Purification and characterization of an inhibitor (soluble tumor necrosis factor receptor) for tumor necrosis factor and lymphotoxin obtained from the serum ultrafiltrates of human cancer patients.

Abstract

Serum ultrafiltrates (SUF) from human patients with different types of cancer contain a blocking factor (BF) that inhibits the cytolytic activity ofhuman tumor necrosis factor a (TNF-a) in vitro. BF is a protein with a molecular mass of28 kDa on reducing sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE). The active material was purified to homogeneity by a combination of affinity chromatography, PAGE, and high-pressure liquid chromatography. Amino add sequence analysis revealed that BF is derived from the membrane TNF receptor. Purified BF blocks the lytic activity ofrecombinant human and mouse TNF-a and recombinant human lymphotoxin on murine L929 cells in vitro. However, BF inhibits the lytic activity of TNF-a more effectively than it does that of lymphotoxin. The BF also inhibits the necrotizing activity ofrecombinant human TNF-a when cou jected into established cutaneous Meth A tumors in BALB/c mice. The BF may have an important role in (i) the regulation and control of TNF-a and lymphotoxin activity in cancer patients, (ii) interaction between the tumor and the host antitumor mechanisms, and (ii) use of systemically administered TNF-a in clinical trials with human cancer patients.

The regulation of TNF receptor mRNA synthesis, membrane expression, and release by PMA- and LPS-stimulated human monocytic THP-1 cells in vitro

“…We also demonstrated [35S]cysteine-labeled 30-kDa material binding to unlabeled TNFa. The molecular weight of this material is close to the MW of soluble TNFa receptors found in urine (18,19) and in cancer patient's serum (23). This BF may be responsible for the drop in supematant TNFa activities observed in these cultures.…”

“…Collectively, these studies have led to the concept that release of soluble receptors may represent a new mechanism to specifically control cytokine activity. This concept is supported by the recent report of Gatanaga et al (23) that human soluble TNF-R can block the anti-tumor activity of recombinant human TNFa when injected into Meth-A tumor-bearing BALB/c mice. It is not yet clear what the cell and tissue source of these BF may be; however, a recent report by Porteu and Nathan (27) indicates that activated human neutrophils can release TNF-R derived from both 55 and 68-75 kDa receptors.…”

“…Recently, a soluble form of the extracellular domain of the 55-kDa TNF membrane receptor has been isolated and identified in cancer patient serum (23) (23). These data suggested that these soluble TNF-R may have an important role in controlling the action of TNFa and LT activities.…”

“…These soluble TNF receptors have molecular weights of 28 to 30 kDa and appear to be derived from the N-terminal extracellular region of the 55-and 75-kDa TNF cell membrane receptors (23). Other groups have identified cell surface receptors in biological fluids that are released and specifically bind to other biological response modifiers such as IL-2, IL-4, and growth factors (24)(25)(26).…”

Elevation of plasma-soluble tumour necrosis factor receptors (TNF-R) in sarcoidosis

“…The soluble forms originating from the extramembranous portion of the TNF-RI (sTNF-RI) and TNF-RII (sTNF-RII) can be found in the culture supernatants of lymphocytes, monocytes and neutrophils [15,[19][20][21] and biological fluids [22,23]. The elevation of sTNF-R in serum/plasma and biological fluids reflecting a variety of inflammatory disorders has been shown in several diseases [24][25][26][27][28][29][30][31].…”