When cells were treated with L-OHP for 24 h, the click here drug-resistant cells in S phase increased in numbers, and parental cells in G2/M phase increased. That is, drug-resistant cells were arrested in G2/M phase by L-OHP, and parental cells were arrested in S phase. Meanwhile, apoptosis rates of both cell types were significantly enhanced, although the apoptosis rate in drug-resistant cells was less than the rate in parental cells (P < 0.05). Table 1 Cell cycle distribution of OCUM-2MD3/L-OHP cells. Cell Cell cycle Apoptosis rate (%)   G 0 /G 1 S G 2 /M   Control group            OCUM-2MD3 47.93 ± 0.35 46.83 ± 2.31 5.22 ± 2.50 1.00 ± 0.11    OCUM-2MD3/L-OHP

GSK1838705A mouse 66.03 ± 0.28* 10.4 ± 1.06* 23.25 ± 0.78* 5.21 ± 0.55* Treatment group            OCUM-2MD3 24.80 ± 0.52 49.37 ± 1.59 25.77 ± 1.30Δ 35.53 ± 0.73    OCUM-2MD3/L-OHP 50.80 ± 2.00 27.80 ± 0.86Δ 21.40 ± 2.79 29.43 ± 0.91* * Comparisons of different cells in the same group P < 0.05 MI-503 clinical trial Δ Comparisons of different cells in different groups P < 0.05 Figure 3 Cell cycle. (A). OCUM-2MD3/L-OHP (Control group); (B). OCUM-2MD3 (Control group); (C). OCUM-2MD3/L-OHP (Treatment group); (D). OCUM-2MD3

(Treatment group). Figure 4 Cell apoptosis. (A). OCUM-2MD3/L-OHP (Control group); (B). OCUM-2MD3 (Control group); (C). OCUM-2MD3/L-OHP (Treatment group); (D). OCUM-2MD3 (Treatment group). Sensitivity and RI of drug-resistant cells to L-OHP As shown in Fig. 5, with the rise of L-OHP concentration, inhibition rates of L-OHP on the two cell types gradually increased, and the inhibition rate of L-OHP on drug-resistant cells was significantly less than the inhibition rate of parental cells (P < 0.05). IC50 values of L-OHP on drug-resistant cells and parental cells at 24 h were 8.32 μg/mL and 1.92 μg/mL, respectively. In addition,

the RI value of drug-resistant cells in response G protein-coupled receptor kinase to L-OHP was 4.3. Following repeated passages, cryopreservation and recovery, the RI value remained stable. Figure 5 Inhibition rate of various concentrations of L-OHP on drug-resistant cells. Detection of MDR in drug-resistant cells As is shown in Fig. 6, the inhibition rates of 10 chemotherapeutics, including L-OHP, CDDP, CBDCA, 5-Fu, ADM, MMC, GEM, VCR, IH and PTH, on drug-resistant cells were significantly less than inhibition rates in parental cells (P < 0.01). An inhibition rate less than 50% was set as the criterion for drug resistance, and parental cells showed drug resistance to MMC, VCR and IH. The drug-resistant cells were not only resistant to L-OHP, but their sensitivity to CDDP, ADM and PTX was also degraded and showed cross-resistance to CBDCA, 5-Fu, MMC, GEM, VCR and IH. Figure 6 Inhibition rates of different chemotherapeutics in drug-resistant cells. Expression of P-gp and Livin in drug-resistant cells As shown in Table 2 and Fig. 7, expression of P-gp and Livin was seen in both cell types.