Sensitization and apoptosis augmentation of K562/ADM cells by anti-multidrug resistance gene peptide nucleic acid and antisense oligodeoxyribonucleotide.

AIM: To investigate the reversal effect and apoptosis enhancement of peptide nucleic acid (PNA) and antisense oligodeoxyribonucleotide (ASODN) targeted to multidrug resistance gene (mdr1) on human multidrug resistant leukemia K562/ADM cells. METHODS: A 15-mer PNA and the same sequence of ASODN, complementary to the 5' end of the AUG initiator codon-containing region of mdr1 messenger RNA (MDR1-PNA, MDR1-ASODN), were designed and synthesized. Proliferation and sensitivity to adriamycin of K562/ADM cells treated with MDR1-PNA- and MDR1-ASODN were analyzed with a MTT colorimetric assay. Apoptotic morphologies, P-glycoprotein (P-gp) expression, intracellular adriamycin accumulation, and cell cycle were measured. RESULTS: MDR1-PNA 1 to 10 micromol/L and MDR1-ASODN 2 to 20 micromol/L alone had no inhibitory effects on the proliferation of K562/ADM cells, but significantly inhibited the growth of K562/ADM cells cultured in adriamycin-containing medium. After treatment with MDR1-PNA and MDR1-ASODN, intracellular adriamycin accumulation in K562/ADM cells increased greatly and P-gp synthesis was strikingly reduced. The resistance to adriamycin of the drug-resistant cells was partly reversed and the cells were induced to apoptosis by adriamycin. The reversal efficacy of MDR1-PNA was 3.1-fold higher than that of the same sequence of MDR-ASODN, but neither MDR1-PNA nor MDR1-ASODN could completely block the mdr1/P-gp expression. CONCLUSION: Sequence-special PNA targeted to mdr1 gene more effectively than the same sequence of MDR1-ASODN inhibited the expression of P-glycoprotein to overcome the drug-resistance.

[Arsenic trioxide inhibits P-glycoprotein expression in multidrug-resistant human leukemia K562/ADM cell line that overexpresses mdr-1 gene and enhances their chemotherapeutic sensitivity].

OBJECTIVE: To investigate the effects of arsenic trioxide (As(2)O(3)) on the apoptosis and P-glyco-protein (P-gp) expression of multidrug-resistant human leukemia K562/ADM cells, and the combined effects of As(2)O(3) with conventional chemotherapeutic agents. METHODS: Multidrug-resistant human leukemia cell line K562/ADM that overexpresses mdr-1 gene was used as the target cells. The cell proliferating activity was assessed with a MTT assay. Cell morphology was examined by light microscopy, confocal microscopy and electron-microscopy. P-gp expression, cell-cycle status were determined by flow cytometry. RESULTS: K562/ADM cells were highly resistant to adriamycin, and cross-resistant to daunorubicin and etoposide. As(2)O(3) at concentrations of 0.5 to 20 micromol/L inhibited the proliferation of K562/ADM cells, and K562/ADM cells were more sensitive to As(2)O(3) than their parent K562 cells did. As(2)O(3) induced marked apoptosis of K562/ADM cells showed by typical apoptotic morphological changes and the appearance of high sub-G(1) cell population. As(2)O(3) significantly inhibited the P-gp expression in K562/ADM cells, and exerted a synergistic effect on the enhancement of the cell sensitivity to adriamycin, daunorubicin and etoposide. CONCLUSION: As(2)O(3) induces growth-inhibition and apoptosis of multidrug-resistant K562/ADM cells, and augments synergistically the sensitivity of the cells to conventional chemotherapeutic agents via down-regulation of P-gp expression.