In a parallel study, using the same subjects and general methods, Rotter and colleagues [114] also measured CB1 and CB2 expression and CB1 promoter methylation. CB1 expression was significantly different between all three groups, as was CB1 promoter methylation, with cannabis dependent subjects having the highest level of methylation (89%), followed by cigarette smokers (84.4%) and non-smokers (62.5%). CB1 promoter methylation was negatively correlated with expression in all three groups as a whole. CB1 expression levels also correlated significantly with clinical variables including craving. As in the previous study, cotinine and cannabinoids were not measured for comparison, analyses were not adjusted for blood cell composition, and site-specific CpG methylation levels could not be assessed. Despite this, these results suggest CB1 promoter methylation and gene expression as additional potential biomarkers for THC dependence.
