1. Autophagy is Required to Regulate Mitochondria Renewal, Cell Attachment, and All-trans–Retinoic Acid–Induced Differentiation in NB4 Acute Promyelocytic Leukemia Cells
- Author
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Ugur Akar, Bulent Ozpolat, Ibrahim Tekedereli, S. Neslihan Alpay, and Gabriel Lopez-Berestein
- Subjects
Acute promyelocytic leukemia ,Health, Toxicology and Mutagenesis ,Cellular differentiation ,Cell ,ATG5 ,Retinoic acid ,Toxicology ,Pathology and Forensic Medicine ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Leukemia, Promyelocytic, Acute ,Cell Line, Tumor ,Autophagy ,Cell Adhesion ,medicine ,Humans ,Protein Glutamine gamma Glutamyltransferase 2 ,Phosphorylation ,neoplasms ,Mechanistic target of rapamycin ,PI3K/AKT/mTOR pathway ,biology ,TOR Serine-Threonine Kinases ,organic chemicals ,Cell Differentiation ,General Medicine ,medicine.disease ,biological factors ,Mitochondria ,Cell biology ,Gene Expression Regulation, Neoplastic ,medicine.anatomical_structure ,Proto-Oncogene Proteins c-bcl-2 ,chemistry ,030220 oncology & carcinogenesis ,biology.protein ,Beclin-1 - Abstract
All-trans-retinoic acid (ATRA) is a potent inducer of cellular differentiation, growth arrest, and apoptosis as well as a front-line therapy for acute promyelocytic leukemia (APL). The present study provides evidence that induction of autophagy is required for ATRA to induce differentiation of APL (NB4) cells into granulocytes. ATRA treatment causes ~12-fold increase in the number of acidic vesicular organelles and induces marked up-regulation of LC3-II, autophagy-related 5 (ATG5), and Beclin-1. Transmission electron microscopy (TEM) revealed a decrease in mitochondria and ATRA-induced differentiation. To determine the role of autophagy in the differentiation of APL, we knocked down ATG5 in NB4 cells to find that ATRA-induced differentiation is significantly inhibited during ATG5 knock down in cells, indicating the role of autophagy in differentiation of APL. Further experiments revealed restriction of autophagy during ATRA-induced differentiation and inhibition of tissue transglutaminase 2 (TG2) and phospho-focal adhesion kinase (p-FAK), which are known to have roles in differentiation and cell attachment. We examined expression of Beclin-1 and B-cell lymphoma-2 (Bcl-2) and levels of mechanistic target of rapamycin (mTOR) after ATRA treatment. ATRA inhibits Bcl-2, up-regulates Beclin-1 expression, and reduces induction of mTOR activation/phosphorylation in NB4 cells. Our results reveal that autophagy has roles in regulation of differentiation, mitochondria elimination, and cell attachment during ATRA-induced APL differentiation.
- Published
- 2019