Thyroid carcinoma after successful treatment of osteosarcoma: a report of three patients

Metastatic Thyroid Osteosarcoma With Concomitant Multifocal Papillary Carcinoma Presenting as a Collision Tumor

Metastatic involvement of the thyroid occurs rarely, by either hematogenous spread or direct extension from adjacent organs. The most frequent metastatic tumors are clear cell, renal cell, lung, breast, and squamous cell carcinoma.

The occurrence of osteosarcoma and papillary thyroid carcinoma in the same patient is rare, with only a few reported cases in the literature. On the other hand, only one case of osteosarcoma thyroid metastasis has so far been reported.

We herewith present another case with metastatic osteosarcoma and multifocal papillary thyroid carcinoma presenting as a collision tumor and review the relevant literature.

Broken by the Cut: A Journey into the Role of Topoisomerase II in DNA Fragility

DNA topoisomerase II (TOP2) plays a critical role in many processes such as replication and transcription, where it resolves DNA structures and relieves torsional stress. Recent evidence demonstrated the association of TOP2 with topologically associated domains (TAD) boundaries and CCCTC-binding factor (CTCF) binding sites. At these sites, TOP2 promotes interactions between enhancers and gene promoters, and relieves torsional stress that accumulates at these physical barriers. Interestingly, in executing its enzymatic function, TOP2 contributes to DNA fragility through re-ligation failure, which results in persistent DNA breaks when unrepaired or illegitimately repaired. Here, we discuss the biological processes for which TOP2 is required and the steps at which it can introduce DNA breaks. We describe the repair processes that follow removal of TOP2 adducts and the resultant broken DNA ends, and present how these processes can contribute to disease-associated mutations. Furthermore, we examine the involvement of TOP2-induced breaks in the formation of oncogenic translocations of leukemia and papillary thyroid cancer, as well as the role of TOP2 and proteins which repair TOP2 adducts in other diseases. The participation of TOP2 in generating persistent DNA breaks and leading to diseases such as cancer, could have an impact on disease treatment and prevention.

DNA fragile site breakage as a measure of chemical exposure and predictor of individual susceptibility to form oncogenic rearrangements

Chromosomal rearrangements induced by non-radiation causes contribution to the majority of oncogenic fusions found in cancer. Treatment of human thyroid cells with fragile site-inducing laboratory chemicals can cause preferential DNA breakage at the RET gene and generate the RET/PTC1 rearrangement, a common driver mutation in papillary thyroid carcinomas (PTC). Here, we demonstrate that treatment with non-cytotoxic levels of environmental chemicals (benzene and diethylnitrosamine) or chemotherapeutic agents (etoposide and doxorubicin) generates significant DNA breakage within RET at levels similar to those generated by fragile site-inducing laboratory chemicals. This suggests that chronic exposure to these chemicals plays a role in the formation of non-radiation associated RET/PTC rearrangements. We also investigated whether the sensitivity of the fragile RET region could predict the likelihood of rearrangement formation using normal thyroid tissues from patients with and without RET/PTC rearrangements. We found that normal cells of patients with thyroid cancer driven by RET/PTC rearrangements have significantly higher blunt-ended, double-stranded DNA breaks at RET than those of patients without RET/PTC rearrangements. This sensitivity of a cancer driver gene suggests for the first time that a DNA breakage test at the RET region could be utilized to evaluate susceptibility to RET/PTC formation. Further, the significant increase of blunt-ended, double-stranded DNA breaks, but not other types of DNA breaks, in normal cells from patients with RET/PTC-driven tumors suggests that blunt-ended double-stranded DNA breaks are a preferred substrate for rearrangement formation, and implicate involvement of the non-homologous end joining pathway in the formation of RET/PTC rearrangements.

The role of fragile sites in sporadic papillary thyroid carcinoma

The incidence of thyroid cancer is increasing, especially papillary thyroid carcinoma (PTC), making it currently the fastest-growing cancer among women. Reasons for this increase remain unclear, but several risk factors including radiation exposure and improved detection techniques have been suggested. Recently, the induction of chromosomal fragile site breakage was found to result in the formation of RET/PTC1 rearrangements, a common cause of PTC. Chromosomal fragile sites are regions of the genome with a high susceptibility to forming DNA breaks and are often associated with cancer. Exposure to a variety of external agents can induce fragile site breakage, which may account for some of the observed increase in PTC. This paper discusses the role of fragile site breakage in PTC development, external fragile site-inducing agents that may be potential risk factors for PTC, and how these factors are especially targeting women.

Secondary thyroid papillary carcinoma in osteosarcoma patients: report of two cases

We report two cases of papillary thyroid carcinoma occurring after the successful treatment of osteosarcoma. One of the patients was administered with several alkylating agents and topoisomerase II inhibitor as part of the primary treatment of osteosarcoma. The onset of thyroid carcinoma occurred after 5 and 12 yr after cessation of the osteosarcoma therapy. All the patients involved in this study are alive and free of their malignancies. There have been eight case reports of these two malignancies occurring in the same patient. Thyroid carcinoma rarely occurs in patients with osteosarcoma; however, vigilant surveillance and long-term follow-up should be emphasized for all survivors.

Multiple Primary Cancers in Patients With Osteosarcoma

One hundred thirty-five patients younger than 30 years with osteosarcoma were treated at the Chiba Cancer Center between 1976 and 1999. They included six patients with second cancer after cure of osteosarcoma (group A) and three patients with osteosarcoma as second cancer after cure of childhood cancers (group B). Third cancer occurred in one patient of group A. The clinical features of these nine patients were studied. The diagnoses of second cancer in group A consisted of two acute myelogenous leukemias, two breast carcinomas, one malignant phyllodes tumor of breast, and one ovarian carcinoma. The third cancer was uterine leiomyosarcoma. Second cancer occurred an average of 7.2 years after occurrence of osteosarcoma. The diagnoses of first cancer in group B consisted of one adrenocortical carcinoma, one malignant teratoma of sacrum, and one ovarian carcinoma (yolk sac tumor). Osteosarcoma occurred on average 12.7 years after occurrence of first cancer. Two patients had germ-line p53 gene mutation. Anticancer drugs and genetic factors are presumed to be concerned with occurrence of second cancer. The frequency of multiple primary cancers in patients with osteosarcoma is by no means low. Strict follow-up is thus needed over a long period.