Combination therapy with interleukin-2 and alpha-interferon for the treatment of patients with advanced cancer

Hormonal and immunological regulation of 2', 5'-oligoadenylate synthetase activity in human peripheral blood mononuclear cells

A newly developed method for assaying 2', 5'-oligoadenylate (2, 5A) synthetase activity by polyacrylamide gel electrophoresis was applied to peripheral blood mononuclear cells (PBMC) from normal subjects, HIV-positive subjects, and renal cell carcinoma (RCC) patients. Sex differences were observed in 2, 5A synthetase activity of PBMC from normal young adults, males having eightfold higher activities of this enzyme than females. Moreover, compared to values for postmenopausal (PM) females receiving estrogen replacement, untreated PM females had higher activities. Collectively, these results suggest that estrogen downregulates 2, 5A synthetase activity. Activities of 2, 5A synthetase were investigated in two disease states associated with altered immune function. In one patient with AIDS-related Kaposi's sarcoma, interferon-alpha (IFN-alpha) therapy increased 2, 5A synthetase activity twofold. In addition, combined therapy with interleukin-2 (IL-2) and IFN-alpha increased 2, 5A synthetase activities in eight of nine patients with RCC. Therefore, in patients receiving immunotherapy with IL-2 and IFN-alpha, our new assay could contribute to evaluation of immune stimulation. In general, studies in vitro confirmed these observations; however, exposure of PBMC from RCC patients revealed that in vitro IL-2 failed to induce this enzyme activity as it did in PBMC from normal volunteers.

Interleukin 2 and interferon alpha modulation of the lymphocyte non-major histocompatibility-restricted lytic activity in glioblastoma patients

We studied the non-major histocompatibility-restricted cytotoxic activity induced by interleukin 2 (IL-2) and interferon alpha (IFN-alpha) in mononuclear cells of peripheral blood (PBMNC) from glioblastoma patients. We observed a depressed cytotoxic activity against natural killer (NK)-sensitive target cells in PBMNC from all the patients studied. Culture of these PBMNC with IFN-alpha for 5 days augmented the cytotoxic activity against NK-sensitive target cells in a small group of patients. Incubation with IL-2 for 5 days normalizes the decreased cytotoxic activity against NK-sensitive target cells of PBMNC from all the glioblastoma patients studied. When PBMNC from these patients were incubated with IL-2 for 5 days and IFN-alpha was added to the culture medium in the last 2 h of culture, an enhancement of non-major histocompatibility-restricted cytotoxic activity was observed compared with that obtained with either IL-2 or IFN-alpha alone. This improvement of the cytotoxic activity was more relevant when it was tested against NK-resistant target cells. The potential utility of the sequential use of the two cytokines in generating non-major histocompatibility cytotoxic activity in glioblastoma patients is discussed.

Systemic therapy in disseminated melanoma

There is no standard treatment for advanced melanoma. As long as metastases are satellites or in-transit metastases localized in a leg or arm, the prospects for curative treatment by isolation perfusion are good. But as soon as metastases have spread via the circulation, curative treatment with cytotoxic agents becomes virtually impossible. When the tumor burden is not too extensive, however, palliative treatment can be of clinical value. Some combinations of cytotoxic agents or combinations of biologic response modifiers have been shown to induce worthwhile remissions. Toxicity remains a problem, however. The advantages of the newer immunological approaches, especially with interleukin-2 (IL-2) and T-cell lymphocytes, is that treatment for a short period may result in good remissions at an early stage. Much clinical research is still needed to improve these costly approaches.

Cytokines in tumour therapy

Cytokines are low molecular weight proteins released by cells of the immune system that have therapeutic potential in cancer. They include the interleukins, the interferons, tumour necrosis factor and the colony-stimulating factors. Cytokines are capable of producing significant and sustained responses against a number of tumours. Clinically, the highest response rates to cytokine immunotherapy have been seen in melanoma and renal cell cancer. Current efforts aim to reduce treatment-related toxicity while maintaining the efficacy of cytokines. The therapeutic potential of these agents may be increased with genetic manipulation by introducing genes encoding cytokines into tumour-infiltrating lymphocytes and certain tumour cells. However, immunotherapy remains time consuming and expensive, and further developments are necessary before it can have a definitive role in tumour management.

Adoptive immunotherapy of cancer: biological response modifiers and cytotoxic cell therapy

Immunotherapy has been developed for the treatment of metastatic cancers refractory to conventional therapies. Immunotherapy utilizes immune cells and/or biological response modifiers (BRMs) to induce an anti-tumor response mediated by the patient's immune system. BRMs, including lymphokines and cytokines, are used as single agents or in combination for cancer therapy. Some BRMs, particularly interleukin 2 (IL-2), can activate and expand in vitro lymphocytes with anti-tumor reactivity which will be adoptively transferred to the patient. To enhance the therapeutic effect of immunotherapy, gene therapy is currently under investigation and involves the insertion of cytokine genes in immune cells or in tumor cells. The development and future of cancer immunotherapy will be discussed in this review.

Evaluation of basic procedures for adoptive immunotherapy for gastric cancer

Peripheral blood lymphocytes (PBL) of gastric cancer patients in advanced stages showed lymphokine activated killer (LAK) activities comparable to those of healthy donors, suggesting potential applicability of LAK cells induced from PBL stimulated with recombinant interleukin-2 (rIL-2) in adoptive immunotherapy (AIT) for gastric cancer. In order to generate a large number of LAK cells from PBL, lymphocytes were cultured with both rIL-2 and phytohemagglutinin (PHA). In this culture, the numbers of cells increased to a greater extent than those in culture with rIL-2 alone but cytotoxic activity did not augment, thus suggesting that this procedure would not afford sufficient clinical effects. On the other hand, a large number of LAK cells with high anti-tumor activities were efficiently induced from spleen cells of the patients by culture of rIL-2; hence clinical usefulness of these LAK cells is anticipated. In regional lymph node lymphocytes (RLNL) cultured with rIL-2, the cytotoxic activities were lower than in those induced in PBL, and a characteristic increase of CD8 + CD11 + suppressor T cells was observed after incubation with rIL-2. Nevertheless, an increase of CD4 + 4B4 + helper inducer T cells was also observed in RLNL after the culture with rIL-2. Furthermore, high cytotoxic activities were induced in RLNL in some cases in which metastasis to the regional lymph nodes was not detected. When gastric cancer patients were pretreated with biological response modifiers (BRM), especially with Lentinan, LAK cells from PBL showed higher NK and LAK activities as compared with those of patients without BRM pretreatment.

