Tenofovir, COX inhibitors and zileuton during cancer immunotherapies: up-regulated TNF-alpha increases antigen driven lymphocyte proliferation

Current attempts at active immunization of patients to their adenocarcinomas have heretofore met with a curiously little success. The carrier anti-ens, viral vector proteins, and other co-administered antigens typically elicit strong cell-mediated or humoral responses while the relevant cancer antigen elicits undetectable or feeble responses and often minimal if any retardation of malignant tissue growth is seen. There are exceptions but clearly more effective cancer antigen immunization strategies are needed. Adenylate cyclase, AC, catalyses the conversion of ATP to cyclic adenosine monophosphate (cAMP). Increased cAMP down regulates tumor necrosis factor-alpha, TNF, and decreased cAMP reliably up-regulates synthesis and release of TNF. TNF enhances dendritic cell (DC) maturation processes started by other stimuli. TNF promotes antigen responding CD4+ and CD8+ lymphocytes' proliferation, and suppresses suppressor T cells during primary immunization. Tenofovir is an oral antiviral drug currently used in anti-HIV treatments. It is an acyclic nucleoside analogue of adenosine monophosphate that also happens to increase TNF. The mechanism hits not been established but antagonism of cAMP's inhibition of TNF is the likely path. Prostaglandin E (PGE) is a stimulatory allosteric modifier of AC and thus suppresses TNF via the resultant increase of cAMP. Since cyclooxygenase, COX, is the rate-control ling enzyme in PGE production, COX inhibitors, otherwise known as non-steroidal anti-inflammatory drugs (NSAID), increase TNF synthesis and release by depriving AC of PGE. Indomethacin, diclofenac and ketorolac are COX inhibitors that have been on the market for many years that would be well suited for use to increase TNF levels. This paper reviews the data on TNF up-regulation by tenofovir and COX inhibitors and the consequent augmented antigen driven lymphocyte proliferation secondary to increased TNF and suggests exploration of tenofovir and COX inhibitors like indomethacin, diclofenac or ketorolac in augmentation of current cancer immunotherapy attempts. Profound COX inhibition can lead to a compensatory leukotriene increase and leukotrienes have been identified as growth and survival factors in various gastrointestinal cancers. Therefore, zileuton, an orally active 5-lipooxygenase inhibitor that prevents leukotriene synthesis, should be added whenever profound COX inhibition is undertaken in cancer immunotherapies. (C) 2003 Elsevier Ltd. All rights reserved.