LGR5 and digestive system neoplasm: By utilizing an ISCs-relevant mouse model (Lgr5+ mice) and a GI tumor surrogate model (Lgr5+Apc1638N/+ mice), we investigated the long-term effects of radiation exposure on oxidative stress, DNA damage, cellular senescence, and the development of a senescence-associated secretory phenotype (SASP) that may predispose astronauts to GI dysfunction and carcinogenesis during and after prolonged space missions.