The effects of taurolidine alone and in combination with doxorubicin or carboplatin in canine osteosarcoma in vitro.

BACKGROUND: Osteosarcoma (OS) affects over 8000 dogs/year in the United States. The disease usually arises in the appendicular skeleton and metastasizes to the lung. Dogs with localized appendicular disease benefit from limb amputation and chemotherapy but most die within 6-12 months despite these treatments. Taurolidine, a derivative of taurine, has anti-tumor and anti-angiogenic effects against a variety of cancers. The following in vitro studies tested taurolidine as a candidate for adjuvant therapy for canine OS. Tests for p53 protein status and caspase activity were used to elucidate mechanisms of taurolidine-induced cell death. RESULTS: Taurolidine was cytotoxic to osteosarcoma cells and increased the toxicity of doxorubicin and carboplatin in vitro. Apoptosis was greatly induced in cells exposed to 125 µM taurolidine and less so in cells exposed to 250 µM taurolidine. Taurolidine cytotoxicity appeared caspase-dependent in one cell line; with apparent mutant p53 protein. This cell line was the most sensitive to single agent taurolidine treatment and had a taurolidine-dependent reduction in accumulated p53 protein suggesting taurolidine's effects may depend on the functional status of p53 in canine OS. CONCLUSION: Taurolidine's cytotoxic effect appears dependent on cell specific factors which may be explained, in part, by the functional status of p53. Taurolidine initiates apoptosis in canine OS cells and this occurs to a greater extent at lower concentrations. Mechanisms of cell death induced by higher concentrations were not elucidated here. Taurolidine combined with doxorubicin or carboplatin can increase the toxicity of these chemotherapy drugs and warrants further investigation in dogs with osteosarcoma.

Nonmuscle myosins II-B and Va are components of detergent-resistant membrane skeletons derived from mouse forebrain.

Myosins are actin-based molecular motors that may have specialized trafficking and contractile functions in cytoskeletal compartments that lack microtubules. The postsynaptic excitatory synapse is one such specialization, yet little is known about the spatial organization of myosin motor proteins in the mature brain. We used a proteomics approach to determine if class II and class V myosin isoforms are associated with Triton X-100-resistant membranes isolated from mouse forebrain. Two nonmuscle myosin isoforms (II-B and Va), were identified as components of lipid raft fractions that also contained typical membrane skeletal proteins such as non-erythrocyte spectrins, actin, alpha-actinin-2 and tubulin subunits. Other raft-associated proteins included lipid raft markers, proteins involved in cell adhesion and membrane dynamics, receptors and channels including glutamate receptor subunits, scaffolding and regulatory proteins. Myosin II-B and Va were also present in standard postsynaptic density (PSD) fractions, however retention of myosin II-B was strongly influenced by ATP status. If homogenates were supplemented with ATP, myosin II-B could be extracted from PSD I whereas myosin Va and other postsynaptic proteins were resistant to extraction. In summary, both myosin isoforms are components of a raft-associated membrane skeleton and are likely detected in standard PSD fractions as a result of their intrinsic ability to form actomyosin. Myosin II-B, however, is more loosely associated with PSD fractions than myosin Va, which appears to be a core PSD protein.