Objective: To investigate the effects of anti-PML (promyelocytic leukemia) or anti-PML/RARa (promyelocytic leukemia/retionic acid receptora) antisense oligonucleotides on cell growth, expression of PML-RARa mRNA and PML-RARa/PML protein location of NB4 cell lines. Methods: RT-PCR was used for detecting PML-RARa mRNA expression, trypan blue exclusion for cell count, methylcellose assay for leukemic colony forming unit detection, immuno- fluorescence for PML-RARa/PML protein location. Results: Both anti-PML start codon region antisence (STAS) and anti-PML-RARa fusion region antisence (FUAS) could inhibit cell growth and the formation of acute myelocytic colony forming unit of cells(AML-CFU). Cells become partial differentiated at days 5, being more obvious in FUAS-treated cells than in STAS ones. Down regulation of PML-RARa mRNA expression occurred at 24 hours in STAS and FUAS-treated cells and maintained for up to 72 hours. Immuno-fluorescence analysis with anti-PML monoclonal antibody showed a remarkable decrease even complete disappearance of microgranules. The residual granules became enlarged as discrete dots (<10 per cell), similar to normal POD structure in some STAS-treated cells at 24 hours. At 72 hours, nearly all the granules disappeared. Similar changes were observed in FUAS-treated cells. Conclusion: Both PML and PML-RARa antisence oligonucleotides can specially block the expression of PML-RARa at mRNA and protein levels. PML protein is implicated in the regulations of cell differentiation.
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