ABORDAJE GENÉTICO DEL CÁNCER DE MAMA Y OVARIO HEREDITARIO
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ABORDAJE GENÉTICO DEL CÁNCER DE MAMA Y OVARIO HEREDITARIO
- 1. 1 Abordaje genético del cáncer de mama y ovario hereditario Dra. Sara Alvarez de Andrés Dirección Médica NIMGentics, S.L Conflicto de Intereses: Socio de NIMGenetics, SL
- 2. 2 Contenidos: 1. Selección de pacientes para el estudio del Cáncer de Mama y Ovario hereditario 2. Técnicas para la identificación de las Mutaciones 3. Tipos de Mutaciones en BRCA1 y BRCA2 4. Utilidad y Aplicaciones de los Paneles Multigen en el Ca de Mama y Ovario hereditario
- 3. 3 1 Selección de Pacientes para el estudio del Cáncer de Mama y Ovario Hereditario
- 4. 4 Esporadico 80% Familiar 10-15% Hereditario 5-10% PROPORCIÓN DE CANCER DE MAMA HEREDITARIO
- 5. Evaluación de los Factores de riesgo que incrementan el riesgo relativo de desarrollo de Ca de Mama • Edad (>65a vs <65a, con un incremeto progresivo del riego hasta los 80a ) • Determinadas Mutaciones germinales heredadas (BRCA1 y/o BRCA2) • Antecedentes personales de Patología mamaria • Dos o más familiares de primer grado con Cáncer de mama diagnosticados a edades tempranas • Historia Personal de Cáncer de Mama (>40 años) • Niveles Hormonales elevados de estrógenos ó testosterona (postmenopaúsicas) • Radioterapia torácica previa • Un antecedente familiar de Cáncer de Mama de primer grado • Historia menstrual (>12a y >55a) • Historia reproductiva (Nuliparidad, 1ºemb>30ª, No lactancia, No embarazos a término) • Antecedentes personales de herencia Ashkenazi (Europa del Este) • Hº personal de cáncer de endometrio, ovario y colon. • Terapias Hormonales sustitutivas ó contraceptivas • Otros: Obesidad, Consumo Alcohol, status socioeconómico alto, estatura alta. Breast Cancer. Facts and Figures 2013-2014 Riego Relativo >4 2.1-4 1.1-2.0
- 6. - ELEVADA INCIDENCIA DEL CANCER DE MAMA- familias con múltiples casos pueden agrupar casos de Cáncer hereditario y esporádico. - PENETRANCIA VARIABLE del GEN CAUSAL dependiente del género, la edad, y de factores no genéticos - HETEROGENICIDAD DE LOCUS- Diferentes genes son responsables de la predisposicíon al Cáncer de Mama en las diferentes familias con HBOC - HETEROGENICIDAD ALÉLICA- Diferentes Alelos alterados en los diferentes genes causales en las diferentes familias. 6 Factores que dificultan el diagnóstico clínico del Cáncer de Mama y Ovario Hereditario Mary-Claire King, Science 343, 1462-65 (2014)
- 7. Criterios de Selección de la SEOM+NCCN 2014 para el estudio de los genes BRCA1 y BRCA2 en pacientes con Cancer de Mama 1) Independientemente de la historia familiar si: • Antecedente de una mutación conocida ó herencia Ashkenazi • SEOM: Paciente con cáncer de mama y cáncer de ovario sincrónico o metacrónico vs NCCN: Cáncer de ovario epitelial, cáncer tubárico o primario peritoneal • Pacientes >60años con Cáncer de Mama triple negativo • SEOM: Un caso de cáncer de mama en paciente de 30 años ó menor vs NCCN<45a • Un caso de cáncer de mama bilateral en menor de 40 años. 2) Familias con dos miembros afectos con cáncer de mama y/o cáncer de ovario y al menos una de las siguientes características: • Varón con cáncer de mama. • Uno de ellos es un Cáncer de ovario, cáncer tubárico o primario peritoneal. • Ambos casos diagnosticados en menores de 50 años 3) Familias con 3 ó más individuos con cáncer de mama y/o cáncer de ovario en la misma rama de la familia. 4) Familias con dos familiares (1º, 2º ó 3º grado) con Cáncer de páncreas y y/o prostata (Gleason score 7) Cáncer Hereditario II ed. Alonso A et al. Ed. SEOM, 2010; pp:428
