cancer hereditario - investigación en cancer · 2011. 9. 9. · el riesgo de cáncer de ovario en...

CANCER HEREDITARIO

Dr. José MordohMaestría en Biología Molecular Médica

2011

ALFRED KNUDSON

CANCER DE MAMA Y OVARIO HEREDITARIOS

17q2117q21BRCA1BRCA1

MaryMary--Claire King, 1990Claire King, 1990

BCLC: Breast Cancer Linkage ConsortiumBCLC: Breast Cancer Linkage Consortium““The BCLC represents virtually all of the The BCLC represents virtually all of the groups conducting breast cancer linkage groups conducting breast cancer linkage analysis worldwide. The members have analysis worldwide. The members have meeting on a biennal basis since 1989 meeting on a biennal basis since 1989 sharing their linkage results at each sharing their linkage results at each meetingmeeting”” Easton et al, Am J Hum Genet, Easton et al, Am J Hum Genet, 19931993

Mark SkolnickMark SkolnickMyriad Genetics, 1994Myriad Genetics, 1994

2cM2cM

BCLC, 1993BCLC, 1993

Breast cancer tumor suppressor genes

Breast cancer affects 1 in 10 women and represents 31% of cancers in women (~215,990 women diagnosed each year, 2004 estimate).

~5% of breast cancers are hereditary; age of onset for hereditary breast cancer is earlier than other forms (mutations at 2 alleles).

Many genes involved; BRCA1 and BRCA2 are thought to be tumor suppressor genes.

BRCA1 is important for homologous recombination, cellular repairof DNA damage, and transcription of mRNA.

Mutations in BRCA1 also are involved in ovarian cancer.

BRCA2 plays a role in timing of mitosis in the cell cycle.

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CÁNCER DE MAMA Y OVARIO

Breast Cancer Tumor Suppressors

A small proportion of breast cancer is heritable. Two genes are associated with predisposition to developing breast cancer.

BRCA1 on chromosome 17BRCA2 on chromosome 13

Normal function of both is in repair of ds DNA breaks.

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Posibles roles para la proteína BRCA1

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SWI/SNF

Figure 1. Location and Tumor Specificity of the 27 BRCA1 Mutations Identified in Families with Breast Cancer. Exon 1 and the coding region of BRCA1 are depicted, with exons 1, 2, 11, and 24 included for reference. The translation start site is located at the mutation Met1Ile.

Maestría en Biología Molecular Médica –

Dr. José Mordoh 2011

Figure 1. Identification and Location of BRCA2 Mutations That Truncate the Polypeptide Chain. The BRCA2 gene is encoded by 27 exons, the second of which contains the initiator codon (ATG) at nucleotide position 229. The coding sequence spans 10,254 nucleotides, encoding 3418 amino acids. Each truncating mutation results in the insertion of a premature stop codon in the sequence. Detecting these mutations by a protein-truncation assay involves making a complementary DNA copy of the BRCA2 transcript, performing two rounds of nested PCR amplification, and synthesizing messenger RNA and protein in vitro from the PCR-generated templates. Abnormally shortened protein products are created when there is a truncating mutation in one of the two BRCA2 alleles; these products can be detected by electrophoresis.



Different large BRCA1 rearrangements reported in 20025’

E2 I2 E3 I3 E5 I5E6 I6 E7 I7 E8 I8 E9I9E10I10E11I11E12 I12 E13I13 E14I14E15I15E16I16E17I17E18I18E19 I19 E20I20 E21I21E22I22E23I23E24

3’

I13

14 kb deletion

0.5 kb deletion

14 kb deletion1kb deletion

3 kb deletion24 kb deletion

4 kb deletion

6 kb duplication

? kb deletion

? kb deletion

11 kb deletion

13.2 kb deletion7 kb deletion

5 kb deletion

1 kb deletion

•• Contribution of rearrangements to the spectrum of Contribution of rearrangements to the spectrum of BRCA1BRCA1 mumu-- Dutch families: 36%, Dutch families: 36%, PetrijPetrij--Bosch et al, Nature Genet 1997Bosch et al, Nature Genet 1997-- American families (H Lynch): 15%, American families (H Lynch): 15%, Puget et al, Cancer Res 19Puget et al, Cancer Res 19-- French Families: 10%, French Families: 10%, Gad et al, Gad et al, Oncogene, 2002Oncogene, 2002

11.6 kb deletion

17.2 kb duplication

8.6 kb duplication

> 80 kb deletion

Figure 1. Kaplan–Meier Estimates of the Incidence or Risk of Breast Cancer. Panel A shows the reported incidence of breast cancer among first-degree female relatives of subjects who carried a BRCA1 or BRCA2 mutation and those of subjects who did not. Panel B shows the estimated risk of breast cancer and 95 percent confidence intervals among carriers and noncarriers of a BRCA1 or BRCA2mutation. The difference in risk between the two groups was statistically significant by the age of 35. Panel C shows the estimated risk of breast cancer among carriers of each of the three mutations. The 95 percent confidence intervals are not shown but are about 50 percent wider than the upper curve in Panel B and are widely overlapping.


