Name: through the looking glass: time-lapse microscopy and longitudinal tracking of single cells to study anti-cancer therapeutics
Uploaded: 2016-05-14T15:00:00
Description: Watch this Scientific Journal Video about Through the Looking Glass: Time-lapse Microscopy and Longitudinal Tracking of Single Cells to Study Anti-cancer Therapeutics at JoVE.com

We thank Joshua Marcus for technical support and Jolien Tyler, Ph.D., Director of the Richard J. McIntosh Light Microscopy Core Facility, for technical advice. This work was supported by funds from the University of Colorado Boulder and the University of Colorado Boulder Graduate School to J.D.O. R.T.B. is partially supported by pre-doctoral training grant from the NIH (T32 GM008759). We thank Karyopharm Therapeutics, Inc. for selinexor and Merck Serono for Kinesin-5 inhibitor. FUCCI plasmids are from Atsushi Miyawaki (RIKEN, Japan) via MTA. mCherry-BP1-2 was from Addgene. HeLa expressing H2b-mCherry and &#946;-tubulin-EGFP are from Daniel Gerlich (IMBA, Austrian Academy of Sciences, Austria).

&#160;The following protocol uses parameters defined by the experiments in Figures 4 and 6 regarding acquisition settings and experimental conditions. Many of these parameters can be modified to fit other experiments (i.e., exposure times, binning, fluorescent channels, etc.). All procedures must adhere to institutional guidelines and regulations and be approved by the institutional biosafety committee. Microscope manufacturer websites contain excellent information for ...

Advantages of Time-lapse Microscopy and Longitudinal Tracking
The microscope is an ideal instrument for longitudinal studies of drug response as it allows investigators to track individual cells and their fates as well as the entire population. Variability in drug response within a population of cells is a major issue for anti-cancer therapeutic design. Longitudinal tracking of single cells allows investigators to observe this variability and begin to understand the underlying...

Live-cell microscopy and longitudinal tracking of single cells is not a new technique. From the earliest microscopes, enthusiasts and scientists have observed and studied single cells and organisms, their behaviors, and development1-3. A famous example from the late David Rogers at Vanderbilt University in the 1950s shows a human neutrophil in a blood smear chasing a Staphylococcus aureus bacterium and eventually the process of phagocytosis4. This live-cell movie is an excellent illustration of how multiple processes can be observed and correlated in a single experiment: sensing of a chemical gradient, mechanics and speed of cell motility, cell shapes dynamics, adhesion, and phagocytosis of a pathogen.
The advent of fully automated microscopes and highly sensitive digital cameras has resulted in an increasing numbers of investigators using microscopy to ask fundamental questions in cell biology ranging from how cells move5,6 and divide7,8 to organelle dynamics and membrane trafficking9-11. Non-fluorescent, brightfield microscopy, including phase-contrast (PC), which garnered the Nobel Prize for Frits Zernike in 1953, and differential interference contrast (DIC) allow for the observation of cells and nuclei but also sub-cellular structures including microtubule bundles, chromosomes, nucleoli, organelle dynamics, and thick actin fibers12. Genetically encoded fluorescent proteins and the development of fluorescent dyes against organelles have dramatically impacted time-lapse microscopy13-15. While not the focus of this article, imaging in cell spheroids and in situ (intravital microscopy) using confocal and multiphoton microscopy represent another expansion of the approach, and there are outstanding articles that use and discuss these approaches16-19.
The responses of cells to anti-cancer drugs or natural products are determined on the molecular and cellular scale. Understanding cell responses and fates following treatment often involves population averaging assays (e.g., immunoblotting, whole well measures), or fixed time-points with immunofluorescent detection and flow cytometry, which measure single cells. Heterogeneity in single cell responses to drugs within a population, in particular in tumors, may explain some of the variability in response seen across cell lines and tumors that are treated with the same drug at saturation. Long-term longitudinal approaches to follow a given single cell or a population of cells is a less common but very powerful approach that allows for the direct study of molecular response pathways, different phenotypes (e.g., cell death or cell division), observation of cell-to-cell variability within a population, and how these factors contribute to population response dynamics20-22. Optimistically, being able to observe and quantify single cell responses will help improve our understanding of how drugs work, why they sometimes fail, and how to best use them.
The technique of long-term time-lapse microscopy, longitudinal tracking, and analysis of drug responses is available to many investigators and can be simple, using only transmitted light to observe phenotype responses20,21. The main components of the approach include: appropriate preparation of the cells of interest, an automated microscope with environmental chamber, a camera integrated with a computer to acquire and store the images, and software to review the time-lapse and measure and analyze the cells and any fluorescent biosensors. We provide a detailed protocol with many tips for conducting time-lapse microscopy of cultured cells for as long as several days using brightfield and/or widefield epifluorescent microscopy. This protocol can be used for any cell line that can be grown in culture to study their responses to anti-cancer therapies. We provide examples of data acquired and analyzed using multiple different genetically-encoded fluorescent biosensors and an example of phase-contrast microscopy, briefly discuss different types of probes, the advantages and disadvantages of long-term time-lapse and longitudinal tracking, what can be learned for this approach that is difficult to understand from non-direct approaches, and some variations that we hope will be of interest and value to inexperienced researchers who have not considered using the approach, and to experienced researchers.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Taxol (paclitaxel)</td>
			<td>Sigma</td>
			<td>T7191</td>
			<td>microtubule stabilizing drug</td>
		</tr>
		<tr>
			<td>etoposide</td>
			<td>Selleckchem</td>
			<td>S1225</td>
			<td>topoisomerase II inhibitor</td>
		</tr>
		<tr>
			<td>selinexor</td>
			<td>Karyopharm Therapeutics</td>
			<td>na</td>
			<td>XPO1/CRM1 inhibitor, gift</td>
		</tr>
		<tr>
			<td>Kinesin-5 inhibitor</td>
			<td>Merck Serono</td>
			<td>na</td>
			<td>gift, also available from American Custom Chemicals Corporation. CAS 858668-07-2</td>
		</tr>
		<tr>
			<td>cell growth medium</td>
			<td>HyClone (Fisher) or Mediatech</td>
			<td></td>
			<td>many companies available</td>
		</tr>
		<tr>
			<td>5% CO2/balance air, certified</td>
			<td>Airgas</td>
			<td>Z03NI7222004379</td>
			<td></td>
		</tr>
		<tr>
			<td>35mm dish, 20mm glass bottom</td>
			<td>Cellvis</td>
			<td>D35-20-1.5-N</td>
			<td>many companies available</td>
		</tr>
		<tr>
			<td>35mm 4 well dish, 20mm glass bottom</td>
			<td>Cellvis</td>
			<td>D35C4-20-1.5-N</td>
			<td>many companies available</td>
		</tr>
		<tr>
			<td>35mm dish, gridded glass bottom</td>
			<td>MatTek</td>
			<td>P35G-2-14-CGRD</td>
			<td>many companies available</td>
		</tr>
		<tr>
			<td>multi-well, glass bottom</td>
			<td>Cellvis</td>
			<td>P12-1.5H-N</td>
			<td>many companies available</td>
		</tr>
		<tr>
			<td>Olympus IX81 inverted epifluorescence microscope</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus IX2-UCB controller</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PRIOR LumenPro200</td>
			<td>Prior Scientific</td>
			<td>Lumen200PRO</td>
			<td></td>
		</tr>
		<tr>
			<td>PRIOR Proscan III motorized stage</td>
			<td>Prio Scientific</td>
			<td>H117</td>
			<td></td>
		</tr>
		<tr>
			<td>STEV chamber</td>
			<td>InVivo Scientific</td>
			<td>STEV.ECU.HC5 STAGE TOP</td>
			<td></td>
		</tr>
		<tr>
			<td>Environmental Controller Unit</td>
			<td>InVivo Scientific</td>
			<td>STEV.ECU.HC5 STAGE TOP</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamamatsu ORCA R2 CCD with controller</td>
			<td>Hamamatsu</td>
			<td>C10600</td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon Eclipse Ti</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon laser launch</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SOLA light engine</td>
			<td>lumencor</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>iXon Ultra 897 EM-CCD</td>
			<td>ANDOR&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TOKAI HIT inclubation chamber</td>
			<td>TOKAI HIT</td>
			<td>TIZSH</td>
			<td></td>
		</tr>
	</tbody>
</table>

