Smoking and Infectious Diseases “Our individual life history is
inscribed in our epigenome,” states Toshikazu Ushijima, Ph.D.,
chief of the carcinogenesis division at the National Cancer
Center Research Institute, Tokyo. Dr. Ushijima and collaborators
screened genes that were silenced in esophageal squamous cell
carcinomas and demonstrated that methylation levels in five
promoters are significantly correlated with the duration of
tobacco smoking, indicating that chronic smoking induces
methylation changes in many of these genes. This finding
supports the idea that smoking induces an epigenetic field of
cancerization, a term that was previously described for breast,
colon, liver, and stomach cancers, and is used to denote
epigenetic modifications that occur during the early stages of
carcinogenesis. Back in 2006, Dr. Ushijima and colleagues used
real-time methylation-specific quantitative PCR to conduct a
temporal characterization of DNA-methylation levels in the
gastric mucosa in patients infected with Helico