Array comparative genomic hybridisation analysis of gamma-irradiated human thyrocytes

Abstract

The susceptibility of thyroid epithelium to radiation-induced carcinogenesis is well recognised. In this context, thyroid carcinogenesis is associated with specific somatic ret/papillary thyroid carcinoma (PTC) rearrangements and morphologically with the papillary phenotype. Previous studies have demonstrated the possibility of inducing ret rearrangements in vitro using X-rays. The purpose of our study was to assess whether gamma (gamma) radiation using a Caesium 137 source can induce specific ret rearrangements in a human thyroid epithelial cell culture model. We further hypothesised that if radiation-induced thyroid carcinogenesis is associated with non-random rearrangement events, then DNA copy gain and loss induced by irradiation may also occur in a non-random manner. We irradiated SV40-immortalised human thyroid epithelial cells with incremental doses of gamma-radiation and, using TaqMan reverse-transcription polymerase chain reaction, looked for the presence of the common ret rearrangements. Cohorts showing evidence of ret/PTC chimeric transcripts were further analysed using microarray comparative genomic hybridisation (CGH) to detect copy gain and loss associated with radiation. Four Grays of gamma-radiation was sufficient to induce ret/PTC-3. In this model, transcripts of ret/PTC-1 were not detected, and we suggest that the type of radiation may influence the resulting rearrangement that occurs. Using array CGH, we have demonstrated a predominant pattern of subtelomeric deletions occurring in association with this radiation cohort and raise the possibility that chromosome 10 may be a hotspot for radiation-induced damage for as yet unknown reasons.

Array CGH demonstrates characteristic aberration signatures in human papillary thyroid carcinomas governed by RET/PTC

“…To our knowledge, this represents the first array CGH study on PTCs, which includes post-Chernobyl thyroid tumours. We report Finn et al, 2004;Richter et al, 2004). The similarity in the results from conventional and array CGH demonstrates the reliability of the array CGH approach we used.…”

A Radiation-Induced Gene Signature Distinguishes Post-Chernobyl from Sporadic Papillary Thyroid Cancers

“…A recently published CGH study concluded that, in particular, DNA gains in post-Chernobyl thyroid cancers appeared to be influenced by radiation exposure (28), which should have an impact at the transcription level. Another group demonstrated the possibility of inducing RET rearrangement in vitro using X rays (29). Using array CGH, they detected a predominant pattern of…”

Thyroidectomies from patients with history of therapeutic radiation during childhood and adolescence have a unique mutational profile

“…16 In that report, the authors described using array CGH in cultured g-irradiated human thyrocytes to examine the molecular events that occurred in the postradiation setting. The study describes extensive copy number changes at multiple loci at specific spots in the genome.…”

“…However, the molecular changes in this population are much less well studied. In an in vitro model of radiation-induced thyroid carcinogenesis, Finn et al 16 used array comparative genomic hybridization (CGH) to study copy number changes in the genome of cultured irradiated rat thyrocytes. They documented a variety of gains and losses across the genome in fairly consistent and specific sites.…”

“…To select the tumor suppressor gene loci, we utilized the reported array CGH data to include the loci with high deletion frequency. 16 …”