Molecular characterization of a bladder pleomorphic rhabdomyosarcoma in an adult patient

Establishment of a novel experimental system using single cell-derived pleomorphic rhabdomyosarcoma cell lines expressing K-RasG12V and deficient in p53

Pleomorphic rhabdomyosarcoma (PRMS) predominantly arises in adult skeletal musculature and is usually associated with poor prognosis. Thus, effective treatments must be developed. PRMS is a rare tumor; therefore, it is critical to develop an experimental system to understand the cellular and molecular mechanisms of PRMS. We previously demonstrated that PRMS develops after p53 gene deletion and oncogenic K-Ras expression in the skeletal muscle tissue. In that study, oncogenic K-Ras-expressing cells were diverse and the period until disease onset was difficult to control. In this study, we developed an experimental system to address this problem. Single cell-derived murine cell lines, designated as RMS310 and RMSg2, were established by limiting the dilution of cells from a lung metastatic tumor colony that were positive for various cancer stem cells and activated skeletal muscle-resident stem/progenitor cell marker genes by RT-PCR. All cell lines stably recapitulated the histological characteristics of human PRMS as bizarre giant cells, desmin-positive cells, and lung metastases in C57BL/6 mice. All subclones of the RMSg2 cells by the limiting dilution in vitro could seed PRMS subcutaneously, and as few as 500 RMSg2 cells were sufficient to form tumors. These results suggest that the RMSg2 cells are multipotent cancer cells that partially combine the properties of skeletal muscle-resident stem/progenitor cells and high tumorigenicity. Thus, our model system's capacity to regenerate tumor tissue in vivo and maintain stable cells in vitro makes it useful for developing therapeutics to treat PRMS.

Rhabdomyosarcoma in Adults: Case Series and Literature Review

Rhabdomyosarcoma, a common soft tissue malignant tumor in children and adolescents, is exceedingly rare in adults. Nevertheless, The outcome in adults is very poor, especially when compared to outcomes in children in whom significant improvements in treatment has been achieved. The first case was of a 24-year-old pregnant Chinese woman with a rare primary site of rhabdomyosarcoma in the perineal body. She presented with a perineal mass and was diagnosed during the second trimester of pregnancy, which is a very rare occurrence. The second case was a 70-year-old Chinese woman who suffered from right lower abdominal pain for 1 month and was misdiagnosed with an epithelial ovarian carcinoma. Mesenteric pleomorphic rhabdomyosarcoma was later confirmed by postoperative pathology. Both cases had undergone preoperative examination with chest and abdominal computed tomography (CT) and pelvic magnetic resonance imaging (MRI) examinations, as well as examination of complete blood count, liver panel, renal panel, and serum tumor markers. Diagnosis was based on histopathology and immunohistochemistry. The patient in the first case received chemotherapy after which the mass decreased in size; however, the patient was lost to follow-up. The second case underwent tumor resection and received chemotherapy and radiotherapy.