Genetic Basis of Pituitary Adenoma Predisposition

_____________________________________________________________________________________8 REVIEW OF THE LITERATURE___________________________________________________________________10 1. The human genome and tumorigenesis ________________________________________________________10 1.1 Oncogene activation ______________________________________________________________________11 1.2 Loss of tumor suppression_________________________________________________________________11 1.3 Loss of genomic stability __________________________________________________________________12 1.4 Genetic predisposition to tumor development ________________________________________________13 1.5 Identification of tumor predisposing genes___________________________________________________16 2. The pituitary gland __________________________________________________________________________17 2.1 Morphology and histology ________________________________________________________________18 2.1.1 Posterior lobe________________________________________________________________________18 2.1.2 Anterior lobe ________________________________________________________________________18 2.1.3 Regulation of hormone secretion _______________________________________________________20 2.1.3.1 Positive regulation _______________________________________________________________20 2.1.3.2 Negative regulation ______________________________________________________________20 2.2 Benign tumors of the anterior pituitary lobe and pathological features ___________________________21 2.2.1 Incidence and prevalence______________________________________________________________21 2.2.2 Tumor characteristics and classification _________________________________________________21 2.2.3 Clinical features______________________________________________________________________22 2.2.3.1 Prolactinomas ___________________________________________________________________22 2.2.3.2 Somatotropinomas _______________________________________________________________22 2.2.3.3 Adrenocorticotropinomas _________________________________________________________24 2.2.3.4 Thyrotropinomas and gonadotropinomas ___________________________________________25 2.2.3.5 Clinically non-functioning pituitary adenomas (NFPA)________________________________25 2.3 Pediatric pituitary adenomas_______________________________________________________________25 2.4 Carcinomas of the anterior pituitary lobe ____________________________________________________26 3. Genetic features of pituitary tumorigenesis _______________________________________________________26 3.1 Sporadic pituitary adenomas_______________________________________________________________27 3.1.1 GNAS / gsp oncogene _________________________________________________________________27 3.1.2 Other features of sporadic pituitary tumorigenesis ________________________________________27 3.2 Pituitary adenomas in familial endocrine-related tumor syndromes _____________________________29 3.2.1 Multiple Endocrine Neoplasias_________________________________________________________29 3.2.1.1 Multiple Endocrine Neoplasia type I (MEN1) ________________________________________29 3.2.1.2 MEN1-like (MEN4)_______________________________________________________________31 3.2.2 Carney Complex (CNC)_______________________________________________________________33 3.2.3 Isolated Familial Somatotropinomas (IFS)________________________________________________34 3.2.4 Familial Isolated Pituitary Adenomas (FIPA)_____________________________________________35 AIMS OF THE STUDY ___________________________________________________________________________36 SUBJECTS AND METHODS______________________________________________________________________37 1. Subjects____________________________________________________________________________________37 1.1 Familial cases (I) _________________________________________________________________________37 1.2 Other pituitary adenoma patient cohorts (I, II, IV)_____________________________________________37 1.3 Other tumor samples (III) _________________________________________________________________38 1.4 Healthy controls (I, II, III, IV) ______________________________________________________________38 2. DNA/RNA extraction (I, II, III, IV) ____________________________________________________________39 3. Disease locus identification (I) ________________________________________________________________39 Genetic Basis of Pituitary Adenoma Predisposition 5 3.1 SNP arrays ______________________________________________________________________________39 3.2 Linkage analysis _________________________________________________________________________39 3.3 Fine mapping and haplotype analysis _______________________________________________________39 3.4 Gene expression profiling _________________________________________________________________40 3.4.1 Gene expression microarrays __________________________________________________________40 