Autophagy: a novel mechanism of synergistic cytotoxicity between doxorubicin and roscovitine in a sarcoma model.
Doxorubicin is a genotoxic chemotherapy agent used in treatment of a wide variety of cancers. Significant clinical side effects, including cardiac toxicity and myelosuppression, severely limit the therapeutic index of this commonly used agent and methods which improve doxorubicin efficacy could benefit many patients. Because doxorubicin cytotoxicity is cell cycle specific, the cell cycle is a rational target to enhance its efficacy. We examined the direct, cyclin-dependent kinase inhibitor roscovitine as a means of enhancing doxorubicin cytotoxicity. This study showed synergistic cytotoxicity between doxorubicin and roscovitine in three sarcoma cell lines: SW-982 (synovial sarcoma), U2OS-LC3-GFP (osteosarcoma), and SK-LMS-1 (uterine leiomyosarcoma), but not the fibroblast cell line WI38. The combined treatment of doxorubicin and roscovitine was associated with a prolonged G(2)-M cell cycle arrest in the three sarcoma cell lines. Using three different methods for detecting apoptosis, our results revealed that apoptotic cell death did not account for the synergistic cytotoxicity between doxorubicin and roscovitine. However, morphologic changes observed by light microscopy and increased cytoplasmic LC3-GFP puncta in U20S-LC3-GFP cells after the combined treatment suggested the induction of autophagy. Induction of autophagy was also shown in SW-982 and SK-LMS-1 cells treated with both doxorubicin and roscovitine by acridine orange staining. These results suggest a novel role of autophagy in the enhanced cytotoxicity by cell cycle inhibition after genotoxic injury in tumor cells. Further investigation of this enhanced cytotoxicity as a treatment strategy for sarcomas is warranted.
Lambert
Laura A
LA
Departments of Surgical Oncology, Experimental Radiation Oncology, and Systems Biology, University of Texas - M. D. Anderson Cancer Center, Houston, Texas.
Qiao
Na
N
Hunt
Kelly K
KK
Lambert
Donald H
DH
Mills
Gordon B
GB
Meijer
Laurent
L
Keyomarsi
Khandan
K
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D003603:Cytotoxins / Q000008:administration & dosage / Q000494:pharmacology; D004317:Doxorubicin / Q000008:administration & dosage* / Q000494:pharmacology; D004357:Drug Synergism; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D008954:Models, Biological; D011687:Purines / Q000008:administration & dosage* / Q000494:pharmacology; D000077546:Roscovitine; D012509:Sarcoma / Q000188:drug therapy* / Q000473:pathology; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D003603:Cytotoxins; D011687:Purines; D000077546:Roscovitine; D004317:Doxorubicin