Effect of Viscum album preparations on gastric chief cells and DNA methylation by N-methyl-N′-nitro-N-nitrosoguanidine

Abstract

The protective effect of extracts of mistletoe Viscum album (Iscador) with reference to carcinogenesis was tested on in vitro cultured porcine gastric chief cells. Putative protection against in vitro methylation of lambda DNA by N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) was studied with restriction endonucleases. Preparations of Iscador from mistletoe grown on oak as host tree had a high cytotoxic effect on gastric chief cells, with an LC50 after 24 hrs that ranged between 0.01 and 0.03 mg/ml. At 0.01 mg/ml, Iscador was also found to protect lambda DNA from methylation or destruction by MNNG. During the course of this study a high variability was found both in cytotoxicity and protection rate against methylation which we attribute to batch to batch differences. Thus the LC50 for Iscador MH 86 L12 was 0.005 mg/ml, while for MH87 D24 it was 0.05 mg/ml after 24 hrs. The Iscador batch W frf 50 mg/ml, which was made from a fresh plant extract at the Hiscia Institute, showed less variability. Results are therefore given for this batch of Iscador only.

Key Words

Carcinogenesis - Gastric chief cell culture - DNA methylation - Mistletoe - Viscum album L. - Iscador - N-methyl-N′-nitro-N-nitrosoguanidine