Doxorubicin modulates telomerase activity in Ewing's sarcoma in vitro and in vivo.
Since most tumours escape replicative senescence by re-activation of the enzyme telomerase, telomerase is a promising target in the treatment of cancer and a promising marker for diagnosis and therapeutic response. We evaluated the effects of doxorubicin, one of the most active drugs in the treatment of Ewing's sarcoma, on telomerase in the human Ewing's sarcoma cell line STA-ET-1 in vitro and in STA-ET-1 xenografts in vivo. Telomerase activity (TA) was examined by TRAP-assay and real-time PCR. Real-time PCR was also used to quantify the mRNA expression of the catalytic subunit of telomerase (hTERT). In vitro growth inhibition was determined by the MTT-assay. Tumour xenografts were analyzed for tumour volume, apoptosis, necrosis, and proliferation. Doxorubicin concentrations that inhibited in vitro growth of STA-ET-1 by 50% compared to untreated controls ranged between 0.14 microM after 24 h and 0.01 microM after 72 h. Compared to untreated controls doxorubicin reduced TA in STA-ET-1 at toxic concentrations, but increased TA at non-toxic concentrations. In comparison with untreated xenografts, TA was reduced to 65% and hTERT expression dropped to 25% within 72 h in xenografts treated with 17.5 mg/kg doxorubicin i.p.; both recovered to initial values after 264 h. The rate of proliferating cells dropped to 70% within 96 h and increased thereafter. The highest rates of necrosis and apoptosis were seen after 96 h. hTERT expression co-varied significantly with proliferation but not with TA, apoptosis, and necrosis. No correlation was observed between TA, proliferation, apoptosis and necrosis. The results suggest doxorubicin induces down-regulation of hTERT gene expression that at least in part modulates TA in these tumours.
Lanvers-Kaminsky
Claudia
C
University Children's Hospital, Department of Pediatric Hematology and Oncology, Albert-Schweitzer Str. 33, 48129 Muenster, Germany. lanvers@uni-muenster.de
Winter
Barbara
B
Koling
Susanne
S
Frodermann
Bernd
B
Braun
Yvonne
Y
Schaefer
Karl-Ludwig
KL
Diallo
Raihanatou
R
Koenemann
Stephan
S
Wai
Daniel
D
Willich
Normann
N
Poremba
Christopher
C
Schuck
Andreas
A
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology* / Q000627:therapeutic use; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012512:Sarcoma, Ewing / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays
D000903:Antibiotics, Antineoplastic; D012333:RNA, Messenger; D004317:Doxorubicin; D019098:Telomerase