SMPD3 and cancer: Of the seven CpG sites in the data set, we included only those five known to be located within the promoter CpG island of SMPD3 in our analysis (cg00891541, cg15201635, cg10556064, cg22116290, cg23758485) as hypermethylation of this genomic region has been linked to cancer progression through repression of tumor suppressor genes [15].