BeSHG 2016: Hereditary basis of cancer specifics for genetic counseling. Dr Anne De Leener Centre de Génétique Humaine

Transcription

1 BeSHG 2016: Hereditary basis of cancer specifics for genetic counseling Dr Anne De Leener Centre de Génétique Humaine

2 Heredity? It is estimated that 5-10% of the cancers are due to inherited gene mutation or deletion. However, a much higher proportion of cancers (30-40%?) may be due to moderately penetrant cancer susceptibility gene coupled with exposure to carcinogens. 2

3 Familial history of cancer: when do we have to think about heredity? Retinoblastoma,12 month Breast, 65 y Retinoblastoma, 4 month Breast, 55 y 3

4 Familial history of cancer: when do we have to think about heredity? Retinoblastoma,12 month Breast, 65 y Retinoblastoma, 4 month Breast, 55 y Retinoblastoma risk: 1/ new cases/year in France, and familial cases are 5 times more frequent than expected by coincidence! Breast cancer risk: 1/10 10% of FDR will have a breast cancer < 70y There are family histories by coincidence 4

5 «Il ne suffirait pas en effet de compter combien de cancéreux sur cent ont eu des cancéreux dans leur famille. Il faudrait démontrer que ce chiffre est supérieur à celui qu on pourrait attendre d une coïncidence pure et simple». - Familial history of breast cancer : Méta- analyse : Collaborative Group on Hormonal Factors in Breast Cancer - Lancet 2001 RR=1,80 RR=2,93 RR=3,90 - Familial history of ovarian cancer : Schildkraut JM et al - Am J Hum Genet 1989 RR=1,60 Traité des tumeurs Tome 1 Des tumeurs en général, p150 P Asselin éditeur, Paris,

6 Retinoblastoma : very rare disease, very simple genetics Retinoblast à Retinocyte à Retinoblastoma 90% of the cases: No familial history ü 60% unilateral ü 30% bilateral 10% of the cases: familial history 6

7 Retinoblastoma : very rare disease, very simple genetics Sporadic cases ü Late, unilateral and unique ü No risk for the children ü No risk for other cancers Hereditary cases ü A.D. transmission with high (but incomplete) penetrance (90%) ü Early bilateral and/or multifocal ü sporadic early bilateral cases are hereditary cases caused by neomutations 7

8 Comparison of the presentation of hereditary versus non hereditary retinoblastoma Non hereditary cases (60%) 1. Always unique and unilateral 2. age (80% of cases) 2 years 3. No risk of other cancers 4. No risk for the children Hereditary cases (40%) 1. Often bilateral (25%) and/or multifocal 2. 15% of retinoblastomas are unique but hereditary 3. age (90% of cases) 2 years 4. Increased risk of other cancers 5. Autosomal dominant transmission with very high penetrance Knudson s problem: Finding explanation to 1- clinical presentation and 2- AD transmission 8

9 Knudson et Comings 1971, Knudson model - 2 genetic alterations in one cell of the retina are needed (but maybe not enough) - In the bilateral forms: one mutation is constitutional (inherited or the novo in the early embryogenesis), the other mutation is acquired - In the unilateral forms, both mutations are somatic 1973, Comings hypothesis - The 2 mutations necessary for the apparition of a retinoblastoma correspond to the inactivation of both alleles of the same gene 9

10 Knudson model Sporadic form, without predisposition With predisposition Mutation 1 : acquired Mutation 1 : constitutional Mutation 2 : acquired Mutation 2 : acquired D après Catherine Bonaïti-Pellié 10

11 Revisiting the dogma: 2 hits are not enough! Retinoma (non/low proliferative status) Retinoblastoma (highly proliferative) Progressive genomic instability > additional mutational events How diverse could be these «speedways» to tumorigenesis? 11

12 Two key concepts of Knudson s two-hit hypothesis 1. Retinoblastoma is a genetic somatic disease caused by the purely stochastic accumulation of two mutations within one retinoblast. 2. Retinoblastoma prone children carry a germline mutation that is normally acquired during the development of any sporadic retinoblastoma. TAKE-HOME MESSAGE PREDISPOSITION = ONE STEP-SHORTER CARCINOGENESIS 12

13 Knudson s hypothesis predictions: the semiology of genetic cancer predisposition 1. Autosomal dominant transmission of the risk 2. High but incomplete penetrance 3. Age at diagnosis < usual age in sporadic cases 4. Multifocal and/or bilateral disease 5. Risk of another cancer in another tissue 6. Cancer developing in the context of predisposition are a priori identical to sporadic cancers 13

