OBJECTIVETo observe the in vitro growth inhibitory and apoptosis-inducing effects of paclitaxel on the human osteosarcoma cell line U-2 OS.

METHODSU-2 OS cells were treated with various concentrations of paclitaxel. Proliferation was determined by cell count in a neubauer cytometer chamber. Viability was assessed by trypan blue dye exclusion. Paclitaxel-induced morphologic alterations were visualized using light and transmission electron microscopy. The extent of paclitaxel-induced apoptosis was determined by flow cytometry and immunohistochemical detection (TdT-mediated dUTP nick end labeling technique, TUNEL).

RESULTSThe cells treated with paclitaxel initially showed G(2)/M arrest, which was followed by apoptosis. The characteristic apoptotic changes, including nuclear disintegration and chromatin agglomeration, were displayed. Large amounts of micronuclei cells appeared, something not observed in those cells treated with cisplatin and adriamycin for contrast. Also, extensive DNA-cleavage was detected using TUNEL.

CONCLUSIONThis study demonstrates that paclitaxel has an apoptotic-inducing effect on osteosarcoma cells through the initiation of G(2)/M arrest and inhibiting mitosis in both a time-dependent and dose-dependent manner.