Paclitaxel-induced apoptotic changes followed by time-lapse video microscopy in cell lines established from head and neck cancer

Abstract

Paclitaxel (Taxol) is a potent chemotherapeutic drug for squamous-cell carcinoma (SCC) of the head and neckin vitro with microtubule-stabilizing activity that arrests cells in G2-M. To study the mechanism of its cytotoxic effect on SCCin vitro, we exposed five laryngeal SCC cell lines to 10 nM paclitaxel. The cell lines were studied by time-lapse video microscopy for 96 h, and by agarose gel electrophoresis. Paclitaxel blocked the cells in the premitotic phase for 6–24 h, after which the cells died morphologically by apoptosis. Mitotically arrested cells were seen within a few minutes after exposure to paclitaxel. No mitoses were seen in the paclitaxel-treated cells. A few apoptoses were also seen in the control cultures grown without paclitaxel, but they represented only 6%–20% of the frequency of apoptoses seen in the paclitaxel-treated group. In some paclitaxel-treated cultures the cells escaped the mitotic arrest without cytokinesis and formed multinucleated cells that eventually died. Agarose gel electrophoresis showed oligonucleosomal DNA fragmentation characteristic of apoptosis. We conclude that time-lapse video microscopy is an efficient method of observing drug-induced morphological changes in cell culture. Paclitaxel at a 10 nM concentration rapidly induces a premitotic block, which usually leads to apoptotic cell death. In some cases multinucleated cells are formed that morphologically also eventually die by apoptosis.