Formation of carcinogenic chromosomal rearrangements in human thyroid cells after induction of double-strand DNA breaks by restriction endonucleases.
Ionizing radiation (IR) exposure increases the risk of thyroid cancer and other cancer types. Chromosomal rearrangements, such as RET/PTC, are characteristic features of radiation-associated thyroid cancer and can be induced by radiation in vitro. IR causes double-strand breaks (DSBs), suggesting that such damage leads to RET/PTC, but the rearrangement mechanism has not been established. To study the mechanism, we explored the possibility of inducing RET/PTC by electroporation of restriction endonucleases (REs) into HTori-3 human thyroid cells. We used five REs, which induced DSB in a dose-dependent manner similar to that seen with IR. Although all but one RE caused DSB in one or more of the three genes involved in RET/PTC, rearrangement was detected only in cells electroporated with either PvuII (25 and 100  U) or StuI (100 and 250  U). The predominant rearrangement type was RET/PTC3, which is characteristic of human thyroid cancer arising early after Chernobyl-related radioactive iodine exposure. Both enzymes that produced RET/PTC had restriction sites only in one of the two fusion partner genes. Moreover, the two enzymes that produced RET/PTC had restriction sites present in clusters, which was not the case for RE that failed to induce RET/PTC. In summary, we establish a model of DSB induction by RE and report for the first time the formation of carcinogenic chromosomal rearrangements, predominantly RET/PTC3, as a result of DSB produced by RE. Our data also raise a possibility that RET/PTC rearrangement can be initiated by a complex DSB that is induced in one of the fusion partner genes.
Department of Pathology, University of Pittsburgh, 200 Lothrop Street, PUH, Room C-606, Pittsburgh, Pennsylvania 15213, USA.
Viktoria
V
Evdokimova
Manoj
M
Gandhi
Jayanagendra
J
Rayapureddi
James R
JR
Stringer
Yuri E
YE
Nikiforov
D002460:Cell Line; D002478:Cells, Cultured; D002588:Cesium Radioisotopes; D053903:DNA Breaks, Double-Stranded; D004262:DNA Restriction Enzymes / Q000494:pharmacology; D005720:Gamma Rays; D015321:Gene Rearrangement; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D013961:Thyroid Gland / Q000166:cytology
D002588:Cesium Radioisotopes; D015514:Oncogene Proteins, Fusion; D011505:Protein-Tyrosine Kinases; C093573:ret-PTC fusion oncoproteins, human; D004262:DNA Restriction Enzymes