Rapid, Massively Parallel Single-Cell Drug Response Measurements via Live Cell Interferometry

Abstract

A central question in cancer therapy is how individual cells within a population of tumor cells respond to drugs designed to arrest their growth. However, the absolute growth of cells, their change in physical mass, whether cancerous or physiologic, is difficult to measure directly with traditional techniques. Here, we develop live cell interferometry for rapid, real-time quantification of cell mass in cells exposed to a changing environment. We used tunicamycin induction of the unfolded protein stress response in multiple myeloma cells to generate a mass response that was temporally profiled for hundreds of cells simultaneously. Within 2 h, the treated cells were growth suppressed compared to controls, with a few cells in both populations showing a robust increase (+15%) or little change (<5%) in mass accumulation. Overall, live cell interferometry provides a conceptual advance for assessing cell populations to identify, monitor, and measure single cell responses, such as to therapeutic drugs.

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

“…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.…”

“…Cell mass, by contrast, is the direct result of biosynthetic and degradative processes within a cell and is therefore a more precise indicator of cell size 2 . Cell mass measurements may also be the preferred approach when the outcome of interest is tightly linked to changes in cell mass: for example, during cell death 7 or in response to drug treatments affecting anabolic 8 or degradative 9 pathways. Because the factors that regulate size are still not fully understood, cell mass measurements should be used in conjunction with volume measurements to study the regulation of cell size 10,11 .…”

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.…”

“…Illumination was provided by a 530-nm fiber-coupled LED (Thorlabs). Mouse L-cell fibroblasts and M202 human melanoma cells 32 were cultured as described previously 7,10,33 in phenol-red free Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum (Omega Scientific), 1× nonessential amino acid solution (Invitrogen), 2 mM glutamine (Invitrogen) and antibiotics.…”

Nanoscale fluctuations on epithelial cell surfaces investigated by scanning ion conductance microscopy

“…[11][12][13] However, the optical refractive index of the cells may fluctuate according to the remodeling of the intracellular cytoskeletal network and/or the displacement of subcellular organelles. Thus, non-optical techniques for directly measuring flexible cell surface positions are required to quantify nanoscale fluctuations on adherent cell surfaces.…”