A phase II study of interleukin-2 and interferon-alpha in head and neck cancer

The capacity to modulate host response against metastatic head and neck cancer may eventually lead to improved survival. This phase II study in patients with advanced head and neck cancer evaluated the efficacy of combination systemic recombinant interleukin-2 (IL-2) and interferon-alpha (INF-a) and evaluated laboratory correlates between tumor response and a) tumor differentiation and b) NK cell activation. Five of fourteen patients responded; two had partial responses and three had transient responses (one complete and two partial, each lasting less than four weeks). Patients that responded had relatively lesser tumor burden and poorly-differentiated metastases. No response was observed in those few individuals in whom natural immune function was only minimally enhanced by therapy. Major toxicity, including but not limited to fever, fatigue and pulmonary compromise, allowed only 3 of 14 patients to complete three cycles of therapy. This preliminary phase II study shows that combination IL-2/INF-a therapy has clinical anti-tumor activity and that the level of NK cell activation and the degree of tumor differentiation may correlate with response.

Heteroconjugated antibodies enhance lymphocyte-mediated tumour cell lysis in vitro and in vivo

Covalent linkage of an antitumour antibody specific for a tumour cell surface antigen to an antilymphocyte antibody specific for the T lymphocyte receptor complex produces a heteroconjugated antibody that can activate and redirect cytotoxic T lymphocytes to lyse tumour cells. The ability of an antilymphocyte-antitumour heteroconjugate (500A2 x 96.5) to direct the lysis of murine melanoma cells by cultured murine lymphocytes was tested in vitro using a 4-h chromium release assay and in vivo with a tumour neutralization assay. In vitro, the addition of heteroconjugated antibody significantly increased tumour lysis by murine C3H/HeN lymphocytes (median specific lysis 82.7 per cent with lymphocytes plus heteroconjugate versus 9.5 per cent for lymphocytes alone, P less than 0.001). In vivo, treatment with heteroconjugated antibody plus lymphocytes significantly reduced the development of pulmonary metastases after intravenous tumour administration (median number of pulmonary metastases 28.5 for combined treatment versus 250 for heteroconjugate or lymphocytes alone, P less than 0.001).

An outpatient phase I study of a subcutaneous interleukin-2 and intramuscular alpha-2a-interferon combination in advanced malignancies

The aim of this phase I study was to exploit the potential efficacy of an alpha-2a-interferon (alpha-2a-IFN)-subcutaneous interleukin-2 (IL-2) combination, bypassing the toxicity usually associated with bolus or continuous infusion of IL-2. Therefore, nineteen patients with metastatic malignancies (7 melanomas, 6 renal cell carcinomas and 6 soft tissue sarcomas) were treated according to a dose escalating schedule of subcutaneous IL-2 combined with intramuscular alpha-2a-IFN for 5 days/week for 3 consecutive weeks. Cycles were repeated every 2-4 weeks unless disease progressed. Alpha-2a-IFN (3 MU/die) was given continuously, including during the rest weeks. IL-2 doses were started at 2 MIU/day/sqm and the MTD of 6 MIU/day/sqm was progressively reached. The dose of IL-2 was given twice daily every 12 hours. Both of the cytokines were administered in an outpatient setting. The main side effects were fever, chills, fatigue, hypotension, nausea and vomiting. Toxicity was correlated with IL-2 dose level. It was found to be mild at 2 and 4 MIU/day/sqm, while, in contrast, grade III toxicity was observed only at the highest dose of 6 MIU/day/sqm. However, this grade III toxicity was manageable and did not prevent continuation of the treatment as long as the dose was not increased above 6 MIU/day/sqm. Three patients, one with melanoma and two with renal cell carcinomas, obtained clinical partial responses. In eight patients, stable disease, and in the remaining eight, progression, were observed. The data suggest that the combined use of the two BRMs has manageable side effects and would seem to be efficacious. A phase II study at the recommended dose of 6 MIU/day is now necessary.

Surgical resection of metastatic renal cell carcinoma and melanoma after response to interleukin-2-based immunotherapy

Thirty-one patients with disseminated melanoma or renal cell cancer (RCC) who had a limited relapse or persistent disease after a partial or complete response to interleukin-2 (IL-2)-based immunotherapy underwent resection of progressing tumors or residual sites of disease. There were no surgery-related deaths. The median time to disease progression after resection for patients with RCC (n = 16) and melanoma (n = 15) was 11 and 5 months, respectively. All patients with melanoma had tumor progression within 10 months of surgery. Seven of 16 patients with RCC were free of tumor progression 4 to 44 months after surgery. Three of 12 patients with RCC rendered disease-free by surgery remain disease-free after 2 years. These data suggest that surgical resection is a reasonable option in selected patients who have a relapse after responding to IL-2-based immunotherapy. Although this retrospective study could not determine the relative survival benefits of surgery and immunotherapy, it showed that resection of metastatic disease after a response to immunotherapy can result in significant disease-free survival in patients with RCC but not melanoma.

Interleukin-2 by inhalation: local therapy for metastatic renal cell carcinoma

We report the use of inhaled natural interleukin-2 in patients with metastatic disease. Six patients with metastatic renal cell carcinoma received 100,000 units natural interleukin-2, 5 times per day by inhalation in addition to a 4-day cycle of intravenous natural interleukin-2 every 2 weeks and subcutaneous interferon 5 days per week. Response was clearly correlated with metastatic site. Distinct tumor burden and the poor condition of the patient did not impair success. Pulmonary metastases responded in 5 of 5 patients. Metastases in the mediastinum, liver, abdomen and pelvis were stabilized in 4 patients. No response was noted in 3 solitary bone metastases, which were successfully removed surgically after several months of therapy, and a pleural metastasis progressed despite a clear response of the pulmonary disease in the same patient. New metastases did not develop in any of the patients during treatment (median followup 183 days of treatment, range 97 to 296 days). The over-all importance of the low toxicity of this novel route of administration (World Health Organization classification not exceeding grade 1) making long-term outpatient treatment possible must be emphasized because limitations of systemic interleukin-2 application are mainly caused by pulmonary side effects, for example pulmonary capillary leakage syndrome and edema. However, this new type of topical natural interleukin-2 application and combination with low dose intravenous interleukin-2 achieved considerable antitumor responses.