through the looking glass: time-lapse microscopy and longitudinal tracking of single cells to study anti-cancer therapeutics

The response of single cells to anti-cancer drugs contributes significantly in determining the population response, and therefore is a major contributing factor in the overall outcome. Immunoblotting, flow cytometry and fixed cell experiments are often used to study how cells respond to anti-cancer drugs. These methods are important, but they have several shortcomings. Variability in drug responses between cancer and normal cells, and between cells of different cancer origin, and transient and rare responses are difficult to understand using population averaging assays and without being able to directly track and analyze them longitudinally. The microscope is particularly well suited to image live cells. Advancements in technology enable us to routinely image cells at a resolution that enables not only cell tracking, but also the observation of a variety of cellular responses. We describe an approach in detail that allows for the continuous time-lapse imaging of cells during the drug response for essentially as long as desired, typically up to 96 hr. Using variations of the approach, cells can be monitored for weeks. With the employment of genetically encoded fluorescent biosensors numerous processes, pathways and responses can be followed. We show examples that include tracking and quantification of cell growth and cell cycle progression, chromosome dynamics, DNA damage, and cell death. We also discuss variations of the technique and its flexibility, and highlight some common pitfalls.

Long-term time-lapse microscopy and direct longitudinal tracking allows for the study of many anti-cancer effects during drug response. Following the general outline in Figure 1, multiple examples of cells are shown expressing validated fluorescent reporters that treated with anti-cancer drugs, tracked, and analyzed using different approaches.
Phase contrast microscopy alone is very informative and robustly repo...

Watch this Scientific Journal Video about Through the Looking Glass: Time-lapse Microscopy and Longitudinal Tracking of Single Cells to Study Anti-cancer Therapeutics at JoVE.com

Through the Looking Glass: Time-lapse Microscopy and Longitudinal Tracking of Single Cells to Study Anti-cancer Therapeutics

Here, we describe a method of long-term time-lapse microscopy to longitudinally track single cells in response to anti-cancer therapeutics.

The response of single cells to anti-cancer drugs contributes significantly in determining the population response, and therefore is a major contributing ...

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