In vitro activity: Paclitaxel inhibits non-endothelial type human cells at 104 - to 105 -fold higher concentrations, with IC50 of 1 nM-10 nM. The selectivity of Paclitaxel inhibition of cell proliferation is also species specific, as mouse ECs are not sensitive to Paclitaxel at ultra low concentrations. Inhibition of human ECs by Paclitaxel at ultra low concentrations does not affect the cellular microtubule structure, and the treated cells do not show G2/M cell cycle arrest and apoptosis, suggesting a novel but as yet unidentified mechanism of action. In an in vitro angiogenesis assay, Paclitaxel at ultra low concentrations blocks human ECs from forming sprouts and tubes in the three-dimensional fibrin matrix. In the presence of SMF, the efficient concentration of Paclitaxel on K562 cells is decreased from 50 to 10 ng/mL. The cell cycle arrest effect of Paclitaxel with or without SMF on K562 cells is correlated with DNA damage. Paclitaxel alone causes a time-dependent inhibition of CDK1 in four cell lines including A549 cells, H358, H1395 cells and H1666 cells.

Cell Assay: Cells including human neonatal dermal microvascular ECs (HMVECs), human umbilical vein ECs (HUVECs), human umbilical artery ECs (HUAVECs), normal human astrocytes (NHAs), normal human dermal fibroblasts (NHDFs), normal human epidermal keratinocytes (NHEKs), human mammary epithelial cells (HMEpCs), human prostate epithelial cells (PrEpCs) and human umbilical artery smooth muscle cells (UASMCs) are cultured. Cell proliferations are performed in 96-well plates using cells between passages 6 and 12. Cells are seeded at 3000–5000 cells/well and allowed to attach for 4 hours. Paclitaxel, diluted in culture medium, is added in quadruplicate wells and the cells ae incubated for 3 days before MTS reagents are added to quantitate the live cells in each well.

Anticancer Drugs. 2003 Jan;14(1):13-9; Breast Cancer Res Treat. 2012 Aug;134(3):969-80.