The FOXO1 transcription factor belongs to the Forkhead family and is known as a tumour suppressor that regulates the expression of a series of cancer‐associated genes, such as cyclin D1, IGFBP‐1, p130, p27, p21, cyclin D2, FasL and Bim.27, 28, 29, 30, 31, 32. The gene discussed is CCND2; the disease is cancer.