Exome sequencing reveals mutant genes with low penetrance involved in MEN2A-associated tumorigenesis

Abstract

Activating rearranged during transfection (RET) mutations function as the initiating causative mutation for multiple endocrine neoplasia type 2A (MEN2A). However, no conclusive findings regarding the non-RET genetic events have been reported. This is the first study, to our knowledge, examining genomic alterations in matched MEN2A-associated tumors. We performed exome sequencing and SNP array analysis of matched MEN2A tumors and germline DNA. Somatic alterations were validated in an independent set of patients using Sanger sequencing. Genes of functional interest were further evaluated. The germline RET mutation was found in all MEN2A-component tumors. Thirty-two somatic mutations were identified in the nine MEN2A-associated tumors, of which 28 (87.5%) were point mutations and 4 (12.5%) were small insertions, duplications, or deletions. We sequenced all the mutations as well as coding sequence regions of the 12 genes in an independent sample set including 35 medullary thyroid cancers (20 MEN2A) and 34 PCCs (22 MEN2A), but found no recurrent mutations. Recurrent alterations were found in 13 genes with either mutations or alterations in copy number, including an EIF4G1 mutation (p. E1147V). Mutation of EIF4G1 led to increased cell proliferation and RET/MAPK phosphorylation, while knockdown of EIF4G1 led to reduced cell proliferation and RET/MAPK phosphorylation in TT, MZ-CRC1, and PC-12 cells. We found fewer somatic mutations in endocrine tumors compared with non-endocrine tumors. RET was the primary driver in MEN2A-associated tumors. However, low-frequency alterations such as EIF4G1 might participate in MEN2A-associated tumorigenesis, possibly by regulating the activity of the RET pathway.

Exome Sequencing: Current and Future Perspectives

“…Examples of diseases for which exome sequencing has been used to detect a causative variant include Leber congenital amaurosis ( Wang et al 2011 ), Alzheimer disease ( Sassi et al 2014 ), maturity-onset diabetes of the young ( Johansson et al 2012 ), high myopia ( Shi et al 2011 ), autosomal recessive polycystic kidney disease ( Xu et al 2014 ), amyotrophic lateral sclerosis ( Johnson et al 2010 ), immunodeficiency leading to infection with human herpes virus 8 causing Kaposi Sarcoma ( Byun et al 2010 ), acromelic frontonasal dystois ( Smith et al 2014 ), and a number of cancer predisposition mutations ( e.g. , Yan et al 2011 ; Greif et al 2012 ; Snape et al 2012 ; Kiiski et al 2014 ; Cai et al 2015 ).…”

GEP- NETS UPDATE: Genetics of neuroendocrine tumors

“…MTC from MEN2 patients rarely show any other somatic driver mutations (103). Investigating the genomic landscape of sporadic MTCs revealed mutually exclusive oncogenic mutations in RET and RAS subtypes K and H in 75 and 15% respectively (104,105,106).…”

Neuroendocrine tumors: current therapies, notch signaling, and cancer stem cells

“…[148] Exome sequencing of MTCs associated with MEN2A also identified the expected RET mutations, but also suggested that low frequency mutations such as those found in EIF4G1 may also play a role in MEN2Aassociated tumorigenesis by indirectly altering the RET pathway. [158] A similar study was undertaken by Smith et al [159] in MTCs lacking an identifiable RET mutation. Interestingly, this group found a recurrent mutation in the ESR2 gene which encodes the estrogen receptor beta (ER).…”