Azoxymethane-induced colorectal tumorigenesis in hypertensive rat models

To compare the tumor susceptibility between the hypertensive Dahl salt-sensitive rats (S) rat and S.LEW(10)x12x2x3x5 (S.LEW) congenic strain, one of the S.LEW congenic strains our laboratory previously constructed on rat chromosome 10 [Hypertension. 2007 Nov;50(5):891-8], Azoxymethane (AOM)-induced colon tumorigenesis in rats was assessed. At six weeks of age, both S and S.LEW congenic rats received intraperitoneal (IP) injection of AOM in sterial saline at a dose of 15mg/kg body weight once a week for two consecutive weeks. At 30 weeks of age, all the rats were euthanized through carbon dioxide inhalation. The colon tissue was harvested, dissected longitudinally, and washed with saline. The number and size of the colon tumors were recorded. We found that the total number of colon tumors was significantly higher in the S.LEW congenic strain compared with the S rat. To further study the genetic and molecular mechanisms causing the higher tumor susceptibility in the S.LEW congenic strain, we have employed the whole genome microarray expression profiling to identify genes and signaling pathways that are differential between the S and S.LEW congenic strain. At six weeks of age, both S and S.LEW congenic rats received intraperitoneal (IP) injection of AOM in serial saline at a dose of 15mg/kg body weight once a week for two consecutive weeks. At 30 weeks of age, all the rats were euthanized through carbon dioxide inhalation. The colon tissue was harvested, dissected longitudinally, and washed with saline. RNA from the harvested colons of 3 S and 3 S.LEW congenic rats were prepared for the microarray study.