- 8. 8 Criterios de NCCN 2014 para considerar la realización de Estudios Genéticos 1) En pacientes AFECTOS: • Antecedente de una mutación conocida • Cáncer de ovario, cáncer tubárico o primario peritoneal • Cáncer de mama: – En paciente de <45años – Cáncer Triple Negativo – Cáncer de Mama en varón – Cáncer de mama bilateral ó dos tumores ipsilaterales sincrónicos ó asincrónicos • Con Antecedentes familiares de: – 1 familiar con Ca de mama<50 años – 1 familiar con Ca de Ovario a cualquier edad – 2 familiares con Ca de mama y/o cancer de páncreas de cualquier edad – Pertenecer a una población de riesgo (pej: Ashkenazi) – 1 familiar con Ca de mama y otro con Ca de pancreas, prostata, SNC, endometrio, Leucemia/linfoma, Tiroides, alteraciones dermatológicas, macrocefalia, hamartomas GI ó cancer gástrico difuso. 2) En individuos NO AFECTOS con Hª familiar de: – Mutación conocida – Cáncer de mama bilateral ó dos tumores ipsilaterales sincrónicos ó asincrónicos – Más de dos individuos con Cáncer de mama en la misma familia – cancer de ovario – Cáncer de mama en <45 años – 1 familiar con Ca de mama y otro con Ca de pancreas, prostata, SNC, endometrio, Leucemia/linfoma, Tiroides, alteraciones dermatológicas, macrocefalia, hamartomas GI ó cancer gástrico difuso. – Cancer de mama en Varon
- 9. • Aspectos Legales – Liberación de la Patente de Myriad (U.S Supreme court, Junio 2013) – “The Genetic Information Nondiscrimination Act of 2008 (Public Law 110–233)” • Desarrollo Científico/Tecnológico: – Identificación de múltiples genes de predisposición al desarrollo del Cáncer de Mama y Ovario hereditario. – Desarrollo de la Secuenciación masiva • Evidencias epidemiológicas* – Más del 50% de las mutaciones en BRCA1 y BRCA2 son heredadas de progenitores NO AFECTOS. – El 50% de las mujeres con mutaciones en BRCA1 y BRCA2 tienen poca o ninguna historia familiar de Ca de mama u ovario (familias NO INFORMATIVAS) 9 Pérdida de Barreras para el Estudio mutacional de BRCA1/2 “Hasta que no se erradique en Ca de Mama y Ovario en mujeres portadoras la carrera de los BRCAs no se habrá finalizado”-Mary-Claire King, 2014 * M.-C. King, Science 302, 643–646 (2003).
- 10. 10 2 Técnicas para la Identificación de Mutaciones
- 11. 11 Se analizan simultáneamente todos los exones y las regiones de splicing -20 a +20, al menos -10 a +10 de BRCA1/BRCA2 >1 nt F1 F2 R2R1 +20 Los amplicones son solapantes Aplicación de la Secuenciación masiva al Estudio mutacional de BRCA1/2
- 12. Coverage: • 100% ORF • All, but 1 amplicon, >100x • Mean per amplicon: 2100 ± 302 Análisis Simultáneo de 8 muestras en una sola carrera BRCA1 cds exon Depthofcoverage BRCA2 cds exon Depthofcoverage Aplicación de la Secuenciación masiva al Estudio mutacional de BRCA1/2
- 13. 13 Nonsense Frameshift deletion Frameshift insertion Missense Normal mRNADNA C T CA A G GCG C T A A C T GU U C C GC GA U U GA GU U C U U G A CA A G A A C T GU U U A G C A A A C T CA A G C G A A C T GU U C G C U U GA GU U C G A U U GA CA A G C T A A C T Clasificación de las Mutaciones Puntuales PROTEINA TRUNCADA Y DEGRADADA POR EL SISTEMA NMD (Nonsense Mediated Decay) PROTEINA CON UN AMINOACIDO DISTINTO A LA PROTEINA WT
- 14. 14 Identificación de los Grandes Reordenamientos Detección de las pérdidas y ganancias de regiones del genoma en una muestra de ADN Hibridar y Escanear MLPA (Multiplex ligation dependent probe amplification) aCGH de Alta Resolución (Comparative Genomic Hybridization)
