Fig. 2: Measuring the mass response of cancer cells to treatment.

a First, isolated cancer cells are dosed and incubated with drugs to be tested (blue and purple) or vehicle-treated control (gray). The mass of individual cells from each population are measured by the SMR instrument to determine the mass distribution of treated cells (blue and purple curves) and untreated reference cells (gray curve). b Mass distributions of the treated and reference cells are compared to determine the mass response to treatment. The mass response signal is the statistical distance between the two mass distributions calculated by the Earth Mover’s Distance (Methods). Comparing two similar distributions (purple vs gray) yield a smaller mass response signal, whereas comparing diverging distributions (blue vs gray) results in a larger mass response signal. c Schematic representation showing the structure of the mass response test. Vehicle-treated control cells are measured both before and after the cells that are treated with the drugs being tested. This approach enables measuring a baseline mass response signal between two control populations (reference vs control), which captures possible time-varying mass changes due to in vitro effects. d Mass response plot showing the mass response signals of the control and treated cells shown in (a) and (b). 95% confidence intervals, shown as lines overlaid on each point, are calculated by bootstrapping using single-cell mass data (Methods). The p values are determined by comparing the mass response magnitude difference of TEST and CTRL to a “limit of decision” threshold of 3% (Methods). * indicates p < 0.05, ns indicates p > 0.05.