Effects of long-term treatment of human carcinoma cells with interferon alpha

Host humoral and cellular immune mechanisms in the continued suppression of Friend erythroleukemia metastases after interferon alpha/beta treatment in mice

DBA/2 mice were injected intravenously with 2 x 10(6) 3C18 Friend erythroleukemia cells (FLC), a cell line resistant to interferon alpha/beta (IFN-alpha/beta). Although daily administration of mouse IFN-alpha/beta markedly increased the mean survival time, most IFN-treated mice continued to harbor FLC in different organs. To investigate the mechanisms responsible for this persistent suppression of FLC growth in IFN-treated mice, we undertook a series of adoptive transfer experiments with sera and spleen cells. Sera from FLC-injected, IFN-treated mice were very effective in conferring protection on DBA/2 mice even when injected systemically (intravenously) 18-24 h before intravenous challenge with FLC. These sera also exhibited antitumor activity when injected subcutaneously or intraperitoneally together with FLC. The protective factor in serum was shown to be an immunoglobulin. FLC-injected, IFN-treated mice developed antibodies to FLC demonstrable by radioimmunoassay and complement-dependent cytotoxicity. Sera from these mice recognized a specific 65-kD FLC membrane antigen(s) not detectable on membrane extracts from RBL-5 or ESb tumor cells, or on normal spleen cells. FLC-injected, IFN-treated mice also developed a specific cellular response demonstrable by transfer of protection with spleen cells injected intravenously or subcutaneously. Analysis of the responsible spleen cell populations indicated that the effector cells were neither T nor B cells. These results demonstrating the importance of host humoral and cellular immune mechanisms in the persistent suppression of FLC in IFN-treated mice may be relevant to the use of IFN-alpha/beta in patients in whom tumors may regress and tumor cells may then remain latent for extended periods of time.

Interferon alpha-2a and 5-fluorouracil for advanced colorectal carcinoma. Assessment of activity and toxicity

Preclinical data showed that the cytotoxic effects of 5-fluorouracil (5-FU) are augmented by interferon (IFN). In a small study, 13 of 17 patients with advanced colorectal cancer responded to a regimen of 5-FU with IFN. Using the same dose and schedule as in this pilot study, 38 previously untreated patients with metastatic colorectal carcinoma were treated with continuous intravenous (IV) infusion of 5-FU 750 mg/m2 daily for 5 days, followed by weekly bolus 5-FU at 750 mg/m2 and subcutaneous IFN at 9 million units three times per week. Of 35 evaluable patients, nine (26%) had a partial response (95% confidence limit, 11% to 41%), with a median response duration of 7.5 months (range, 4.4 to greater than 11.7 months). Seven patients (20%) had a minor response, and ten (28%) had stable disease. The most common toxicities observed were stomatitis (52%) and diarrhea (43%). Neurotoxicity was seen in 34% of patients and consisted of gait disturbance, dizziness, confusion, memory loss, and dementia. Because of toxicity, 84% of patients required a reduction of the IFN dose by at least 50%, and 63% required reduction of the 5-FU dose by at least 25%. Although the combination of 5-FU and IFN in patients with advanced colorectal carcinoma has some activity, the regimen was toxic, and the observed response rate (26%) was not substantially superior to alternative 5-FU programs.

Future developments in interferon therapy

The antitumour effects of interferons in animals and humans are well known. Despite the fact, however, that the 3 types of human interferon, leukocyte alpha-interferon, fibroblast beta-interferon and immune gamma-interferon are available in large amounts through recombinant DNA technology, the practical applicability of interferon therapy in cancer is still not clear. An initial approach to this problem is to determine the mechanism of action of interferons and to find out why, in certain circumstances, they are inactive. There are various ways in which interferon may control tumours--i.e. antiviral action, inhibition of cell growth, stimulation of cell differentiation, changes in cells modulating the susceptibility to immune rejection, or effects on the host immune systems (natural killer system and cytotoxic proteins). The implications of these data in the use of interferon in cancer therapy need to be evaluated. Both alpha- and beta-interferons may have beneficial effects on growth inhibition and differentiation, but gamma-interferon is probably more effective in boosting the immune recognition and rejection of tumour cells. A combination of alpha- and gamma-interferon may give the best results in vivo, since they often act synergistically in vitro. The sensitivity of individual tumour cells to the various types of interferon needs to be evaluated by measurement of oncogenes mRNA inhibition, G0/G1 arrest and increase in various H-La antigens. Finally, the aim of any treatment (antiviral action, tumour regression, prevention of metastasis, decreased tumour growth and increased cell differentiation) should be an important consideration in whether interferon therapy is chosen. A major problem remains in understanding why only a small proportion of patients usually show an objective response to interferon.(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-induced phenotypic changes in human tumor cells relative to the effects of interferon on c-ras oncogene expression

Three human tumor cell lines derived from an osteosarcoma (OHA cells), a bladder carcinoma (EJ cells), and a gastric sarcoma (SHAC cells) were passaged serially in the presence of human interferon-alpha (IFN-alpha) for extended periods of time. The long-term IFN-alpha treatment induced a partial reversion of OHA tumor cell phenotype as exemplified by inhibition of cell proliferation, lack of cellular overlapping in confluent cultures and marked reduction in tumorigenicity. In contrast, under the same conditions, long-term IFN treatment did not reverse but even potentiated some of the phenotypic characteristics (including tumorigenicity) of EJ and SHAC cells. In the three tumor cell lines, the transforming ability, genomic level, or expression of activated oncogenes, c-Ki-ras, c-Ha-ras, and N-ras, respectively, were unaltered with long-term IFN-alpha treatment. Our data indicate that IFN-induced phenotypic changes are not necessarily associated with changes in oncogene expression.