A novel mutated cell line with characteristics of dedifferentiated chondrosarcoma

Abstract

Abstract. Dedifferentiated chondrosarcoma (CS) is a rare, highly malignant variant of CS in which a high-grade sarcoma coexists with a low-grade chondroid tumor. In this study, a novel dedifferentiated CS cell line, MS0812, was spontaneously established from mutated human embryonic muscle cells. Several features of the cell line were investigated, including growth characteristics, cytogenetics, electron microscopic features, expression of various antigenic markers and tumor formation. MS0812 has been cultured continuously for more than 3 years. The growth characteristics of MS0812 are similar to the immortalized cell lines as reported. The cell line exhibited complex karyotypes and hyperploidy, the chromosome number ranged from 50 to 158. MS0812 was positive for vimentin, desmin and muscle actin, indicating their muscle origin. With specific inductive condition, MS0812 differentiates into neural cells and adipocytes. Deletion of the p16 gene, which seemed to play a major role in the malignant phenotype of this cell line, was confirmed by PCR and immunocytochemistry. MS0812 formed tumors in nude mice, and the tumor revealed a fibrosarcoma with chondroid components, which were consistent with dedifferentiated CS as reported. Chondroid components showed metachromasia by Alcian blue and toluidine blue and were S100 and collagen-II positive. To our knowledge, this is the first report of the establishment of a human dedifferentiated chondrosarcoma from mutated human embryonic muscle cells, and it is a useful model for the study of the molecular pathogenesis of dedifferentiated CS. IntroductionChondrosarcoma (CS) is the second most frequent primary malignant bone tumor after osteosarcoma and is characterized by basic neoplastic histology with cartilaginous stroma. The most frequent locations are the femur, pelvis and humerus, and 62% of patients are in the fourth, fifth and sixth decades of life (1-4). About 10% of CS undergoes regional anaplastic change, resulting in a high-grade noncartilaginous sarcoma arising within a typically low-grade CS, known as dedifferentiated CS (1-4), this concept was first introduced by Dahlin and Beabout in 1971 (5). They reported 33 cases of well-differentiated CS of bone with additional malignant mesenchymal components, such as fibrosarcoma or osteosarcoma. Some authors prefer instead to use the term CS with additional malignant mesenchymal component because of the morphogenesis of the tumor (5).Dedifferentiated CS is a highly lethal malignancy. Despite adequate, aggressive, initial, wide surgical resection or even amputation, unfortunately, metastases occur early and frequently and commonly involve the lungs, lymph nodes, and viscera (5-12). It is the poorly differentiated component that metastasizes. The prognosis is dismal, with an estimated 5-year survival rate of <10-25% (5-12). Many analyses of dedifferentiated CS are available at the clinico-pathological level, and the cell biology of this neoplasm is still not clearly understood. To our knowledge, there is only one report descr...

Tumor suppressor gene alterations of spontaneously malignant transformed cells from human embryonic muscle in vitro

“…It might be associated with the activation of oncogenes and inactivation of tumor suppressor genes, such as the amplification of c-myc and the inactivation of CDKI family (6,8,14,21). We found that human embryonic muscle cells cultured in vitro long-term could become immortalized spontaneously, and have obtained 6 novel cell lines (10). This type of tumor cell lines expressed actin, vimentin and desmin in vitro, which suggest that these malignant cells were originated from embryonic muscle cells, and these cell lines could develop sarcoma in nude mice (10).…”

“…We found that human embryonic muscle cells cultured in vitro long-term could become immortalized spontaneously, and have obtained 6 novel cell lines (10). This type of tumor cell lines expressed actin, vimentin and desmin in vitro, which suggest that these malignant cells were originated from embryonic muscle cells, and these cell lines could develop sarcoma in nude mice (10). However, malignant transformation mechanism in gene level is not clear yet.…”

“…We have found that human embryonic muscle cells which were cultured in vitro longterm could become spontaneously immortalized, and we obtained 6 novel malignant cell lines, this new type of cell lines were named human embryonic muscle-derived malignant transformed cells (hEMTCs). These hEMTCs could be passaged stably and showed characteristics of sarcoma in vivo (10).…”

“…M5B and M5C were from the same embryo but transformed malignantly in different culture time. The characteristics of line MS0812 was described clearly in our previous report (10). MS0504, M3, M4 and M5C could lead to fibrosarcoma in nude mice.…”

The molecular pathogenesis of dedifferentiated chondrosarcoma

“…p16 regulates cell cycle through the inhibition of cdk4 and cdk6 32. Analysis of a dedifferentiated chondrosarcoma cell line, MS0812, suggests that deletion of the p16 gene may play a major role in the malignant phenotype of dedifferentiated chondrosarcoma 12. Moreover, aberrant promoter methylation of the p16 gene has also been reported in both components of dedifferentiated chondrosarcoma 25.…”