FIG 4.

Paclitaxel is able to block the cell cycle in G₂/M as well as improve viral replication even after its withdrawal from cells. (A) Suit2 cells were either treated with a compound (500 nM paclitaxel or 500 nM ruxolitinib) for 24 h before infection with VSV-ΔM51 (“preinfection treatment”) or first infected with VSV-ΔM51 and then treated with a compound (“postinfection treatment”). The level of GFP fluorescence was measured over the time from 1 until 72 h p.i. The data are representative of results from two independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, nonsignificant. The significance of the data was determined using two-way ANOVA with a Tukey posttest at a 95% confidence interval for comparison of VSV plus paclitaxel or VSV plus ruxolitinib versus VSV alone. (B) Suit2 cells were treated with 500 nM paclitaxel (or mock treated) for 24 h and then monitored by a cell cycle analysis 0, 8, or 24 h after compound removal. Cell cycle stages were analyzed by flow cytometry with DAPI staining to determine nuclear DNA content, which was used to calculate the percentages of cells in different cell cycle phases. Single cells were gated via DAPI area and DAPI width signals and analyzed from a DAPI area histogram. (C) Suit2 cells either were treated with 500 nM paclitaxel (PAC) or remained untreated for 24 h. Paclitaxel (or medium) was then removed for 0 or 24 h before infection with VSV-ΔM51 (MOI of 1 or 10 PFU/cell [the MOI was calculated based on virus titration on BHK-21 cells]). After virus infection, incubation of cells continued for 12 h. The percentage of GFP-positive (GFP⁺) cells as well as the mean fluorescence were analyzed by flow cytometry and are indicated on the top right of each graph. The data represent results from at least two independent experiments.