Abstract: Gene expression patterns were analyzed that identified multiple genes associated with radiation enhanced colon carcinogenesis. Some of the genes modulated by radiation exposure may be involved in up-regulating the Wnt/?-catenin signaling pathway and promote colon carcinogenesis. Consumption of a fish oil/pectin diet caused a general down-regulation of genes encoding proteins involved in cell adhesion and receptor activity, which may be involved in down-regulating the Wnt/?-catenin signaling pathway. The data suggest that dietary fish oil/pectin may be an effective countermeasure against radiation-induced colon carcinogenesis. In accordance with this, gene expression profiles can be monitored to reduce the risk of radiation induced carcinogenesis in high risk personnel (i.e., for example, astronauts) before, during, and/or after radiation exposure (i.e., for example, spaceflight), and/or to detect radiation-induced carcinogenesis so that an appropriate countermeasure administration can be implemented.