SP1 and rheumatoid arthritis: Our previous identified hypomethylated cg17330251 was located at the PON1 promoter, and interestingly, there were several functional SNPs such as the −108C/T (rs705379) locus located inside cg17330251 island, which may affect the binding of the transcription factor Sp1 (specificity protein 1, Sp1) (Deakin et al., 2003) It is worth noting that, according to the literature, there are currently no studies on the association between the PON1 gene DNA methylation, SNP rs705379, and the response to LEF in RA patients.