BRCA1 and BRCA2 germline muta-ons in Moroccan breast/ovarian cancer families

Transcription

1 BRCA1 and BRCA2 germline muta-ons in Moroccan breast/ovarian cancer families A Tazzite a, H Jouhadi b, A Benider b, K Hamzi a and S Nadifi a a Genetics and Molecular Pathology Laboratory, Medical School of Casablanca, Casablanca, Morocco b Department of Oncology, Ibn Rochd University Hospital, Casablanca, Morocco

2 CEDoc Faculté de médecine Casablanca Ecoles Doctorales Sciences de la Santé PhD Subject : Gene$cs of breast cancer in Moroccan pa.ents Amal Tazzite H Jouhadi, S Nadifi

3 Introduc.on ü The most breast cancer cases are sporadic ü about 5 to 10% are due to hereditary predisposi-on ü Gene-c linkage studies and posi-onal cloning have iden-fied two major BRCA1 and BRCA2 genes associated to hereditary breast cancer suscep-bility ü In Morocco, breast cancer seems to be the most common type of cancer among women ü incidence of 35 and 35.8 per 100,000 women (Casablanca and Rabat respectively). ü The relevance of BRCA1/2 mutations in the Moroccan population: not studied.

4 Objec.ve to inves-gate the spectrum of BRCA1 and BRCA2 germline muta-ons in early onset and familial breast/ovarian cancer among Moroccan pa-ents.

5 Pa-ents : Pa.ents and Methods 39 Moroccan breast cancer women treated in oncology center of Ibn Rochd University Hospital of Casablanca ( ). Inclusion criteria: a. 3 1 st or 2 nd degree rela-ves with breast cancer diagnosed at any age in the same familial branch (n=17) b. 2 1 st degree rela-ves with breast cancer, with at least one early onset breast cancer case ( 40 years) or male breast cancer case or ovarian cancer case (n=16)

6 Pa.ents and Methods Pa.ents : Inclusion criteria: c. Single cases were selected from pa-ents diagnosed with breast cancer before age 40 or with breast and ovarian cancer (n=6). WriZen informed consent was obtained and blood samples (2x5ml) were taken from at least one affected woman of each family.

7 Pa.ents and Methods Molecular analysis DNA was extracted using the sal-ng out method. All exons and exon intron boundaries of BRCA1 and BRCA2 genes were amplified Purified PCR products were sequenced using BigDye Terminator v3.1 cycle sequencing kit (Applied Biosystems) on a ABIPRISM 3130 XL Gene-c analyzer (Applied Biosystems). Sequence analyses were performed using SeqScape v2.6 (Applied Biosystems). All muta-ons and variants : Human Genome Varia-on Sequence systema-c nomenclature using GenBank entries: U14680 for BRCA1 / U43746 for BRCA2. The Breast Cancer Informa-on Core (BIC) nomenclature.

8 Pa.ents and Methods In silico predic.on To iden-fy non- synonymous amino acid changes likely to disrupt BRCA1/2 genes func-on we used three compara-ve evolu-onary bioinforma-c programs: ü Sor+ng Intolerant From Tolerant (SIFT) ü Polymorphism Phenotyping v2 ü and Align GVGD.

9 Results and Discussion Results A total of nine BRCA1 and BRCA2 muta-ons were found in ten unrelated families with a frequency of 25.64% (10/39). Four novel muta.ons which have not been reported before in the BIC database were found: q BRCA1 (c.2805dela/2924dela) q BRCA2(c.3381delT/3609delT;c.7110delA/7338delA,c.7235insG/7463insG )

10 Results Results and Discussion

11 Results and Discussion The majority of mutated patients in our series are familial cases selected according to two criteria: In the group a 29.4% (5/17) carried BRCA1/2 mutations In the group b 25% (4/16) carried BRCA1/2 mutations Concerning single cases, one out of 6 was found mutated with a frequency of 16.6% (1/6). family history and early onset of breast cancer are two important selection criteria for the identification of patients carrying BRCA1/2 mutations.

12 Results and Discussion ü The deleterious mutation c.798_799deltt (917delTT) was reported in : four Algerian families three unrelated Tunisian families (North African founder mutation). ü The c.181t>g (300T>G) mutation has been previously reported as founder mutation in Central European populations and also observed in an Algerian study. ü The presence of this mutation in Morocco and Algeria too suggests the possibility that this mutation represents a mutational hotspot.

13 Results and Discussion Results ü The c delGTT (p.v1688delgtt) is a common mutation among Italian families reported in BIC database as variant of uncertain significance. ü a recent multimodal analysis confirms the pathogenicity of this mutation, altering the protein stability and function.

14 Results and Discussion All BRCA2 mutations were novel! except one rare pathogenic splice site mutation IVS6-1G>A which has been cited one time in BIC database in Western Europe the novel BRCA2 frameshift mutation c.7235insg (7463insG) was detected in two unrelated families. Therefore, this alteration could be a recurrent mutation in our population but the number of patients enrolled in the study is too small to confirm this conclusion.

15 Results Results and Discussion

16 Results and Discussion All BRCA2 mutations were novel! except one rare pathogenic splice site mutation IVS6-1G>A which has been cited one time in BIC database in Western Europe the novel BRCA2 frameshift mutation c.7235insg (7463insG) was detected in two unrelated families Therefore, this alteration could be a recurrent mutation in our population but the number of patients enrolled in the study is too small to confirm this conclusion.

17 Results Results and Discussion

18 Results and Discussion We iden-fied fi?y one variants (22 BRCA1 and 29 BRCA2) including dis-nct polymorphisms and unclassified sequence variants. Three novel non trunca-ng variants have been detected in the coding and intronic sequences of : q BRCA1 (IVS9-67G>T) q BRCA2 (IVS19-143G>A, R2488G)

19 Results and Discussion

20 Results and Discussion

21 Conclusion BRCA1 and BRCA2 are responsible for a significant propor-on of familial breast cancer in Moroccan pa-ents. Furthermore, the muta-on detec-on rate seems to be influenced by the presence of breast cancer history and the early age at diagnosis It is important to note that nearly 50% of the muta-ons found are unique to this country.

22 Conclusion ü 100 samples of Breast cancer ü Recurent mutations ü Studying polymorphisms and variants in Healthy Moroccan population

23 Acknowledgments ü We thank the patients and their families for their participation. ü Grant from the Istituto Toscano Tumori ü to Professor Generoso Bevilacqua and staff of Divisione di Anatomia Patologica e Diagnostica Molecolare ed Ultrastrutturale for their support and hospitality. ü the clinicians and all the staff of Oncology department for their assistance in data and sample collection.