Mutation and genomic amplification of the PIK3CA proto-oncogene in pituitary adenomas

Brazilian Journal of Medical and Biological Research

C.b. Murat²  P.b.s. Braga²  M.a.h.z. Fortes²  M.d. Bronstein¹  M.l.c. Corrêa-giannella²  R.r. Giorgi² 

[1] ,Universidade de São Paulo Faculdade de Medicina Laboratório de Endocrinologia Celular e Molecular (LIM-25)São Paulo SP ,Brasil

关键词: Pituitary adenomas;    PIK3CA proto-oncogene;    Genomic amplification;    Somatic mutation;   

DOI  :  10.1590/S0100-879X2012007500115

来源: SciELO

【 摘 要 】

The tumorigenesis of pituitary adenomas is poorly understood. Mutations of the PIK3CA proto-oncogene, which encodes the p110-α catalytic subunit of PI3K, have been reported in various types of human cancers regarding the role of the gene in cell proliferation and survival through activation of the PI3K/Akt signaling pathway. Only one Chinese study described somatic mutations and amplification of the PIK3CA gene in a large series of pituitary adenomas. The aim of the present study was to determine genetic alterations of PIK3CA in a second series that consisted of 33 pituitary adenomas of different subtypes diagnosed by immunohistochemistry: 6 adrenocorticotropic hormone-secreting microadenomas, 5 growth hormone-secreting macroadenomas, 7 prolactin-secreting macroadenomas, and 15 nonfunctioning macroadenomas. Direct sequencing of exons 9 and 20 assessed by qPCR was employed to investigate the presence of mutations and genomic amplification defined as a copy number ≥4. Previously identified PIK3CA mutations (exon 20) were detected in four cases (12.1%). Interestingly, the Chinese study reported mutations only in invasive tumors, while we found a PIK3CA mutation in one noninvasive corticotroph microadenoma. PIK3CA amplification was observed in 21.2% (7/33) of the cases. This study demonstrates the presence of somatic mutations and amplifications of the PIK3CA gene in a second series of pituitary adenomas, corroborating the previously described involvement of the PI3K/Akt signaling pathway in the tumorigenic process of this gland.

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