Supplementary Material for: Genetic polymorphisms of rs9949644 in MAPK4 are associated with clinical response to methotrexate in patients with psoriasis

Background The study aimed to investigate the relationship of MAPK4 genetic variants with the efficacy of MTX in psoriasis patients. Methods Patients treated with MTX were classified as responders or nonresponders if the Psoriasis Area and Severity Index (PASI) at week 12 was reduced to greater than 75% or lower than 75%, respectively. The genotypes of 14 MAPK4 single nucleotide polymorphisms (SNPs) in 310 patients were analyzed. The expression levels of MAPK4 protein were detected by western blot. Results Only rs9949644 polymorphisms were associated with the efficacy after adjusting for the confounding factors. Patients with the rs9949644 AG or GG genotype had a better clinical response compared to patients with the AA genotype. Rs9949644 polymorphisms were significantly associated with the PASI improvement rate. Besides, the protein level of MAPK4, positively associated with the psoriasis severity, was higher in patients. There were no significant differences of MAPK4 protein levels among three groups. While after treatment, MAPK4 levels in the AG or GG group showed a significantly down-regulated trend. Conclusions By demonstrating the significant association of MAPK4 with the efficacy of MTX, this study indicates that MAPK4 may be involved in the psoriasis progression and act as a predictor of therapeutic response.