14 Genetic predisposition to cancer: Predisposition : one step shorter 1 Mutation in the cells 1/ Constitutional step: mutation in a gene involved in the tumor process gene gatekeeper 2/ High level of mutation: gene involved in the DNA repair gene caretaker 2 Sensibility of the organism to the mutagens: anomalies in detoxification, sensibility to oncogenes virus etc 14

15 Very important facts about caretaker-syndromes Categories Genes Functions p53 Transcription factor Germline mutation causes Syndrome de Li-Fraumeni Comment Acquired mutations in 50% of all cancers Gatekeepers Rb1 Transcriptional regulator Predisposition to retinoblastoma Often mutated in other cancers APC Regulates β- catenin function Autosomal dominant familial polyposis Common loss of function at the earliest polyp stage BRCA1 DNA repair Breast-ovary syndrome Mutations exceptional in sporadic cancers Caretakers BRCA2 DNA repair MLH1 MSH2 MSH6 Mismatch repair Breast-ovary syndrome Lynch syndrome Evolution of caretaker-linked cancers typically is very fast 15

16 The caretaker exception to Knudson s hypothesis prediction Rule: cancers developing among genetically high-risk individuals are identical to sporadic cancers Exception: cancers observed in syndromes caused by a caretaker syndrome very often belong to a minor genetic subtype of cancers with a very particular behavior that includes a very rapid evolution once carcinogenesis has started 16

17 Other particularities of cancers among caretaker carriers Acquired mutations differ from those acquired in common cancers Special tumour phenotype that includes not only rapid evolution but also 1. Pathological characteristics 2. Exquisite sensitivity to certain drugs and/or resistance to other drugs (that contrasts with the usual drug sensitivity of the cancers developed in the considered tissue) 17

18 Almost constant characteristic of caretaker mutation carriers At-risk people have a normal phenotype (most mutator cells disappear silently) You won t recognize them before they get cancer unless you got the chance to offer them predictive testing and show that they carry the responsible mutation IMPORTANT COROLLARY: You must have identified the mutation in the family 18

19 Last two facts to know about caretaker syndromes 1. Caretakers mutations are the most frequent cause of cancer predisposition (so that the caretaker exception is the rule) 2. Caretaker syndromes predispose to cancers that are frequent in the general population (breast cancers, colon cancers) {1,2} You will miss the diagnostic unless you systematically use the check-list derived from Knudson s hypothesis in front of any patient affected by a cancer 19

20 Definitions Genetic predisposition to cancer : relative notion : corresponds to an increase in an individual s inherited risk of developing cancer(s), or a given cancer, as compared to the mean risk in the general population; this increase can be expressed as a relative risk diagnostic genetic tests can be offered in the case of genetic predispositions to cancer if the risk of developing a tumor has been well established, and if the there is a defined strategy for managing the affected individuals; the aim is to reduce the morbidity and the mortality; early surveillance is the most common approach 20

21 Definitions Penetrance = the likelihood a given gene will result in disease High penetrance genes : rare mutations very high risk of disease independent of other risk factors Low penetrance genes frequent genetic variants interact with exogenous factors to cause the diseases 21

22 Hereditary cancer syndromes The ramification of having one of these (inherited cancer) diseases are significant for BOTH the patient and their family, with a high risk of developing a malignancy in many organs at an early age. Clinicians should be prepared to recognize and manage these diseases. This is not as simple as it sounds. C. Neal Ellis,

23 Risk notion? which risk? Role of the geneticist: clarify the risk Probability of inherited syndrome? Risk to have a pathogenic mutation?? Criteria to refer in genetic counselling? Criteria to perform genetic analysis? Screening of predisposed patients 23

24 Genetic Counseling in cancer Usually 2 (or 3) visits (standard genetic counseling < convention): ü Risk Assessment visit ü Genetic testing visit ü Result disclosure / follow-up 24

25 Risk assessment: Collecting and interpreting cancer histories Accurate and complete family history: systematic series of questions to gather relevant personal and family medical information. Definition and purpose of the pedigree Breast cancer Miscellaneous cancer Genitourinary cancer Gastrointestinal cancer 25

26 Collecting and interpreting cancer histories v Identify a cancer syndrome v Determine the need for genetic testing v Assist with management recommendation v Uncover other syndromes v Identify the disorder s inheritance pattern and other relatives at risk v Ethnic background v The pedigree is an important clinical record, it is crucial for pedigrees to reflect the most accurate information that is possible: ü Pathology report ü Physician note ü Genetic test result v Prior permission from the relative in question is needed 26

