Acute promyelocytic leukemia cell line AP-1060 established as a cytokine-dependent culture from a patient clinically resistant to all-trans retinoic acid and arsenic trioxide

AP-1060 is a newly established acute promyelocytic leukemia (APL) cell line from a multiple-relapse patient clinically resistant to both all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). The line was initially derived as a granulocyte colony-stimulating factor-dependent strain that underwent replicative senescence and, following ethylnitrosourea treatment, as a phenotypically similar immortalized line. Immortalization was associated with broadened cytokine sensitivity but not growth autonomy, in contrast to three previously derived APL lines. Both the AP-1060 strain and line had shortened telomeres and low telomerase activity, while the line had higher expression of many genes associated with macromolecular synthesis. The karyotype was 46,XY,t(3;14)(p21.1;q11.2),t(15;17)(q22;q11) [100%]; the unique t(3;14) was observed in 4/9 t(15;17)-positive metaphase cells at previous relapse on ATRA therapy. The PML-RARα mRNA harbored a missense mutation in the RARα-region ligand-binding domain (Pro900Ser). This was associated with a right-shift and sharpening of the ATRA-induced maturation response compared to ATRA-sensitive NB4 cells, which corresponded to the transcriptional activation by PML-RARαω Prog900Ser of a cotransfected ATRA-targeted reporter vector in COS-1 cells. AP-1060 also manifested relative resistance to ATO-induced apoptosis at ≥ 1 μM, while 0.25 μM ATO stimulated limited atypical maturation. These findings suggest that AP-1060 will be useful for further assessing molecular elements involved in APL progression and drug response/resistance.