A phase II study of high dose tamoxifen in progressive, metastatic renal cell carcinoma

Thirty-four patients with progressive advanced renal cell carcinoma (RCC) were treated with high-dose tamoxifen (HD-TAM) 100 mg/m2 p.o. daily until progression. The overall remission rate was 12%, including 1 complete remission. Seventeen of the thirty-four (50%) patients had minor remission or no change. Taking into consideration the documented progression prior to tamoxifen therapy, further tumour growth could be arrested in 62% (1 CR, 3 PR, 17 MR/NC) of the patients. Median response duration for CR/PR was 20 months (range 6-21+) and median progression-free survival for MR/NC was 6 months (range 2-15). The one-year survival rate was 41%. Patients with only pulmonary metastases, good performance status and prior nephrectomy seemed to have a better survival. Side effects were comparable to those of conventional doses of tamoxifen (20-30 mg p.o. daily). These data suggest that HD-TAM may be a useful therapeutic approach with low toxicity, considering that, in metastatic RCC, the treatment intent is at best palliative.

Chemo-adoptive immunotherapy of nude mice implanted with human colorectal carcinoma and melanoma cell lines

The antitumor effects of chemotherapy, recombinant human interleukin-2 (IL-2), recombinant human interferon alpha A/D (IFN alpha), allogeneic human lymphokine-activated killer (LAK) cells, and antitumor monoclonal antibody (mAb), administered alone and in various combinations, were tested in athymic nude mice carrying human tumor xenografts. Treatment began 6-18 days after i.v. or i.p. inoculation of colorectal carcinoma or melanoma cell lines, when macroscopic growths were evident. Chemotherapy consisted of two or three courses of 5-fluorouracil (5-FU) or dacarbazine. IL-2 and/or IFN alpha were administered three to five times weekly for 1-3 weeks, usually starting 2-5 days after chemotherapy. Human LAK cells were infused once or twice weekly for 2 or 3 weeks concurrently with IL-2. In some experiments, murine anticolorectal carcinoma mAb (SF25) was administered. In both tumor systems, chemotherapy alone or immunotherapy alone (IL-2, IL-2 + LAK cells, IFN alpha, IL-2 + IFN alpha +/- LAK cells) had little or no therapeutic effects. Additive effects were obtained by combining chemotherapy with IL-2 and LAK cells or with IL-2 and IFN alpha. In the majority of the experiments, the most effective combination was chemotherapy + IL-2 + IFN alpha + LAK cells. Treatment with mAb was beneficial in the colorectal carcinoma system when combined with 5-FU + IL-2 or 5-FU + IL-2 + IFN alpha. Homing experiments with radiolabeled human and mouse LAK cells injected i.v. showed increased early accumulation in the liver and lungs, whereas freshly explanted mouse splenocytes localized mostly in the spleen and liver. The tissue distribution pattern of human LAK cells was similar in normal and tumor-bearing mice (with lung metastases). These findings suggest that combination of chemotherapy with cytokines and LAK cells can be partially effective for advanced solid human tumors even in the absence of the host's T-cell immune response. Preliminary experiments showed that tumor-specific, anti-melanoma T-cell clones were effective in local (s.c.) tumor growth inhibition (Winn assay) following coinjection with the autologous tumor cells.

Clinical applications of interleukin-2

Interleukin-2 (IL-2) is a cytokine with potent immunomodulating properties which has shown considerable antitumour activity in preclinical models. In clinical trials, the effects of IL-2 given by various routes and schedules have been investigated. IL-2 has been administered either as single drug or in combination with other cytokines and immunomodulating agents, chemo therapeutic agents, or reinfusions of ex vivo activated autologous cytotoxic effector cells. The results of published clinical studies with IL-2 based immunotherapy are reviewed in this paper.

Current status of interleukin-2 therapy in cancer

In vitro studies and animal experiments showed the existence of a physiological immune response against tumors. Interleukin-2 was the first immunological agent which demonstrated an anti-tumor effect by activating immune effectors. In vitro IL2 may generate Lymphokine Activated Killer (LAK) cells from peripheral blood lymphocytes or Tumor Infiltrating Lymphocytes (TIL) expanded from tumor. In melanoma and renal cell carcinoma, IL2 alone or associated with LAK cells or TIL, mediated clinical responses. However, their clinical efficacy was associated with some toxicity related to a capillary leak syndrome. This implies an improvement in the selection of patients and in the understanding of IL2 action. Future directions in immunotherapy included combination IL2 with other cytokines or monoclonal antibodies or chemotherapy. Lymphokine gene therapy is designed to introduce IL2 or other cytokine genes into tumor infiltrating lymphocytes or directly into tumors to reduce systemic toxicity and to achieve high local cytokine concentration. Animal models and the first human trials make this approach promising.

Immunotherapy with interleukin-2 and alpha-interferon in patients with metastatic renal cell cancer with in situ primary cancers: a pilot study

A total of 12 patients with stage 4 renal cell carcinoma and primary renal tumors in situ was entered into a pilot study using treatment with interleukin-2 and alpha-interferon followed by radical nephrectomy. Of the patients 11 underwent nephrectomy after an initial course of immunotherapy. Ten patients were able to receive a second course of immunotherapy given after nephrectomy. One patient achieved a complete response of lung and mediastinal metastases without any change in the primary renal tumor but after nephrectomy the patient remained in complete remission for greater than 11 months. A total of 3 patients achieved a partial response at some extrarenal sites but they had progression elsewhere. Toxicity was similar to previous experience with this immunotherapy regimen. Therefore, we demonstrated that metastatic tumor regression is possible with primary renal tumors in situ and that aggressive interleukin-2-based immunotherapy can be tolerated in the presence of a large renal tumor.

