A germline mutation (A339V) in thyroid transcription factor-1 (TITF-1/NKX2.1) in patients with multinodular goiter and papillary thyroid carcinoma.
BACKGROUND
The genetic factors that determine the risk of papillary thyroid carcinoma (PTC) among patients with multinodular goiter (MNG) remain undefined. Because thyroid transcription factor-1 (TTF-1) is important to thyroid development, we evaluated whether the gene that encodes it, TITF-1/NKX2.1, is a genetic determinant of MNG/PTC predisposition.


METHODS
Twenty unrelated PTC patients with a history of MNG (MNG/PTC), 284 PTC patients without a history of MNG (PTC), and 349 healthy control subjects were screened for germline mutation(s) in TITF-1/NKX2.1 by sequencing of amplified DNA from blood. The effects of the mutation on the growth and differentiation of thyroid cells were demonstrated by ectopic expression of wild-type (WT) and mutant proteins in PCCL3 normal rat thyroid cells, followed by tests of cell proliferation, activation of cell growth pathways, and transcription of TTF-1 target genes. All statistical tests were two-sided.


RESULTS
A missense mutation (1016C>T) was identified in TITF-1/NKX2.1 that led to a mutant TTF-1 protein (A339V) in four of the 20 MNG/PTC patients (20%). These patients developed substantially more advanced tumors than MNG/PTC or PTC patients without the mutation (P = .022, Fisher exact test). Notably, this germline mutation was dominantly inherited in two families, with some members bearing the mutation affected with MNG, associated with either PTC or colon cancer. The mutation encoding the A339V substitution was not found among the 349 healthy control subjects nor among the 284 PTC patients who had no history of MNG. Overexpression of A339V TTF-1 in PCCL3 cells, as compared with overexpression of WT TTF-1, was associated with increased cell proliferation including thyrotropin-independent growth (average A339V proliferation rate = 134.27%, WT rate = 104.43%, difference = 34.3%, 95% confidence interval = 12.0% to 47.7%, P = .010), enhanced STAT3 activation, and impaired transcription of the thyroid-specific genes Tg, TSH-R, and Pax-8.


CONCLUSIONS
This is the first germline mutation identified in MNG/PTC patients. It could contribute to predisposition for MNG and/or PTC and to the pathogenesis of PTC.
Ngan
Elly S W
ES
Department of Surgery, University of Hong Kong, Pokfulam, Faculty of Medicine Building, 21 Sassoon Rd, Hong Kong, SAR, China. engan@hku.hk
Lang
Brian H H
BH
Liu
Tingting
T
Shum
Cathy K Y
CK
So
Man-Ting
MT
Lau
Danny K C
DK
Leon
Thomas Y Y
TY
Cherny
Stacey S
SS
Tsai
Sophia Y
SY
Lo
Chung-Yau
CY
Khoo
Ui-Soon
US
Tam
Paul K H
PK
Garcia-Barceló
Maria-Mercè
MM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000409:Alanine; D000818:Animals; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D002648:Child; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018095:Germ-Line Mutation; D006044:Goiter, Nodular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D008156:Luciferases; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D015854:Up-Regulation; D014633:Valine; D055815:Young Adult
C000614412:NKX2-1 protein, human; C000614416:Nkx2-1 protein, rat; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D008156:Luciferases; D014633:Valine; D000409:Alanine