Sino-orbital osteochondroma with malignant transformation to osteosarcoma.

Purpose: Osteosarcoma is an aggressive malignant osteogenic tumor that commonly arises in long bones of pediatric populations. Primary osteosarcomas of the head and neck are rare, comprising less than 0.5% of malignancies in this region, usually affecting the mandible or maxilla. Here we present an extraordinary case of a rare benign osteochondroma of the ethmoid sinus and bilateral orbits evolving to an intermediate grade osteosarcoma. Observations: An 80-year-old woman with a history of right orbital tumor resection 20 years ago presented to our clinic with right eye proptosis and palpable bony prominence of the right orbit and nasal bridge. Partial resection demonstrated sino-orbital osteochondroma. Relapse a year later prompted repeat partial resection with unchanged histology. The patient was followed clinically until an abrupt relapse four years after initial presentation. Imaging demonstrated a large bony mass involving the right orbit, ethmoid and frontal sinuses, and anterior cranial fossa. Repeat debulking confirmed transformation to intermediate grade osteosarcoma. Conclusions: Osteochondroma is an extremely rare tumor in the orbit with only three cases previously reported. This patient is the first known case of benign osteochondroma of the orbit undergoing malignant transformation to osteosarcoma. Rapid progression of orbital osteochondroma should raise the suspicion of malignant transformation to osteosarcoma and prompt biopsy. Our patient subsequently underwent palliative radiation treatment and is stable with no gross progression.

Isolation of organelles and prefractionation of protein extracts using free-flow electrophoresis.

One of the major obstacles in the analysis of proteomes is the extreme complexity of any particular cell or biological fluid. Free-flow electrophoresis (FFE) is a powerful tool for reduction of this complexity, which is a prerequisite for systematic and comprehensive protein analyses. Protocols are provided in this unit for sample fractionation at two different stages: on the protein level by isoelectric focusing FFE fractionation of crude protein mixtures such as whole cell lysates, and on a subcellular level by zone-electrophoretic FFE purification of organelles.

Improved proteome analysis of Saccharomyces cerevisiae mitochondria by free-flow electrophoresis.

The analysis of complex cellular proteomes by means of two-dimensional gel electrophoresis (2-DE) is significantly limited by the power of resolution of this technique. Although subcellular fractionation can be a fundamental first step to increase resolution, it frequently leads to preparations contaminated with other cellular structures. Here, we chose mitochondria of Saccharomyces cerevisiae to demonstrate that an integrated zone-electrophoretic purification step (ZE), with a free-flow electrophoresis device (FFE), can assist in overcoming this problem, while significantly improving their degree of purity. Whereas mitochondrial preparations isolated by means of differential centrifugation include a considerable degree of non-mitochondrial proteins (16%), this contamination could be effectually removed by the inclusion of a ZE-FFE purification step (2%). This higher degree of purity led to the identification of many more proteins from ZE-FFE purified mitochondrial protein extracts (n = 129), compared to mitochondrial protein extracts isolated by differential centrifugation (n = 80). Moreover, a marked decrease of degraded proteins was found in the ZE-FFE purified mitochondrial protein extracts. It is noteworthy that even at a low 2-DE resolution level, a four-fold higher number (17 versus 4) of presumably low abundance proteins could be identified in the ZE-FFE purified mitochondrial protein extracts. Therefore these results represent a feasible approach for an in-depth proteome analysis of mitochondria and possibly other organelles.