Immunological evaluation of patients with hematological malignancies receiving ambulatory cytokine-mediated immunotherapy with recombinant human interferon-alpha 2a and interleukin-2

Immunological parameters were evaluated in patients treated with cytokine-mediated immunotherapy (CMI) consisting of low doses of recombinant human interferon alpha 2a (rIFN alpha) and recombinant human interleukin-2 (rIL-2) administered either concomitantly or sequentially by subcutaneous self-injections in an outpatient setting. Twenty-six patients with hematological malignancies and 2 metastatic melanoma patients in a progressive stage were enrolled in this clinical trial. Of the 26 patients, 24 were at a stage of minimal residual disease, including 14 patients who had received autologous bone marrow transplantation (ABMT) 2-5 months previously, 7 chronic myelogenous leukemia (CML) and 3 acute myeloid leukemia (AML) patients. Two patients (1 CML and 1 mult. myeloma) were treated at a stage of progressive disease. Non-MHC-restricted cytotoxicity directed against natural-killer(NK)-resistant (Daudi) and NK-sensitive (K562) target cells was assessed before, during and after CMI, either in fresh peripheral blood samples (spontaneous activity) or after in vitro rIL-2 activation (induced activity). Spontaneous killing activity was low prior to treatment, but increased upon termination of treatment in 10/15 evaluated cycels. rIL-2-activated cytotoxicity in vitro was markedly elevated in 8/12 and 6/8 patients after one and two cycles, respectively, of sequential treatment, as well as in 3/8 CML and 5/6 patients after one and two cycles, respectively, of concomitant treatment. Activation of the T cell mitogenic response was demonstrated in 6/9 patients after concomitant CMI, while no such effect was observed throughout a sequential treatment in lymphoma and leukemia patients after ABMT. Although a direct correlation between immune stimulation and the in vivo antitumor response cannot yet be determined, our clinical observations support a beneficial therapeutic effect in a substantial number of patients. These results indicated that the ambulatory CMI protocol of rIL-2 and rIFN alpha could stimulate the host defense immune system and may be helpful in mediating the in vivo antitumor response in patients with minimal residual disease.

Chemo-immunotherapy of murine solid tumors: enhanced therapeutic effects by interleukin-2 combined with interferon alpha and the role of specific T cells

The aim of the present study has been to assess the therapeutic efficacy of various cytokines, singly or in combination, with and without chemotherapy (cyclophosphamide, Cy), in mice carrying advanced, weakly immunogenic tumors (MCA-105 sarcoma, M109 carcinoma). Treatment of animals with i.p. growths or experimental pulmonary metastases began 8-18 days after i.p. or i.v. tumor cell inoculation respectively. None of the cytokines tested [interleukin-2 (IL-2), interferon alpha (IFN alpha), tumor necrosis factor alpha (TNF alpha) and macrophage-colony-stimulating factor (M-CSF)] nor Cy had by itself a significant curative effect. A synergistic therapeutic effect was obtained with IL-2 or IFN alpha (but not with TNF alpha or M-CSF) in combination with Cy. The most efficacious regimen (65%-90% cure of mice carrying i.p. tumors) was the combination of Cy+IL-2+IFN alpha. Preliminary experiments suggested that sequential administration of these cytokines might be more beneficial than concurrent administration. Following successful immunotherapy, long-term (3-6 months) survivors showed a tumor-specific resistance to a second tumor challenge and their spleen contained an increased number of specific antitumor cytotoxic T lymphocyte precursors (5- to 20-fold, compared to control mice). In vitro and in vivo cell-depletion experiments using monoclonal antibodies revealed that T cells (primarily CD8), but not NK cells, are crucial for the therapeutic effects. This study indicates that a potent specific antitumor T cell immunity can be elicited against advanced weakly immunogenic tumors by combining chemotherapy (Cy) with IL-2 and IFN alpha.

The out-patient use of recombinant human interleukin-2 and interferon alfa-2b in advanced malignancies

We studied the safety, tolerance, and clinical effects of the combined administration of subcutaneous recombinant human interleukin-2 and interferon alfa-2b in 54 patients with advanced cancer, for whom no effective standard therapy was available. Treatment courses consisted of a 2-day interleukin-2 pulse (14.4-18 million units (MU) m2/day), followed by 3.6 up to 4.8 MU/m2/day, 5 days per week, over 6 consecutive weeks and interferon alfa-2b at 3 up to 6 MU/m2, administered two-three times weekly for 6 weeks. Overall, patients received more than 90% of the projected dose of interleukin-2 and interferon alfa-2b, respectively. Of 54 evaluable patients (32 renal cell cancer, 12 melanoma, eight colorectal cancer, one B-cell lymphoma, one Hodgkin's disease), four complete responses occurred in patients with renal cell carcinoma, and a greater than 50% reduction in tumour size (partial response) in six renal cell carcinoma patients and one melanoma patient. Moreover, 21 patients (13 renal carcinoma) had stable disease. The median duration of response was 19 months (range 16-22 months) in complete responders. Clinical responses were associated with a mean peripheral blood eosinophil count of more than 1,000/microL (P less than 0.05 versus non-responders). Systemic toxicities included fever, chills, nausea, anorexia, and hypotension limited to WHO grades I and II in more than 80% of patients treated. No treatment-related deaths occurred. This combination of subcutaneously administered recombinant interleukin-2 and interferon alfa-2b has significantly diminished the side effects normally observed with high-dose intravenous recombinant interleukin-2, which requires admission to hospital. It has been shown to induce objective tumour regression in out-patients with progressive metastatic renal cell carcinoma and malignant melanoma.

Thyroid dysfunction associated with immunotherapy for patients with cancer

The authors performed a prospective study to evaluate thyroid dysfunction in 130 patients with cancer who were receiving interleukin-2 (IL-2)-based immunotherapy. Primary hypothyroidism was the most common abnormality, occurring in 12% of patients before, 38% during, and 23% after immunotherapy. Hyperthyroidism occurred in 1%, 4%, and 7% of patients at those time intervals. Among patients initially euthyroid (n = 111), primary hypothyroidism developed in 32% during and 14% after immunotherapy, persisting a median of 54 days. Three patients required levothyroxine. Hyperthyroidism developed in 2% of patients during immunotherapy and 6% after. Thyroid dysfunction was not a function of sex, diagnosis, type of treatment, or response to immunotherapy. Elevated titers of antithyroglobulin and antithyroid microsomal antibodies were detected after treatment in 9% and 7%, respectively, of all patients without prior antibody abnormalities and did not correlate with response to therapy. The high incidence of therapy-induced thyroid dysfunction suggests that thyroid function should be carefully monitored in all patients receiving IL-2-based immunotherapy.

Thyroid dysfunction can predict response to immunotherapy with interleukin-2 and interferon-2 alpha

Thyroid dysfunction is a well-recognised side-effect of treatment with interleukin-2 (IL2). We assessed the correlation between the development of abnormal thyroid function and tumour response in 13 patients receiving IL2 and interferon-2 alpha (IFN2 alpha) for advanced malignancy. Seven patients had normal thyroid function during treatment, and all of these patients have since died of progressive disease. Of six patients who did develop thyroid dysfunction during treatment, one patient has died of progressive disease. However, statistically we were unable to confirm a definite correlation between the development of thyroid dysfunction and survival in this small group of patients.

