Connie R. Faltynek

Differential modulation of two interferon-α binding proteins on a human lymphoblastoid cell line

Abstract The interaction between human interferon (IFN)-α or IFN-β with its receptor was originally described as the binding to a single class of high-affinity receptors. However, more recently, biphasic Scatchard plots as well as multiple IFN-α receptor cross-linked complexes have been reported. In this study using the Daudi B lymphoblastoid cell line, two primary IFN-α receptor cross-linked complexes with apparent M r of 115 and 135 kilodaltons (kDa) were obtained. Both complexes were observed under a variety of cross-linking conditions, including the addition of a mixture of protease inhibitors throughout the binding reaction and solubilization of the cells. These two complexes appear to be caused by the binding and cross-linking of 125 I-rIFN-αA to two separate proteins because we also observed two IFN-α binding proteins using a ligand-blotting technique. At low concentrations of 125 I-rIFN-αA, it was found that the intensity of the signal in the 135-kDa cross-linked complex was greater than that of the 115-kDa complex. Addition of increasing concentrations of unlabeled rIFN-αA to a 4°C binding reaction reversed the ratio in intensities of the two complexes. Moreover, after pretreatment of the cells at 37°C with low concentrations of unlabeled rIFN-αA, there was preferential down-regulation of both the 135-kDa complex and the higher affinity binding component of the biphasic Scatchard plot. These results suggest that the 135-kDa complex represents the binding of 125 I-rIFN-αA to a protein having higher affinity for IFN than the protein that gives rise to the 115-kDa complex. These two proteins also appear to have different half lives in the plasma membrane in the absence of IFN because treatment with cycloheximide also caused a preferential decrease in the subsequent formation of the 135-kDa complex.

Cytokine-Based Combined Modality Approaches to the Treatment of Murine Renal Cancer

Biological response modifiers (BRM) are being developed as a potential fourth modality for cancer treatment to supplement the three currently accepted modalities, chemotherapy, radiotherapy, and surgery (1). There are several possible approaches to the use of immunoactive cytokines as part of combined modalities for cancer treatment. First, cytokines can be used in combination with one or more of the traditional modalities for cancer treatment. The rationale for such an approach is that either the mechanisms for the antitumor effects of the cytokines versus those of the other modality will differ leading to enhanced antitumor effects, or that the effects of one will enhance the activity of the other. In either case the efficacy of the combination should be greater than either modality alone. Second, different combinations of cytokines should be complementary based on their interaction as part of the cytokine cascade that regulates immune responses. We are studying different preclinical models that fall into both types of combined modality approaches. It has been reported that interleukin 1 (IL-1) can protect mice from the acute toxicity of some chemotherapeutic drugs (2–4) and that this ability to dose escalate chemotherapy translates into enhanced antitumor efficacy (4), although some late toxicity becomes evident (4). In addition, we are studying the hematoimmunological effects of various T cell-stimulating cytokines (5–7) under the hypothesis that the enhancement of the appropriate T cell functions will lead to increased antitumor efficacy.