GSTP1 and asthma: The fact that well-replicated asthma candidate genes (i.e., IL4, GSTP1, STAT6, ADRB2, TNF, TGFB1, etc) [61] are not listed as GWAS hits, and that low-ranked SNPs contribute to predict asthma-related phenotypes in children [52], suggests that gene-gene interactions, gene-environment interactions and epigenetics may be of relevance.