Impact of DNA Repair Mechanisms on Resistance to alkylating therapeutic agents
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Impact of DNA Repair Mechanisms on Resistance to alkylating therapeutic agents
description
Impact of DNA Repair Mechanisms on Resistance to alkylating therapeutic agents. NH 2. NH 2. C. O. C. O. N. N. N. N. N. N. CH 3. CH 3. N. NH 2. N. N. H. O. C. O. N. N. N. N. CH 3. CH 3. N. TMZ. MTIC. DITC. NH 2. CH 3. O. C. O. N. N. N. N. N. H 2 N. N. - PowerPoint PPT Presentation
Transcript of Impact of DNA Repair Mechanisms on Resistance to alkylating therapeutic agents
Impact of DNA Repair Mechanisms on Resistance to alkylating therapeutic agents
TMZ
MTIC
N
N N
C
N
N
O N
NH2
CH3
O
N
C
N
O N
NH2
CH3
N
CH3
N
C
N
O N
NH2
H
N
CH3
DITC
H2N
O CH3
N
N
N
N
O6mG
N7mG
N
C
N
O N
NH2
H
N
CH3
H2N
O CH3
N
N
N
NMTIC
TMZ
Repair Pathways Responsible for ProcessingMethyl DNA Adducts
TMZ
O6mG (6%)
N7mG (70%)N3mA (9%)
MGMT & MMR
BER
Direct Repair of O6mG Mediated by AGT
AGT
0.1 % 1 % 10 % 100 %
0
500
1000
1500
0 10 20 30 40 50 60Days
Tu
mor
Volu
me (
mm
3)
100 10 1 0.1 0
The Correlation of MGMT Activity to the Drug Resistance
BCNU 30 mg/kg
Cancer Res. 1997
H2N
O
N
N
N
HN
Reaction of O6-benzylguanine and AGT Protein
MGMT
CysS
MGMT
CysS
H2N
O
N
N
N
N
-
O6-benzylguanine (BG) Guanine
O6-Methylating Agent
AGT
Mismatch Repair
Cytotoxicity Cell Survival
AGT
MGMT Repair
O6mGT/C
O6mG
MSH6
O6mG
Cytotoxicity
Mismatch Repair
T/C
MSH2
MLH1
PMS2
MSH2
MutH
1
10
100
0 500 1000 1500 20001
10
100
0 500 1000 1500 2000
TMZ(µM)
1
10
100
0 500 1000 1500 2000
SW480 (MMR+) HCT 15 (MSH6 mut) HCT 116 (MLH1 mut)
Resistance of MMR Deficient Colon Cancer Cells to TMZ
+BG
+BG
+BG
Cancer Res. 1996
Repair Pathways Responsible for ProcessingMethyl DNA Adducts
TMZ
O6mG (6%)
N7mG (70%)N3mA (9%)
MGMT & MMR
BER
AP site
MPG
APE
BER pathway N7mG
XRCC1
XRCC1
XRCC1
PARP
DNA pol
LigaseIII
Methoxyamine
MX
CO H
APE
5’ P P P 3’
MPG
5’ P P P 3’
CH3
CHO H
HNO
5’ P P P 3’
Methoxyamine binds to aldehyde group in an AP site
AP site
AP-MX site AP SiteAP-MX Site
APE+ - + -
MX bound AP Site is Resistant to Cleavage by AP-endonuclease
UDG
MX
NHOCH3
U
40 mer
20 mer
AP site-ARPAP site3’
OH5’
O
3’
OH5’
N O StrepHRP
NN
O
H
H
OO
NH2
Strepta.HRP
0
1
2
3
4
5
6
0 0.375 0.75 1.5 3 6
r2 = 0.993Un
it o
f D
ensi
ty
AP-DNA substrate (g)
3’
OH5’
N O
AP site-MX3’
OH5’
O
AP site
NH-O- CH3 CH3
AP
sit
es
(un
it o
f d
ensi
ty)
TMZ (uM)TMZ (uM)
0
2
4
6
8
10
12
14
0 187 375 750 1500
TMZ
TMZ+ MX
0
2
4
6
8
10
12
14
0 187 375 750 1500
TMZ
TMZ+ MX
MX-AP
Control
TMZ (175µM)
TMZ (175µM)+MX(25 mM)
TMZ (350µM)
TMZ (750µM)
TMZ (350µM)+MX(25 mM)
TMZ (750µM)+MX(25 mM) 0
2.5
5
7.5
10
0 94 187 375 750 1500
r = 0.995
TMZ(µM)
Cell Death
Block DNA Synthesis
Methoxyamine Interrupt BER Pathway
CH3
P P P 3’5’
CHO H
HNO
ChromosomalAberration
Apoptosis
MX APE
0
500
1000
1500
2000
0 25 50 75
Days
MX+TMZ
BG (30mg/kg)+TMZ
TMZ(120mg/kg)
MX (0.2mg/kg)
Control
SW480 Tumor Growth in Nude Mice
Clin. Cancer Res. 2002
0
500
1000
1500
2000
0 25 50 75 100
Days
BG+MX+TMZ
MX (0.2 mg/kg)+TMZ
BG (30 mg/kg +TMZ)
TMZ 40mg/kg
Control
Inhibition of SW480 Tumor GrowthBy BG plus MX and TMZ in Nude Mice
HCT116 Tumor Growth in Nude Mice
0
500
1000
1500
2000
0 5 10 15 20 25 30
Days
MX+TMZ
MX (0.2 mg/kg)
BG (30 mg/kg)+TMZ
TMZ (120 mg/kg)
Control
Compared to TMZ alone, the combination of MX+TMZ has No additive toxicity,
Compared to BG+TMZ, the combination of MX+TMZ has No toxic death
Less body weight loss
Less myelosuppression
Blocking BER efficiently potentiate TMZ-antitumorEffect bypassing MMR and p53 genetic status.
Liu & Gerson. Clin Cancer Res 2006;12:328-331
