Comparative proteomic analysis of all-trans-retinoic acid treatment reveals systematic posttranscriptional control mechanisms in acute promyelocytic leukemia

All-trans-retinoic acid (ATRA) induces growth inhibition, differentiation, and apoptosis in cancer cells, including acute promyelocytic leukemia (APL). In APL, expression of promyelocytic leukemia protein retinoic acid receptor-α (PML-RARα) fusion protein, owing to the t(15; 17) reciprocal translocation, leads to a block in the promyelocytic stage of differentiation. Here, we studied molecular mechanisms involved in ATRA-induced growth inhibition and myeloid cell differentiation in APL. By employing comprehensive high-throughput proteomic methods of 2-dimensional (2-D) gel electrophoresis and amino acid-coded mass tagging coupled with electrospray ionization (ESI) mass spectrometry, we systematically identified a total of 59 differentially expressed proteins that were consistently modulated in response to ATRA treatment. The data revealed significant downregulation of eukaryotic initiation and elongation factors, initiation factor 2 (IF2), eukaryotic initiation factor 4AI (eIF4AI), eIF4G, eIF5, eIF6, eukaryotic elongation factor 1A-1 (eEF1A-1), EF-1-δ, eEF1γ, 14-3-3ε, and 14-3-3ζ/δ (P < .05). The translational inhibitor DAP5/p97/NAT1 (death-associated protein 5) and PML isoform-1 were found to be up-regulated (P < .05). Additionally, the down-regulation of heterogeneous nuclear ribonucleoproteins (hnRNPs) C1/C2, UP2, K, and F; small nuclear RNPs (snRNPs) D3 and E; nucleoprotein tumor potentiating region (TPR); and protein phosphatase 2A (PP2A) were found (P < .05); these were found to function in pre-mRNA processing, splicing, and export events. Importantly, these proteomic findings were validated by Western blot analysis. Our data in comparison with previous cDNA microarray studies and our reverse transcription-polymerase chain reaction (RT-PCR) experiments demonstrate that broad networks of posttranscriptional suppressive pathways are activated during ATRA-induced growth inhibition processes in APL.