APC and neoplasm: While spectral karyotyping of tumors revealed aneuploidy, suggesting a role of CIN in tumor progression in the CPC;Apc mouse model [10], CDX2P9. 5-G19Cre;Apcflox/flox and CDX2P9. 5-G22Cre;Apcflox/flox mice provided evidence for MSI-induced colorectal carcinogenesis resulting from the elimination of both Apc alleles by Cre recombinase activity following a frameshift reversion mutation in a 19- or 22-guanine repeat sequence [11].