27 The signs you must be looking for (and note) when taking the anamnesis Autosomal dominant transmission means 1. Cancers in 2 generations / One branch of family 2. Risk transmission = ½ for men and for women 3. Beware of incomplete penetrance and/or sex-related expressivity Tumor risk is very often restricted to one or to a few tissues (spectrum > syndrome) People getting cancer in high risk families are often younger than people in sporadic cases often develop a 2 nd cancer within the same tissue or in another tissue 27

28 Ways to classify family history of cancer v Hereditary cancer syndrome ü Mostly dominant pattern ü 3 individuals with similar or related cancers ü 2 generations of cancer cases and ü 1 person diagnosed at an unusually young age v Familial Cluster of Cancer ü 2 or more relatives who have developed similar cancers but the family does not have any features suggestive of an hereditary cancer syndrome v Sporadic forms of cancer ü Most cases of cancer occur randomly without an obvious underlying risk factor. v Environmentally caused cluster of cancer 28

29 Determine the likelihood that the family could have a hereditary predisposition to cancer. HIGH risk: Strong evidence (Retinoblastoma) Pattern consistent with a specific hereditary cancer syndrome. MODERATE Risk: Some features suggestive of cancer syndrome but may not meet criteria for the syndrome. LOW Risk: Negative or noncontributory history of cancer: although there are several cases of cancer in the family, the cancer types are ones that frequently occur among older individuals 29

30 Guidelines for genetic testing ( Informed consent is mandatory Discuss about the possible test results, limitations, risk and benefits, logistics of testing, including any cost associated with the testing process. Discuss about how the results will be transmitted (follow-up visit, phone, etc), and the TAT. 30

31 Result disclosure Cancer genetic test results are mainly disclosed in a counseling visit. It can be disclosed by phone but the mode of result disclosure has to be announced in the pretest visit. Disclose the result early in the conversation (anxiety for the patient) Use direct and clear language. Allow patient time to react. Counseling about cancer. Katherine A. Schneider. 31

32 Diagnostic test, presymptomatic test & Predictive test v Diagnostic test confirms or exclude a genetic disorder in an individual who had malignancy and features of hereditary cancer syndrome. ü There is a good likelihood that the genetic test results will come negative. ü The cancer syndrome may be caused by alteration in more than one gene. v When a mutation is available in the family, presymptomaticor predictive testing has to be offered in at risk asymptomatic individuals. v Presymptomatictest determines if an asymptomatic individual carries a gene mutation that is associated with an absolute likelihood of cancer (or other syndromic features). APC gene for example. v Predictive test determines if an asymptomatic individual carries a gene mutation that is associated with an increased but not absolute risk of cancer or other syndromic features. BRCA for example. 32

33 5 steps procedure ü Importance of the pretest counseling: discuss about the potential risk and benefits of testing. ü Psychological assessment (before and after genetic testing). ü Genetic testing (2 blood samples, not the same day) ü Result disclosure. ü Follow-up. 33

34 Inherited breast cancer Inherited colon cancer Other inherited cancer predispositions Dr Anne De Leener Centre de Génétique Humaine

35 1. INHERITED BREAST CANCER Introduction Breast cancer : clinicopathological features hormone receptor level (ER and PgR) HER2 histological grade (1 to 3) proliferation index (e.g. Ki67) size ( 2cm, 2.1-5cm, >5cm) peritumoral vascular invasion axillary lymph node involvement Ann Oncol Aug;;20(8):

36 Introduction Breast cancer : multidisciplinary team surgeon / gynaecologist medical oncologist radiation oncologist radiologist pathologist geneticist 36

37 Breast cancer: risk factors Sex 1 M / 100 F Age the risk increases with age but 15-20% before the age of 50 Family history Personal history Environmental factors (geographic migration) Prolonged exposure to oestrogens: Early menarche Late menopause Late first pregnancy, few pregnancies Lack of breast-feeding Other breast lesions (in situ carcinoma, atypical hyperplasia, radial scar,...) Controversies: endocrine treatment for menopausal status, weight, alcohol, tobacco, 37

38 Introduction Breast cancer genetic risk Familial cases Hereditary syndrome 15% of healthy women have at least one 1 st degree relative with breast cancer à risk x 2 Breast cancer risk increases with the number of 1 st degree relatives with breast cancer 1: x 1.8 2: x 2.9 3: x 3.9 BRCA1 and BRCA2 germlinemutations are responsible for 20-40% of familial breast cancer cases, but < 5% of all breast cancers > 50% of the genetic predisposition to familial breast cancer remains unexplained 38