- 15. Deteccion de grandes delecioness Se ha detectado una deleción patogénica en la citobanda 13q12.2, coordeandas genómicas chr13: 32,890,289-32,890,740. El análisis bioinformático con el Software Alamut ESES predice que la deleción identificada implica una inactivación del gen BRCA2, debido al cambio del marco de lectura generándose una proteína truncada. Deleciónde 451 pb (Exón 2 de BRCA2)
- 16. 16 3 Estudio Mutacional de BRCA1/2
- 17. 17 BRCA1/2 Son proteínas implicadas en la reparación del DNA
- 18. 18 Knudson “two-hit” Model Genes Supresores de Tumores Primera mutacion (Portador) GEN NORMAL Regula el Crecimiento tumoral Segunda Mutación (Desarrollo del tumor) Cáncer Esporádico Cáncer Familiar Mayor riesgo a desarrollar un Cáncer Menor Edad de presentación Asociación con múltiples tumores Habitualmente con un patrón de Herencia AD
- 19. BRCA1 (Chr17) BRCA2 (Chr13) ~1800 mutaciones ~2000 mutaciones Splice-site Nonsense/Frameshift Missense Díez O, et al . Hum Mutat 2003;22:301-312 ≠ Locus y ≠ alelos = fenotipo Mutaciones fundadoras-Estudios dirigidos Más de 1M de individuos han sido testados en las últimas dos décadas El panorama mutacional de BRCA1/2 BRCA1 (14% de las mutaciones) BRCA2 (2.6%de las mutaciones) GRANDES REORDENAMIENTOS MUTACIONES
- 20. 20 La pentrancia interfamilias depende del dominio proteíco alterado en función de la localización de la mutación Missense Nonsense/Frameshift >Riesgo de Ca de Ovario Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) Las mutaciones en BRCA1 y BRCA2 presentan una Penetrancia variable e incompleta Mutaciones en 3´y 5´ >Riesgo de Ca de Mama
- 21. 21 1.- Variante Benigna 2.- Variante Probablemente Benigna 3.-Variante de Significado incierto 4.- Variante probablemente patogénica 5.- Variante Patogénica Interpretación de las variantes genómicas en el informe Clínico de diagnóstico Genético VARIANTES INFORMADAS Son aquellas que NO pueden ser clasificadas como NEUTRALES ó PATOGÉNICAS VUS: 2 al 10% de las variantes Cheon et al. Genome Medicine 2014, 6:121
- 22. 22 Variantes de Significado Incierto (VUS) 1. Las VUS incluyen variantes missense, intronicas, y pequeños Indels in frame. 2. La clasificación de estas variantes se depura a través de bases de datos como Clinvar (repositorios de los resultados de diversos laboratorios) 3. La evaluación de la patogenicidad de las variantes se realiza por sistemas de predicción in sílico y el desarrollo de consorcios como el “Evidence-based Network for the Interpretation of Germline Mutant Alleles (ENIGMA)”*. 4. La probabilidad de patogenicidad de cada variante en base a: *N. M. Lindor et al., Hum. Mutat. 33, 8–21 (2012). • Nivel de conservación evolutiva de la variante (Align-GVGD) • Segregación familiar • Características AP del tumor • Efectos en el RNA splicing • Ensayos “in vitro” • Recurrencia de la variante ¿Problemas éticos y de Regulación?
- 23. 23 Variantes de Riesgo bajo Moderado (Hipomórficas) Mutaciones en BRCA1/2 que REDUCEN la actividad de la Proteína pero NO la anulan. Se asocian a un riesgo bajo ó moderado de Ca de Mama y Ovario Inhibe la expresión del microRNA-155 BRCA1 p.Arg1699Gln (R1699Q) Afecta al dominio BRCT domain Riesgo acumulado del 24% a los 70 años Vs el 12% de la Población general Se estima que en el futuro una caracterización mas precisa de las variantes BRCA1 y BRCA2 de riesgo moderado permitirá el desarrollo de estrategias terapéuticas específicas y distintas de las que se aplican a los pacientes de alto riesgo S. Chang et al., Nat. Med. 17, 1275–1282 (2011).
