Amplification and overexpression of mutant RET in multiple endocrine neoplasia type 2-associated medullary thyroid carcinoma.
We have previously identified two second hit mechanisms involved in the development of multiple endocrine neoplasia type 2 (MEN 2)-associated tumors: trisomy 10 with duplication of the mutant RET allele and loss of the wild-type RET allele. However, some of the MEN 2-associated tumors investigated did not demonstrate either mechanism. Here, we studied the TT cell line derived from MEN 2-associated medullary thyroid carcinoma with a RET germline mutation in codon 634, for alternative mechanisms of tumorigenesis. Although we observed a 2:1 ratio between mutant and wild-type RET at the genomic DNA level in this cell line, fluorescence in situ hybridization analysis revealed neither trisomy 10 nor loss of the normal chromosome 10. Instead, a tandem duplication event was responsible for amplification of mutant RET. In further studies we could for the first time demonstrate that the genomic chromosome 10 abnormalities in this cell line cause an increased production of mutant RET mRNA. These findings provide evidence for a third second hit mechanism resulting in overrepresentation and overexpression of mutant RET in MEN 2-associated tumors.
Huang
Steve C
SC
Molecular Pathogenesis Unit, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
Torres-Cruz
Joshua
J
Pack
Svetlana D
SD
Koch
Christian A
CA
Vortmeyer
Alexander O
AO
Mannan
Poonam
P
Lubensky
Irina A
IA
Gagel
Robert F
RF
Zhuang
Zhengping
Z
D018276:Carcinoma, Medullary / Q000235:genetics*; D002869:Chromosome Aberrations; D002879:Chromosomes, Human, Pair 10 / Q000235:genetics; D005784:Gene Amplification; D015870:Gene Expression; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics*; D051096:Proto-Oncogene Proteins c-ret; D012333:RNA, Messenger / Q000096:biosynthesis; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D020080:Tandem Repeat Sequences; D013964:Thyroid Neoplasms / Q000235:genetics*; D014407:Tumor Cells, Cultured
D015513:Oncogene Proteins; D012333:RNA, Messenger; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D020794:Receptor Protein-Tyrosine Kinases