Tumor Necrosis Factor in the Pathogenesis of Human Diseases

Abstract

This paper will deal with the role of tumor necrosis factor (TNF) in the pathogenesis of various diseases. However, it will be important to remember that originally TNF was characterized as an antitumor factor. In fact, it was known that endotoxin was able to induce hemorrhagic necrosis of some tumors in mice. In 1975 Carswell et al. demonstrated the presence of a tumor necrotizing activity (termed “tumor necrosis serum”) in the sera of mice primed with C. parvum or BCG, and subsequently injected with endotoxin (1). Later it was found that this factor was a macrophage product and was termed TNF. In vivo TNF induced hemorrhagic necrosis of Meth A sarcoma and in vitro demonstrated cytotoxic activity against various tumor cell lines (2). In 1984, TNF was purified and its cDNA was cloned, and the production of substantial amounts of recombinant TNF allowed the characterization of its various biological activities (3).

In parallel to these studies on tumor necrosis, the group of Cerami, at the Rockefeller University in New York was studying the mechanisms of cachexia and wasting associated with infection. They found that infection or injection of endotoxin in laboratory animals resulted in a marked hypertrygliceridemia, which was associated with an inhibition of lipoprotein lipase. They hypothesized that a host-derived mediator was responsible for this and other metabolic derangements observed in infection. This factor, which was termed “cachectin”, was later found to be produced by macrophages, and once it was purified and sequenced it became clear that TNF and cachectin were identical (4).