E2F4 and cancer: Over-expression of XPO1 enables cancer cells to prematurely export Tumour Suppressor Proteins (TSPs) such as p53, p73, p21, p27, FOXO (1, 3a, and 4), PP2A, BRCA1 and BRCA2, and E2F4 and evade apoptosis and promote malignancy14,23,47,48.