PTPRG is expressed at low levels in CML cells, but the PTPRG expression is not negatively regulated by BCR-ABL1 (data not shown) and low PTPRG levels in CML cells may be the result of a long-term selection process, possibly based on a small growth advantage of cells with lower PTPRG levels caused by PTPRG promoter methylation [22, 27]. This evidence concerns the gene PTPRG and chronic myelogenous leukemia, BCR-ABL1 positive.