39 Risk of breast cancer predisposition Robson & Offit, NEJM

40 Familial history:? Genetic impact Foulkes WD, NEJM

41 Low- risk breast cancer susceptibility genes/alleles 20x BRCA1, BRCA2, TP53, PTEN, STK11 Multiple riskalleles Population frequency<0,1% Relative risk fold Disease Risk 10x 5x ATM, BRIP1, CHEK2, PALB2 Multiple risk alleles in each gene Population frequency <0,7% Relative risk 2 4 fold rs (FGFR2), rs (TNRC9), rs (MAP3K1), rs (LSP1), rs (8q), rs (2q), rs (CASP8) Population frequency 10-50% Relative risk 1,25-1,65 fold 0,1% 5% 50% Allele frequency 41

42 BRCA1 and BRCA2 Genes: Encode proteins that are mainly involved in DNA repair : Loss of function à genomic instability à tumor development BRCA1 : chr 17q21 BRCA1 BRCA2 Proteins BRCA2 : chr 13q13 81 kbp 22 exons 84 kbp 26 exons 42

43 BRCA1 and BRCA2 Exact pathophysiology remains unknown; tumor progression arises from different cellular subtypes : BRCA1 mainly triple negative (ER-, PgR-, HER2-) basal-like subtype BRCA2 mainly ER+ luminal subtype 43

44 BRCA1 and BRCA2 Thousands of different sequence variants have been identified : 1) mutations that are known or likely to be deleterious and diseaseassociated: class 5 or 4 2) variants of unknown function : class 3 = UV : unclassified variants 3) genetic variants that are likely to be neutral and without clinical importance: class 2 or 1 Help for interpretation of the variants: Ø Databases: dbsnp, UMD, Ø Look for conservation of the AA, functional site, etc Ø Align: Grantham variation/granthamdeviation: look for the impact of AA changes Ø Splice site prediction (Alamut, etc) EMQN Best Practice Guidelines

45 BRCA1 and BRCA2: High penetrance : high risk of disease if mutation is found But risk also depends on: Sex 1 M / 100 F Age the risk increases with age but 15-20% before the age of 50 Personal history Environmental factors (geographic migration) Prolonged exposure to estrogens: Early menarche Late menopause Late first pregnancy, few pregnancies Lack of breast-feeding Other breast lesions (in situ carcinoma, atypical hyperplasia, radial scar,...) Controversies: endocrine treatment for menopausal status, weight, alcohol, tobacco, 45

46 BRCA1 and BRCA2 High penetrance : BRCA1 : breast (women) : young age, 82% cumulative risk at age 80 years ovary : 54% cumulative risk at age 80 years colon prostate BRCA2 : breast (women) : cumulative risk same as BRCA1 ovary : lower cumulative risk than BRCA1 (23% at age 80 years) breast (men) : increased risk (10% of breast cancers in males have a BRCA2 mutation) pancreas colon prostate larynx BJMO (4), pp Am. J. Hum. Genet. 72: ,

47 Aims of the genetics consultation Provide answers to an individual who is looking for the origin of their personal and family history of cancer Establish whether tumor risk is higher or similar to the risk of the general population Recommend how patients should be taken care of 47

48 Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 aged 39 Br. T, 40 48

49 BRCA1 and BRCA2: who should be tested? BRCA1 and BRCA2 analyses: expensive in terms of manpower and material à define a sub-population in which the mutations are frequent à improvement of the cost / benefit ratio Criteria to take into account : family history (family tree up to 3 rd generation) age at onset triple negative breast cancer male case in the family Ashkenazi Jewish origin other types of cancer in the same patient or in the family 49

50 BRCA1 and BRCA2: How to interpret the results? Many mutations, different from one family to another A clearly deleterious mutation cannot be identified in all cases à 2-step process : Index case (usually a family member treated for cancer at a young age) then analyze the relatives, if appropriate (usually asymptomatic) If no mutation could be identified after the analysis of the index case, the test should be considered as non informative, because the presence of a deleterious mutation cannot be excluded, and no presymptomatic test can be offered to the relatives If a mutation is identified, a predisposition test can be offered to the relatives : if it is negative, it can be concluded that the relative has not inherited the familial predisposition factor Minors : no indication to test 50

