Vinorelbine is a semisynthetic vinca alkaloid. Vinorelbine binds to tubulin and prevents the formation of the mitotic spindle, resulting in the arrest of tumor cell growth in metaphase.
Vinorelbine (0.5-5 nM) inhibits cell proliferation by 50% (IC50) at concentrations of 1.25 nM. At concentration of 8 nM vinorelbine, no cells are in anaphase. Vinorelbine time-dependently induces the p53 and p21WAFI/CIP1 expression in androgen-dependent (AD) and- independent (AI) prostate cancer cell lines. Vinorelbine stimulates reporter genes in a concentration-dependent manner.
After vinorelbine treatment, the first neutropenicepisode occurred after the first (4 dogs), second (1), or sixth(1) vinorelbine treatment in the dogs. Vinorelbine is tolerated at a weekly interval in tumor-bearing cats, with an MTD of 11.5 mg/m2.
Reverse transcriptase assays: Reverse transcriptase assays are carried out in a reaction mixture (50 μL) containing 50 mM Tris-HCl (pH 7.5), 5 mM DTT, 100 mM potassium chloride, 0.01% Triton X-100 or NP40, 10 μg/ml (dT)15.(A)n as template primer and [3H] deoxythymidine triphospahate. The reaction mixture is incubated for 1 hr at 37 ℃ and stopped by the addition of 50 μg of yeast tRNA and 2 mL of 10% solution of trichloroacetic acid containing 1 mM sodium pyrophosphate. The samples are filtered on filters (0.45 μm), washed first with 5% TCA solution for 5 times and then with 2 ml of 70% ethanol. The filters are dried, scintillation fluid is added and the radioactivity counted in a counter.