Promoting effect of Roussin's red identified in pickled vegetables from Linxian China.

Roussin's red (dimethylthiotetranitrosodiiron) has been identified as a non-alkylating N-nitroso compound present in pickled vegetables from Linxian, a high risk area for oesophageal cancer in China. In vitro experiments showed that Roussin's red had no significant mutagenic and transforming activities at the doses used, but it did enhance transformation in C3H/10TI/2 cells initiated with 3-methylcholanthrene (0.1 microgram/mI) and it decreased the number of sebaceous glands and increased the epidermal thickness in short term skin tests. In this respect Roussin's red resembled 12-O-tetradecanoyl-phorbol-13-acetate and the results indicate that it may be a new naturally-occurring tumour promoter. The in vitro promoting effect of extracts of pickled vegetables that has been previously reported can be explained, at least in part, by the presence of Roussin's red. The possible role of Roussin's red in the aetiology of oesophageal cancer is discussed.