interferon therapy in man a research programme has been initiated at the Karolinska Hospital. Established cell lines obtained from patients with Burkitt's and other types of lymphoma, leukaemia, osteosarcoma, mammary carcinoma and fibrosarcoma and from fibroblast cultures displayed a variable sensitivity to the cell multiplication inhibitory activity of interferon. All the monolayer cultures tested were found to be sensitive to interferon at concentrations between 10 and 300 units/ml. Some lymphoma cell lines were not sensitive to interferon even at concentrations as high as 10.000 units/ml, while others were sensitive at concentrations between 2 and 300 units/ml. The interferons tested appeared to show a degree of tissue specificity. Controlled studies in vivo are being performed on osteosarcoma, juvenile papilloma of the larynx, multiple myeloma and small-cell carcinoma of the lung. The clinical results of this research obtained to date, together with the results obtained in model experiments, would appear to warrant accelerated production of human interferon.

Effect of human leucocyte interferon on DNA synthesis in human psoriatic skin cultured in diffusion chambers

Pieces of human psoriatic skin were cultured for five days in diffusion chambers implanted intraperitoneally in mice. Partially purified human leucocyte interferon was injected into the experimental animals daily during the culture period. Phosphate buffered saline and, in one experiment, also mock interferon were used as control materials. On the fifth day, incorporation of 3H-thymidine into the epidermal cells was studied autoradiographically. The results showed that human leucocyte interferon does not depress DNA synthesis in human psoriatic epidermal cells cultured by this method. In fact, DNA synthesis seemed to be stimulated in two of the three experiments but the effect was not statistically significant.

Enchancement of leukemogenesis in mice after prolonged administration of anti-interferon or normal rabbit globulin

The prolonged adminstration of rabbit anti-mouse L cell interferon globulin had a marked potentiating effect on Rauscher Murine Leukemia Virus (MuLV-R) infection in BALB/c mice, as shown by spleen size. Normal rabbit globulin had a lesser, but still significant, augmenting effect on splenic enlargement. It was possible to discriminate quantitatively between the non-specific enhancement of splenomegaly in MuLV-R infected mice due to antigenic stimulation with normal rabbit globulin and the effects due to elimination of endogenous interferon by specific antibodies. The difference in the spleen-enlarging activity between the anti-interferon IgG and normal rabbit IgG was found to be maximal 3-4 weeks after infection when potent, diluted anti-interferon IgG (58 microgram protein per dose) was used. It would appear that the endogenous interferon, even prodcued in undetectable amounts, plays an essential role in controlling infection with an oncogenic virus.

Interferon and murine leukemia. VII. Therapeutic effect of interferon preparations after diagnosis of lymphoma in AKR mice

Daily administration of potent mouse interferon preparations, begun after clinical diagnosis of lymphoma in AKR mice, increased average survival by approximately 100%. Interferon treatment delayed the evolution of the lymphoma but regression of tumour was not observed. The therapeutic effects observed with interferon in AKR mice compare favorably with reported results obtained using standard anti-cancer drugs.

Growth inhibition of human lymphoblastoid Daudi cells in vitro by interferon preparations

Human interferon (HIF) preparations inhibited the propagation of Daudi cells in stationary suspension cultures, while a control preparation showed no such effect. The growth inhibition (= anticellular) activity of differently pretreated HIF preparations was determined by the reduction of 14C-labelled thymidine (14C-TDR) uptake in a microassay system. These studies demonstrated that the degree of anticellular activity is directly proportional to the antiviral activity of different HIF preparations. These preparations were obtained from peripheral leukocytes (lHIF) or diploid fibroblasts (fHIF). Together with gel chromatography results, and the sensitivity of the anticellular activity to tryptic digestion and heat inactivation, these results suggest that the anticellularly active substance is a protein which is very similar to, or identical with, interferon.

Studies on the role of the host immune response in recovery from Friend virus leukemia. I. Antiviral and antileukemia cell antibodies

The humoral immune response to Friend virus leukemia was studied in congenic F1 mice differing in their incidence of recovery from leukemia. Antiviral neutralizing antibodies rose in titer in vivo concurrently with disappearance of viremia and fall in spleen virus levels. Cytotoxic antileukemia cell antibodies also appeared at this time. Passive transfer of these antibodies could inactivate low numbers of leukemia cells in vivo; however, mice of both high and low recovery genotypes produced antibodies in equal titer and recovered from viral infection in spite of striking differences in recovery from leukemic splenomegaly. Mice lacking C57BL genes did not produce antibodies or recover from viremia except in rare instances. Recovery from splenomegaly was found to be influenced by three or more C57BL genes independent of the H-2 complex.

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.

Influence of exogenous interferon on the peripheral white blood cell count in mice

The effect of interferon (IF) injected intraperitoneally on the peripheral white blood-cell (WBC) count in mice was studied. Mouse serum or brain IF produced in vivo in different mouse strains by injecting various viral inducers depressed the lymphocyte count from 3 to 24 h after the injection. The effect was correlated to the antiviral titer of the preparations. The inhibitory factor exhibited physico-chemical properties of IF. Crude IF preparations obtained from mouse cell cultures, human IF and mock preparations devoid of anti-viral activity exerted no lymphocytopenic effect.

"Early" virus-specific RNA may contain information necessary for chromosome replication and mitosis induced by Simian Virus 40

Simian Virus 40 (SV40) induces in "contact-inhibited" tissue culture cells of mouse kidney an abortive infection that leads to the appearance of intra-nuclear SV40-specific tumor (T-) antigen, followed by replication of the mouse-cell chromatin and mitosis, while no viral progeny DNA or capsid protein is produced. Synthesis of "early" SV40-specific RNA ("19S RNA") begins a few hours before the appearance of T-antigen and appears to be switched off after the onset of chromatin replication. As the most simple working hypothesis that can account for the experimental results available, we assume that early SV40 RNA contains information necessary for production of T-antigen and that this antigen (or an unknown early virus-specific function that would simply parallel the appearance of T-antigen) activates or de-inhibits a cellular regulatory element that governs chromosome replication and mitosis. The experimental results agree with the idea that SV40 acts primarily as a mitogen.