Cell lines and the development of taxane-resistance variants

We analysed 18 ovarian carcinoma cell lines for taxane sensitivity, ABCB1 expression, and growth characteristics. Four lines (3 serous: A2780/1A9, MES-OV and OVCAR-3; and one clear cell: ES-2) were chosen as parental lines for the generation of taxane-resistant variants, and cultured as described previously (Wang et al, 2006). These lines were chosen because they were the most sensitive to taxanes, did not express high levels of ABCB1, and grew readily in vitro (doubling times of ⩽48 h in standard tissue culture media). The 3 parental serous lines did not express P-gp, and the clear cell line expressed very low but detectable levels.

Each cell line was exposed to docetaxel or paclitaxel at IC₅₀ levels (the concentration required to kill 50% of the population), with or without the P-gp inhibitor valspodar (2 μmol l⁻¹). The concentration of the taxanes used for selection of drug resistance was gradually increased until the resulting variants displayed at least a 10-fold resistance to the selecting agents. The results of selection by taxanes without a P-gp inhibitor, resulting in resistant variants expressing high levels of P-gp, have been published (Wang et al, 2006).