Figure 1.

1A9/A8 and 1A9/B10 cells exhibit impaired in vivo tubulin polymerization. Drug-sensitive parental 1A9 and the Epo^R clones, 1A9/A8 and 1A9/B10, were treated for 5 h with or without (0) various concentrations of PTX and Epo A as indicated. After cell lysis, the polymerized (P) and the soluble (S) protein fractions were separated by centrifugation, resolved by SDS/PAGE, and immunoblotted with an antibody against β-tubulin. The percent of polymerized tubulin (% P) was determined by dividing the densitometric value of polymerized tubulin by the total tubulin content (the sum of P plus S). The results shown are from a representative experiment of four independent observations.