RERF Report No. 4-14

Paper published in Oncology Reports§“A Novel RET Rearrangement (ACBD5/RET) by Pericentric Inversion, inv(10)(p12.1;q11.2), in Papillary Thyroid Cancer from an Atomic-bomb Survivor Exposed toHigh-dose Radiation”
Kiyohiro Hamatani, Hidetaka Eguchi, Kazuaki Koyama, Mayumi Mukai, Kei Nakachi, andYoichiro Kusunoki
Oncol Rep 2014 (August); 32:1809–14(doi: 10.3892/or. 2014.3449)
Study Findings
Our analysis has shown that a novel type of RET rearrangement (ACBD5-RET fusiongene) that was identified in papillary thyroid cancer (PTC) cells of an atomic bomb survivor
constitutively activates the MAPK-signaling pathway* and can lead to the development oftumors, as is the case with other types of RET fusion genes.
*The term “signaling pathways” denotes the mechanism by which protein kinases
phosphorylate (in other words, activate) other protein kinases and cascade signals
downstream. The MAPK-signaling pathway is one such pathway.
Explanation
Through chromosomal inversion or translocation, radiation-related PTC cases such asadult PTC among A-bomb survivors and childhood PTC that developed after the Chernobyl
nuclear accident often exhibit rearranged RET genes, that is fusion genes such as
CCDC6-RET and NCOA4-RET, between the tyrosine kinase domain of the RET gene andother gene sites. These fusion genes are believed to be significantly involved in papillary
thyroid carcinogenesis.
We analyzed the structure and function of a novel RET rearrangement (ACBD5-RETfusion gene) found in the PTC of an A-bomb survivor exposed to high-dose radiation.
Figure (Inversion)
p15
p14
ACBDS gene 5’ p13
ACBD5遺伝子p12
3’ p11
3’5’
ACBDS-RET融合遺伝子
fusion gene
ACBD5-RET3’

RET gene 5’ q11
RET遺伝子q21
チロシンキナーゼ領域
Tyrosinekinase domain q22Centromere
動原体

q23
q24
q25
q26
10 番染色体
Chromosome
10This figure shows the ACBD5-RET fusion gene formed by a pericentric inversion.
Inversions occur when a chromosome breaks in two places and the resulting
fragment of DNA is inverted and re-inserted into the chromosome. Inversions thatinvolve the centromere (the constricted region of the chromosome) are called
pericentric inversions.
1.

Objectives1

RERF Report No. 4-14
To elucidate, through in vitro and in vivo experiments, whether the ACBD5-RET fusion
gene found in the PTC of the A-bomb survivor activates the MAPK-signaling pathway andinduces tumor formation.
2. Methods(1) Expression vectors, i.e., plasmid DNA with a promoter sequence needed for gene
expression, containing cDNA (DNA synthesized from an RNA template by reverse
transcriptase and complementary to mRNA) of the ACBD5-RET fusion gene wereintroduced into mouse NIH3T3 cells (immortalized fibroblasts established from mouseskin cells). This process was undertaken to determine, using Western-blotting*, whether
phosphorylation (or, activation) of protein kinase in the MAPK-signaling pathway isenhanced.
*Western-blotting is an analytical technique for detecting specific proteins. It uses
gel electrophoresis to separate protein samples, transfers and fixes them to amembrane (filter paper for blotting), and identifies specific proteins based on
antigen-antibody reactions.
(2) We introduced the cDNA of the ACBD5-RET fusion gene into NIH3T3 cells, injected theresultant NIH3T3 cells subcutaneously into nude mice, and examined tumor formation toevaluate the tumorigenicity of the ACBD5-RET fusion gene.
3. Results(1) We determined that the ACBD5-RET fusion gene is formed via inverse binding between abreak point in the tyrosine kinase domain of the RET gene located in the long arm ofchromosome 10 and the 5’ end of the ACBD5 gene located in the short arm of the same
chromosome (pericentric inversion) (see Figure).
(2) Accelerated phosphorylation of protein kinase was observed in the NIH3T3 cells with an
ACBD5-RET fusion gene.
(3) After injection into the nude mice, the NIH3T3 cells with an ACBD5-RET fusion gene
continued proliferating and formed tumors.
This study showed that the ACBD5-RET fusion gene found in the PTC of an A-bomb
survivor is significantly involved in papillary thyroid carcinogenesis, as is the case with other
RET fusion genes such as CCDC6-RET and NCOA4-RET. RET gene rearrangement induced
either directly or indirectly by radiation is therefore suggested to be closely involved inpapillary thyroid carcinogenesis among PTC patients exposed to relatively high doses ofradiation.
The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring inHiroshima and Nagasaki for more than 60 years. RERF’s research achievements are considered theprincipal scientific basis for radiation risk assessment by the United Nations Scientific Committee on
the Effects of Atomic Radiation (UNSCEAR) and for recommendations regarding radiation protection
standards by the International Commission on Radiological Protection (ICRP). RERF expresses its
profound gratitude to the A-bomb survivors and survivors’ offspring for their cooperation in ourstudies.
§Oncology Reports is an international journal devoted to fundamental and applied research inoncology, and is published monthly as a comprehensive peer-reviewed journal focusing on oncology,
particularly carcinogenesis, metastasis, and epidemiology. (Impact factor in 2013: 2.191)

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