Blancos moleculares en cáncer

8/14/2019 Blancos moleculares en cáncer

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Blancos molecularesen Oncología

Ernesto Gil DezaInstituto Oncologico Henry Moore

Universidad de Salvador

domingo 20 de septiembre de 2009



Historia




Composición química de la

célula

Albrecht Kossel Premio Nobel de Medicina de 1910: "in recognition of the contributionsto our knowledge of cell chemistry made through his work on proteins,including the nucleic substances"




Cromosomas y herencia

Thomas Hunt Morgan

Premio Nobel de Medicina de 1933




Mutagenicidad

Hermann Joseph Muller

Premio Nobel de Medicina de 1946“for the discovery of the production of mutations by means of X-rayirradiation"




Regulación y recombinación

genética

George Wells Beadle Edward LawrieTatum

Joshua Lederberg





Síntesis de ADN y ARN

Severo Ochoa Arthur Kornberg





Estructura de ADN ytransmisión de la información

Francis HarryCompton Crick

James DeweyWatson

Maurice HughFrederick Wilkins

Premio Nobel de Medicina de 1962domingo 20 de septiembre de 2009



Control enzimático en la

replicación viral

François Jacob André Lwoff Jacques Monod




Tumores inducidos por virus

Peyton Rous





Genes y síntesis de

proteínas

Robert W. Holley Har Gobind Khorana Marshall W. Nirenberg




Integración de virus tumorales almaterial genético

David Baltimore Renato Dulbecco Howard Martin Temin




Enzimas de restricción y

ADN

Werner Arber Daniel Nathans Hamilton O. Smith





Factores de crecimiento

Stanley Cohen Rita Levi-Montalcini





Oncogenes

J. Michael Bishop Harold E. Varmus





Regulación de ciclo celular

Leland H.Hartwell

R. Timothy (Tim)Hunt

Sir Paul M. Nurse





Apoptosis

Sydney Brenner H. Robert Horvitz John E. Sulston





Hannahan and Weinberg Cell 2000



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Preinvasive

Invasive

¿Qué buscar?




Objetivos

Identicación de blancos

Diseño de fármacosSelección de tumores

Selección de pacientes




Hipótesis y dicultades




Hipotesis y dicultades“ Targeting a specific gene or protein is simple in concept. Antitumor agents can be designed based on known sequence data rather than

depending on empirically screening a large number of compounds.However, there are still many caveats to successful use of theseapproaches. Targeting one gene may have limited impact onproliferation of neoplastic cells. In many cases, it is not obviouswhich gene(s) should be targeted. Genes important in the processof becoming a neoplastic cell may not be important for continued

proliferation or survival of the cell and, therefore, may be irrelevanttargets for treating established malignancies. Inhibition of manygenes (or function of these genes), even if they are important for neoplastic cell growth, may only be cytostatic. It would be moreuseful to target genes whose inhibition (or stimulation) induces celldeath (i.e., by apoptosis) or terminal differentiation. 1 Ultimately,these approaches must be capable of eliminating (or at least leadingto prolonged growth suppression of) all tumor cells, either bythemselves or in combination with other agents, if they are to beeffective in curing patients. Agents with cytostatic effects might needto be used in combination with other therapy. It is important that thetargeted protein in the neoplastic cell either be sufficiently different(if mutant) or not be critical for survival of normal cells to prevent

toxicity. “ (B. Chabner Cap. XXX)




Cuidados 1

1. Is the function of the overexpressed or mutated targetessential to the transformed behavior of the tumor? Doesinhibition of the gene product change the phenotype of themalignant cell? Because many mutations in cancer cellsappear late in their progression and may not be essential tomaintaining growth or metastasis, these questions must beanswered in the affirmative. Experiments in which thesubject gene is mutated, deleted, or neutralized with

antisense oligonucleotides can help answer thesequestions.




Cuidados 2

2 - Are the subject gene and its proteinfound in human tumors, and is thereselective expression in tumors versusnormal tissues?




Cuidados 3

3 - If overexpressed in tumors, is the proteinalso expressed in key proliferating normal tissues,such as intestinal epithelium and bone marrowprogenitors, or even nonproliferating tissues, suchas heart, kidney, or brain? Does a knockout of thegene have fatal consequences for the host (inanimal models)? Patterns of drug toxicity are oftendifficult to predict, but the profile of gene

expression in normal tissue may provide helpfulclues about potential selectivity of an agentdirected against that target.




Cuidados 4

4 - Are there closely related genes that are essentialfor normal tissue function and survival of the host thatmight make a molecularly targeted inhibitor nonselective?These considerations become paramount in determiningthe choice of target and the probability of success.Obviously, even the most validated target may not beamenable to a drug discovery strategy for any number of reasons, the most important being failure to understandthe function of the target and related proteins in humans.

Unanticipated toxicities, interactions with previouslyinapparent receptors or proteins, pharmacologic problemsin drug distribution, and pharmacokinetics (PK) maydefeat the most rational strategy.




Objetivos

Identicación de blancos

Diseño de fármacosSelección de tumores

Selección de pacientes




¿A qué nivel lo busco?




¿Con qué lo busco?

DNACitogenéticaFISH - CISHCGH

CGH arrays

SNPs

PCRSouthern blotMicrosatelliteinstability

Microarray

RNATransc. ProlingNorthern blot

RT-PCR• ISH, FISH & CISH

• Proteins

• Western blot• 2D electrophoresis• MALDI-TOF• SELDI-TOF• IHC




Algunos problemas...




Muestra analizadaTumorPAF

Microdisección tisular

Parana

Tejido congelado

Tejido fresco




Human Genome

Nuclear 3000 Mb

~30.000 genes

Mitocondrial16.6 kb

37 genes

Genes30 %

Extragenetic70 %

Encoded Non encoded

Low number of copies

Higher number of copies10% 90%

80%20%

Cuantitativo




Estadístico20.000 - 50.000 cambios genéticos

• Pero sólo tres evoluciones:

Rta / No rta

Recurrencia / Norecurrecia

Vivo / muerto• Altas chances de resultados positivos




Patogénesis




Aplicaciones clínicas


Clí i



Clínica

Predicción de riesgoDiagnóstico oncológico

Diagnóstico diferencial

Subtipicación tumoral

Fármaco-genética

Factores predictivos

Nuevos blancosModied Workman & Johnsto JCO October 10th 2005




Predicción de riesgo

Baja penetrancia y alto riesgoBRCA1

BRCA2

Alta penetrancia y bajo riesgo




Bioética




Subtipicación tumoral


CDI b



CDI tumor subtypes

70% CDI NOS

Tubullar Cribiphorm MucinousMedullar Micropapillar Apocrine

Courtesy Dr. Diaz, Dr. Emina, Dr. Japaze




Subtipos moleculares

Carey - ASCO 2005domingo 20 de septiembre de 2009



Texto

Classication requirements




Pronóstico


P ó i hi i l



500 BC18702000

Pronóstico e historia natural




“Due to the nature of the genes included in the21 gene assay, which are mainly proliferation genesand ER-related genes, it could be argued that theassay is an expensive replacement for ER and Ki67

inmunohistochemical assays”Paik and Kim, page 21




El ejemplo de Her2neu




Discordancias en Her-2-neu




¿En todas las pacientes

Her2neu positivas hayque emplear

trastuzumab?




Trastuzumab




Trastuzumab junto a




Cardiotoxicidad




¿Si progresa atrastuzumab los nuevosinhibidores son útiles?


Blancos moleculares en cáncer

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