- 24. Fergus J. Couch et al. Science (2014) 34; 1466-1477 Síndrome de Cáncer de Mama y Ovario Hereditario CHECK2 1100delC: •1.2% de los controles europeos •4.2% de los casos de Ca de Mama familiar BRCA1/BRCA2-negativos •Riesgo de Ca de Mama del del 35% en >70a PALB2 1592delT: •Riesgo de Ca de Mama del 14% a los 50a y del 35% en >70a •Se asocia a T. triple negativos y de Mal pronóstico BRCA1: Riesgo de Ca de Mama del 50-70% a los 70a BRCA2: Riesgo de Ca de Mama del 40-60% a los 70a Weischer M, J Clin Oncol. 2008 Feb 1;26(4):542-8
- 25. 25
- 26. 26 1.- Síndrome de Li-Fraumeni • Gen TP53 • Criterios de Chompret ó mujeres con Ca de Mama <35 años BRCA negativas • Se asocia a tumores HER2+/ER+/PR+ 2.- Síndrome de Cowden/PTHS • Gen PTEN y SDHB-D, PIK3A, AKT1 • Riesgo de desarrollar Ca de Mama del 85% con una penetrancia del 50% a partir de los 50 as (Ca de mama criterio mayor) 3.- Síndrome de Peutz-Jeghers • Gen STK11/LKB1 • Riesgo de Ca de mama 44-50% y de Ca de ovario 18-21% 4.- Síndrome Hereditario del Cáncer Gástrico Difuso • Gen CDH1 • Riesgo de Ca de mama 39-52%
- 27. 27 Win et al. Breast Cancer Research 2013, 15:R27
- 28. 28
- 29. ….RESULTADOS DE UN PANEL NGS AMPLIADO (39 genes) Estudio de 198 pacientes de Alto riesgo: - 57 pacientes BRCA positivas - 141 pacientes BRCA negativas - Se identificaron 16 variantes patogénicas en los genes: MLH1 ATM SLX4 BLM NBN CDH1 MUTYH CDKN2A PRSS1 AllisonW. Kurian, et al J Clin Oncol (2014)32: pp1-9 Problema: 428 Variantes de Significado incierto eran identificadas en 39 genes Rentabilidad Diagnóstica: 11,3% en mujeres con Ca de Mama e Historia familiar Cx profiláctica salpingo-ooforectomía Vigilancia Intensiva Mama y/o Gastrointestinal
- 30. Paneles de NGS multigen 30 1. Los paneles de NGS han demostrado ser una herramienta coste/efectiva para la identificación de individuos y familias de alto riesgo. 2. Pueden dirigir decisiones clínicas y estrategias terapéuticas (pej: identificación de mutaciones en genes de reparación) A favor.. 1. La interpretación clínica de los resultados es complicada. Así, la penetrancia del cáncer de mama y el riesgo de desarrollo de otros tumores no ha sido todavía establecido para las mutaciones patogénicas. 2. En la mayoría de los paneles hay un elevado número de VUS, cuya interpretación causa ansiedad en la paciente y en el médico 3. Diversos paneles contienen genes no claramente asociados al Cáncer de mama (pej: APC ó VHL) En contra..
- 31. Gracias !!!! Sara Alvarez, MD, PhD salvarez@nimgenetics.com
Notas del editor
- En cuanto a la Tasa de detección general, solo comentarte lo que probablemente ya sepas y es que BRCA1 y BRCA2 representan aproximadamente el 20-25% de los cánceres hereditarios de Mama (1) y aproximadamente un 5-10% del total de los cánceres de Mama (2). Además, estas mutaciones representan el 15% de los casos de Cáncer de Ovario(3). Estos números resultan difíciles de estimar desde el laboratorio dado que en muchos casos la historia de la paciente es insuficiente y no hacemos seguimiento de posterior de los casos.
- Paología mamaria que incrementa el riesgo en >4 Cáncer de Mama (<40 años) Carcinoma Lobular in situ hiperplasia atípica confirmada Tejido mamario de alta densidad Terapias Hormonales como el Diethylstilbestrol
- El Dx clínico es complejo PORQUE el HBOC es altamente heterogéneo a nivel biológico y genético debido a: The discovery of BRCA1 and its sister genes illustrates that the degree of biological complexity underlying a phenotype is an excellent predictor of its genetic heterogeneity (30).
- Antecedente de una mutación conocida Comentarios: NCCN- National Comprehensive Cancer Network Evidentemente sin antecedentes familiares de mutación previa Según el US el antecedente de un cáncer de mama bilateral ya es criterio para hacer el test En familias judías: un antecedente de familiar de primer grado con mama u ovario dos familiares de segundo grado en la misma rama de la familia con cáncer de mama u ovario. - En el grupo 2) también se incluye el antecedente de bilateralidad
- Dadas la implicaciones terapeúticas de la identificación de estas mutaciones, el estudio mutacional de BRCA1/2 debería ser incluido en el cribado de salud de mujeres adultas jóvenes…y como cualquier screening la frecuencia de resultados positivos sería baja, pero para aquellas mujeres en las que se detectase las consecuencias serían una mesurables e implicarían salvar una vida. So what next? Given that 50% of BRCA1 and BRCA2 mutations are inherited from unaffected fathers, and given the small size of modern families, almost 50% of women with BRCA1 and BRCA2 mutations have little or no family history of breast or ovarian cancer. Yet, cancer risks to mutation carriers with no cancer family history are as high as risks to mutation carriers from severely affected families (36). Identification of cancer-causing mutations in BRCA1 and BRCA2 has clear and actionable implications for prevention. BRCA1 and BRCA2 screening as part of routine health care for young adult women is sensible and feasible. As in any population-screening program, genetic or otherwise, few participants will prove positive, but for women who learn that they carry mutations in BRCA1 or BRCA2, the consequences are enormous, addressable, and life-saving. Until there are no more breast or ovarian cancers among women with BRCA1 or BRCA2 mutations, the real race is not over. 36. M.