51 BRCA1 and BRCA2 Software for risk assessment e.g. BOADICEA 51

52 Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 aged 39 Br. T, 40 52

53 Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 INDEX CASE aged 39 Br. T, 40 53

54 Hypothesis 1 Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 INDEX CASE: BRCA1 mt aged 39 Br. T, 40 54

55 Hypothesis 1-a Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 INDEX CASE: BRCA1 mt aged 39 BRCA1 mt Br. T, 40 55

56 Hypothesis 1-b Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 INDEX CASE: BRCA1 mt aged 39 BRCA1 wt Br. T, 40 56

57 Hypothesis 2 Br. T, 54 Br. T, 42 Br. T, 45 Br. T, 56? Br. T, 36 Br. T, 34 INDEX CASE: BRCA1 wt aged 39 Br. T, 40 57

58 BRCA1 and BRCA2 Software for risk assessment e.g. BOADICEA 58

59 In case of BRCA1 / BRCA2 mutation Breast cancer screening: From 20 y.o.: Physical examination every 6 months From 25 y.o. if BRCA1 (or 30 y.o. if BRCA2): Physical examination every 6 months MRI 1x/year Ultrasound (+/- mammogram at 35 40y) 1x/year 59

60 In case of BRCA1 / BRCA2 mutation Alternative to breast cancer screening Prophylactic mastectomy 60

61 In case of BRCA1 / BRCA2 mutation Ovarian cancer prevention No screening technique is effective Preventive removal of the ovaries never if childbearing wish not before 35 y.o. ideally at the latest at 40 y.o. if BRCA1 at 50 y.o. if BRCA2 indication validated by a multidisciplinary team consultation with the team s psychologist clinical and psychological follow-up 61

62 The benefics of prophylactic salpyngo-oophorectomy Kauff et al, NEJM

63 Treatment of breast cancer in case of BRCA1 or BRCA2 mutation Adjuvant treatment: Same as if no mutation Often younger age of onset and thus more chemotherapy Endocrine therapy if ER+ Herceptin if HER2+ Metastatic treatment: Same as if no mutation Sensitivity to platins The future: PARP inhibitors? 63

64 2. Other inherited cancer predisposition (breast cancer risk) TP53 Li-Fraumeni syndrome : prevalence : 1-9/100,000 due to TP53 germline mutation association : breast cancer Sarcoma: osteosarcoma, soft tissue sarcoma, Adrenocortical carcinoma leukemia brain tumor Others (lung, colon, genitourinary, skin, prostate etc) occurrence at a young age, multiple cancers Incomplete penetrance has been described Avoid radiation Accumulation of defective protein in the cell: Loss of transcriptional activity Eur J Hum Genet Jun;;17(6):

65 Li-Fraumeni syndrome: heterozygous TP53 mutation Brain T, 35 Sarcoma, 39 Br. T, 38 Br. T, 39 Sarcoma, 15 Br T, 41 Lung T, y.o. 21 y.o. Brain T, 6 Brain T, 9 65

66 66

67 Rare syndromes Peutz Jeghers syndrome : frequency : 1-9/100,000 heterozygous germline mutations of STK11 (tumor suppressor gene) association : gastro-intestinal polyps(hamartomas) IG (jéjunum proximal) > Colon > Rectum > Estomac abnormal pigmentation of the skin and mucosa increased risk of various cancers including breast cancer (ductal carcinoma) : 45% risk at age 70 years Gynecologic cancer Ovarian cancer Sex cord tumors with annular tubules (SCTAT) Eur J Hum Genet Jun;;17(6):

68 68

69 Rare syndromes Cowden syndrome frequency : 1-9/1,000,000 germline mutations of PTEN (tumor suppressor gene) association : Macrocephaly multiple hamartomas (skin, breast, thyroid, gastro-intestinal tract, endometrium, brain) increased risk of various cancers: including breast cancer : 30-50% at age 70 years Thyroid: carcinoma trichilemnoma Eur J Hum Genet Jun;;17(6):

70 70

71 71

72 Rare syndromes CDH1 mutations (tumor suppressor gene) : Epithelial cadherin Somatic alteration: loss of E-Cadherin expression association : diffuse gastric cancer lobular breast cancer (risk 60% at 80y), bilateral Fitzgerald, R. C., R. Hardwick, et al. (2010). "Hereditary diffuse gastric cancer: updated consensus guidelines for clinical management and directions for future research." J Med Genet 47(7): Eur J Hum Genet Jun;;17(6):

