SNPs and Cancer
SNPs and Drug Interactions
Transporter
Drug
Absorption in the breast
Drug in breast tissue
Metabolism in the liver
Excretion in the kidney
Drug becomes inactive or toxic
Transportation in the blood
Drug in bloodstream
SNPs A SNPs B
SNPs C SNPs D
SNPs May Be the Solution
KANSER FARMAKOGENTİĞİ
Kemoterapi Rejimi vücut yüzey alanına göre
Neden kanser tedavileri başarısız olabiliyor?
Tümör hücrelerinin ilaca azalmış hassasiyeti, ilaca karşı direnç gelişimi
- doğal veyaprimer rezistans
- kazanılmış veya sekonder rezistans (kemoterapiden sonra da gelişebilir)
Tedavi (Eş zamanlı ilaç kullanımı)
Genetic polimorfizm
- İlaç metabolize eden enzimler
- ilaç hedef molekülleri (enzimler, reseptörler)
Genotyping tests in clinical oncology
I- Gene polymorphisms for toxicity of chemotherapeutics
5-FU,irinotecan, thiopurin
DPD, UDP glucuronyltransferase, thiopurin S methyl
transferase, metabolysing enzymes for purin-pyrimidin
analogs, folat metab. enzymes, CYP enz (CYP2B6, CYP2C8,
CYP3A), transferases, transport proteins, receptors
2- Tests for response to molecular therapeutics
Imatinib- BCR- ABL gene mutations
Rituximab- FCGR3A and FCGR2A gene mutations
Gefitinib- EGFR gene mutations
Trastuzumab- HER2 expression
Cisplatin- ERCC1 ve BRCA1 mutation
Biomarker
Label Context
Representative Label Test Drug
Her2/neu Over-expression
Overexpresion of Her2/neu necessary for selection of patients appropriate for drug therapy 1 Trastuzumab (Herceptin)
UGT1A1 Variants
UGT1A1 mutation in patients, exposure to drug and hence their susceptibility to toxicity 2
Irinotecan
(Campto)
EGFR expression Epidermal Growth Factor Receptor presence or absence- 3
Cetuximab
Gefitinib(Iressa)
Erlotinib (Tarceva)
Examples of Valid Genomic Biomarkers
Kanser ilaçlarının metabolizması ile ilişkili enzimler ve genler
Tiopurin metil transferaz (TMPT)
Dihidropirimidin dehidrogenaz (DPD)
Sitokrom p 450 (CYP)
5,10 metiltetrahidrofolat redüktaz (MTHFR)
N-asetil transferaz (NAT)
UDP glukoroniltransferaz (UGT1 ve UGT2)
Multi-drug direnç geni (MDR1)
DNA hasar onarım geni(ERCC1)
Sulfotransferaz SULT1A1)
Onkolojide kullanılan farmakogenetik testler
GEN İLAÇ SONUÇ TMPT
(Tiopurin S-metil Transferaz)
6-MP
Lösemide etkinlik ve yan etki
DHD
(DihidropirimidinDehidrogenaz)
MTHFR
(5’-10’ metilen tetrahidrofolatreduktaz
TSER(TS)
(Timilat sentaz)
5-FU
5-FU toksisitesi
UGT1A1
(UDP-Glukuronozil Transferaz)
irinotekan
Metabolizma ve toksisite
ERCC1
(Nükleotid eksizyon tamir genleri)
GST
(Glutatyon S-transferazlar)
platinum
Tümör cevabı ve sağkalımda azalma
CYP2D6
(Sitokrom p450 enzimleri)
TMX
(Tamoksifen)
Adjuvan sonuçları etkiler
MTHFR
(5’-10’ metilen tetrahidrofolatreduktaz)
MTX
(Metotreksat)
5-FU
Toksisite riski artar
Kemoterapötiklerin Toksisitesinin Belirlenmesinde Kullanılan Testler ve Kanser Tedavisinde Sıklıkla Kullanılan İlaçları Metabolize Eden Enzimler
1. Pürin-pirimidin analoglarını metabolize eden enzimler
2. Folat metabolizmasında görevli enzimler,
3. Sitokrom P450 enzimleri (CYP 450)
4. Transferazlar,
5. Taşıyıcı proteinler,
6. Reseptörler.
Pürin-pirimidin analoglarını metabolize eden enzimler
Tiopurinler: losemi tedavisinde yaygın olarak kullanılan ilaclardır.
