ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: In addition, Sales and co-workers [66] described that FEPS cells presents a low transcript expression level of BCR-ABL1 compared to K562, indicating that the BCR–ABL1-independent mechanism of resistance, that occurs in CML patients with overexpression of P-glycoprotein (P-gp) is also found in the FEPS cell line model [67].