Viscum album preparations inhibit DNA methylation by preventing DNA methyltransferase-induced methyl group transfer

Interactions between viscum album (Iscador) and DNA were studies by amplification of specific human pepsinogen A gene promoter sequences by polymerase chain reaction (PCR). Gel retardation assays showed no binding of Viscum album to these promoter sequences. Incubation of plasmid constructs consisting of human pepsigen A promoter fragments coupled to thechloramphenicol acetyl-transferase (CAT) reporter gene with Iscador had no effect on transcriptional activity. Promoter sequences incubated with Iscador became insensitive to methylation by specific DNA methyltransferases by destruction of DNA methyltransferase activity

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

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 24hrs 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 MH86L12 was 0.005 mg/ml, while for MH87 D24 it was 0.05 mg/ml after 24hrs. 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