Dr. José M ordoh 2011

Figure 2. Estimates of the Risk of Ovarian Cancer. Panel A shows the estimated risk of ovarian cancer and 95 percent confidence intervals among carriers and noncarriers of BRCA1 or BRCA2 mutations. The differences were statistically significant by the age of 45. Panel B shows the estimated risk of ovarian cancer among carriers of each mutation. Although not shown, the 95 percent confidence intervals are widely overlapping.



Figure 3. Estimates of the Risk of Prostate Cancer. Panel A shows the estimated risk of prostate cancer and 95 percent confidence intervals among carriers and noncarriers of BRCA1 or BRCA2 mutations. The differences were statistically significant by the age of 67. Panel B shows the estimated risk of prostate cancer among carriers of each mutation. Although not shown, the 95 percent confidence intervals are widely overlapping.

•Any male relatives with breast cancer at any age.

Family History Questionnaire for Breast and Ovarian Cancer

Please place a check mark in the boxes below, for yourself and for each family member who has had cancer as indicated.Breast CancerBefore Age 50

Breast CancerAt or After Age 50

Ovarian CancerAt Any Age

YourselfYour Mother

Your Sister(s)Your Daughter(s)

Mother's Side:Grandmother

Aunt(s)Cousin(s)

Father's Side:Grandmother

Aunt(s)Cousin(s)

Father or Mother's Side: Any Males with breast cancer at any

ageAsk your physician to evaluate your hereditary risk of breast and ovarian cancer if there are:

•Two (2) or more check marks in the above table, OR

•One (1) check mark in the above table and you are of Ashkenazi Jewish descent,

OR

Breast T, 36

Breast, 42Breast T, 45Breast T, 56

Breast T, 40

68 yrs

39 yrs

?

It is needed to identify the responsibleBRCA mutation from the testing of anaffected case to be able to offer an Informative genetic testing in unaffected relatives

Breast T, 341: test of the index case 2: test of a relative

Definition of Penetrance:

Complete Penetrance: Every individual who inherits a mutated gene develops the related disease

Ex: Huntington disease

H h

h h

Ex: BRCA1 Mutation:

B b

b b

Incomplete Penetrance: Less than 100% of the carriers of the mutation develop the disease

100% Incidence of Huntington Disease

100% Normal Individuals

Greater probability of developing breast cancer, but another mutant factor (from environment, other genes) is also needed

May develop sporadic breast cancer

Factors Affecting Penetrance

Hormonal/ reproductive

factors

Modifier genes Carcinogens

Response to DNA damage

Not everyone with an altered gene develops cancer

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“A Genetic Counselor’s Nightmare”

• Many genes control breast cancer– it’s not a Mendelian trait

• Not all mutations in BRCA1 cause cancer• Not all individuals with a mutant BRCA1 allele

develop cancer– BRCA1 is “incompletely penetrant”

Consulta inicial

Sana

Enferma

Hist. Fam. Alto Riesgo

Sin Hist. Fam. Alto Riesgo

Hist. Fam. Alto Riesgo

Sin Hist. Fam. Alto Riesgo

Pariente Enferma

No Disponible

> 50 Años

< 40 Años

> 50 Años

< 40 Años

Test Pariente Test Consulta

+-

-

- -

+

+

-

?

-

?

?

ALGORITMO

Abuelos Paternos del Paciente

Abuelos Maternos del Paciente

PadresTios/as del Pcte.

(Via Materna)Tios/as del Pcte. (Via Paterna)

Hermanos/as del Paciente

PACIENTEESPOSO/A

HIJOS

Referencias:HombreMujerCasamientoCáncerPaciente o Sujeto a Determinar Maestría en Biología

Molecular Médica –Dr. José Mordoh 2011

TIPOS DE BRCA- ANÁLISIS

1- Total: para determinar mutación por primera vez se secuencia todo el gen.

2- Sitio Único: para pacientes con parientes cuya mutación BRCA1/BRCA2 es conocida.

3- Multisitios: para individuos Ashkenazi.Detecta la presencia de mutaciones en tres sitios diferentes.185 del AG, 5382 insC y 6174 del T

Conclusión: en mujeres con mutación BRCA1 o BRCA2,la mastectomía total profiláctica bilateral reduce la incidencia de cáncer de mama luego de 3 años de follow-up.

El riesgo de cáncer de ovario en portadoras de mutacionesBRCA1 o BRCA2, disminuye con cada nacimiento pero nocon duración aumentada de anticonceptivos orales. Es pre-maturo recomendar el uso de anticonceptivos orales paraquimioprevención de cáncer de ovario en portadoras de talesmutaciones

En cáncer de mama con mutaciones en BRCA1 o BRCA2 se expresan grupos de genes diferentes

CANCER DE COLON HEREDITARIO

Adenomatous polyposis coli (APC)

Tumor suppressor gene

First characterized because of its association with familial adenomatous polyposis

Further study proved its role in sporadic cases of colon cancer

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Figure 3. Role of the Cadherins in Establishing Molecular Links between Adjacent Cells. Cadherin dimers gather at adherens junctions to form a zipper-like structure that maintains adjacent cells in close contact. Cadherins are linked to the cytoskeleton through the catenins. These cytoplasmic molecules appear to be essential for normal cadherin function and the formation of adherens junctions. The cadherin itself is linked to -catenin (or related plakoglobin), and -catenin associates with actin microfilaments.