A phase I study of an outpatient regimen of recombinant human interleukin-2 and alpha-2a-interferon in patients with solid tumors

This study was undertaken to define the maximum tolerated dose (MTD) of recombinant interleukin-2 (IL-2) that could be combined with a fixed dose of alpha-2a-interferon (alpha-IFN) in an outpatient setting. The schedule called for IL-2 to be given by a 2-hour intravenous infusion 5 days a week for 4 weeks. The alpha-IFN was given at a dose of 6 x 10(6) U/m2/d intramuscularly 3 days per week (Monday, Wednesday, and Friday). The IL-2 dose was escalated in four dose levels from 1 to 4 x 10(6) U/m2/d. The MTD in this study of 17 patients was at the fourth dose level of IL-2 (4 x 10(6) U/m2/d). In addition to the usual IL-2 toxicities, debilitating fatigue limited outpatient administration of this dose. Although the response rate was low, with partial responses seen in only 1 of 15 patients, 2 of 5 patients with melanoma treated at the higher dose levels had objective tumor shrinkage with one partial and one minor response. Thus, an IL-2 dose of 3 x 10(6) U/m2/d combined with a recombinant alpha-2a-IFN dose of 6 x 10(6) U/m2/d is recommended for Phase II studies.

A phase II trial of interleukin-2 by continuous infusion and interferon by intramuscular injection in patients with renal cell carcinoma

Fifteen patients with advanced, measurable renal cell carcinoma entered a Phase II clinical trial of interleukin-2 (IL-2) (Teceleukin, Hoffmann-La Roche Inc., Nutley, NJ) and interferon (IFN) (Roferon A, Hoffmann-La Roche Inc.). IL-2 was administered by continuous infusion daily for 4 days and IFN was administered by intramuscular injection daily for 4 days; therapy continued for 4 weeks. Eight men and seven women were treated in this trial (median age, 61 years). Toxicity was moderate to severe with fatigue, nausea, vomiting, hypotension, and elevated blood urea nitrogen bunion and creatinine levels seen in all patients. Two patients achieved a complete remission and two patients achieved a partial remission. The median duration of response was 18 months. IL-2 and IFN is an active combination in the treatment of renal cell carcinoma and warrants further investigation.

Interferon alpha in combination with other biologics: the scientific rationale

Interferon alpha (IFN alpha) has widely pleiotropic effects, on both the immune system and tumour cells, and any of these effects might provide the basis for additive or synergistic effects when administered in combination with other biologics. Some of the main sites of action to consider include the ability of IFN alpha to: inhibit the growth of tumour cells; induce differentiation, and/or MHC expression on tumour cells; and stimulate the activation and/or differentiation of natural killer (NK) cells, cytotoxic T lymphocytes, and cytotoxic macrophages. Other biologics with similar sites of action might be expected to provide additional effects when combined with IFN alpha, and factors with other, complementary anti-tumour effects might synergize. Potentially important therapeutic effects have been observed when IFN alpha has been combined with IFN gamma, interleukin 2, tumour necrosis factor, interleukin 1, monoclonal antibodies, and retinoids. The development of therapeutic strategies on the basis of hypotheses as to how IFN alpha might effectively interact with another biologic, coupled with careful assessment of effects on the tumour cells and/or serial monitoring of immunologic parameters, might be expected to lead most expeditiously to successful therapeutic combinations of IFN alpha with other biologics.

Colonic ischemia complicating immunotherapy with interleukin-2 and interferon-alpha

Colonic ischemia (CI) is a rare complication of high-dose interleukin-2 (IL-2) immunotherapy. This complication occurred in three of 141 patients (2.1%) with metastatic cancer treated with high-dose IL-2 therapy; CI only developed in patients receiving interferon-alpha (IFN) with IL-2 (three of 21, 14%) compared with none of 120 in those patients receiving IL-2 alone (P equals 0.0009). Severe diarrhea (greater than or equal to 7 bowel movements/day) also was significantly more common in patients receiving IFN with IL-2 (six of 21, 29%) than in those receiving IL-2 alone (three of 120, 2.5%, P equals 0.001) and preceded the clinical diagnosis of CI in all three patients. Three of nine patients with severe diarrhea had CI. Hematochezia occurred in four patients, all of whom received IFN with IL-2; three had CI, and the other patient had nonspecific colitis. Differences in vasopressor use did not explain the increased risk of CI in patients receiving IFN; those receiving IFN with IL-2 required phenylephrine less often than patients receiving IL-2 alone (P equals 0.01). The administration of lymphokine-activated killer (LAK) cells had no significant effect on the incidence of CI, severe diarrhea, peritonitis, or vasopressor use; two of three patients with CI, however, had their ischemic episode within 24 hours after the last of three LAK cell infusions. In conclusion, CI is an unusual complication of high-dose IL-2 and IFN immunotherapy. In patients receiving such combination therapy, severe diarrhea is a risk factor for the subsequent occurrence of CI.

Combination of cytokines: current status and future prospects

Clinical trials with individual cytokines and extensive in vitro studies have provided the basis for the in vivo use of these molecules in combination. Animal models, with haemopoietic growth factors as well as preliminary studies in humans--as shown by our studies with the sequential use of IL-3 and GM-CSF in patients receiving intensive chemotherapy--indicate that the selection of the appropriate cytokines could optimize haematological responses according to particular clinical requirements. That immunotherapy with IL-2 can induce regression of disseminated human malignancies serves as an encouraging starting point for combinations with other cytokines with the goal of improving the therapeutic efficacy and reducing toxicity. Future prospects of combination therapy will be discussed.

