Clinical and experimental findings suggest tumor cell quiescence in imatinib-treated GIST
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Transcript of Clinical and experimental findings suggest tumor cell quiescence in imatinib-treated GIST
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Imatinib Mesylatemodulates Regulators of Quiescence in
Gastrointestinal Stromal Tumor (GIST) cells
Joshua A. Parry, Matthew F. Brown, Danushka Seneviratne,Stefan Duensing, Anette Duensing
University of Pittsburgh Cancer Institute,Pittsburgh, PA
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Clinical and experimental findings suggesttumor cell quiescence in imatinib-treated GIST
• Major problems of imatinib therapy: therapy resistance incomplete responses
• Detectable tumor mass under treatment
• Relapse when imatinib therapy is terminated
• Tumor cells that do not respond to imatinib by undergoing apoptosis but remain quiescent may be a reservoir for resistant GIST cells
Holdsworth, Am J Roentgenol 2007;189:W324-W330
transgenic KitV558 /+ mouse
(in collaboration with C. Antonescu and P. Besmer)
PE
TC
T
baseline imatinib
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Tumor cell quiescence
• Definition:
• lack of growth/proliferation, “non-dividing state”
• exit of cell division cycle in G0/G1
• reversible
• In contrast to senescence (= irreversible)
• Molecular regulators:
• p27Kip1
• DREAM complex
• Problem for cancer therapy:
• quiescent cells do not respond to anticancer agents that target proliferating cells
• quiescent cells are unlikely to undergo apoptosis
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Regulation of quiescence
proliferating cellscells in G0/G1
APC inactive
SKP2 high
p27 low
CDK active
SKP2 low
p27 high
CDK inactive
APC active
DREAM active
DREAM inactive
D R E A MD
M
R
E
A
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Effects of imatinib on regulators of quiescence
GIST882GIST882
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p27Kip1 upregulation in mouse xenografts
GIST882xenografts
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p27Kip1 and SKP2 - risk for progression
Risk of progression (NCCN)
< 63.7% p27 pos.
cells
> 63.7% p27 pos.
cellsTotal
None, very low, low, intermediate
6 13 19
High 6 3 9
Total 12 16 28
Risk of progression (NCCN)
≤ 5 SKP2 pos.
cells/HPF
> 5 SKP2 pos.
cells/HPFTotal
None, very low, low, intermediate
17 0 17
High 4 5 9
Total 21 5 26
SKP2 (p<0.0001)p27Kip1 (p=0.0797)
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Non-apoptotic cells enter quiescenceafter imatinib
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Quiescent cells can re-enter the cell cycle
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Imatinib and the DREAM complex
mammalian DREAM complex(DP, RB-like (p130), E2F and MuvB=LIN)
E2F target gene
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Conclusions
imatinib leads to cell cycle exit and cellular quiescence• modulation of the APCCDH1 – SKP2 – p27Kip1 axis• modulation of the DREAM complex members
quiescent cells readily re-enter the cell cycle after removal of
imatinib
compounds that modulate these pathways as potential
antitumor agents in GIST?
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Acknowledgments
Duensing Lab• Joshua Parry• Danushka Seneviratne• Matthew Brown• Julianne Baron• Ying Liu• Sophie Perdreau• Payel Chatterjee• Stefan Duensing
American Cancer Society(#RSG-08-092-01-CCG)GIST Cancer Research FundLife Raft Group (#UPCC-AD-100108)
University of Pittsburgh• Shih-Fan Kuan
Brigham & Women's Hospital• Jonathan Fletcher
Katolieke Universiteit Leuven• Maria Debiec-Rychter• Patrick Schöffski
Dana Farber Cancer Institute• James DeCaprio• Larisa Litovchick
Memorial Sloan Kettering• Peter Besmer• Cristina Antonescu
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Pro-apoptotic Activity of Bortezomib in Gastrointestinal Stromal Tumors (GIST) cells
Sebastian Bauer1, Joshua A. Parry2, Thomas Mühlenberg1,Payel Chatterjee2, Shih-Fan Kuan2, Jonathan A. Fletcher3,
Stefan Duensing2, Anette Duensing2
1University of Duisburg-Essen, Essen, Germany2University of Pittsburgh Cancer Institute, Pittsburgh, PA
3Brigham & Women’s Hospital, Boston, MA
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IMATINIB
KIT activity
tumor cell quiescence
risk of relapsewhen taken off imatinib!
GIST
APCCDH1 - SKP2 - p27Kip1
DREAM complex
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IMATINIB
apoptosis tumor cell quiescence
risk of relapsewhen taken off imatinib!
GIST
APCCDH1 - SKP2 - p27Kip1
DREAM complex
KIT activity
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apoptosis tumor cell quiescence
risk of relapsewhen taken off imatinib!
GIST
OTHEROTHERCOMPOUNDS?COMPOUNDS?
APCCDH1 - SKP2 - p27Kip1
DREAM complex
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Histone H2AX is upregulated after imatinib treatment
• variant of core histone H2A• randomly incorporated into nucleosomes • rapidly phosphorylated at serine 139 in
response to genotoxic stress
γ-H2AX• mediates DNA damage response reactions• potential tumor suppressor
Serine 139
1 142
histone H2AXnucleosome
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Upregulation of H2AX is causatively involved in GIST cell apoptosis
ima
tinib
72
h
imat
inib
72h
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H2AX upregulation is due to increasedprotein stability
IB: ubiquitin
Ubiquitin/26S proteasome pathway
Mani and Gelmann, JCO 2005; 23:4776-4789
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Inhibition of the proteasome inducesapoptosis in GIST
dose response time course
Bortezomib:• Velcade™ (Millennium
Pharmaceuticals)
• proteasome inhibitor
FDA-approved for:• multiple myeloma
• mantle cell lymphoma
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Bortezomib mechanism of action
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Bortezomib mechanism of action
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Mechanism of action of Bortezomib
RT-PCR qRT-PCR
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Bortezomib inhibits ongoing gene transcription
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Bortezomib is effective in imatinib-resistant GIST
24 h
48 h
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Bortezomib is effective in imatinib-resistant GIST
GIST004: imatinib-resistant GIST(short-term culture)
Kit+/K641E transgenic mice
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Inhibition of NF-kB signaling is not involved in Bortezomib-induced apoptosis in GIST
bortezomib
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Conclusions
Bortezomib induces apoptosis in GIST cells
dual mechanism of action• upregulation of H2AX• transcriptional inhibition of KIT
• NOT inhibition of NF-kB signaling
new therapeutic option for imatinib-resistant GIST patients
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Acknowledgments
Duensing Lab• Joshua Parry• Matt Brown • Dee Seneviratne• Julianne Baron• Payel Chatterjee• Anna Chin• Stefan Duensing
American Cancer Society(#RSG-08-092-01-CCG)GIST Cancer Research FundLife Raft Group (UPPCC-AD-100108)
Universität Duisburg-Essen• Sebastian Bauer• Thomas Mühlenberg
Brigham & Women's Hospital• Jonathan Fletcher
University of Pittsburgh• Shih-Fan Kuan
Cleveland Clinic• Brian Rubin
Oregon Health & Science University
• Christopher Corless• Michael Heinrich
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