Pharmacokinetics and tissue distribution of 3,4-diaminopyridine in rats.

Lambert-Eaton myasthenic syndrome (LEMS) is characterized by muscle weakness, amyotrophy, easy fatigability, and depressed tendon reflexes. 3,4-Diaminopyridine (3,4-DAP) is the recommended therapy for the treatment of LEMS. However, estimations of 3,4-DAP pharmacokinetics in human and animals, such as rats, are rarely reported because 3,4-DAP is an orphan drug for the treatment of a very rare disease (LEMS). In particular, little is known about its tissue distribution. Therefore, the pharmacokinetics of 3,4-DAP were studied, with particular focus on tissue distribution, in rats. After intravenous administration of 3,4-DAP to rats, the half-life of 3,4-DAP was 15.9 ± 3.9 min and the volume of distribution at steady-state was 2.8 ± 0.7 L/kg. The tissue-to-plasma partition coefficient (Kp) was high in the kidney, heart, and muscle. In addition, with increased steady state plasma concentration (Css), a tendency toward increased Kp was found in most tissues. In the muscle, a likely target region of 3,4-DAP in LEMS patients, the Kp was higher than in the plasma. Furthermore, more than 68% of 3,4-DAP was distributed to the muscle as determined by the ratio of 3,4-DAP distribution calculated from the apparent volumes of distribution. Hence, 3,4-DAP may provide for more effective and long-lasting effects.

Glycogen synthase kinase 3ß sustains invasion of glioblastoma via the focal adhesion kinase, Rac1, and c-Jun N-terminal kinase-mediated pathway.

The failure of current treatment options for glioblastoma stems from their inability to control tumor cell proliferation and invasion. Biologically targeted therapies offer great hope and one promising target is glycogen synthase kinase-3ß (GSK3ß), implicated in various diseases, including cancer. We previously reported that inhibition of GSK3ß compromises the survival and proliferation of glioblastoma cells, induces their apoptosis, and sensitizes them to temozolomide and radiation. Here, we explore whether GSK3ß also contributes to the highly invasive nature of glioblastoma. The effects of GSK3ß inhibition on migration and invasion of glioblastoma cells were examined by wound-healing and Transwell assays, as well as in a mouse model of glioblastoma. We also investigated changes in cellular microarchitectures, cytoskeletal components, and proteins responsible for cell motility and invasion. Inhibition of GSK3ß attenuated the migration and invasion of glioblastoma cells in vitro and that of tumor cells in a mouse model of glioblastoma. These effects were associated with suppression of the molecular axis involving focal adhesion kinase, guanine nucleotide exchange factors/Rac1 and c-Jun N-terminal kinase. Changes in cellular phenotypes responsible for cell motility and invasion were also observed, including decreased formation of lamellipodia and invadopodium-like microstructures and alterations in the subcellular localization, and activity of Rac1 and F-actin. These changes coincided with decreased expression of matrix metalloproteinases. Our results confirm the potential of GSK3ß as an attractive therapeutic target against glioblastoma invasion, thus highlighting a second role in this tumor type in addition to its involvement in chemo- and radioresistance.

Aberrant glycogen synthase kinase 3ß is involved in pancreatic cancer cell invasion and resistance to therapy.

BACKGROUND AND PURPOSE: The major obstacles to treatment of pancreatic cancer are the highly invasive capacity and resistance to chemo- and radiotherapy. Glycogen synthase kinase 3ß (GSK3ß) regulates multiple cellular pathways and is implicated in various diseases including cancer. Here we investigate a pathological role for GSK3ß in the invasive and treatment resistant phenotype of pancreatic cancer. METHODS: Pancreatic cancer cells were examined for GSK3ß expression, phosphorylation and activity using Western blotting and in vitro kinase assay. The effects of GSK3ß inhibition on cancer cell survival, proliferation, invasive ability and susceptibility to gemcitabine and radiation were examined following treatment with a pharmacological inhibitor or by RNA interference. Effects of GSK3ß inhibition on cancer cell xenografts were also examined. RESULTS: Pancreatic cancer cells showed higher expression and activity of GSK3ß than non-neoplastic cells, which were associated with changes in its differential phosphorylation. Inhibition of GSK3ß significantly reduced the proliferation and survival of cancer cells, sensitized them to gemcitabine and ionizing radiation, and attenuated their migration and invasion. These effects were associated with decreases in cyclin D1 expression and Rb phosphorylation. Inhibition of GSK3ß also altered the subcellular localization of Rac1 and F-actin and the cellular microarchitecture, including lamellipodia. Coincident with these changes were the reduced secretion of matrix metalloproteinase-2 (MMP-2) and decreased phosphorylation of focal adhesion kinase (FAK). The effects of GSK3ß inhibition on tumor invasion, susceptibility to gemcitabine, MMP-2 expression and FAK phosphorylation were observed in tumor xenografts. CONCLUSION: The targeting of GSK3ß represents an effective strategy to overcome the dual challenges of invasiveness and treatment resistance in pancreatic cancer.