“…It is present in the majority of HNPCC and approximately 10% of sporadic colorectal cancers (Ionov et al, 1993;Lothe et al, 1993;Thibodeau et al, 1993;Aaltonen et al, 1994), as well as in tumors arising in extracolonic sites such as the stomach (Rhyu et al, 1994). In addition to containing widespread microsatellite instability at anonymous sequences, most tumors with this mutator phenotype harbor frameshift mutations in coding mononucleotide repeat sequences in cancer related genes TGFb RII, IGF-IIR, BAX, hMSH3, hMSH6 and E2F-4 Souza et al, 1996Souza et al, , 1997aYoshitaka et al, 1996;Rampino et al, 1997;Yin et al, 1997b;Perucho, 1996). Accumulating evidence suggests that tumorigenic pathways, characterized on the one hand by allelic losses and on the other by microsatellite instability, represent alternative processes (reviewed in Kinzler and Vogelstein, 1996).…”