3.4.2 Data analysis ________________________________________________________________________40 4. Genetic analysis (I, II, III, IV) _________________________________________________________________41 4.1 Mutation screening by direct sequencing__________________________________________________41 4.2 Loss of heterozygosity (LOH) study ______________________________________________________41 5. Immunohistochemistry (IHC) (I, II, IV) ________________________________________________________42 6. In silico analysis (II, III, IV) __________________________________________________________________42 7. Ethical issues _______________________________________________________________________________42 RESULTS _______________________________________________________________________________________43 1. Pituitary Adenoma Predisposition (PAP) gene identification (I) ___________________________________43 1.1 PAP locus maps on chromosome 11q13______________________________________________________43 1.2 Candidate locus fine-mapping reveals a founder haplotype of ~7 Mb ____________________________45 1.3 Gene expression profiling reveals AIP as the prime candidate gene for PAP ______________________45 1.4 Candidate gene mutation analysis establishes AIP as the predisposing gene ______________________46 2. Molecular diagnosis of PAP (II) _______________________________________________________________47 2.1 The contribution of AIP in heterogeneous pituitary adenoma patient cohorts of different ethnic origins ___________________________________________________________________________________________47 2.2 Clues into the phenotypic presentation of PAP patients ________________________________________48 2.3 Immunohistochemical detection of AIP protein_______________________________________________48 3. The role of AIP in tumorigenesis of common cancers (III) ________________________________________49 4. The role of AIP in pediatric pituitary tumorigenesis (IV) _________________________________________49 DISCUSSION ___________________________________________________________________________________51 1. AIP is a novel, low penetrance tumor susceptibility gene that causes Pituitary Adenoma Predisposition (PAP) (I)______________________________________________________________________________________51 1.1 Insights into the hereditary predisposition to pituitary adenoma development (I)__________________51 2. Molecular diagnosis of PAP __________________________________________________________________54 2.1 Germline AIP mutations in pituitary adenoma patients of various ethnic origins and clinical settings (II) ___________________________________________________________________________________________54 2.2 The PAP phenotype ______________________________________________________________________55 2.3 The potential of AIP immunohistochemistry as a diagnostic tool (II) _____________________________56 2.4 Overview of the molecular genetics of AIP ___________________________________________________56 3. AIP does not appear to contribute to tumorigenesis of common cancers (III)________________________59 4. Pediatric GH-secreting tumors may arise due to AIP mutations (IV) _______________________________60 5. Implications for genetic counseling and follow-up in PAP _______________________________________61 6. The AIP protein and its cellular functions ______________________________________________________63 6.1 Features of the AIP protein ________________________________________________________________63 6.2 Possible implications of AIP/AHR pathway in AIP-mediated tumorigenesis ______________________65 6.3 Other AIP interaction partners and possible implications in AIP-mediated tumorigenesis___________66 CONCLUSIONS AND FUTURE PROSPECTS_______________________________________________________69 ACKNOWLEDGEMENTS ________________________________________________________________________71 REFERENCES ___________________________________________________________________________________72 APPENDIX______________________________________________________________________________________93 Genetic Basis of Pituitary Adenoma Predisposition 6 LIST OF ORIGINAL PUBLICATIONS This thesis is based on four original articles as listed below. They will be referred to in the text by the Roman numerals I-IV. I O. Vierimaa*, M. Georgitsi*, R. Lehtonen, P. Vahteristo, A. Kokko, A. Raitila, K. Tuppurainen, T.M. L. Ebeling, P. Salmela, R. Paschke, S. Gündogdu, E. De Menis, M.J. Mäkinen, V. Launonen, A. Karhu, L.A. Aaltonen (2006) Pituitary Adenoma Predisposition caused by germline mutations in the AIP gene. Science 312(5777):12281230. II M. Georgitsi*, A. Raitila*, A. Karhu, K. Tuppurainen, M.J. Mäkinen, O. Vierimaa, R. Paschke, W. Saeger, R.B. van der Luijt, T. Sane, M. Robledo, E. De Menis, R.J. Weil, A. Wasik, G. Zielinski, O. Lucewicz, J. Lubinski, V. Launonen, P. Vahteristo, L.A. Aaltonen (2007) Molecular diagnosis of pituitary adenoma predisposition, caused by aryl hydrocarbon receptor