Opium Consumption and the Incidence of Cancer: Does Opium Account as an Emerging Risk Factor for Gastrointestinal Cancer?

Abstract

Some epidemiological studies have shown an association between opium consumption and the incidence of gastrointestinal (GI) cancer. The present study was designed to investigate the effects of opium on the initiation of GI cancer in rats. Forty-five rats were randomly divided into three groups; each received different treatment for 40weeks. The rats in group 1 received purified water, while animals in group 2 were treated with 5mg/kg diethylnitrosamine (DEN) orally for 8weeks and continued with purified water by the end of the experiment. The third experimental group received 300mg/kg opium for 16weeks and then continued with 50mg/kg phenobarbital by the end of the 40th week. The growth of tumors in the treated groups was assessed by histological changes and the up/down expression of p53, cdkn1, cdk2, e-cdh, and n-cdh genes in different parts of GI tract. Histological examinations revealed that DEN was able to induce the growth of tumor in GI tract as shown by active mitotic figure in different regions of GI system and hyperplasia of hepatocytes associated with infiltration of inflammatory cells, intestinal villous hypertrophy, and colorectal adenoma. There was also significant (p < 0.05) overexpression of p53, cdk2, and n-Cdh genes in different parts of digestive system in DEN-treated group. However, these pathological changes and the degradation of gene expression were not observed in the opium-treated group. The results of this study suggest that the opium does not promote the initiation of cancer in GI tract.