Cytokine Receptors: Qualitative and Quantitative Analysis

Much has been written on the possible role of cytokines in hematopoietic malignancies. In some instances, such as interleukin-6 (IL-6) in multiple myeloma, there is evidence for a central role in maintaining malignant growth (1 ). The relationship between IL-6 and multiple myeloma is probably more complex, involving other cytokines that signal through receptors, which share the gp130 chain with the IL-6 receptor. Another strong association is that of IL-2 with acute T-cell lymphoma/leukemia, which express and release large amounts of the IL-2 receptor-α chain (CD25, Tac) (2 ). In other hematopoietic malignancies there is no strong evidence for the involvement of cytokines in the malignant process. Nevertheless, if a malignant clone expresses receptors for a cytokine and that cytokine is available, the end result may be accelerated proliferation or enhanced survival of the malignant cells. Conversely, expression of receptor for cytokines such as transforming growth factor-β (TGF-β), which tend to inhibit proliferation, or molecules like Fas, which induce apoptosis, may control the malignant clone. Thus cytokine receptor expression may provide valuable information on the behavior of the malignant clone (3 ). These considerations make a case for screening of cytokine receptor expression as a part of routine diagnostic evaluation of patients with hematopoietic malignancy. It is emphasized, however, that at present cytokine receptor expression is a research tool, with the possible exception of the determination of soluble IL-2 receptor α chain (Tac, CD25). Measurement of soluble Tac has been widely reviewed (4 ) and will not be described here.