Figure 2. Functional and Pathogenic Properties of APC

Maquinaria de “Mismatch Repair” (MMR)Proteína

Función E-coli Eucariotes

Unión Mismatch MUT S h MSH2h MSH6 (GTBP)

Reclutamiento MUT L h MLH1h PMS1H PMS2

EndonucleaseUnión a DNA hemi- MUT H ?metiladoReparación del gap DNA pol I DNA pol σHelicasa II UVRD ?

MMR: Mismatch RepairGTBP: GT Mismatch Binding ProteinRER+ R li i E P i i MMR

DNA Mismatch Repair Genes

Gene Chromosome Apparent contributionto HNPCC30

hMSH2 2p21-22 31%hMLH1 3p21 33%hPMS1 2q31-33 2%hPMS2 7p22 4%

HNPCC: hereditary nonpolyposis colorectal cancer.

Cancers Usually Result from a Series of Mutations in a Single Cell

Tumor suppressor Tumor suppressorsoncogene

Normal -> proliferating -> benign -> intermed. -> late -> cancerous -> colonepithelium adenoma adenoma adenoma adenoma cancer

with villi

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33

From Roses,2000

What is Retinoblastoma?

A malignant tumor arising in the undifferentiated retina of one or both eyes during infancy or early childhood.

The most common tumor of the eye in early childhood with a frequency of 4 / 1.000.000 NIÑOS < 15 años

Actually begins to form during fetal development, when retinal cells (retinoblasts) are rapidly dividing.

Expressed by 5 years of age in nearly all cases.

leucocoria

Retinoblastoma

Rare malignant tumor arising from immature neurons in the retinaAbout 25-30 % of cases are associated with a germline mutation, and 70-75 % are sporadic. 5-10% of germline cases are inherited germline mutations20-30% are NEW germline mutations

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RetinoblastomapRb; tumor suppressor

deleted in retinoblastoma plays a pivotol role in mammalian cell cycle represses transcription - E2Fregulated by phosphorylation

-underphosphorylate: growth suppressive-hyperphosphorylated: growth promoting

E2F transcription factors• First described as a DNA binding activity for the

adenovirus early region 2 promoter, so called Early 2 Factor.

• An E2F-binding protein was identified (DP-1). (Girling et al., 1993).

• Several E2F-1 related proteins have been identified.

• Evidence for involvement in cell cycle:1. Overexpression of E2F-1 in NIH3T3 cells

prevents them from entering G0 following growth factor withdrawl.

2. Microinjection of E2F-1 into quiescent NIH3T3 cells stimulated entrance into the cell cycle and DNA synthesis.

Retinoblastoma tumor suppressor gene(Rb)

Mapped to gene chromosome 13 and sequenced.

180 kb; codes a 4.7 kb mRNA that produces a 928 amino acid nuclear phosphoprotein, pRB.

pRB is expressed in every tissue that has been examined and regulates the cell cycle.

Retinoblastoma tumor cells possess point mutations or deletions.

In hereditary retinoblastoma, second RB mutation often is identical to the inherited one (a possible example of gene conversion).

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E2F regulates genes required forS-phase

E2F

DP1

target genes

Target genes: Genes encoding proteins involved in DNA

synthesis-DNA polymerase a-thymidine kinase-thymidylate synthase-ribonucleotide reductase

DNA repair proteins-RAD51

Cell cycle regulators- Cdk2 and cyclins A and E.

E/CDK2

D/CDK4/6

Retinoblastoma. Microscopía

Maestría en Biología

M olecular Médica –Dr. José M ordoh 2011

Role of pRB in regulating cell division

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TRATAMIENTOS

– Enucleación– Radioterapia– Laser– Crioterapia– QT con carboplatino

– ¡Se puede curar hasta el 96 % de los niños!

p53 tumor suppressor gene

• 53 kDa nuclear phosphoprotein • the most commonly altered gene

identified in human cancers to date• functions as a tumor suppressor when

normal and a dominant oncogene when mutant

• many mutations result in a prolonged protein half-life and/or overexpression

Effects of DNA damage and

normal (non-mutant) p53

lead to cell growth arrest.

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p53 Protein

G1 and G2 arrest in cells with damaged DNA depends on the p53 tumor suppressor

p53 tumor suppressor geneMutations in p53 are implicated in ~50% of human cancers, including cancers of the:

breast, brain, liver, lung, colorectal, bladder, and blood.

Development of tumors requires mutations on two p53 alleles.

Codes a 393 amino acid protein involved in transcription, cell cycle control, DNA repair, and apoptosis (programmed cell death).

p53 binds to several genes, including WAF1, and interacts with at least 17 cellular and viral proteins.

Transgenic mice with deletions of both p53 alleles are viable, but 100% develop cancer by ten months of age.

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cancer hereditario - investigación en cancer · 2011. 9. 9. · el riesgo de cáncer de ovario en...

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