Direct single gene mutational events account for radiation-induced intestinal adenoma yields in Apc^Min/+ mice

Data on the induction of small intestinal tumors, predominantly adenomas, by X radiation in Apc^Min/+ mice are reported. Comparison of these incidences with estimates of radiation-induced direct single gene mutation frequencies taken from the literature support the hypothesis that direct mutational loss of Apc⁺ is the sole requirement for initiation of adenoma. Furthermore, estimates of radiation-induced initiation of adenoma per target stem cell in this animal model are similar to or less than radiation-induced direct somatic gene mutation frequencies. Therefore, while the data reported here do not preclude a role for genomic instability in tumor progression, it is not necessary in this model to postulate the involvement of radiation-induced transmissible genomic instability in initiation of intestinal adenoma.