73 Rare syndromes Type 1 neurofibromatosis : von Recklinghausen disease frequency : 1-5/10,000 autosomal dominant transmission NF1 germline mutations (tumor suppressor gene) association : cafe au lait spots neurofibromas lentigines Lisch nodules (=hamartomas of the iris) bone problems increased risk of breast cancer standardized incidence ratio : 3.5 Eur J Hum Genet Jun;;17(6):

74 Conclusions I Breast cancer is frequent Genetic predisposition is only partially explained by BRCA1/2 mutations +/- 10% of breast cancers are due to a genetic predisposition < 5% are due to BRCA1 or BRCA2 germline mutations BRCA1 and BRCA2 mutations are rare in the general population (<1/800) But they have a high penetrance Multiple different mutations exist Only patients with a high probability of mutation should be tested Other, rare genetic anomalies exist Future breast cancer treatments will take into account constitutional and somatic GENETIC alterations 74

75 3. INHERITED COLON CANCER 10% Colon cancer 5% 1% 84% Sporadic Familial HNPCC FAP MAP Hereditary HNPCC Hereditary non polyposis colorectal cancer FAP Familial Adenomatosis Polyposis MAP MYH associated Adenomatosis Polyposis 75

76 76

77 2 types of CRC Tumor CIN+ (MSS) Aneuploidy Loss of alleles 18q, 17p, 5q 8p, 22q Frequent mutations in tumor suppressor genes p53 et APC Tumor MSI + (MSI-H) Diploid No allelic loss Rare mutations in tumor suppressor genes p53 et APC Alteration of the genes hmsh2, hmlh1, hmsh6, hmsh3 Frequent mutations of KRAS et PI3KCA Frequent mutations of BRAF et PI3KCA Mutations TGFß recepteur type II, BAX, TCF4, Caspase 5, HNF1a Localization left colon, slow progression Chromosomal instability Localization right colon, rapid progression Genetic Instability

78 International Colorectal Cancer Subtyping Consortium ICCSC Bionetwork Sage initiative (JustinGuinney Steven Friend) Association of different group to provide a common classification of colorectal cancer +TCGA COLON DATA + AGENDIA Unpublished 78

79 Proposedtaxonomy of colorectal cancer, reflecting significantbiological differences in the gene expression-based molecular subtypes Guinney et al Nat Med 2015, 21:

80 Terminology MMR = MisMatch Repair MMRD = Mismatch Repair Deficient hmlh1, hmsh2, hmsh6 & hpms2 = 4 main genes involved in the MMR process RER phenotype (Replication ERror) = mutator phenotype cause by MMRD MSI-H cancer (MicroSatellite Instability-High) = cancer with RER mutator phenotype = MMRD cancer MSS = MicroSatellite Stable = almost synonymous to CIN = Chromosomal INstability 80

81 The mismatch repair (MMR) system Replication errors cause mismatches on new DNA molecule MMR system identifies and repairs misincorporated bases Functions of MMR system: 1 ) Identify the mismatch 2 ) Identify the strand to be corrected 3 ) Remove the wrong sequence 4 ) Synthesize a correct complementary strand G T * G T T A T 81

82 1993 : discovery of cancers with MSI-H phenotype Normal state DNA-Pol is not error-free Errors are repaired by MMR system Replication errors are very rare. Mismatch-repair deficient cancers Loss of MMR function Replication error mutator phenotype Many mutations accumulate at each row of replication. Mutation x / Basal mutation rate 82

83 How to study MMR function in the tumors ü Look for microsatellite instability ü Immunohistochemistry of MMR proteins Simple Specificity = Molecular biology Sensitivity > Molecular biology Other advantage: tells you which molecule is absent 83

84 Microsatellites instability (MSI): 15% of CRC Tumoral Normal Selection of microsatellites : no variation in the population Lynch, N Engl J Med

85 Immunohistochemistry of MMR proteins in CRCs Tested protein: MLH1 MSH2 MSH6 PMS2 MSI-H CRCs (One or more than one protein absent) MSS CRCs (All the MMR proteins are present) Hampel, H. et al. N Engl J Med 2005;;352:

86 Number of mutations accumulated : MSS vs MSI-H CRC MSI-H CRC MSS CRC median number of nonsynonymous mutations per tumor with genome wide tools MSI-H tumors have by far the greatest numbers of mutations B Vogelstein et al. Science 2013;;339:

