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. Author manuscript; available in PMC: 2022 Jan 1.
Published in final edited form as: Mol Cancer Ther. 2021 May 4;20(7):1257–1269. doi: 10.1158/1535-7163.MCT-20-0252

Figure 1. The Rad51 inhibitor, B02 displays differential sensitivity and synergizes with AZD1775 in vitro in HNSCC.

Figure 1.

A , IC50 values for B02 in selected HPV-negative and HPV-positive HNSCC cells treated with various concentrations of the drug for 48 hours and subjected to clonogenic survival assays as indicated. B, number of adherent cells (PCI-13-G245D and UM-SCC-47) measured with Celigo following treatment with B02 and in combination with AZD1775 for 72 hours. C, representative images of clonogenic survival assays in PCI13-G245D and UM-SCC-47 cell lines treated with combination of B02 and AZD1775. D, assessment of the degree of synergy between B02 and AZD1775 in these cells, using the Chou and Talalay method. B02 and AZD1775 were used at constant ratios (25:1 respectively). The CI values for combination of effective drug doses (ED) that result in growth inhibition of 50% (ED50; fraction affected; fa = 0.5), 75% (ED75; fa = 0.75), and 90% (ED90; fa = 0.90) were generated from the conservative isobolograms. The ED50 (red X), ED75 (green crosses) and ED90 (blue circles) graphed against fractional concentrations of B02 and AZD1775 on the y and x-axis, respectively are indicated. The diagonal line is the line of additivity. The conservative isobolograms show CI values less than 1.0 falling below diagonal line, indicate strong synergy. E, Western blot analyses of Rad51 and Wee1 expression at basal levels in representative HNSCC cell lines. The β-actin served as loading control. All treatments were performed in triplicate and each experiment was repeated at least three times. *P< 0.02, indicates significant difference between IC50 mean values for B02 in HPV-negative (blue) and HPV-positive (red) cells.