-C. King, J. H. Marks, J. B. Mandell; The New York Breast Cancer Study Group, Science 302, 643–646 (2003). 2013, the U.S. Supreme Court ruled unanimously that genes are products of nature and therefore cannot be patented (31), nullifying the Myriad patents on BRCA1 and BRCA2. The ruling was a victory for science and for patients and led immediately to broader availability of clinical genetic testing. For nearly 20 years, while Myriad was the only commercial source in the United States for genetic testing of BRCA1 and BRCA2, cost was a major deterrent to widespread screening. The cost to women of BRCA1 and BRCA2 testing is now dropping, due both to the end of the monopoly and to two scientific developments that have changed the landscape. First, there are now enough genes identified with mutations predisposing to breast and ovarian cancer that multigene screening panels can be developed and effectively implemented. Second, genomic technology now offers the opportunity to sequence at costs orders of magnitude lower than the cost of Sanger sequencing (32). Previously, clinical genetic testingwas carried out gene by gene, based on specific clinical indications and family histories, with each test costing thousands of dollars. With the advent of massively parallel sequencing, large panels of genes are now screened simultaneously at far lower cost (33). There was another barrier to genetic testing for inherited breast and ovarian cancer. Some patients and physicians worried that a positive finding would lead to loss of health care coverage. In consequence, mutations were not identified in some womenwho could have been saved by risk-reducing surgery. Clinical guidelines have been established for women harboring damaging mutations in BRCA1 and BRCA2, including increased surveillance, surgical removal of ovaries and fallopian tubes (salpingo-oophorectomy) by age 40 years or younger, and the possibility of risk-reducing mastectomy (34, 35). The Genetic Information Nondiscrimination Act of 2008 (Public Law 110–233), which protects mutation carriers against loss of health care coverage, should have removed fear as a barrier to testing, so that women with mutations in BRCA1 and BRCA2 can be identified without economic reprisal.
- es un mecanismo celular de vigilancia del ARN mensajero para detectar mutaciones terminadoras y evitar la expresión de proteínas truncadas o erróneas. En mamíferos, la NMD se inicia por el complejo de unión de exones (EJC) que se depositan durante el splicing del pre ARNm. Normalmente, un EJC es retirado por el ribosoma durante la primera ronda de traducción del ARNm. No obstante, si se da un EJC en un punto de la secuencia más allá ("downstream") del codón "sin sentido" (también llamado de parada o terminación), entonces este EJC aún permanecerá unido al ARMm cuando el ribosoma llegue al codón de terminación, y de ese modo servirá para desencadenar la NMD, ya que los factores proteicos implicados en esta función identifican la presencia de un EJC "corriente abajo" como un problema, de modo que el ARNm erróneo se degrada, por ejemplo mediante el exosoma.1 Con raras excepciones, un EJC no se deposita corriente abajo de un codón terminador.
- Multiplex ligation-dependent probe amplification (MLPA)[1] is a variation of the multiplex polymerase chain reaction that permits multiple targets to be amplified with only a single primer pair.[1] Each probe consists of two oligonucleotides which recognize adjacent target sites on the DNA. One probe oligonucleotide contains the sequence recognised by the forward primer, the other the sequence recognised by the reverse primer. Only when both probe oligonucleotides are hybridised to their respective targets, can they be ligated into a complete probe. The advantage of splitting the probe into two parts is that only the ligated oligonucleotides, but not the unbound probe oligonucleotides, are amplified. If the probes were not split in this way, the primer sequences at either end would cause the probes to be amplified regardless of their hybridization to the template DNA, and the amplification product would not be dependent on the number of target sites present in the sample DNA. Each complete probe has a unique length, so that its resulting amplicons can be separated and identified by (capillary) electrophoresis. This avoids the resolution limitations of multiplex PCR. Because the forward primer used for probe amplification is fluorescently labeled, each amplicon generates a fluorescent peak which can be detected by a capillary sequencer. Comparing the peak pattern obtained on a given sample with that obtained on various reference samples, the relative quantity of each amplicon can be determined. This ratio is a measure for the ratio in which the target sequence is present in the sample DNA.
