GST-P1 or not to be? TS to be? Heinz-Josef Lenz, MD Associate Professor of Medicine Co-Director, Colorectal Center Co-Director, GI Oncology Program USC/Norris Comprehensive Cancer Center USC Keck School of Medicine
Jan 20, 2016
GST-P1 or not to be?
TS to be? Heinz-Josef Lenz, MD
Associate Professor of Medicine Co-Director, Colorectal Center
Co-Director, GI Oncology Program
USC/Norris Comprehensive Cancer Center
USC Keck School of Medicine
Peripheral Neurotoxicity
• Mechanism not well understood– Dorsal root ganglia neuronopathy– Axonopathy
• Agents implicated: cisplatin, oxaliplatin, taxanes, 5-FU (rare)
• Various mechanisms proposed: Sodium, Calcium Channels, DNA repair, Homocystein pathway, Cox-2
Oxaliplatin-related peripheral neuropathy
• It has 2 components: – acute neurotoxicity: axonopthay – chronic neurotoxicity: dorsal root ganglia
Mechanism of action of oxaliplatin on Na+ channels (Axonopathy)
+
ATP ATP
EXTRA
Membrane
INTRACa2+
oxalate
TTXHg2+
Dach-Pt
Na+
oxaliplatin
Inward Na+current inhibition by oxaliplatin in
patch clamp technique
Inward Na+currentAction
potential
Sodium channels
• Sodium channels regulate excitability of nerve and muscle cells (Ca dependent)
• At least seven different Na+ channels expressed in sensory neurons
• Oxaliplatin increases nerve refractory time through its effect in Na+ channels
Neurotoxicity as reason for treatment discontinuation
Gamelin et al, Clin Cancer Res 2004
0
5
10
15
20
25
30
35
85 100 130
oxaliplatin dosage (mg/m2)
% o
f d
rop
ou
ts f
or
ne
uro
tox
icit
y
CaMg
no CaMg
Folate-Homocysteine
• Elevated homocysteine neuronal damage– NMDA receptor stimulation Ca influx
reactive oxygen species (ROS) neural apoptosis
– Oxidative damage to endothelial cells
• High Thymidylate synthase low Homocysteine levels
DNA repair
• ↓ ERCC1, XRCC1, XPD function ↑ susceptibility of dorsal root ganglia to platinum-damage peripheral neuropathy
• Oxidative Stress leading to damage of dorsal root ganglia (MnSOD, GST)
Cycle to any Mucositis GSTP1-105 Ile/Ile 58 1 Ile/Val 53 1.30 (0.67-2.53) Val/Val 12 4.03 (1.75-9.30) <0.001 COX 2 G/G 83 1 G/C, C/C 40 1.70 (0.94-3.07) 0.061 TS-5’ G C SNP G/G 60 1 G/C 56 0.60 (0.32-1.15) C/C 7 2.14 (0.81-5.65) 0.020 Cycle to grade 2+ Neurotoxicity
XPD 312 Asp/Asp, Asp/Asn 99 1 Asn/Asn 24 0.43 (0.15-1.21) 0.084 TS-5’ G C SNP G/G, G/C 116 1 C/C 7 2.37 (0.83-6.77) 0.082
USC Data on 130 patients treated with CIFOX prospectively in second line
Lipid peroxidationDNA damage
Off Due to Neurotoxicity P-Value*
GSTP1 T/T (N=120) C/T (N=130) C/C (N=38)
11 (9%)13 (10%)9 (24%)
0.039
ERCC2 Other G/G
30 (12%)5 (13%)
0.779
XRCC1 Other C/C
16 (10%)17 (13%)
0.572
GSTM1 Absent Present
16 (11%)19 (12%)
0.742
*Chi-square P-value
Polymorphisms and Treatment Discontinuation Due to Neurotoxicity
Polymorphisms and Treatment Discontinuation Due to Neurotoxicity
GSTP1
< 600 mg/m2 < 800 mg/m2
Grade 2/3 Grade 2/3
C/C (N=38)20% 27%
C/T (N=130)
T/T (N=120) 11% 18%
Cumulative OxaCumulative Oxaliplatin-Dose platin-Dose and Early Neurotoxicityand Early Neurotoxicity
Cumulative OxaCumulative Oxaliplatin-Dose platin-Dose and Early Neurotoxicityand Early Neurotoxicity
Chi-Square P = 0.030*
*Fisher’s exact P-value = 0.036
P = 0.143
Future: Neurotoxicity
• To understand the mechanisms of the acute and chronic neurotoxicity
• To investigate the role of oxidative stress such as GST-P1 in neurotoxicity and how to prevent it (antioxidants?)
