Fig. 1
Candidate indicators of anti-cancer drug resistance in cell lines. A The graph indicates anti-cancer drug treatment of cells, and measures the number of living cells, over a certain period of time. The y-axis refers to the number of cells and the x-axis refers to the concentration of anti-cancer drugs. y0 is the number of cells just before exposure to the anti-cancer drug, and yctrl is the number of cells after a certain period of time in the control group of cells that are not treated. IC50 refers to the drug concentration when the number of cells is 50% of that of the yctrl, regardless of the value of y0. GI refers to the inhibition of cell proliferation so that the (yctrl − y0) value becomes a 100% cell proliferation rate. GI50 is the concentration of the drug at which cell proliferation is reduced by 50%, i.e. the concentration at which the number of cells is \( \left({y}_0+\frac{y_{ctrl}-{y}_0}{2}\right) \), and GI100 is the concentration at y0. B In graph A, replacing the cell population with a normalized growth rate takes into account the cell doubling time, resulting in a y-axis value of between − 1 and 1. At this point, the drug concentration corresponding to the y-axis value of 0.5 is the GR50, and the concentration corresponding to 0 is the GR100. This figure is an adaptation of a figure published previously by Brooks et al. [8]