- Genetics revealed that BRCA1 is a tumor suppressor gene following the two-hit model (25): Cancer develops as the result of one inherited loss-of-function mutation followed by a somatic mutation causing loss of the remaining wild-type allele in a vulnerable cell type. The central puzzle is why complete loss of function of BRCA1 leads to cancer. Solving this puzzle has been especially challenging, because the BRCA1 protein is involved inmultiple essential biological functions (26). As part of a multiprotein complex, BRCA1 repairs double-strand DNA breaks via the homologous recombination repair pathway. The C-terminal BRCT domain interacts with histone deacetylase complexes and is involved in transcriptional regulation. The N-terminal RING domain heterodimerizes with a sister domain of BARD1 and acts as a ubiquitin ligase of the estrogen receptor (27). Missense mutations that abrogate the function of the RING domain lead to breast cancer. Virtually all other cancer-causing mutations of BRCA1 are truncations: nonsense mutations, frameshifts, or large genomic deletions or duplications leading to stops and loss of the C-terminal domain
- Las Mutaciones Pathogenicas representan aproximadamente el 30%of high-risk breast cancer families y explican el ~15% de los breast cancer familial relative risk (the ratio of the risk of disease for a relative of an affected individual to that for the general population) (Fig. 1) Genetic testing for mutations in BRCA1, BRCA2, and other breast cancer susceptibility genes has served as a model for the integration of genomics into the practice of personalized medicine, with proven efficacy as a tool to determine eligibility for enhanced screening and prevention strategies,as well as a marker for targeted therapy. Cambios intronicos no representados en el dibujo Todas las mutaciones registradas due to the large number of Alu repeats in the genomic region containing the BRCA1 gene Founder mutations (common mutations in a population arising from a small number of individuals) in BRCA1 and BRCA2 have been described in almost every population studied. The best known are in the Ashkenazi Jewish population, with 3% of individuals carrying one of the three founder mutations, namely BRCA1 c.68_69delAG [185delAG] (1%), BRCA1 c.5266dupC [5382insC] (0.13%), or BRCA2 c.5946delT [6174delT] (1.52%) (14, 15). Other examples are the BRCA1 c.548-?_4185+?del [ex9-12del] mutation found in ~10% of Hispanic BRCA carriers and deletions of BRCA1 seen in Dutch founder populations (16, 17). Thus, targeted screening for specific BRCA1 and BRCA2 mutations before full gene testing is warranted in a number of populations.
- The BRCA1 amino terminus contains a RING domain that associates with BRCA1-associated RING domain protein 1 (BARD1) and a nuclear localization sequence (NLS). The central region of BRCA1 contains a CHK2 phosphorylation site on S988 (Ref. 25). The carboxyl terminus of BRCA1 contains: a coiled-coil domain that associates with partner anbind RAD51. The BRCA2 DNA-binding domain contains a helical domain (H), three oligonucleotide binding (OB) folds and a tower domain (T), which may facilitate BRCA2 binding to both single-stranded DNA and double-stranded DNA46. This region also associates with deleted in split-hand/split-foot syndrome (DSS1)42, 44, 45. The C terminus of BRCA2 contains an NLS and a cyclin-dependent kinase (CDK) phosphorylation site at S3291 that also binds RAD51 (Ref. 53). d localizer of BRCA2 (PALB2); a SQ/TQ cluster domain (SCD) that contains approximately ten potential ataxia-telangiectasia mutated (ATM) phosphorylation sites and spans amino acid residues 1280–1524; and a BRCT domain that binds ATM-phosphorylated abraxas, CtBP-interacting protein (CtIP) and BRCA1-interacting protein C-terminal helicase 1 (BRIP1). The BRCA1–abraxas complex is associated with BRCA1 recruitment to sites of DNA damage19, 20, 108, 109. The BRCA1–BRIP1 complex, which also contains DNA topoisomerase 2-binding protein 1 (TOPBP1), is associated with DNA repair during replication110. The BRCA1–CtIP complex promotes ataxia-telangiectasia and Rad3-related (ATR) activation and homologous recombination (HR) by associating with the MRN complex (which is comprised of MRE11, RAD50 and Nijmegen breakage syndrome protein 1 (NBS1)) and facilitating DNA double-strand break resection22. The