| Abstract: |
Acute promyelocytic leukemia (APL) cells, containing the t(15;17) rearrangement, express the fusion protein, PML/RARα. Clinically, patients respond to all-trans retinoic acid (ATRA) through complete remissions associated with myeloid maturation of leukemic cells. This clinical ATRA response of APL is linked to PML/RARα expression. Unfortunately, these remissions are transient and relapsed APL is often ATRA-resistant. The role PML/RARα plays in the growth and maturation of these APL cells with acquired ATRA resistance has not been fully explored. This study uses an ATRA- resistant NB4 cell line (NB4-R1) to investigate the contribution of PML/RARα expression to ATRA resistance. Targeting of PML/RARα in NB4-R1 cells was undertaken using two approaches: homologous recombination and hammerhead ribozyme-mediated cleavage. Reducing PML/RARα protein in NB4-R1 cells rendered these cells more sensitive to ATRA. These cells were growth- inhibited in ATRA, apoptosis was induced, and there was no apparent signaling of differentiation. Sequence analysis identified a mutation in the ligand binding domain (LBD) of the RARα portion of PML/RARα. Results show that these retinoid-resistant NB4 cells require persistent PML/RARα expression for leukemic cell growth. Taken together, these findings can account for why these cells do not respond to ATRA and how reduction of PML/RARα abrogates the antiapoptotic effect it confers to these leukemic cells. |
| Keywords: |
controlled study; protein expression; oncoprotein; gene translocation; human cell; genetics; antineoplastic agents; antineoplastic agent; metabolism; gene targeting; apoptosis; gene expression; nuclear protein; neoplasm proteins; transcription factor; antineoplastic activity; drug resistance; tumor cells, cultured; transfection; transcription factors; nuclear proteins; leukemia, promyelocytic, acute; cancer regression; amino acid sequence; genetic transfection; cell culture; messenger rna; rna, messenger; nucleotide sequence; tumor suppressor proteins; recombinant proteins; recombinant protein; tumor protein; promyelocytic leukemia; oncogene proteins, fusion; translocation, genetic; dna mutational analysis; tumor suppressor protein; retinoic acid; chromosome 17; chromosomes, human, pair 17; chromosomes, human, pair 15; retinoic acid receptor; tretinoin; receptors, retinoic acid; ribozyme; chromosome 15; chromosome translocation 17; rna, catalytic; pml protein, human; humans; human; priority journal; article; chromosome translocation 15
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