Rapidly quantifying drug sensitivity of dispersed and clumped breast cancer cells by mass profiling

Abstract

Live cell mass profiling is a promising new approach for rapidly quantifying responses to therapeutic agents through picogram-scale changes in cell mass over time. A significant barrier in mass profiling is the inability of existing methods to handle pleomorphic cellular clusters and clumps, which are more commonly present in patient-derived samples or tissue cultures than are isolated single cells. Here we demonstrate automated Live Cell Interferometry (LCI) as a rapid and accurate quantifier of the sensitivity of single cell and colony-forming human breast cancer cell lines to the HER2-directed monoclonal antibody, trastuzumab (Herceptin). The relative sensitivities of small samples (< 500 cells) of four breast cancer cell lines were determined tens-to-hundreds of times faster than is possible with traditional proliferation assays. These LCI advances in clustered sample assessment and speed open up the possibility for therapeutic response testing of patient-derived solid tumor samples, which are viable only for short periods ex vivo and likely to be in the form of cell aggregates and clusters.

Live-cell mass profiling: an emerging approach in quantitative biophysics

“…However, assuming that cell composition does not vary dramatically among treatment groups, the specific value of a is often not important. This is a reasonable assumption, for example, when making relative measurements of cell mass between populations 37 or when measuring the rate of increase in mass over time, which is often normalized to cell mass 21,35 .…”

“…These images are then combined to compute the optical path length distribution across the cell with subnanometer precision 34 ( Table 1 ). This approach has been used to longitudinally track the effects of drug treatments on the growth rate of dozens to hundreds of individual cells within a population in order to assess drug efficacy and variability and quantify drug sensitivity or resistance 9,35 . Phase-shifting interferometry has also been used to track shifts in mass distribution within individual cells during mechanical stimulation 36 and to study the mass accumulation and intracolony mass redistribution characteristics of human pluripotent stem cells during self-renewal and early differentiation 37 ( Fig.…”

“…Ergodic rate analysis is a flexible technique that can measure any cell characteristic that can be labeled fluorescently over the course of the cell cycle—for example, the levels of phosphoproteins—and has significant promise for elucidating the relationships among cell volume, mass and cell-cycle progression. The ergodicity requirement, however, means this approach cannot measure mass responses of single cells to discrete perturbations 7,35 .…”

Hybrid random walk-linear discriminant analysis method for unwrapping quantitative phase microscopy images of biological samples

“…1,2 These samples typically consist of single cells or cell clusters, which are imaged over time to track changes in dry mass 3 or refractive index, 4,5 for example, to monitor cellular growth [6][7][8] and growth regulation, 9 quantify intercellular interactions 10 or subcellular features, 11 and measure mechanical properties of cells, such as red blood cells. [12][13][14] In any interferometric QPI dataset, the phase ambiguities inherent to QPI have to be removed to achieve continuous phase distributions and precise, reproducible measurements of these samples.…”

Label-free high-throughput cell screening in flow

“…Cell protein content measurement can be used in many biomedical applications such as blood doping detection [1], infection monitoring [2], drug development and screening [3], studies of necrosis and apoptosis [4,5], cell cycle progression and differentiation [6][7][8], and in cancer diagnostics [9][10][11]. Current methods for cell protein concentration measurement include electrical methods based on dielectrophoresis [12], mechanical methods based on microchannel cantilevers [1], and optical methods based on scattering patterns [13], emission spectra of external cavity lasers [14], and holographic and phase microscopy [15][16][17][18].…”