Up to now, the most studies in decreased expression of Gadd45 family is Gadd45a and Gadd45 g, and the main mechanism implicated in their decreased expression was due to the promoter methylation, such as many studies showed the frequent occurring of Gadd45a and Gadd45 g promoter methylation in many types of cancers [7, 14, 23, 24]. The gene discussed is GADD45A; the disease is cancer.