- merkaptopurin: ALL (akut lenfoblastik lösemi)
- Tioguanin: AML (akut myeloblastik lösemi)
- Azotiopürin:immün baskılayıcı (Crohn hastalığının tedavisi)
Tiopurin S-metil transferaz (TPMT)
Tiopürinlrin terapötik etkinliği ve toksisitesinden sorumlu
TPMT genindeki polimorfizmler TPMT enzim aktivitesini azaltır
TPMT aktivite azalması : ciddi, hayatı tehdit eden toksisiteler
TPMT ve Merkaptopurin Tedavisi
6-Mercaptopurin
inaktif ön-ilaç
TPMT 6-MeMP
(inactive)
HP
RT
Thioguanin nucleotids
•Antitumor effect
•Myelosupression
TPMT = Tiyopürin metiltransferaz /
6-MeMP = 6-metil merkaptopürin
HPRT = Hipoksantin fosforibozil transferaz : Biochimica et Biophysica Acta, 1603 (2003)
*Polymorp.
6-MP; ALL tedavisinde kullanılan ön ilaç
6-MP transferaz hypoxantine guanin phosphorybosyl (6 thioguanine oluşur) tarafından aktive olur
TPMT inactivates 6-MP by S methylation
6-MP TPM tarafından S metilasyon ile inaktive olur
Tiopurin metil transferaz
Doğal tipi TPMT1
Alelleri :5 adet aleli mevcut TPMT2,TPMT3A,TPMT3B,TPMT3C, TPMT4
Alellerin 3’ü %95’i kapsar
Kişilerin %10’unda aktivite az, %3’ünde hiç yok
heterozigotlar dozun %65’ini tolere edebilir, homozigotlar toksisiteden ölür.
Bu varyantlar nedeniyle doz indirimi yapılan hastalarda sağkalım= doğal tip alel taşıyıcıları
Genotype-Guided 6-MP Dosing
Pharmacogenomics 2002;3(1):89-98.
Genetic polymorphism of TPMT activity and thiopurine therapy
Krynetski & Evans, Am J Hum Genet 1998 63:11-16
Prevalence of TPMT Genotypes-Three Major SNPs (single gene) Define Mutant Alleles
Newly Diagnosed ALL Patients per Year
30,000
Homozygotes
100
None or Low
TPMT Activity
Heterozygotes
3,300
Intermediate
TPMT Activity
Wild Type
26,600
High
TPMT Activity
Two Mutant Alleles
v/v
One Mutant Allele
wt/v
No Known Mutation
wt/wt
ALL, 6MP and polymorphic TPMT
Children TPMT Toxicity
Children TPMT Poor response
6MP
6MP
Pharmacogenetics: Use in drug delivery
HERCEPTIN
Oncology
Breast Cancer – 25-30% of breast and ovarian tumors overexpress HER2
– Overexpression is correlated with prognosis
– Patients positive for HER2 can be treated with Herceptin
– Herceptin is a monoclonal antibody against the HER2 receptor
– Improved survival
Examples……
pharmacodynamics
Breast Cancer abnormally high amounts of HER2 protein in 30% of patients
Herceptin binds to HER2 slowing tumour growth, 70% of patients do not respond
HER-2 Protein and Herceptin
Herceptin (trastuzumab): – Metastatic breast cancer
– Targets tumor cells that over-express the human epidermal growth factor receptor 2 (HER2) protein
– Best response attained in women who over-express the HER2 protein
– HER-2 over-expression in breast cancer cells should be done before patients receive the drug
Herceptin: Prescribing Information
HERCEPTIN (Trastuzumab) as a single agent is indicated for the treatment of patients with metastatic breast cancer whose tumors overexpress the HER2 protein and who have received one or more chemotherapy regimens for their metastatic disease.
HERCEPTIN should be used in patients whose tumors have been evaluated with an assay validated to predict HER2 protein overexpression
Pharmacogenetics = molecular DD Case Study: Herceptin®
Low HER2
High HER2
Bimodal response:
2/3 of patients: addition of Herceptin® to chemoRx
no benefit
1/3 of patients: addition of Herceptin® to chemoRx
50% survival time increased by factor 1.5 (20 29 weeks)
5 fluorouracil and DPD
5 fluorouracil and DPD
5-FU may cause serious gastrointestinal and
hematologic side effects (3-5%).