87 Genotype-phenotype relationship in sporadic colorectal cancers CIN CRCor CIN MSS ou CRC MSS Frequency 85% 15% Localization 70% after splenic angle 80% right-sided Polyp dwell time Adenoma CRC 10 years and rarely Pathology (not rules but correlations) Often well differentiated adenocarcinoma Prognostic reference better Risk factors common Tobacco, lack of First change on the Loss of APC function estrogens First way change to CRC on the Loss of APC function Epigenetic loss of MLH1 way Genetic to CRC FAP and MAP polyposes, function Genetic predisposition to this FAP type and X HNPCC MAP polyposes, Lynch syndrome predisposition disease to this type X HNPCC disease MSI-H CRC Adenoma CRC very rapid ( 1 year) Poor differentiated CRC with lymphoid infiltrate 87

88 MSS CRC: a slowly evolving somatic genetic disease years History of the evolution of MSS CRC Kinzler & Vogelstein 88

89 MSI-H CRC is a disease that evolves very differently from the MSS CRC 1 year 2,8 History of the evolution of MSI-H CRC (modified from Kinzler & Vogelstein) 89

90 Localization of sporadic CRC according to genetic pathway involved MSS polyps and CRC Sporadic MSI-H CRC 2/3 left-sided 8/10 right-sided 90

91 Sporadic MSI-H CRC: epigenetic MLH1 inactivation/methylation Hypermethylation of hmlh1 = the mechanism of MMR loss of function for sporadic MSI-H CRCs When considering a MLH1- negative CRC, 2 biological parameters are in favor of a sporadic disease 1. Hypermethylation of hmlh1 2. Presence of BRAF V600E acquired mutation 91

92 A. HNPCC Genes & LYNCH Syndrome 3% of CRC (2% of endometrial cancers) 9% if before 50 yo Genes: MSH2 (40%), MLH1 (30%), MSH6, (PMS2) MMR: mismatch repair genes Constitutional mutation in MMR gene Somatic mutation in a cell Somatic instability of repeated sequences Microsatellites instability Inactivation of the gene TGF type II, BAX, etc Phenotype MSI Cancer 92

93 LYNCH Syndrome 70-80% lifetime risk of CRC MLH1 MSH2: highest risk (44 yo) 11-19% risk of intestinal type gastric tumor (higher in at risk population: Japan) Woman: risk of endometrial cancer: 30-60% (46 62 y) Risk of ovarian cancer: 9-12% (42y), all types but not borderline tumor Skin lesions: sebaceous carcinomas (Torre-Muir syndrome), keratoacanthomas, epithliomas Other: Bowel, hepatobiliary, urinary tract (typically transitional carcinomas of the ureter and renal pelvis) Brain tumor (glioblastomas): turcot syndroma Pancreas? Relative risk > 8 Effect of tobacco

94 Cancer risks in Lynch syndrome, the AD predisposition to MMRD cancers Colon 80% Rest GI tract < 10% Endometrium 50% Ovaries 5-10% Urothelium 10% Lynch Syndrome-related tumours include colorectal, endometrial, stomach, ovarian, pancreas, ureter, renal pelvis, biliary tract and brain tumors, sebaceous gland adenomas and keratoacanthomas, and carcinoma of the small bowel. 94

95 LYNCH syndrome criteria's Old: Amsterdam I or II: bad sensibility and specificity. 40% of LYNCH families (mutation identified) do NOT present with the Amsterdam criteria's. Bethesda revised: Sensibility:? 62-81% Specificity : 95% for MSH2 and MLH1 Jerusalem criteria s (2010): Cancer before 70 yo 95

96 LYNCH Syndrome Importance of the family history Prediction program: PREMM, MMRpro, MMRpredict 96

97 MSI-H cancer treatment? Better prognosis No response to 5FU Lower interest of chemotherapy in stage II and III New treatments: immunotherapy 97

98 New diagnostic tools Panel 26 genes multiplicom : interest in mixed investivation (ovary) but no CNV analysis 98

99 B. POLYPOSIS About 95% of CRC arise from polyps «Polyp» Hyperplasic Lipoma Adenoma Lymphoma P juvenil Peutz-Jeghers Hamartomas Hamartomatous P

100 Colorectal polyposis «genetically determined» Adenomatous Polyposis Adenomatous polyposis Linked to APC Familial Adenomatous Polyposis (mutation APC) Classic and attenuated forms Adenomatous polyposis linked to MUTYH (bi allelic mut. MUTYH) MYH-Associated Polyposis (MAP) Adenomatous polyposis associated with axin (mutation axin 2) Adenomatous polyposis associated with POL (mutation POLE or POLD1) 100

