Targeted therapy of human osteosarcoma with 17AAG or rapamycin: characterization of induced apoptosis and inhibition of mTOR and Akt/MAPK/Wnt pathways.
Osteosarcoma is highly resistant to current chemotherapy regimens. Novel therapeutic approaches, potentially involving targeting of specific survival pathways, are needed. We used 17-AAG to inhibit Hsp90 and rapamycin to inhibit mTOR, in the osteosarcoma cell lines, HOS and KHOS/NP. HOS and KHOS cells were treated for 24 and 48 h with 17-AAG or rapamycin and studied drug-induced apoptosis, cell cycle, mitochondrial membrane potential and levels of reduced glutathione (GSH), dephosphorylation of signal transduction proteins in the Akt/MAP kinase pathway and mTOR signaling. 17-AAG was a potent inducer of apoptosis, involving effective depletion of GSH and mitochondrial membrane (MM) depolarization, strong activation of caspase-8 and -9 and release of AIF from mitochondria to the cytosol. Furthermore, 17-AAG down-regulated pAkt, p44Erk, p-mTOR, p70S6, TSC1/2 and pGSK-3beta. Treatment with 17-AAG also caused down-regulation of cyclin D1, GADD45a, GADD34 and pCdc2 and upregulation of cyclin B1 and mitotic block. A decrease in Hsp90 and increase in Hsp70 and Hsp70 C-terminal fragments were also observed. Rapamycin was a less potent inducer of apoptosis, involving a small decrease in GSH and MM potential with no activation of caspases or release of AIF. Rapamycin strongly inhibited cell growth with an increase in G1 and a decrease in S-phase of the cell cycle concomitant with down-regulation of cyclin D1. Rapamycin also down-regulated the activity of p70S6, pAkt and p-mTOR, but had no effect on pGSK-3beta, p44Erk, pCdc2, TSC1/2 or Hsp70 or Hsp90. We conclude that Hsp90 inhibition merits further study in the therapy of osteosarcoma.
Gazitt
Yair
Y
Cancer Therapy & Research Center, The University of Texas Health Science Center, San Antonio, TX 78284, USA. gazitt@uthscsa.edu
Kolaparthi
Venkatasubbarao
V
Moncada
Karla
K
Thomas
Charles
C
Freeman
James
J
D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D016227:Benzoquinones / Q000627:therapeutic use*; D001859:Bone Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D047029:Lactams, Macrocyclic / Q000627:therapeutic use*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000502:physiology; D012516:Osteosarcoma / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D011494:Protein Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D020123:Sirolimus / Q000627:therapeutic use*; D058570:TOR Serine-Threonine Kinases
D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D047029:Lactams, Macrocyclic; C112765:tanespimycin; D011494:Protein Kinases; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus