High times for high content screening

It is a nice little twist of fate that money from one of the most toxic substances ever produced is partly responsible for the development of a new technology that allows biologists to screen other toxic substances before they wreak their damage.

Some of the money generated through litigation against tobacco companies in the 1990s in the US was used to put together a new company that developed the first high content screening instruments.

That money helped set up the Life Sciences Greenhouse of Central Pennsylvania in Pittsburgh, which has a mission to commercialise bioscience technologies, as well as a company called Cellomics, set up by Carnegie Mellon University’s Professor Lans Taylor in 1996.

Taylor had the idea of combining three different technologies in one to allow researchers to screen compounds for activity against cells or their contents.

Those technologies were microplate readers, microscopes and flow cytometry, which combined have produced a new methodology for looking at what happens on a cell by cell level.

High content screening (HCS), also known as high content analysis (HCA), is a slower but deeper technology than its predecessor, high throughput analysis, which has long been used in the pharmaceutical industry.

Rebecca Palmer, a senior research scientist with Cellomics, now part of Thermo Scientific, describes high throughput screening as “a plate reader on steroids”. HCS, on the other hand, has a little more substance.

“I teach a course [in HCS] and I like to tell the students that a picture is worth a thousand words, but it’s worth more than a thousand data points,” she says. “But what do you do with all of that data once you have it?”

HCS aims to combine the statistics generated by flow cytometry with the data gained from microplate readers and what you can see through the microscope. All in one instrument, it means that scientists are able to differentiate between cells in a thoroughly unbiased manner.

HCS takes the prejudice of the researcher out of the equation, Palmer says. “And it doesn’t get tired like a post-doc or a grad student, it does it the same way over and over, and it can run literally 24/7, completely unattended.”

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Kill library

Cellomics began manufacturing its ArrayScan instrument in 1999, and the first arrived here in Australia at the University of Queensland’s Diamantina Institute in late 2007.

In the early days of Cellomics, company researchers were looking at the fingerprints of drugs: they had been given a “kill library” by the US Government, containing all of the most toxic substances known, and screened them against cells to see what happened.

“They were looking to see if there were certain patterns and markers and changes,” Palmer says.

“The government was interested in this because if they knew someone they thought was a bioterrorist and they suspected they had dosed the water or the food supply, we could run the test and tell what the poison was.

“We could even tell if it was, God forbid, a new agent that we’d not seen previously. HCA can be used in a similar way in drug discovery; we can reduce the number of failures prior or during clinical trials.”

Sharon Guffogg, cell biology product manager with local Cellomics distributor Millennium Science, says this is where HCA comes into its own: it hits at the beginning.

“This is why pharmaceutical companies are really interested in this technology,” she says.

“HCA has the potential of reducing the time it takes to get a drug to market, therefore increasing the intellectual property value of the drug. HCA also can reduce the number of false positives during the drug discovery phase.

“If a pharma company can see early on that a new drug compound isn’t working, they can cull it immediately – they start knocking down those false positives.”

While pharma drives the widespread uptake of the technology, academia isn’t that far behind. Palmer says there were several key academics who were early adopters of the technology, and the establishment of centres like the one in Pittsburgh, specifically for early compound identification, has been central to this.

For academic groups, however, the possibilities of the technology are even broader than for pharmaceutical companies. In addition to the group at the Diamantina using HCS, the Monash Institute of Medical Research and the Peter MacCallum Cancer Centre are also using the technology, for a variety of purposes.

One is RNA interference work, using both short hairpin and short interfering RNAs, which when used in conjunction with HCA allows the identification of the function of genes that no one is quite clear about.

Studying toxins is an obvious application, but Palmer and Guffogg are also noticing interest from the wider life sciences, such as neuroscience, and even from materials science.

“What they wanted to see was different materials on slides or surfaces and how that affects stem cell growth,” Guffogg says.

“Rather than the cells themselves, they are looking at what changes are made and what makes them differentiate when surface materials are altered. It is fascinating when you start delving into nano-technologies and materials science and surface technologies. It’s a whole other realm.

“One of the key points to this technology is that we take something that is subjective – the image with pretty colours in the nucleus and pretty shapes in the cytoplasm, or a shape being different – and transferring those differences in colour or shape into numbers that mean something.

“Traditionally all cell screening assays are done on microplate readers and you get a single number – or data point – out of a well. No matter what’s in the well, you get a single number. If you want to delve into the internal processes happening in the cell, you have to go to a microscope to look at it at cell-by-cell.

“We are also seeing interest from – and benefit to – users of flow cytometry. Biologists using flow cytometry are used to the large amount of data that they can get out of these systems, but again, it is still another instrument where you can’t actually see anything.

“It is a lot of data that relies on fluorophores giving you the correct answer based on an assumed knowledge of how they react in the environment of the cell. The Cellomics technology has combined the amount of data obtained with flow with the benefits of visualising the cells that you are interested in – many data points from a single image.”

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Future applications

Palmer says Cellomics’s academic clientele has now reached 40 per cent of their user base, which is where the company always wanted to target. And biotech has had a big uptake as well.

“The FDA just cleared Geron Corp to do the first stem cell-based therapeutic trial. Geron has our technology, so we are anxiously watching to see the data they generate.”

The use of HCS in both pharma and biotech will grow, particularly due to moves to phase out animal testing in some countries. With a total ban with few exceptions, animal testing for cosmetics will be illegal across the EU after 2009. Imported cosmetics from countries that use animal testing will also be banned.

“In the US we are probably five years behind, but we will probably see the same thing, mainly because animal testing is not very predictive,” Palmer says.

In the future, users can look forward to the instrument manufacturers placing a great deal of emphasis on information technology and software, Palmer says.

“There are a lot of players now in the field with similar hardware, but now that you’ve got all of this data, what are you going to do with? Refine it, help me shape it, help me get it into easily understandable formats.

“And we are really getting to the point where the modularity is absolutely essential, because some people want some things and some want a very different thing, but they don’t want to pay for the whole lot.

“They want to keep all of the data integrated and not have to put it into another platform. We need to try to make that as easy for them as possible. They are not statisticians – they are biologists and they want to do the science. And they want it all to happen together, seamlessly.”