Clinical experience with the combined use of recombinant interleukin-2 (IL2) and interferon alfa-2a (IFN alpha) in metastatic melanoma

A multicentre study of IL2 and IFN alpha has been performed in 58 patients with metastatic melanoma. The scheme consisted of IL2 3.0 BRMP MU/m2/d as a continuous infusion for 4 d combined with subcutaneous administration of IFN alpha 6 MU/m2/d, day 1 + 4. The cycle was repeated every 2 weeks for a maximum duration of 26 weeks. 54 patients were evaluable for response. One (2%) achieved a complete and 10 (19%) a partial response. 19 (35%) patients were stable and 24 (44%) showed progressive disease. Common side-effects included fever, chills, fatigue, skin rash, anorexia, nausea and diarrhoea. Hypothyroidism was noted in 10% of the patients. These results show that this regimen of IL2 and IFN alpha is active but, in contrast to what could be expected, not superior to IL2 alone possibly due to suboptimal dosing. In an ongoing study in Rotterdam and Nijmegen, a more intense schedule was chosen, consisting of three daily i.v. doses of IL2 4.5 BRMP MU/m2 and IFN alpha 3.0 MU/m2 for 5 d. This regimen is repeated at intervals of 3 weeks for a total of three cycles. Presently, nine patients have been entered. One patient achieved a complete response, four a partial response (overall 56%), three had stable disease and one progressed. Toxicity was severe and treatment was prematurely stopped in five patients: myocardial infarction (one patient), atrial fibrillation (one patient), negative T waves and myocardial hypokinesia (one patient) and psychosis (two patients). This regimen can only be justified if the therapeutic results are superb, which has yet to be awaited.

In vivo treatment with interferon causes augmentation of IL-2 induced lymphokine-activated killer cells in the organs of mice

Interferon-alpha (IFN-alpha) has been shown to synergize with IL-2 in the regression of a variety of established murine tumours and studies are underway to explore this combination in patients with advanced cancers as well. To understand the mechanism of synergy we have studied lymphokine-activated killer (LAK) cell activity in various compartments of mice in response to IFN-alpha and IL-2 administration. The effects of IFN-gamma, TNF-alpha and IL-4 were also examined. C57BL/6 mice were injected intraperitoneally with HBSS, IL-2 alone, IFN-alpha alone or both, two times a day for 7 days. On days 4 and 8, LAK activity was tested in a 4-h chromium release in cells obtained from lungs, spleen, and liver using fresh MCA-102 tumour cells as targets. The cells from control mice failed to lyse the MCA-102 target. IL-2 caused the generation of LAK activity and an increase in total cell yield in all the organs after 3 days of injection. IFN-alpha failed to generate LAK activity but when administered along with IL-2, caused synergistic enhancement of LAK lysis of MCA-102 target cells. Cell yield in this group was lower as compared with the IL-2-treated group. LAK activity tested after 7 days of IL-2 therapy was significantly decreased compared with that observed after 3 days. However, activity remained at as high a level after 7 days of therapy as after 3 days of therapy in animals treated with IFN-alpha and IL-2. FACS analysis revealed that asialo GM-1+ (ASGM-1) and NK1.1+ cells were increased in number in IL-2 and IL-2 plus IFN-alpha-treated spleen; however, the number of these cells was similar in both groups. In the liver, ASGM-1+ cells were higher in the IL-2 plus IFN-alpha group than in the group treated with IL-2 alone. By in vitro depletion utilizing antibody and Rbc' experiments, it was clear that both ASGM-1+ and NK1.1+ cells from the spleen mediated most of the cytotoxicity of MCA-102 targets. Pre-treatment irradiation (5 Gy) of mice completely abrogated the capability of IL-2 or IL-2 plus IFN-alpha to generate LAK activity. IFN-gamma also had a stimulatory effect on IL-2 induction of LAK activity. Tumour necrosis factor-alpha (TNF-alpha) and IL-4 failed to generate LAK activity and, in combination with IL-2, no additional stimulatory effect was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute renal failure with preserved renal plasma flow induced by cancer immunotherapy

Adoptive immunotherapy in patients with advanced cancer produces significant regression of metastatic disease in selected patients, but it is complicated by severe side effects. Prevention of these complications is still limited because their precise mechanisms remain unknown. For this reason we have investigated renal function and hemodynamic parameters in 16 patients with renal cell carcinoma before and during treatment with a combination of high doses of both recombinant interleukin-2 (rIL2) and recombinant alpha-interferon. After patients had received three injections of combined immunotherapy, there was a decrease in mean blood pressure (-20%), glomerular filtration rate (-25%), urine output (-50%), and fractional sodium excretion (-0.8%). This was associated with an increase in heart rate (+30%), plasma creatinine level (+30%), fractional potassium excretion (+14%) and microalbuminuria (+130%). However, renal plasma flow remained constant. The increment in microalbuminuria may reflect an alteration of glomerular capillary permeability. The reduction in GFR may be accounted either for a decrease in efferent to afferent arteriolar resistance ratio, leading to a decrease in glomerular capillary pressure, or for a decrease in ultrafiltration coefficient, or both. Nonsteroidal antiinflammatory drugs, such as ketoprofen, used to minimize side effects, could considerably worsen renal function and should be avoided in patients treated by rIL2. Our results bring new insights into the pathogenesis of functional acute renal failure and provide a rational basis for the use of vasopressors in the treatment of cytokine-induced acute renal failure.

The role of cytokines in oncology

The availability of sufficient quantities of recombinant human cytokines and promising preclinical data have led to their introduction into clinical trials. Cytokines have potential as new therapeutic agents in a variety of hematological disorders as well as in solid tumors. Only a few of the still increasing number of these glycoprotein hormones have been studied in humans so far, either as single agents or in combination with chemotherapy and other cytokines. Their clinical effects, beneficial role in supportive care, and use in the treatment of certain cancer patients are reviewed.

The scientific bases of cancer management: at the interface between fundamental research and clinical practice

From 1950 to 1985 the 5-year survival rate of cancer patients in industrialized countries, has slowly increased from 25% in 1950 to 50% in 1985. This progress has been due to earlier diagnosis and to a gradual improvement of treatment modalities. Clinical needs have stimulated basic research and clinical investigation. In turn, biological research has introduced new concepts and new agents. Clinical investigation and applied research have brought about an improvement in therapeutic methods and a better understanding of the growth and progression of human cancers which has, in particular, led to the concept of adjuvant treatment of occult metastases. The major recent breakthroughs in fundamental research have reinforced the value of close cooperation between clinicians and fundamentalists. Most of the new biologic tools are specific and only active on tumors cells with well-defined characteristics. Furthermore some new techniques such as adoptive immunotherapy can induce complete tumor regression in some patients and have no detectable effects in other patients with apparently similar tumors. Some cytokines have different effects on experimental and human tumors. The cytokine network is so complex that the administration of one of them can induce unpredictable effects. It has been recognized that experimental tumors and in vitro studies can be misleading and there is no substitute for clinical studies on patients. Moreover clinical experience has documented the amazing ability of tumors to become resistant to all these new agents. Numerous new therapeutic methods are being explored, however with the current state of knowledge it appears that although they can help to control tumors, they still fail to eradicate them. We must therefore learn how to integrate them with conventional therapies. Advances in therapy shall be achieved only by well-designed clinical trials. Thus at the interface between fundamental research and clinical practice there is an urgent need for oncologists with a strong scientific background and laboratory scientists with a deep interest in clinical investigations.