5-FU causes grade 4 neutropenia in pts with DPD
deficiency (40-50%)
Polymorphism in 5-fluorouracil (5-FU) Metabolism
(detoksification)
5-FU (activation)
Active metabolit
MTHFR polymorphism
• low MTHFR activity
• 5-FU efficacy increase
TS polymorphism
• TS activity increases
• 5-FU efficacy decreases
DPD polymorphism
• neurologic toxicity
• GI toxicity
• hematologic toxicity
İnactive metabolite
TRENDS in Pharmacological Sciences, 25 (2004)
(TP) thymidin phosphorilase
DPD
MTHFR
TS
prodrug 5-floro 2 deoksiuridin
monofosfat (FdUMP)
Tamoxifen
Pro-drug
widely used treatment in breast cancer patients
inhibits estrogen from binding to its receptor, thus inhibiting estrogen-regulated genes (growth factors and angiogenic factors)
metabolized by cytochrome P450s into N-desmethyltamoxifen (NDM), 4-hydroxytamoxifen (4-OH tamoxifen) and endoxifen
efficacy of tamoxifen therapy among women is heterogeneous due to genetic variants of CYP2D6
On October 18 (2006), a presantation of the study related to Tamoxifen by Dr. Goetz to the FDA led to an advisory committee unanimously recommending a label chance for tamoxifen. This change would include information about the incresaded risk both from genetic factors and drug interactions affecting CYP2D6. The majority of the committee also recommended that CYP2D6 genotype testing as an option for women before they are prescribed tamoxifen.
Jin et al., J. Natl. Cancer Inst. 97:20-39, 2005.
Tamoxifen Biotransformation
Relapse–Free Survival, % Disease–Free Survival
Tamoxifen Pharmacogenomics
Goetz et al., Breast Cancer Res. Treat. 101:113-121, 2007.
Breast Cancer (190 Patients)
Relapse-Free (RF) Probability
by CYP2D6 Genotype
Schroth et al., JCO 25:5187-93, 2007
No Tamoxifen Tamoxifen Tamoxifen
Selective Serotonin Reuptake Inhibitors (SSRIs) & Tamoxifen
antidepressants that are often prescribed to treat hot flashes in women who take tamoxifen
paroxetine, sertraline, citalopram, fluoxetine and venlafaxine
inhibition of CYP2D6 by SSRIs likely to affect metabolism of tamoxifen use of SSRIs associated with a reduced mean plasma concentration of endoxifen (lower response to tamoxifen therapy)
Results
with inhibitor
without inhibitor
Jin et al., 2005
Objectives
examine association between genotype (CYP2D6) and plasma concentrations of tamoxifen and its metabolites
examine effect of CYP2D6 inhibitors on plasma concentrations of endoxifen
examine SSRIs and their association with plasma concentrations of endoxifen
Mary 55 years
PHARMACOGENETICS
Tamoxifen+CYP2D6
CYP2D6 PM CYP2D6*4/*4
!!!
CYP2D6 EM – OK CYP2D6*1/*1
Noeffects, risk of disease relapse
Drug – gene interactions
Improved benefit from tamoxifen
Carol 55 years
Conclusion & Significance
higher plasma endoxifen concentration than 4-OH tamoxifen may mean it has a more important role
efficacy of tamoxifen therapy among women is heterogeneous due to genetic variants of CYP2D6
use of SSRIs associated with a reduced mean plasma concentration of endoxifen (lower response to tamoxifen therapy)
PROJECT Pharmacogenomic and Nutrigenomic Enhancement of CYP2D6 Activity in
Tamoxifen-Resistant Breast Cancer Patients in Turkish, French &Canadian Patients
Presley JF1, Bernard-Gallon D2, Genç E3, Kilic U3, Dejgaard SY1, Yeliz Demirci3, Bignon YJ2, Hizel C 1,
2, 3 ,4
Study Objective/ Hypothesis
to develop an integrated pharmacogenomic & nurigenomic approach to tamoxifen therapy
to gain the capability to significantly improve this outcome with targeted and inexpensive nutritional modification which can alter the expression level of CYP2D6 in IMs.
Hypothesis
nutritional interventions that improve metabolism of tamoxifen will significantly improve survival rates of IM breast cancer patients.
