NOD2 and skin cancer: As a third-round validation, the expression levels of the four genes NOD2, BAX, IL-18 and ADRB2 were investigated in skin cancer samples from the GENT2 database (available at http://gent2.appex.kr/gent2/ accession on 28 May 2021), which collects data from 310 skin cancers samples and 201 controls.