[Reactive oxygen species in the pathogenesis of gastrointestinal tumors. A follow-up study]

Development and growth of gastrointestinal tumors seems to correlate closely with the formation of reactive oxygen intermediates (ROI). It is known, that oxygen-free-radicals are able to induce a precancerous stage and tumor growth by damaging DNA or changing the protein and lipid structure. To investigate, whether the cellular formation of oxygen-free radicals plays a role in the pathogenesis of colorectal carcinoma, we performed the study presented here. 40 patients with colorectal carcinoma were studied over a period of 6 months (before operation, 10 days after operation, 3 months later, 6 months later). Oxygen-free radicals were determined by chemiluminescence response in the whole blood, in granulocytes and in monocuclear blood cells (MBC). At the same time the trace elements selenium, Copper and Zinc, known to play an important role as antioxidants, were measured.

We observed, that the ability of granulocytes for phagocytosis was depleted. However, this effect could be reversed as demonstrated in in vitro stimulation assays. After 6 months the phagocytosis by granulocytes achieved again normal values. Simultaneously a dramatic increase in superoxide-anions generated by mononuclear blood cells was seen. This increase was still obvious after 6 month. Independent of the tumor state selenium deficiency was found in all patients. Since no substitution of selenium was performed after operation, this deficiency was not normalised.

The ability for phagocytosis and therefore the immune response is reduced in a reversible manner. In addition reactive superoxide-anions, that are able to induce tumors, are formed. This risk is increased in the absence of selenium. Thus, clinical follow-up studies are needed to determine subclinical tumor relapses and to investigate the role of oxidative stress by chemi-luminescence. As consequence of this study selenium substitution seems to be indicated.