M. Muto et al., Acetaldehyde production by non-pathogenic Neisseria in human oral microflora: Implications for carcinogenesis in upper aerodigestive tract, INT J CANC, 88(3), 2000, pp. 342-350
Many epidemiological studies have identified chronic alcohol consumption as
a significant risk factor for cancer of the upper aerodigestive tract (UAT
) in human. Although acetaldehyde, the first metabolite from ethanol by alc
ohol dehydrogenase (ADH), is regarded as a carcinogen, how systemic product
ion of acetaldehyde particularly affects the UAT remains unclear. In our st
udy, we searched for the regional source of acetaldehyde in UAT, especially
the involvement of bacteria in the human normal oral microflora. Here we d
emonstrate that, among the bacterial species identified from the human oral
cavity, genus Neisseria had extremely high ADH activity and produced signi
ficant amounts of acetaldehyde when cultured with medium containing ethanol
in vitro. The ability to produce acetaldehyde was more than 100-fold highe
r than that produced by any other genera we studied. Furthermore, alcohol i
ngestion influences the bacterial composition of the oral microflora, resul
ting in an increased proportion of Neisseria. Although Neisseria present: i
n normal oral microflora is generally non-pathogenic, these findings sugges
t that this microbe can be a regional source of carcinogenic acetaldehyde a
nd thus potentially play an important role in alcohol-related carcinogenesi
s in human UAT. Int. J. Cancer 88:342-350, 2000. (C) 2000 Wiley-Liss. Inc.