101 Colorectal polyposis «genetically determined» Hamartomatous polyposis Polyposis of Peutz-Jeghers (mutation STK11/LKB1) Juvenile polyposis (mutation SMAD4 or BMPRA1) Cowden* (mutation PTEN) Ganglioneuromatosis* * Not associated with an increase of RR of CRC Hyperplasic polyposis (gene?) 101

102 Familial Adenomatous Polyposis : clear autosomal dominant transmission APC mutation p.glu412x Easy diagnostic in beginning of the seventies Standard care of family à No death. Responsible APC mutation discovered in 2011 Interest of testing: 1. Avoid colonoscopies 2. Avoid transmission 102

103 FAP and the APC gene Correlation genotype - phenotype AFAP Codons AFAP Codons Polyposeprofuse Codons AFAP Codons CHRPE Codons T. desmoïdes Codons

104 APC is a tumor suppressor gene (Comings hypothesis) APC loss of function is the first acquired genotypic change on the way to sporadic CRC: Loss of APC adenoma Loss of APC initiates MSS CRC carcinogenesis FAP-associated CRCs are slow-growing MSS tumors 104

105 Germline APC mutations and predisposition to CRC ü Incidence: 1/7000 to 1/14000 ü Genesis of adenomatous polyps shortened among people who carry a germline APC mutation ü Stochastic (=random) loss of the WT allele of APC in a colonic stem cell induces a selective advantage leading to the formation of an adenoma. ü Loss of the WT APC allele happens many times (10 7 crypts/colon) hundreds or thousands of polyps ü at different evolutionary stages ü evolutionary potential to cancer identical to sporadic MSS polyps 105

106 Hundreds or thousands of polyps at different evolutionary stages. Evolutionary potential to cancer identical to sporadic MSS polyps 106

107 Germline APC mutations and predisposition to other tumors APC loss-of-function mutations can participate to the development of other tumors that can also occur in FAP: 1. Malignant tumors: thyroid cancer (RR: 7,6), pancreas cancer (RR: 4,46), hepatoblastoma, medulloblastoma 2. Benign tumors: adenomatous polyps of the upper digestive tract, desmoid tumors, osteomas, epidermoid cysts, benign hypertrophy of retina pigment epithelium Skin lesions can occurs very early, before CRC 107

108 Asymptomatic congenital hypertrophy of the pigmented epithelium of the retina (inconstant but almost pathognomonic FAP lesion) Left eye Right eye Holmes, R. L. et. al. Ann Intern Med 2005;143:618-b-619-b 108

109 FAP with osteomas (Gardner syndrome) Bone deformation of the mandibular left angle Radiography osteoma 109

110 110

111 Adenomatous polyposis associated with MUTYH Prevalence 30% of «APC negatives» adenomatous polyposis with attenuated form (15< polyps <100) 10% of «APC negatives» adenomatous polyposis with classical form (polyps >100) Molecular genetic Bi allelic mutation of the MYH gene (MUTYH): recessive Gene involved in the Base Excision Repair system: accumulation of somatic mutations (transversions) Clinical characteristics? Mostly attenuated polyposis (<100), colon and duodenum. Dermatological lesions (sebaceous adenomas, other? 111

112 Conclusion II: Two main genetic varieties of colorectal cancers (CRC) Standard MSS CRC: microsatellite stable Carcinogenesis and clonal expansion starts with APC loss of function MSI-H CRC: a very different disease First phenotypic change on the way to carcinogenesis: loss of MMR caretaker function Slow evolution All MMR caretaker proteins expressed (à sepia color of nuclei in IHC) Respond to 5FU Very rapid evolution once clonal expansion has started 1 MMR protein lost in tumor cells nuclei (detected by IHC) Better prognosis No response to 5FU. ü Immunotherapy

113 Other inherited cancer predispositions Kidney: Von Hippel Lindau (80%) 1 st cause of hereditary renal and pheo. cancers 1/36000 Hemangioblastoma (of the retina) Other genes: MET, FLCN, FH Pancreas: STK11, SPINK1, PRSS1, CDKN2A, BRCA2, MMR, BRCA1, APC Melanoma: CDKN2A Endocrine syndrome: MEN1, MEN2 113

114 General conclusion: 114

115 General conclusion: Partners involved in the correct care Many doctors: - General Pract. - Gynecologist - Radiologist - Surgeon - Oncologist for high risk subjects Geneticists High-risk subjects must be Informed - Oncogeneticist - Molecular biologist THE FAMILY Prevention Normal life with low risk 115

116 Thank you for your attention! 116