central region of BRCA1, which contains the SCD, is phosphorylated by ATM. This phosphorylation is important for BRCA1-mediated G2/M and S-phase checkpoint activation, as expression of a BRCA1 mutant that lacks three of the phosphorylation sites (S1387, S1423 and S1524) fails to rescue defective checkpoint activation and ionizing radiation hypersensitivity in a BRCA1-deficient cell line111, 112. b | The N terminus of BRCA2 binds PALB2 at amino acids 21–39 (Ref. 68). BRCA2 contains eight BRC repeats between amino acid residues 1009 and 2083 that More than 1800 distinct rare variants—in the form of intronic changes, missense mutations, and small in-frame insertions and deletions—have been reported inBRCA1and2000 inBRCA2 (BreastCancer Information Core; www.research.nhgri.nih.gov/bic). In BRCA1, missense mutations that are pathogenic and highly penetrant (i.e., confer a high risk of cancer) are located primarily in the RING finger and BRCT domains (2, 9, 10), which are critical for the DNA repair activity of BRCA1. In BRCA2, highly penetrant, pathogenic missense mutations are located predominantly in the DNA binding domain (11, 12). As studies of BRCA1 and BRCA2 unfolded, it became apparent that the estimates of penetrance (risk) of breast and ovarian cancer varied by the ascertainment criteria for studies, with populationbased studies showing much lower risks than family-based studies (18). In clinical practice, BRCA1 mutation carriers are generally estimated to have a 57% chance of developing breast cancer and a 40% chance of developing ovarian cancer by age 70, whereas BRCA2 mutation carriers are estimated to have a 49% chance of breast cancer and an 18%chance of ovarian cancer (19). Interindividual variability in the risk of breast and ovarian cancer has been attributed to modifying environmental and genetic effects, including the location and type of mutations in BRCA1 and BRCA2. Specifically, early reports focused on the location of mutations in BRCA1/2 suggested that nonsense and frameshift mutations located in the central regions of either coding sequence, termed ovarian cancer cluster regions (OCCR), were associated with a greater risk of ovarian cancer than similar mutations in the proximal and distal regions of each gene (20–22). More recently, a Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) study of 19,581 BRCA1 and 11,900 BRCA2 mutation carriers confirmed relative increases in ovarian cancer and decreases in breast cancer risk for mutations in the central region of each gene and higher risk of breast cancer for mutations in the 5′ and 3′ regions of each gene. Variability in risk is also partly explained by common genetic modifiers of breast and ovarian cancer risk in BRCA1 and BRCA2 mutation carriers that have been identified through genome-wide association studies (23–29). Accounting for these modifiers suggests that the BRCA1 mutation carriers in the highest risk category may have an 81%or greater chance of breast cancer and a 63% or greater chance of ovarian cancer by age 80, whereas BRCA2 mutation carriers at greatest risk may have more than an 83% chance of breast cancer by age 80 (27, 28). In conjunction with other variables modifying risk in BRCA1 and BRCA2 mutation carriers, these data offer the potential for more precise personalized risk estimates.
- The classification of VUS may be further complicated by hypomorphic mutations in both BRCA1 and BRCA2, which retain partial protein activity and may be associated with moderate to low risks of breast and ovarian cancer. The best characterized of thesemutations is the p.Arg1699Gln (R1699Q) missense mutation in the BRCT domain of BRCA1 that abrogates the repression of microRNA-155 (38) and is associated with a cumulative risk of breast cancer of 24% by age 70 (30). This risk is lower than that associated with other BRCA1 mutations but substantially greater than the 12% risk of breast cancer in the general population. In contrast, the well-known polymorphic stop codon in BRCA2, p.Lys3326X, is associated with only a modest increase in breast cancer risk [odds ratio (OR) = 1.26] (39) and appears to have little clinical relevance. As more moderate risk variants in BRCA1 and BRCA2 are validated, risk management strategies distinct from those applied to carriers of high-risk mutations must be developed.
