Expression of interleukin-1 in human pheochromocytoma.

Cytokines and in particular interleukin 1 (IL-1) play a role in the micro-environment of various tumors. In addition, it is well established that IL-1 is a neurotrophic, angiogenetic and fibrogenetic factor. Using in situ hybridization we analyzed the expression of endogenous IL-1 in human pheochromocytoma (PCC). With the help of specific antibodies to B- and T-cells, macrophages, and neuroendocrine cell antigens, we characterized the distribution and localization of various cell types in human PCC. The combination of immunohistochemistry and in situ hybridization was eminently suited to defining the exact cellular source of IL-1 expression. In situ hybridization and immunostaining revealed that IL-1 mRNA was located primarily in the tumor cell itself. IL-1 may therefore constitute an important paracrine/autocrine factor in neuroendocrine tumors.