DNA breaks at fragile sites generate oncogenic RET/PTC rearrangements in human thyroid cells..     ///    "Moreover, exposure of human thyroid cells to these chemicals results in the formation of cancer-specific RET/PTC rearrangements. "    ///    "In this study, we provide structural and biochemical evidence that the RET, CCDC6 and NCOA4 genes participating in two major types of RET/PTC rearrangements, are located in common fragile sites FRA10C and FRA10G, and undergo DNA breakage after exposure to fragile site-inducing chemicals. "