Expression of the mitochondrial ARTS protein, a splice variant of the SEPT4 gene, is lost in the majority of childhood acute lymphoblastic leukemias and SEPT9 expression is down-regulated by promoter methylation in head and neck squamous cell carcinomas, suggesting that both genes can function as tumor suppressor genes [35,36]. This evidence concerns the gene SEPTIN4 and head and neck squamous cell carcinoma.