Furthermore, lots of pathways, such as PI3K/AKT (7), Notch (8), Foxo (9), ATM/ATR (10), MEK/ERK (11), TGFβ (12, 13), Wnt (14), and genes, such as SMAD4 (15), MUC1 (16), RAD54 (17), have been identified to regulate the endogenous signals and contribute to resistance to radiation therapy (RI) in some cancers. Here, SMAD4 is linked to cancer.