A new view of the etiology of nasopharyngeal carcinoma

The epidemiological finding of high geographical similarity seen in the distribution of Croton tiglium, the parental plant for croton oil, as well as other related members of Euphorbiaceae family, and the nasopharyngeal carcinoma (NPC) in southern regions of China, led to the compilation of these data plus our recent laboratory observations on in vitro induction of Epstein-Barr virus (EBV) in human lymphoblastoid cell lines. The EBV genome-carrying P3HR-1 and Raji cells exerted a dramatic increase in EBV antigens when given a combined treatment with n-butyrate and croton oil, in nanogram concentrations. The Fusobacterium and other common microbial inhabitants of the mouth and nasopharynx of man efficiently produce, in laboratory culture fluids, n-butyric acid with EBV-inducer activity. Furthermore, the seeds and plant per se of C. tiglium and other Euphorbiaceae are currently being used as herbal drug in the southern parts of China. We hypothesize that NPC is initiated by persisting EBV as an essential and basic factor plus the combined action of the bacterial fatty acid and traditional intake of promoter substance of plant origin as cofactors, and that the EBV, induced and activated by such mechanisms, initiates the chain of events which ultimately lead to the emergence of the malignant disease.