Inside the Pediatric Cancer Genetics Clinic

Transcription

1 Inside the Pediatric Cancer Genetics Clinic August 23, 2014 Joyce Turner, MS, CGC Children s National Medical Center Washington, DC Pediatric Cancer Genetic Syndromes Aims over next minutes: 1) Case examples 2) Review some newly recognized pediatric cancer genetic syndromes 3) Update on known pediatric cancer genetic syndromes August 23,

2 Test Result Case 1 PMS2 mutations: 1) c.137 G>T (missense) 2) c G>T (novel splice site) -> cis vs. trans?? Process of testing parents Tumor Type and Average Age of Onset Biallelic MLH1/MSH2 vs. MSH6/PMS2 Mutations 2

3 Risk of Recurrence 25% risk CMMRD 50% risk of Lynch syndrome 25% unaffected sib Parents obligate carriers- Lynch syndrome When to Consider CMMRD Café au lait spots and other signs of NF1 Consanguinity Family history of Lynch syndrome cancers Multiple cancers in same individual Siblings with childhood cancers Family may not meet Bethesda guidelines for LS MAY NOT HAVE A SIGNIFICANT FAMILY HISTORY OF CANCER, ESPECIALLY WHEN A PMS2 MUTATION IS PRESENT CMMRD Testing MSI testing may be unreliable in CMMRD brain tumors No validated MSI testing for brain tumors IHC maybe normal if missense mutation present Panel testing maybe best option 3

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5 Case 2 Results Germline mutation c.5465a>g missense mutation Changes an Aspartic acid to Glycine p.asp1822gly DICER1 Syndrome Tumors and Average Age of Occurrence 0-5 years Children & Teens Teens & Young Adults Any Age Pleuropulmonary Blastoma Sertoli-Leydig Sertoli-Leydig Thyroid Nodular Hyperplasia Cystic Nephroma Renal Carcinoma Gynandroblastoma Thyroid Cancer Wilms Tumor Ocular Medulloepithelioma Renal Carcinoma Pineoblastoma Rhabdomyosarcoma Rhabdomyosarcoma Lung Cysts Chondromesechymal hamartoma, Nasal Ocular Medulloepithelioma Pituitary blastoma Chondromesechymal hamartoma, Nasal Chondromesechymal hamartoma, Nasal Screening No official screening guidelines Baseline CT scan in mutation carriers at any age Annual targeted review of systems 5

6 Molecular Features of DICER1 Syndrome Autosomal dominant condition Variable expressivity Decreased penetrance 80% inherited; 20% de novo Germline mutations LOF mutations, occur throughout gene Somatic missense mutations in the hotspot IIIB domain impair function Mutations in DICER1 lead to abnormal processing of mature mirnas and disregulation of gene expression DICER1 Processing August 23, 2014 mirnas mirna incorporated into RNA-inducedsilencing-complex (RISC) RISC targets mrna, which acts by inhibiting mrna translation or targeting their degradation DICER1 is a regulator of genes active during development 6

7 References Wimmer and Kratz. Constitutional mismatch repair deficiency syndrome. Hill D. et. al. DICER1 mutations in familial pleuropulmonary blastoma. Science Aug 21; 325(5943). Haematologica. 2010; 95(5) Durno C. et. al. Oncological surveillance for subjects with biallelic mismatch repair genes mutations: 10 year follow-up of a kindred. Pediatric Blood and Cancer. 2012; 59( ). Brewer Z. et al. Predictive genetic testing in children: Constitutional mismatch repair deficiency cancer predisposition syndrome. Journal of Genetic Counseling. 2014;23( ). Hill D et. al. DICER1 mutations in familial pleuropulmonary blastoma. Science Aug 21;325(5843):965. Anglesio M. et. al. Cancer-associated somatic DICER1 hotspot mutations cause defective mirna processing and reverse-strand expression bias to predominantly mature 3p strands through loss of 5p strand cleavage. Journal of Pathology. 2013; 229( ). Schultz K. et. al. Judicious DICER1 testing and surveillance imaging facilitates imaging early diagnosis and cure of pleuropulmonary blastoma. Pediatric Blood Cancer May 13; epub ahead of print. Schultz K. et al. DICER1-Pleuropulmonary Blastoma Familial Predisposition Syndrome: A Unique Constellation of Neoplastic Conditions. Pathology Case Review. 2014;19(2): Doros L. et. al. DICER1 mutations in childhood cystic nephroma and its relationship to DICER1-renal sarcoma. Modern Pathology. 2014; Torrezan G. et. al. Recurrent somatic mutation in DROSHA induces microrna profile changes in Wilms Tumors. Nature Communications (June 2014). 7