1)Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A2B2, 2) Département d'Oncogénétique du Centre Jean Perrin, 63011 Clermont-Ferrand Cedex 01, France 3)Department of Biochemistry, Faculty of Medicine, Yeditepe University, Istanbul,Turkey. 4) C2H-Vichy Genomics, Vichy,France
References
Garber, K. (2005) J. Natl. Cancer Inst. 97: 412-413.
Jin, Y. et al. (2005) J. Natl. Cancer Inst. 97: 30-39.
Osborne, C.K. (1998) N. Eng. J. Med. 339: 1609-1618.
Stearns, V. et al. (2003) J. Natl. Cancer Inst. 95: 1758-1764.
Irinotecan (CPT-11)
Pro-drug
FDA approved & widely used in treatment of metastatic colorectal cancer
Topoisomerase I inhibitor
Complex metabolic pathway
Wide interindividual variability in drug response and in occurrence of toxic side-effects (severe diarrhea, neutropenia, myelosuppression).
Polymorphisms that affect irinotecan therapy
Relling & Dervieux, Nature Cancer Reviews 1:99-108
Genotype Versus Phenotype
Genotype and Phenotype
_______________________ Genotype Glucuronidation
6/6 851±545
6/7 699±361
7/7 199±118
_______________________
Mean ± Standard Deviation
Fisher et al. Pharmacogenetics, 2000
UGT1A1*28 Genotype and Estradiol
Glucuronidation
0
200
400
600
800
1000
1200
1400
1600
6/6 6/7 7/7
Genotype G
lucu
ron
ide F
orm
ati
on
Ra
te
Current Understanding of PGx and Neutropenia
Group Prevalence Risk of Toxicity
All Patients ----- 10%
Patients That Are 7/7
10% 50%
Patients That Are 6/7
40% 12.5%
Patients That Are 6/6
50% 0%
Based on data from Innocenti et al (2004)
Potential of UGT Testing to Inform Dosing
All Patients with Same Diagnosis
PGx profile for high risk (50%): treat with
alternative drug or dose
PGx Profile for moderate risk (12.5%): treat with alternative drug or dose
PGx Profile for low risk (0%): treat with
conventional dose
Conclusions “UGT1A1 genotype (UGT1A1*28)and total bilirubin levels are strongly associated with
severe diarrhea & neutropenia.”
UGT 1A1*28 is a variant allele
» Variation in the TA repeats in the promoter region Normal allele: 6 TA repeats (6/6)
Variant allele: 7 TA repeats (7/7)
UGT 1A1*28 is associated with reduced gene expression and reduced glucuronidation in human liver microsomes.
Grade 4 neutropenia is more common (p=0.001) in patients with 7/7 genotype patients
A strong correlation between genotype and diarrhea (P=0.01)
Utility of UGT1A1 Polymorphism in the Use of Irinotecan
Excluding 7/7 patients from standard dose of irinotecan treatment will reduce the overall incidence of grade 4 neutropenia from 10.1% to 5.7%.
7/7 genotype patients may get a alternate irinotecan regimen?
Genotypic testing combined with bilirubin levels will allow better patient selection for Irinotecan therapy. Physicians will be better informed about use of Irinotecan as a single agent or in combination therapy.
Genotypic testing will allow 7/7 genotype patients with a choice for equally efficacious alternate therapy.
6-Mercaptopurine (6MP) and Childhood Acute Lymphoblastic Leukemia (ALL)
ALL is a life-threatening disease and 6MP can cause life-threatening toxicities
Dose titration (dosing size, duration and intensity) is major determinant of long-term EFS and myelosuppressive effects
6MP is metabolized to pharmacologically active thiopurine nucleotides by thiopurine methyltransferase (TPMT)
TPMT activity shows trimodal variation in the general population
TPMT Genetic Polymorphism
Well-documented, causal link between TPMT polymorphism and clinical effects, including toxicity
Genotypes with reduced (10% of the population) or no (0.3% of the population) activity are at a substantially increased risk of myelosuppression and secondary cancer
Pharmacogenetic tests are available and feasible to use for identifying these patients and guide optimal dosing
CYP2D6 and Metabolism of Tamoxifen
CYP2D6 enzyme activity directly
related to:
• Common genetic polymorphisms
• Concomitant medications that
inhibit CYP2D6 activity
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