Epothilone B  (Synonyms: EPO 906; Patupilone)

Asp-Glu-Val-Asp (DEVD)ase activity is determined in cytosolic cell extracts. Cells are treated with increasing concentrations of Epothilone B (Patupilone) for 6, 12, 24, and 48 h. Cells are harvested thereafter by trypsin/EDTA, centrifuged, and washed with precooled PBS. The cell pellet is suspended in 5 volumes of precooled buffer A (20 mM HEPES-KOH [pH 7.5], 10 mM KCl, 1.5 mM MgCl₂, 1 mM sodium EDTA, 1 mM sodium EGTA, 1 mM dithiothreitol [DDT], 250 mM sucrose, and 0.1 mM phenylmethylsulfonyl fluoride [PMSF] supplemented with protease inhibitors [5 mg/mL pepstatin A, 10 mg/mL leupeptin, 2 mg/mL aprotinin, 2 mg/mL DTT, and 1 mM of PMSF]). After incubation on ice for 15 min, the cells are disrupted by freezing and thawing. Cell lysates are centrifuged at 1000g for 10 min at 4°C, and the supernatant is further centrifuged at 100 000g for 30 min. The resulting supernatant (S-100 fraction) is stored at −80°C. To determine caspase 3-like activity, 75 μg of protein from the S-100 fraction is incubated at 37°C with the colorimetric caspase 3 substrate N-acetyl-Asp-Glu-Val-Asp p-nitroanilide (100 mM; Ac-DEVD-pNA) and 1 mM dATP in a final volume of 120 μL. Cleavage of the caspase substrate is monitored at 405 nm using a GenTec spectrophotometer^[3].

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Human glioblastoma cells (U87MG, ATCC) are routinely maintained at 37°C and 5% CO₂ in EMEM medium, with NEAA, containing 10% fetal bovine serum, 2 mM of glutamine, 1% penicillin and streptomycin. U87MG cells are used for no more than 15 passages. Cells are seeded in 96-well plates (5000 cells/well). After 24 h cells are treated with Epothilone B. Growth inhibition of U87MG cells is measured after 72 h of drug treatment by using the MTT cell proliferation assay^[2].

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Mice^[3]
D425Med cells (6×10⁶) are injected subcutaneously on the backs of 4-6-week-old athymic nude mice. Tumor volumes are determined from caliper measurements of tumor length (L) and width (l) according to the formula (L×l²)/2. Tumors are allowed to expand to a volume of 200 mm³ (±10%) before treatment start. With the use of a customized shielding device, mice are given strictly loco regional radiotherapy of 3×3 Gy on 3 consecutive days using a Gulmay 200 kV X-ray unit at 100 cGy/min at room temperature. Epothilone B (2 mg/kg; dissolved in 30% PEG-300/70% saline) is applied intravenously 24 h before the first treatment with ionizing radiation (at day 0 of the treatment; n=5 per group). Tumor growth is monitored daily.

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• [1]. Regueiro-Ren A, et al. Synthesis and biological activity of novel epothilone aziridines. Org Lett. 2001 Aug 23;3(17):2693-6.  [Content Brief]

  [2]. Pagano A, et al. Epothilone B inhibits migration of glioblastoma cells by inducing microtubule catastrophes and affecting EB1 accumulation at microtubule plus ends. Biochem Pharmacol. 2012 Aug 15;84(4):432-43.  [Content Brief]

  [3]. Oehler C, et al. The microtubule stabilizer patupilone (epothilone B) is a potent radiosensitizer in medulloblastoma cells. Neuro Oncol. 2011 Sep;13(9):1000-10.  [Content Brief]