Continuous interleukin-2 and tumor-infiltrating lymphocytes as treatment of advanced melanoma. A national biotherapy study group trial

Melanoma metastases were harvested from 82 patients for the purpose of growing and expanding tumor-infiltrating lymphocytes (TIL). Tumor tissue cell suspensions were incubated with interleukin-2 (IL-2), followed by repeated exposure to tumor antigen with or without OKT3 monoclonal antibody (MoAb). Initial growth success was achieved in 56 of 82 cultures (72%). Efforts were made to expand 26 of these 56 cultures for therapeutic TIL; 23 of 26 early cultures (88%) were successfully expanded for in vivo therapy. It took a mean of 78.5 +/- 25.4 days to grow sufficient TIL for treatment. Therapy included cyclophosphamide (1 g/m2) on day 1, followed by a 96-hour continuous infusion of IL-2 (18 x 10(6) IU/m2/d) on days 2 to 5, and approximately 10(11) (mean 1.49 +/- 0.93 x 10(11)) TIL on day 2. Patients who responded received monthly IL-2 as a 96-hour infusion. Median patient age was 45 years of age. Sixty-seven percent of the patients were men. Performance status was 0 to 1 in 77% of patients. Thirty-four percent of the patients had liver metastases. The usual IL-2 toxicities were seen. Response rate for 21 patients was 24% (95% confidence interval, 10% to 49%). One complete response was achieved with cells 98% CD4+; four partial responses were achieved with cells 80%, 94%, 98%, and 98% CD8+, respectively. Four of eight patients who received TIL, which had never been stimulated with OKT3, had tumor response. The authors conclude that a treatment plan for IL-2/TIL is technically difficult, costly, and effective for only a minority of patients. Overall, clinical results are not clearly superior to those obtained with other IL-2 regimens.

Therapeutic use of cytokines in dermatology

Cytokines are glycoproteins produced by many different cells. Via binding to specific receptors on target cells they regulate the activation, differentiation, and proliferation of immune and nonimmune cells. After injury keratinocytes synthesize and release cytokines such as interleukins, colony stimulating factors, and growth factors. In addition, a network of interacting cytokines appears to be crucial to maintain proper balance. Dysregulation may contribute to certain diseases, particularly those of infectious and autoimmune origin. Therefore many of these mediators appear to be promising candidates to treat infectious and malignant diseases. This article briefly discusses the most important cytokines. Newly developed regimens with cytokines to treat cutaneous disorders will be reviewed.

Clinical use of biologic response modifiers in cancer treatment: an overview. Part II. Colony-stimulating factors and interleukin-2

Colony-stimulating factors (CSFs) are hematopoietic growth hormones that stimulate the production, maturation, and function of white blood cells. The best studied are granulocyte-macrophage CSF (GM-CSF) and granulocyte CSF (G-CSF), both of which can be produced by recombinant DNA technology. Clinical indications for these agents include bone marrow failure secondary to administration of chemotherapeutic drugs or radiation, bone marrow transplantation, and a variety of congenital or iatrogenic neutropenias. Toxicity in usual clinical doses is mild, and consists mainly of bone pain and constitutional symptoms such as fever, headache, and myalgias. Interleukin-2 (IL-2) is a lymphokine that stimulates that multiplication of several types of killer cells. These cells can recognize and destroy foreign substances, such as tumors, without destroying normal cells. Major applications of IL-2 include treatment of patients with renal cell carcinoma, in whom the overall objective response rate is 15-30 percent, and malignant melanoma with response rates of about 18 percent. Combination therapy with other biologics and conventional cytotoxic drugs may increase IL-2's efficacy against these tumors. Toxicity is generally severe, but reversible. Hemodynamic toxicity, consisting of hypotension, edema, weight gain, and decreased renal function, is most characteristic. Suggestions are given for pharmacologic management of these and other IL-2 toxicities.

Interleukin-2 immunotherapy followed by resection of residual renal cell carcinoma

We administered 10 (E5) units per kg. interleukin-2, 3 times daily, with or without lymphokine-activated killer cells, to 10 patients with metastatic renal cell carcinoma. All patients had metastases to the lung, and 3 of 5 patients who had previously undergone nephrectomy had metastases to the renal fossa. Of the 9 patients who completed at least 1 course of therapy 3 had complete regression of disease outside the abdomen, including 2 who were rendered disease-free after subsequent cytoreductive surgery (nephrectomy in 1 and resection of the renal fossa recurrence in 1). Viable tumor comprised less than 1% of each surgical specimen. Our results support the view that initial treatment with interleukin-2 immunotherapy, followed by abdominal cytoreductive surgery if the peripheral metastases have regressed, may be preferable to the practice of performing abdominal cytoreductive surgery before administering interleukin-2 immunotherapy for patients with widely metastatic renal cell carcinoma.

Induction of cytotoxic T lymphocyte development from murine thymocytes by IL-1 and IL-6

Cytotoxic T lymphocytes (CTL) are believed to play an important role in the regression of advanced malignancies in response to adoptive immunotherapy with interleukin-2 (IL-2) and lymphokine-activated killer cells or tumor-infiltrating lymphocytes. Because the current limitations to the use of adoptive immunotherapy are the IL-2 dose-dependent toxicities and the difficulty in expanding the effector cell population, recent investigations have focused on the development of newer methods for generating CTL in vitro. IL-1 and IL-6 have been shown to synergistically promote thymocyte proliferation; however, their effect on CTL development has not been studied. We investigated the ability of these two cytokines to induce CTL development from immature thymocytes. Thymocytes from 5-week-old BALB/c mice were cultured for 72 hours in the presence of Con A and recombinant IL-1, IL-6, or IL-1 plus IL-6. Cytotoxicity against 51Cr-labeled P815 target cells was then measured in the presence of submitogenic doses of PHA. Neither IL-1 nor IL-6 induced a significant number of CTL from immature thymocytes. However, these two cytokines synergistically induced maximal CTL development. The monoclonal antibody to IL-4 completely abrogated CTL development induced by IL-1 and IL-6, but antibody to the IL-2 receptor had no effect. The data suggest that IL-1 and IL-6 can provide an additional method for in vitro CTL generation in adoptive immunotherapy of advanced tumors.

