With the development of array-based methylation profiling, investigators have been able to look more broadly at candidate and genome-wide loci. Four studies using Illumina’s GoldenGate array platform for methylation were found. Two of the studies used the cancer candidate gene focused panel available from the manufacturer [43,94], while two others by the same group [95,96] used custom arrays for alcohol-related candidate genes on the same platform. Although limited by a small sample size of 29, Christensen and colleagues [43] reported 12 hypermethylated CpGs and 20 hypomethylated CpGs at candidate cancer genes, the latter including HTR1B. The other study using the cancer candidate gene focused platform found no significant differences due to smoking, and only 5 sites with a delta beta of more than 5%. Interestingly, in a subgroup of alcoholic smokers versus their abstinent siblings, a significant difference was found in mean methylation. Among the two studies by the same group using the custom array, positive associations with HTR3A were found in one study, though in European Americans only [95], and in the other, no associations with alcohol use alone
