CTLA4 and cancer: Despite the CTLA-4 gene having more than 100 variants, in recent years, a genetic variant of variable-number tandem repeat (VNTR) located in the 3′-untranslated region (3’-UTR) of exon 4, known as (AT)n, has been found to have an essential role in genetic expression and be associated with a higher susceptibility to some types of cancer.