ABO and cancer: From regular A transferase with LeuGlyGly or B transferase with MetGlyAla, at least 3 or 2 nucleotide substitutions are necessary to change to GlyGlyAla, respectively, and actually, no mutations at the tripeptide sequence resulting in LeuGlyGly266–268GlyGlyAla or MetGlyAla266–268GlyGlyAla substitution have been reported of ABO gene in cancer, either.