Is TS prognostic, predictive or both?
• Prognostic markers (survival, recurrence)– Not applicable for individual patients – Usually used high/low, presence/absence
• Predictive markers (response, survival, toxicity)– Used for an individual patient– Usually absolute number
Iqbal et al. Iqbal et al. Curr Gastroenterol RepCurr Gastroenterol Rep. 2003;5:399-405.. 2003;5:399-405.
Metabolism and mechanism of action of 5-Fluorouracil (5-FUra)
5-FUra H2FUra
-F--alaFdUrd
dThd phosphorylase
DPD
FdUMP
dUMP
thymidylate synthase
dTMP DNA
DNADNA
mRNAmRNA
ProteinProtein
Type of ChangeNature of Change
Tools Used to Study
Polymorphisms
Allelic deletions (LOH)
Qualitative
Static
PCR
DNA Sequencing
Gene expressionQuantitative
Dynamic
Quantitative RT- PCR
Microarrays
Protein expression Protein function
Quantitative Dynamic
Enzyme assays
IHC
Iqbal et al. Iqbal et al. Curr Gastroenterol RepCurr Gastroenterol Rep. 2003;5:399-405.. 2003;5:399-405.
Assessment of TS Expression
TS and Adjuvant Chemotherapy Evaluation by IHC
Author # of patients
Patient Characteristics
Outcome
Johnston, PG
294 Rectal cancer, Dukes B, CAdj Ctx
TS an independent prognosticator of DFS and OS; adj ctx for high TS equiv to low TS (with and w/o ctx)
Edler, D 862 30% rectal cancer, 70% colon cancer Dukes B & CAdj ctx
TS of no prognostic value; low TS better OS, high TS higher rate of recurrence, Pts with low TS and adj ctx had worst OS
Allegra, C
709 465 Patients220 Dukes B2245 Dukes C
TS prognostic of OS and DFS; high TS assoc with high recurrence
TS Protein Expression• 5 studies have evaluated TS in adjuvant
chemotherapy for CRC• 4/5 studies consistently show TS as an independent
prognosticator of DFS and OS• Conclusions
– Patients with high TS who received chemotherapy did as well as patients with low TS with or without chmotx.
– The advantage to receiving adjuvant ctx for patients with low TS was less than for patient with high TS
– Patients with low TS have a better outcome– The benefit of adjuvant chemotherapy demonstrated
in patients with high TS
Thymidylate Synthase Expression and Prognosis in
Colorectal Cancer: A Systematic Review and Meta-Analysis:
13 studies with 887 patients MCRC7 studies 2610 patients LCRC
Popat et al J Clin Onc February 2004, 529-536
Popat et al J Clin Onc February 2004, 529-536
TS IHC versus RT-PCR
The value of TS expression in predicting poor OS seems strongest in studies using RTPCR and not IHC.
Popat et al J Clin Onc February 2004, 529-536
TS Repeat Polymorphisms in 221 patients with Dukes C
Patients with the 3R/3R polymorphism (n = 58, 26%) showed no significant long-term survival benefit from chemotherapy (RR = 0.62, 95% CI: 0.30-1.25, P = 0.18)
Patients with the 2R/2R or 2R/3R genotype (n = 163, 74%) showed significant gains in survival from this treatment (RR = 0.52, 95% CI: 0.52-0.82, P = 0.005).
High TS
Low TS
5-FU
NO 5-FU
It all makes sense again?
• High TS associated with poor outcome• High TS does not benefit from 5-FU adjuvant
chemotherapy • Consistent with data from meta analysis and
data from TS polymorphisms and gene expression data.
• Controversial data due to difference in technologies, cut off levels, patients populations
Overall Survival by TS Intensity (Stage II)S
UR
VIV
AL
(Pro
ba
bil
ity
Ra
te)
Years since surgery
P=0.47
High TS
Low TS
SU
RV
IVA
L (
Pro
ba
bil
ity
Ra
te)
YEARS SINCE SURGERY
Overall Survival by Treatment within high TS Staining Tumours (Stage IIIC)
5-FU
No 5-FUP=0.12
The is a partial list of some common external causes of free radicals:
• Toxins – carbon tetrachloride – paraquat – benzo(a)pyrene – aniline dyes – Toluene
• Drugs – Adriamycin,bleomycin,nitrofurantoin – chlorpromazine
• Air pollution: Primary sources – carbon monoxide, nitric oxide – passive tobacco smoke
• Ingested substances – alcohol – smoked and barbecued food – peroxidized fats in meat and cheese – deep-fried foods – trans fats in processed foods