With these premises, we supposed that the epigenetic control exerted by the Polycomb family genes could be at least one of the causes of the resistance to TKIs in CML: as we have already demonstrated in our previous work BMI1 could represent a new valid, predictive marker of response to imatinib, independently from the BCR-ABL1 behavior or ABL1 mutations (16). The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.