RMCE on KH2 cells inserted into the 3'UTR a RNU6 promoter driving expression of tandem guide RNAs targeting murine Apc 12 bp immediately upstream of the NGG protoscpacer-adjacent motif (PAM) sequence and Trp53 followed by a tetracycline response element promoter driving inducible expression of a GFP report gene, IRES sequence, human codon optimized CRISPR-associated endonuclease cas9 (derived from Streptococcus pyogenes CRISPR associated protein 9 [SpCas9]) and polyadenylation sequence.