Fig 4. CXCR4^High can be a useful target for OVC treatment.

(A) CXCR4-KLA (labeled with FITC) specifically bound to CXCR4^High. Cells were incubated with the peptide (5 μM) in 1.5% (w/v) FBS containing medium for 2h at 37°C prior to performing FACS analysis. (B) CXCR4-KLA displays the preferential cell killing of CXCR4^High compared to CXCR4^Low. MTS assays were performed on the cells 72 h after incubation with different concentrations (0–100 μM) of the peptide. (C) The specificity of CXCR4-KLA was confirmed by a reduction of the CXCR4^High fraction of both CXCR4^High and A2780/ADR after treatment with a suboptimal concentration (2 μM) of CXCR4-KLA for 72 h. (D) CXCR4-KLA is more potent than the conventional CXCR4 antagonists, including AMD3100 and CTCE9908, toward A2780, A2780/ADR, and SKOV3. Cells were incubated with the peptide (10 μM) for 72 h prior to determine the cell viability using MTS assay. (E) Using a combination of drugs (doxorubicin or cisplatin) and CXCR4-KLA (at suboptimal concentrations) showed synergistic cell-killing effects on CXCR4^High and CXCR4^Low (two way ANOVA, ***p<0.001). (F) The drug-peptide combinations also show synergistic cytotoxicity toward A2780, A2780/ADR, and SKOV-3. The drug dosages were selected according to the IC₅₀ values of the drug or peptide alone against individual cell lines. All the experiments were performed in triplicate and the results were presented as means ± SD of three independent experiments (t-test, *p<0.05, **p<0.01, ***p<0.001).