ADRB2 and melanoma: As a second validation, the expression levels of NOD2, BAX, IL-18, ADRB2, ITGAV and MYO9B were analyzed in GEPIA2 database (available at http://gepia2.cancer-pku.cn/#index, accessed on 17 May 2021), a public database reporting expression data from 461 melanoma patients and 558 healthy skin controls.