Proopiomelanocortin producing cells of spleen: increase after transplantation with opioid-peptide producing Ehrlich ascites tumor cells

: Proopiomelanocortin (POMC) peptides are produced by many cell systems, including a population of macrophage-like cells in mouse spleen. After transplantation of mice with Ehrlich ascites tumor cells, the number of POMC producing spleen cells increase up to 10-fold by 5 to 6 days. The POMC peptides produced by these cells increase even more, as evidenced by radioimmunoassay. Thus, these data indicate both proliferation of splenic POMC cells and increased production of POMC peptides per cell after tumor challenge. Characterization of the peptides by sequence-specific radioimmunoassays and high performance liquid chromatography documents the presence of both ACTH(1-39) and of ACTH(1-14) in these cells. These peptides have multifacetted effects on immune parameters and may exhibit a general antiinflammatory action, partly mediated through inhibition of interleukin 1-stimulated events. The tumor cells themselves do not produce POMC peptides, but display met- and leu-enkephalin immunoreactivity. Also cultured tumor cells display such immunoreactivity, indicating endogenous production of opioid peptides. The opioid peptides of the tumor cells may both affect host immune defenses and play intratumoral autocrine or paracrine roles.