Studies have shown an increased spontaneous TNF alpha production, and the 24--rhythmicity of TNF blood concentration in patients with advanced cancer. The present study investigates whether diurnal rhythmicity of endogenous TNF alpha is associated with the induction of circulating sTNF Rp55 in advanced gastrointestinal neoplasm. The levels of endogenous TNF alpha and sTNF Rp55 in serum were measured at 8 a.m., 2 p.m., 6 p.m., 10 p.m., 2 a.m., and again at 8 a.m.
Results: There is circadian rhythm in the secretion of endogenous TNF alpha in patients with advanced gastrointestinal cancer, however no diurnal rhythm of sTNF Rp55 was observed. Since it has been suggested that human tumors susceptible to TNF alpha may escape destruction by secreting or inducing the secretion of sTNF Rp55 to block the effects of TNF alpha, the possibility that the observed fluctuations could also reflect the complexation of a proportion of the receptor molecules with their ligand should be considered.