Prolonged interleukin-2 (IL-2) treatment can augment immune activation without enhancing antitumor activity in renal cell carcinoma

Natural killer cells: role in local tumor growth and metastasis

Historically, the name of natural killer (NK) cells came from their natural ability to kill tumor cells in vitro. From the 1970s to date, accumulating data highlighted the importance of NK cells in host immune response against cancer and in therapy-induced antitumor response. The recognition and the lysis of tumor cells by NK cells are regulated by a complex balance of inhibitory and activating signals. This review summarizes NK cell mechanisms to kill cancer cells, their role in host immune responses against tumor growth or metastasis, and their implications in antitumor immunotherapies via cytokines, antibodies, or in combination with other therapies. The regulatory role of NK cells in autoimmunity is also discussed.

All-trans-retinoic acid improves differentiation of myeloid cells and immune response in cancer patients

Abnormal dendritic cell differentiation and accumulation of immature myeloid suppressor cells (ImC) is one of the major mechanisms of tumor escape. We tested the possibility of pharmacologic regulation of myeloid cell differentiation using all-trans-retinoic acid (ATRA). Eighteen patients with metastatic renal cell carcinoma were treated with ATRA followed by s.c. interleukin 2 (IL-2). Eight healthy individuals comprised a control group. As expected, the cancer patients had substantially elevated levels of ImC. We observed that ATRA dramatically reduced the number of ImC. This effect was observed only in patients with high plasma concentration of ATRA (>150 ng/mL), but not in patients with lower ATRA concentrations (<135 ng/mL). Effects of ATRA on the proportions of different dendritic cell populations were minor. However, ATRA significantly improved myeloid/lymphoid dendritic cell ratio and the ability of patients' mononuclear cells to stimulate allogeneic T cells. This effect was associated with significant improvement of tetanus-toxoid-specific T-cell response. During the IL-2 treatment, the ATRA effect was completely eliminated. To assess the role of IL-2, specimens from 15 patients with metastatic renal cell carcinoma who had been treated with i.v. IL-2 alone were analyzed. In this group also, IL-2 significantly reduced the number and function of dendritic cells as well as T-cell function. These data indicate that ATRA at effective concentrations eliminated ImC, improved myeloid/lymphoid dendritic cell ratio, dendritic cell function, and antigen-specific T-cell response. ATRA treatment did not result in significant toxicity and it could be tested in therapeutic combination with cancer vaccines.

Cytokines as clinical adjuvants: how far are we?

In spite of the explosive growth in the discovery of cytokines and chemokines and in the understanding of their modes of action, clinical use of such agents as adjuvants has been primarily restricted to patients with cancer or chronic viral infections suffering from various levels of immune impairment and for whom the chemotherapeutic armamentarium, as well as other forms of immunotherapy, have been exhausted. This cautious approach has been justified by the difficulties inherent to the biological function and delivery of such pleiotropic agents, where doses needed to achieve the targeted immune enhancement often result in serious side effects, especially during systemic administration. In addition, optimization of dosages, administration schedules and biological effects in humans often do not correlate well with preclinical data derived from animal models. Nevertheless, novel preventive immunization strategies that target a precise type of immune response in immunocompetent individuals are expected to greatly benefit from the incorporation of cytokines and chemokines. This review provides an overview of current clinical administration of cytokines as well as a description of select Phase I testing of new agents designed to enhance immune defenses in vivo.

Interleukin 2 maintains biologic stability and sterility over prolonged time

The FDA approved interleukin 2 (IL2) for clinical use in 1992 in a high-dose bolus intravenous infusion schedule. IL2 administered by continuous low- and intermediate-dose infusion can result in a variety of immunologic effects including the expansion of the Natural Killer (NK) cell pool and immune reconstitution in immune-deficient hosts. These immune modifications are essential for augmentation of both currently available and evolving immunotherapies. The manufacturer's data indicate stability of the IL2 for a period of 6 days. This time frame is not practical for prolonged infusional schemes necessitating frequent changes of drug depots. We tested the biologic stability and sterility of the commercially available recombinant IL2 preparation (aldesleukin; Proleukin, Chiron) under clinical conditions for up to 30 days. Our results confirm that IL2 retains its biologic activity and sterility under these conditions for prolonged periods. This information will simplify IL2 outpatient regimens, allowing for convenient intervals for drug depot renewal, leading to improved patient compliance and conserved health care expenditures.