De la farmacogenética a la farmacogenómica

Javier BenitezPrograma Genética del Cáncer Humano

Centro Nacional Investigaciones OncológicasMadrid Junio 06

Antitumoral treatments

-They are agressives, inspecifics and with a limited therapeutic margin.

- Risk of toxicity , treatment failure or even death

- Wide interpatient variability in effects

Antitumoral treatments II

-Children with ALL. 75% get total remision (cure)

25% with treatment failure and/or severe toxicity

-Sarcomas: 50-75% long term survival (cure)

Cases with severe toxicity CNS and GUS

- Breat cancer: Tamoxifen for ER and PR positive tumors (50%)

Secondary effects in some patients: Uterine cancer, tromboembolims

- Genetic variability might explain many of these situations.

-Their study could lead to individualised treatment and new drug developments.

-Pharmacogenetics: It studies candidate genes

-Pharmacogenomics: It describes a broader strategy to identify many genes that are relevant to the pharmacological effects of a given medication. It is based in a targeted (candidate pathways) or whole genome analysis.

Genetic bases of farmacological response

Enzimatic activity of TPMT-6MP according to genotype

Cheok et al, Nat Review 2006

Correlation between TPMT genotype and 6MP toxicity

Cheok et al, Nat Review 2006

Gene SNP Freq_Spain Freq_CaucCYP11B1 rs4736346 0,47 0,45CYP11B1 rs4736349 0,44 0,42CYP11B2 rs1799998 0,45 0,42CYP11B2 rs3097 0,29 0,30CYP17A1 rs10883783 0,30 0,31CYP17A1 rs6163 0,41 0,39CYP1A1 rs4646421 0,11 0,07CYP1A1 rs4886605 0,16 0,10CYP2A7 rs1017384 0,28 0,26CYP2A7 rs1042389 0,19 0,20CYP2A7 rs12461727 0,15 0,12CYP2A7 rs2032898 0,30 0,31CYP2A7 rs2054675 0,27 0,27CYP2A7 rs2279345 0,35 0,41CYP2A7 rs3745275 0,30 0,29CYP2A7 rs3844443 0,24 0,25CYP2A7 rs3889806 0,35 0,38CYP2A7 rs4803397 0,26 0,22CYP2A7 rs7251532 0,28 0,27CYP2A7 rs7251950 0,30 0,29CYP2A7 rs7254188 0,43 0,44CYP2D6 rs5751231 0,21 0,23CYP2D6 rs5758589 0,44 0,45CYP2E1 rs2515641 0,14 0,10CYP2E1 rs915908 0,15 0,17MTHFR rs1476413 0,26 0,34MTHFR rs1801131 0,29 0,36MTHFR rs1801133 0,40 0,24NAT1 rs4921880 0,29 0,21NAT1 rs4986783 0,02 0,03NAT1 rs7829368 0,36 0,37NAT1 rs8190845 0,13 0,13NAT2 rs1208 0,46 0,42NAT2 rs1799929 0,45 0,41NAT2 rs7013253 0,32 0,36NAT2 rs721398 0,27 0,29NAT2 rs7832071 0,45 0,39TPMT rs1142345 0,05 0,08TPMT rs1800462 0,02 0,01TPMT RS1800460 0,01 0,03MTRR RS1801394 0,47 0,50SHMT1 RS1979277 0,25 0,33

40 SNPs from 14 genes

No differences with other populations

More genes under study

Allelic frequencies in Spanish Population (www.bioinfo.cnio.es)

MTFR and MTX

TPMT and 6MPG238C

G460A

A719C

100 patients with ALL

(http://bioinfo.cnio.es/cgi-bin/cegen/frequencies.cgi)

1

23

4

1- Entry

2- Degradation

3- target

4- metabolyze

5-……………..

………….

They study 32 genes from this pathway and identify some of them associated to MTX resistence. They found differences among ALL subtypes.

Strategy II. MTX pathway (folate analogue)

Kager et al. J Clin Invest 2005

Strategy III. Genome Wide Approach

Global gene expression profiling using DNA microarrays can identify:

- genes with levels of expression that are related to drug response.

- New drug targets

It is a complementary strategy to the identification of SNPs in genes that alter protein function and drug response.

Expression Profiling of T-Cell Lymphomas Differentiates Peripheral and Lymphoblastic Lymphomas and Defines Survival Related Genes

Martinez Delgado et al.Clin. Cancer Res, 2004.

PTCLLB

NFkNFkBBNFkNFkBB

Median OS = 10 months

P=0.0001

>10 m

<10 m

Treatment response/ survival

Genetic signature: 6 genes

165 genes differenciate both groups

CYP3A4CYP3A7 CYP51CYP8B1

A cluster of CYP3As genes is associated with evolution

Martinez Delgado et al. Leukemia 2005

PTCLs

Norm

alize

d C

YP

3A

4 e

xp

ressio

n

Log Rank p=0.001

Expression of CYP3A4 is associated to survival of PTCLs

•CYP3A4 is an important drug metabolizing enzyme,

CYP3A4 expression in tumors could then be mediating

the response to chemotherapy.

•Detection of CYP3A4 expression could have clinical

interest by identifying tumors more resistant to

chemotherapy at the time of diagnosis. An alternative

treatment?

Martinez Delgado et al. (in preparation)

1

2

3

4

5

6

7

8

9

10

PROLIFERATION

Genes correlated to proliferation not specifically related to cell cycle regulation: HSP90

Inhibitors of HSP90 (17AAG) under study

-No effect in normal lymphocytes

-Good response in peripheral T cell lines

Marta Cuadros et al. In preparation

Periferal T-cell lymphomas: HSP90 as drug target

HSP90 is a chaperone

HSP family inhibits apoptotic pathways

Overexpression of HSP90 - bad prognosis

Conclusions

- Pharmacogenetics is starting to be introduced and applied in the clinical practice (6MP; MTX.....)

- The study of the response based on multiple genes (polygenic model) is now underway

- Pharmacogenomics permits the identification of new therapeutic targets and groups of genes that modulate the pharmacological response.

- It is still necessary to validate data. Problems with population variability, techniques, platforms etc....

Acknowledgements

Human Genetics Lab:Lara P. FernandezEva BarrosoGoria RibasBeatriz MartinezMarta Cuadros

CeGen Madrid Genotyping Lab: Emilio Gonzalez Roger Milner Ana Gonzalez Charo Jesus Mari

Endocrine Group:Mercedes Robledo Fátima MercadilloCristina Rodriguez

Genotyping Lab