title: An imbalance between Beclin-1 and p62 expression promotes the proliferation of myeloma cells through autophagy regulation.
abstract: Autophagy occurs in tumor cells acquiring cytotoxic drug resistance and its activation may impair their susceptibility to apoptosis in response to apoptogen agents. We investigated the pro-apoptotic effect of dexamethasone (Dex) on MM cell lines (U266, INA-6, LR5-8226, LIG, and MCC2) and primary malignant plasma cells from naïve and refractory/relapsed patients. We evaluated the transcriptional and ultrastructural events leading to autophagy by measuring Beclin-1 and p62 levels and transmission electronic microscopy. Autophagy was inhibited by hydroxychloroquine (HCQ), whereas the ability of Dex-resistant MM cells to recover the susceptibility to apoptosis was measured. A direct relationship between autophagy and Beclin-1 or LC3/Atg8 levels was observed, whereas their mRNAs were inversely correlated to p62 expression. Starvation strongly activated autophagy by inducing cellular, transcriptional, and ultrastructural modifications that were reversed by HCQ. Taken together, these data suggest that autophagy is a potential mechanism leading to drug resistance in MM, and suggest Beclin-1 and p62 as early markers of cell susceptibility to apoptosis. The combination of HCQ with novel agents may thus be considered to improve the therapeutic response in relapsed/resistant MM patients.
authors: Department of Biomedical Sciences and Clinical Oncology, University of Bari 'Aldo Moro', Bari, Italy. Electronic address: marco.tucci@uniba.it.
authors: Marco
authors: M
authors: Tucci
authors: Department of Biomedical Sciences and Clinical Oncology, University of Bari 'Aldo Moro', Bari, Italy.
authors: Stefania
authors: S
authors: Stucci
authors: Department of Biomedical Sciences and Clinical Oncology, University of Bari 'Aldo Moro', Bari, Italy.
authors: Annalisa
authors: A
authors: Savonarola
authors: Department of Emergence and Organ Transplantation, University of Bari 'Aldo Moro', Bari, Italy.
authors: Leonardo
authors: L
authors: Resta
authors: Department of Biomedical Sciences and Clinical Oncology, University of Bari 'Aldo Moro', Bari, Italy.
authors: Mauro
authors: M
authors: Cives
authors: Department of Emergence and Organ Transplantation, University of Bari 'Aldo Moro', Bari, Italy.
authors: Roberta
authors: R
authors: Rossi
authors: Department of Biomedical Sciences and Clinical Oncology, University of Bari 'Aldo Moro', Bari, Italy.
authors: Franco
authors: F
authors: Silvestris
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000071190:Autophagy-Related Protein 8 Family; D000071186:Beclin-1; D045744:Cell Line, Tumor; D003907:Dexamethasone / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006886:Hydroxychloroquine / Q000494:pharmacology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics; D009101:Multiple Myeloma / Q000473:pathology*; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D000071456:Sequestosome-1 Protein; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000071190:Autophagy-Related Protein 8 Family; C491997:BECN1 protein, human; D000071186:Beclin-1; C498698:GABARAPL2 protein, human; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D006886:Hydroxychloroquine; D003907:Dexamethasone