Clinical and immune modulatory effects of alternative weekly interleukin-2 and interferon alfa-2a in patients with advanced renal cell carcinoma and melanoma

The clinical and immune modulatory effects of interleukin-2 (IL-2) and interferon (INF) alfa-2a were examined in a phase II study in patients with metastatic renal cell carcinoma (six patients) and melanoma (eight patients). Treatment consisted in IL-2 3 MU/m2 continuous infusion days 1-4 and INF alfa-2a 6 MU/m2 subcutaneously day 1 and 4, both given on alternate weeks. Tumour response was assessed after four cycles of treatment or earlier, if necessary. Patients with stable disease or response were to be continued for another nine cycles or up to disease progression. The 14 patients received a total of 60 cycles of treatment. Major toxicities (WHO Grade III/IV) were fever, capillary leak syndrome with hypotension, nausea and vomiting, erythema with pruritus, leuco- and thrombopenia and sepsis with staphylococcus aureus. Five of 14 patients (36%) developed a self limiting autoimmune thyroiditis with HLA-DR expression on thyrocytes. Long term treatment toxicity was moderate with an average weight loss of 5% and an average fall in Karnofsky index of 10% compared to baseline. No responses were seen in renal cell carcinoma, two patients with melanoma had a partial and two a minor response with a duration of 1-7 months. Serial measurements of immune modulatory parameters showed a functional response to treatment with an increase of NK- and LAK-activity during the first two cycles, followed by a plateau and decrease during the third and fourth cycles. These findings were paralleled by a successive decline in treatment induced INF gamma response. These findings suggest, that alternative weekly treatment with IL-2 and INF alfa-2a results in an exhaustion of lytic capacity of NK- and LAK-cells and an attenuation of secondary cytokine release.

The immunotherapy of human cancer with interleukin 2: present status and future directions

Interleukin-2 (IL-2) is the principal soluble factor responsible for the proliferation of activated T cells. In animal models and humans, administration of IL-2 can induce regressions of established cancers. These antitumor effects may be partially mediated by cytotoxic effector cells activated by IL-2, including lymphokine-activated killer (LAK) cells and cytotoxic T lymphocytes. IL-2 has additional effects on other components of the cellular immune system, including B cells and macrophages, and induces secretion of other soluble mediators, including tumor necrosis factors (TNF) alpha and beta, and interferon-gamma. These effects may contribute to the antitumor activity of IL-2 as well as its dose-related toxicity. Multiple Phase I and II trials have been completed or are ongoing evaluating the clinical and biological effects of IL-2 given by diverse routes and schedules, both alone and in combination with infusions of ex vivo IL-2-activated autologous LAK cells. Other studies have begun to explore the potential for antitumor synergy when IL-2 is combined with the different interferons, TNF, monoclonal antibodies, and cytotoxic drugs. The biology, toxicity, and clinical activity documented in IL-2 clinical trials to date are reviewed, and prospects for future directions outlined.

A phase I study of recombinant human interleukin-2 and alpha-interferon-2a in patients with renal cell cancer, colorectal cancer, and malignant melanoma

Preclinical data suggest synergy of interleukin-2 (IL-2) combined with alpha-interferon (IFN). In addition, toxicities of IL-2 may be decreased by intermittent continuous infusion. The purpose of this trial was to determine the maximum tolerated dose (MTD) of recombinant IL-2 combined with alpha-IFN in patients with renal cancer, colon cancer, melanoma, and malignant B-cell disease. IL-2 was given by continuous i.v. infusion at an initial dose of 5 X 10(5) units (U)/m2/d for 4 days plus IFN at 6 X 10(6) U/m2/d intramuscularly days 1 and 4 weekly for 4 weeks. Patients who achieved a response or stable disease received an additional 4 weeks of therapy. IL-2 doses were increased to 1, 2, 3, 5, and 7 X 10(6) U/m2/d with three to eight patients at each dose level, at each of the two participating institutions. The dose of IFN was 6 X 10(6) U/m2 days 1 and 4 for all but five patients whose IFN dose was doubled to 12 X 10(6) U/m2/d. Forty-three patients were entered on this study with 34 completing at least 4 weeks of therapy. Six patients were taken off study because of Grades III or IV pulmonary, neurologic, or cardiac toxicity; one for progressive disease; one for CNS metastases, and one for personal reasons. All of the toxicities were reversible. Chills and fever were universal, especially on days 1 and 4. Mild and moderate nausea, vomiting, diarrhea, anorexia, malaise, and cutaneous erythema were present in most patients. Fluid retention and occasional pleural effusions were observed at the higher IL-2 doses but were not dose-limiting. Significant hypotension associated with oliguria was seen, and these patients were treated with vasopressors and colloids. None of the patients required ICU admission. Thirty-four patients were evaluable for response. There were 4/18 (22%) renal cell patients who experienced a partial response. No responses were seen in patients with melanoma, lymphoma, or colorectal cancer. The combined debilitating symptoms of fatigue, diarrhea, hypotension, fluid retention, and anorexia defined the MTD as 5 X 10(6) U/m2/d of IL-2 and 6 X 10(6) U/m2 of alpha-IFN.

Clinical use of biologic response modifiers in cancer treatment: an overview. Part I. The interferons

Interferons are proteins with antiviral, antiproliferative, and immune-regulating activity. They are classified as alfa, beta, or gamma on the basis of antigenicity and biologic properties. Alfa interferons as single-agent therapy produce clinical improvement in approximately 90 percent of patients with hairy-cell leukemia, and up to 70 percent of patients with chronic myelogenous leukemia (CML) in early-stage disease. Prolonged suppression or elimination of the leukemic cell clone by interferon may ultimately increase survival of patients with CML. Interferon is not effective single-agent therapy for multiple myeloma, but improves response rate when combined with conventional agents. AIDS-associated Kaposi's sarcoma demonstrates a 40 percent objective response rate to interferon, with less risk of immune system suppression than conventional cytotoxics. Other applications of alfa interferon include malignant melanoma and renal cell carcinoma. Beta interferon is similar to the alfa subtype and may have utility in treatment of brain tumors. Gamma interferon is an important immune regulator with qualitative and quantitative differences in its efficacy and toxicity when compared with alfa interferon.