Malignant fibrous histiocytoma(MFH) is a rare primary neoplasm that constitutes less than 1% of the malignant tumors of bone, and involvement of the skull is very rare. We present a case of malignant fibrous histiocytoma of the skull, presenting an intraosseous lesion in a 43-yr-old woman. She had a rapidly growing, tender mass in the right parietal region. A plain radiograph showed an osteolytic lesion of the right parietal bone. Magnetic resonance imaging revealed that the lesion showed heterogeneous low signal intensity on T1-weighted images and slightly high signal intensity on T2-weighted images. No evidence of an extraosseous extension to the adjacent dura and soft tissue was found, and a wide excision of the parietal bone was performed. Histologically, the tumor was a typical MFH displaying pleomorphic spindle cells in a storiform pattern. The results of immunohistochemical stainings revealed that the tumor cells were positive for vimentin, alpha-1-antitryp-sin, and p53, and negative for smooth muscle actin, S100 protein, desmin, and MyoD1. Three months later, a mainly cystic, recurrent mass was developed at the previously operated site. Before the resection, we first performed the percutaneous aspiration cytology, revealing diagnostic multinucleated pleomorphic cells. There-after, she had to receive repetitive resections of recurrent or residual lesions, and she died of postoperative meningoencephalitis two years after the first operation.
Actins/biosynthesis ; Adult ; Brain/pathology ; Desmin/biosynthesis ; Female ; Giant Cells/metabolism ; Histiocytoma, Fibrous/*diagnosis ; Human ; Immunohistochemistry ; Magnetic Resonance Imaging ; Mitosis ; Muscle, Smooth/metabolism ; MyoD Protein/biosynthesis ; Protein p53/biosynthesis ; S100 Proteins/biosynthesis ; Skull Neoplasms/*diagnosis ; Tomography, X-Ray Computed ; Vimentin/biosynthesis ; alpha 1-Antitrypsin/biosynthesis

OBJECTIVESTo evaluate the expression profile of myoD microRNA-29 (miR-29) family in L6 myoblast differentiated to myotube of L6 myotube treated by glucose and insulin, and to further probe the molecular mechanism of myoD regulating the expression of miR-29 clusters.

METHODSThe expression of myoD and miR-29 family was detected by using real-time PCR and Western blot analysis. The potential promoter and transcription factors binding sites of miR-29 clusters were predicted by Promoter scan and transcriptional factor search. The promoter sequence of miR-29b1-a and miR-29b2-c cluster was cloned into a luciferase reporter plasmid and the regulatory effect of myoD was analyzed by using dual luciferase reporter assay. Electrophoretic mobility shift assay was further conducted to indicate the binding of myoD on specific sequence. Moreover, overexpression of myoD was achieved by a recombinant adenovirus system (Ad-myoD). L6 cells were infected with Ad-myoD and real-time PCR was conducted to analyze the expression of miR-29b and miR-29c.

RESULTSThe expression levels of myoD, miR-29a, miR-29b, and miR-29c were increased in L6 myoblast differentiated to myotube. The expression of myoD, miR-29b, and miR-29c was up-regulated in L6 myotube treated with glucose and insulin, but miR-29a depicted no significant change. Dual luciferase reporter gene assay showed that myoD functioned as a positive regulator of miR-29b2-c expression and myoD could bind to the specific sequence located at the promoter region of miR-29b2-c cluster. Enforced expression of myoD led to a marked increase of miR-29b and miR-29c levels in L6 cells.

CONCLUSIONMyoD might act as a crucial regulator of myogenesis and glucose metabolism in muscle through regulating the expression of miR-29b2-c.

Animals ; Cell Differentiation ; drug effects ; physiology ; Cell Line ; Gene Expression Regulation ; drug effects ; physiology ; Glucose ; pharmacology ; Hypoglycemic Agents ; pharmacology ; Insulin ; pharmacology ; Mice ; MicroRNAs ; biosynthesis ; genetics ; Multigene Family ; physiology ; Muscle Fibers, Skeletal ; cytology ; metabolism ; MyoD Protein ; genetics ; metabolism ; Myoblasts ; cytology ; metabolism ; Sweetening Agents ; pharmacology