Preoperative radiation therapy in the management of recurrent orbital hemangiopericytoma.

A 77-year-old man presented for evaluation of a recurrent right orbital hemangiopericytoma. It had been excised twice over the past 6 years. After the second resection, the tumor rapidly recurred and was insensitive to systemic chemotherapy, and the patient was thus referred to the authors' institution. The patient had proptosis, restricted ocular movement, and binocular diplopia on presentation. Orbital imaging confirmed a well-circumscribed right extraconal mass in the medial orbit. Preoperative radiation therapy was given, which reduced the tumor volume considerably and allowed a successful complete surgical excision of the mass.

Adjacent DNA sequences modulate Sox9 transcriptional activation at paired Sox sites in three chondrocyte-specific enhancer elements.

Expression of the type XI collagen gene Col11a2 is directed to cartilage by at least three chondrocyte-specific enhancer elements, two in the 5' region and one in the first intron of the gene. The three enhancers each contain two heptameric sites with homology to the Sox protein-binding consensus sequence. The two sites are separated by 3 or 4 bp and arranged in opposite orientation to each other. Targeted mutational analyses of these three enhancers showed that in the intronic enhancer, as in the other two enhancers, both Sox sites in a pair are essential for enhancer activity. The transcription factor Sox9 binds as a dimer at the paired sites, and the introduction of insertion mutations between the sites demonstrated that physical interactions between the adjacently bound proteins are essential for enhancer activity. Additional mutational analyses demonstrated that although Sox9 binding at the paired Sox sites is necessary for enhancer activity, it alone is not sufficient. Adjacent DNA sequences in each enhancer are also required, and mutation of those sequences can eliminate enhancer activity without preventing Sox9 binding. The data suggest a new model in which adjacently bound proteins affect the DNA bend angle produced by Sox9, which in turn determines whether an active transcriptional enhancer complex is assembled.