- Fig. 1. Genetic variants that predispose to breast cancer. The pie chart on the left shows the estimated percentage contribution of mutations in highpenetrance (BRCA1/2, TP53, CDH1, LKB1, and PTEN) and moderate-penetrance (e.g., CHEK2, ATM, and PALB2) genes and common low-penetrance genetic variants to familial relative risk. “Known SNPs” are SNPs associated with breast cancer through GWAS, as listed on the right. The odds ratios refer to the increase (or, in some cases, the reduction) in risk conferred by the rare allele of the variants. “Other predicted SNPs” refers to the estimated contribution of all SNPs, other than known loci, that were selected for replication of breast cancer GWAS (5, 39). Women with an abnormal PALB2 gene have a 14% risk of developing breast cancer by age 50 and a 35% risk of developing breast cancer by age 70. In comparison, women with an abnormal BRCA1 gene have a 50%-70% risk of developing breast cancer by age 70. Women with an abnormal BRCA2 gene have a 40%-60% risk of developing breast cancer by age 70. The other breast and ovarian cancer genes also harbor many different rare, recent damaging mutations with effect sizes ranging from twofold increased risk for CHEK2 to 10-fold for TP53. Of the seven families in our 1990 linkage analysis with young-onset breast cancer (3), six families harbor mutations in BRCA1, and one harbors a mutation in BRCA2. Of the 16 families in that analysis that we predicted would not carry mutations in BRCA1, six are explained by BRCA2; one each is explained by PALB2,CDH1, andSLX4; and seven remain unsolved. There are more breast cancer genes to be found. The critical genes known thus far encode proteins in the same and related pathways. Genetic variants that predispose to breast cancer. The pie chart on the left shows the estimated percentage contribution of mutations in highpenetrance (BRCA1/2, TP53, CDH1, LKB1, and PTEN) and moderate-penetrance (e.g., CHEK2, ATM, and PALB2) genes and common low-penetrance genetic variants to familial relative risk. Common genetic variants are denoted as SNPs. “Known SNPs” are SNPs associated with breast cancer through GWAS, as listed on the right. The odds ratios refer to the increase (or, in some cases, the reduction) in risk conferred by the rare allele of the variants. “Other predicted SNPs” refers to the estimated contribution of all SNPs, other than known loci, that were selected for replication of breast cancer GWAS (5, 39). Li-Fraumeni syndrome (caused by germline mutations in TP53), Cowden disease (caused by germline mutations in PTEN), and Peutz-Jeghers syndrome (caused by germlinemutations in STK11) These panels have proven effective in identifying individuals and family members at elevated risk of breast and other cancers. However, clinical interpretation of results from the panels is complicated by several factors. In particular, breast cancer penetrance and risk of other cancers has not yet been established for pathogenicmutations in most of the panel genes, and guidelines for clinical management of individuals found to carry these mutations have not been developed (77). Additionally, as is true for BRCA1/2, there is a high rate of VUS in the panel genes, the interpretation of which causes anxiety for both the patient and the physician. Furthermore, several commercial panels contain genes such as APC and VHL, which have not been clearly associated with susceptibility to breast cancer (78). Although continued clinical research is needed to responsibly integrate panel testing to practice, such approaches may provide guidance for critical clinical decisions such as whether a patient is at high risk of contralateral breast cancer and/or should undergo risk reduction surgeries. Conceivably, panel testing also may prove useful for selecting patients for treatment with PARP inhibitors, because several of the genes in current panels encode proteins involved in double-strand break repair, which may influence responsiveness to platinum and potentially PARPi (79).
- BRCA1 y BRCA2 representan el 20-25% de los cánceres de Mama INCIDENCIAS BRCA 1/500-2500 PTEN 1/200.000 LYNCH 1/200-1000 PJ 1/120.000 LI FRAMUNENI Ycancer gástrico difuso RARO Cowden syndrome tb llamado PTHS (PTEN hamartona tumor Syndrome) Fijar en Dermatológico (Hamartomas)/circunferencia craneal/Tiroides El Ca de Ovario de PJ es habitualmente cordoma El ca en mutaciones CDH1 es lobular
- INCIDENCIA DE LYNCH 1/200-1000
- Asi mismo, los paneles que contienen genes implicados en la reparación del DNA de doble cadena pueden identificar pacientes potencialmente resistente a platinos y candidatos a tratamientos específicos como los inhibidores PARP These panels have proven effective in identifying individuals and family members at elevated risk of breast and other cancers. However, clinical interpretation of results from the panels is complicated by several factors. In particular, breast cancer penetrance and risk of other cancers has not yet been established for pathogenicmutations in most of the panel genes, and guidelines for clinical management of individuals found to carry these mutations have not been developed (77). Additionally, as is true for BRCA1/2, there is a high rate of VUS in the panel genes, the interpretation of which causes anxiety for both the patient and the physician. Furthermore, several commercial panels contain genes such as APC and VHL, which have not been clearly associated with susceptibility to breast cancer (78). Although continued clinical research is needed to responsibly integrate panel testing to practice, such approaches may provide guidance for critical clinical decisions such as whether a patient is at high risk of contralateral breast cancer and/or should undergo risk reduction surgeries. Conceivably, panel testing also may prove useful for selecting patients for treatment with PARP inhibitors, because several of the genes in current panels encode proteins involved in double-strand break repair, which may influence responsiveness to platinum and potentially PARPi (79). As part of personalizing risk assessment, these genomic insights may soon form a rational and cost-effective basis for selection of women for breast cancer screening (91, 92). Going forward, the reduced cost and increased access to genomic profiling of breast tumors will likely identify new therapeutic targets. However, the anticipated increased uptake of sequencing will require new approaches for communication to patients of findings from germline DNA that suggest increased risk for treatment toxicities or risk for disorders other than breast cancer (90, 93, 94). Two decades after the cloning of the BRCA genes, clinical application of findings of breast cancer genetic research continues to drive new paradigmsparadigms of “personalized” genomics and precision medicine.