Abstract
BRAF V600E mutation, RET rearrangements, and RAS mutations are the common genetic alterations in differentiated thyroid carcinomas derived from follicular thyroid cells. However, the relationship between these alterations and iodine intake is still controversial. To clarify the influence of iodine intake on the occurrence of differentiated thyroid carcinomas, we performed molecular analyses for two differentiated carcinomas, papillary thyroid carcinomas (PTCs) and follicular thyroid carcinomas (FTCs), from an iodine‐rich country (Japan) and an iodine‐deficient country (Vietnam). We examined 120 PTCs (67 Japanese and 53 Vietnamese) and 74 FTCs (51 Japanese and 23 Vietnamese). We carried out allele‐specific polymerase chain reaction (AS‐PCR) for BRAF V600E, PCR and direct sequencing for RAS mutations (codon 12, 13, and 61 in NRAS,HRAS, and KRAS), and RT‐PCR for RET/PTC1 and RET/PTC3. BRAF V600E was present in 55/67 (82.1%) Japanese PTCs and 44/53 (83%) Vietnamese PTCs. RET/PTC1 was identified in only one PTC from each country, and no samples had RET/PTC3. NRAS mutation was found in 17/51 (33.3%) Japanese FTCs and 4/23 (17.4%) Vietnamese FTCs. NRAS mutation was cited in codon 61 (20 cases) and codon 12 (one case). None of FTCs had KRAS or HRAS mutations. There were no significant differences in the prevalence of BRAF V600E,RET/PTC, or RAS mutations between the two countries. Our study showed no differences in genetic alterations of thyroid cancers from iodine‐rich and iodine‐deficient countries, possibly suggesting that iodine intake might not affect the genetic alterations of differentiated thyroid cancer.
Highlights
Iodine intake is considered a risk factor for thyroid carcinogenesis, especially in iodine-deficient countries [1, 2]
Allele-specific PCR clearly demonstrated the band (126 bp) of BRAF V600E mutation in papillary thyroid carcinomas (PTCs) samples that were microdissected from formalin-fixed paraffin- embedded (FFPE) sections
According to World Health Organization (WHO) data, Vietnam is an iodine-deficient country with endemic goiter in up to 45% of the population in some regions [36]
Summary
Iodine intake is considered a risk factor for thyroid carcinogenesis, especially in iodine-deficient countries [1, 2]. After the release of these national surveys, the Vietnamese government downgraded the NIDDC program from a national target to a routine program. This led to a critical decline, by 2009, of the national median urinary iodine concentration (UIC) to less than 83 μg/L, which was the lowest level of the last 10 years and below the optimal range of 100–199 μg/L recommended by the World Health Organization (WHO) [5]. The mean or median UIC of Japanese residents ranges from 281 to 3300 μg/L in many regions of Japan [8,9,10,11,12,13,14]
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