Tissue Stem Cells, Tumors, Toxicity and Time

Ann Nguyen:
Welcome, everybody, to this podcast from Cambridge Healthtech Institute for the 14th Annual World Preclinical Congress in Boston, Massachusetts, running June 10-12 in 2015. I'm Ann Nguyen, Associate Conference Producer of the 3D Cellular Models conference. Today we're happy to be chatting with Dr. James Sherley, Director of Asymmetrex LLC, launched in 2013 as “The Adult Stem Cell Technology Center”. He'll be one of our speakers during the session on Applying 3D Models for Toxicology Research.

James, delighted to have you here.

You’ve focused on cancer cell molecular biology and tissue stem cell bioengineering for many years, from your studies to your jobs at Fox Chase Cancer Center, MIT and the Boston Biomedical Research Institute. Why those areas of research and what's it like to work on them now at Asymmetrex?

James Sherley:
I have to say, it's been very exciting to be continuing the development of the research, from my career in Asymmetrex, my new company. I mean, I was like a lot of undergraduates back in the '80s when I first started in science and I had the goal of curing cancer like a lot of people did at that time.

I set myself on a path to become a cancer cell molecular biologist and in my postdoc days, I decided to work on the p53 chain because at the time it was one of the most exciting genes, proteins in cancer biology and I wanted to be involved in that research. And so my goal at the time was to establish cell lines where p53 could be regulated and its level could be changed as a way of understanding what function it played in cells, in terms of regulating their growth.

I did something different than most people were doing at the time. I made inducible cell lines where the goal was past physiological levels of change, so instead of having a big increase in p53 expression, these cell lines would increase p53 maybe 50%, maybe double. And that decision led to pretty much all the rest of the research I've done in my career, because what I found in those engineered cell lines was that when p53 was upregulated slightly, cells that were previously growing like cancer cells start to grow like normal cells, and not only did they start growing like normal cells, they started to grow like normal stem cells.

At the time, this division that I was looking at, which we now associate with asymmetric self-renewal divisions, just seemed odd because instead of the cells stopping in their tracks, which is what people had expected for p53 regulations, some of the cells stopped dividing, some of the cells kept dividing. And at the time I was looking for my first position, I interviewed at the Fox Chase Cancer Center with Al Knudson, and I was much more excited about talking with Al about these new observations I had made than I was even about getting a position there.

Turns out Al decided to hire me and in that meeting, Al raised the issue of something I had forgotten from medical school, and that was the issue of replenishment growth, as he called it. It's a type of growth that takes place in normal tissues where stem cells divide. They produce two different types of cells. One cell is a double stem cell and the other cell is a differentiating cell, and that's what I decided to study as a new investigator, because that type of process, disrupted, could lead to cancer.

The fact that I was looking at p53, a very important gene in regulating growth that if lost, led to tumors, could have this unique ability to make cells grow like adult tissue stem cells, it seemed like a very important area to be working on and that's what I started working on at Fox Chase Cancer Center. It was at Fox Chase Cancer Center that I started to realize that what was going on in my in vitro cell cultures was very likely a reflection of what was going on in the tissues of the body. And one of the problems that the stem cell biology field was facing and continues to face is a problem of being able to produce adults stem cells in large number.

I basically came up with the idea that the problems that we were seeing with just growing tissue stem cells in culture were related to their intrinsic property of asymmetric self-renewal that was regulated by p53. That idea led to identifying pathways which were responsible for p53's ability to regulate cells in a stem cell-like position mode, and that has led to pretty much all of the technologies that are now the basis for Asymmetrex. Our company is focused on producing adult stem cells in large numbers. We'd like to make trillions of cells for application in transplantation medicine.

The asymmetric self-renewal is also associated with a very special form of chromosome segregation and so it's so unique to adult tissue stem cells that these are avenues to finding specific biomarkers for adult stem cells and the company has some of those that are now available that we study. Probably the most important thing is just the idea that one could look at how tissues grow in culture and based on this idea of asymmetric self-renewal being a limiting factor, one can deduce properties of tissue stem cells and that ability is responsible for one of the technologies in the company now, which is a technology for being able to detect tissue stem cells which provides the way to be able to look at how different kinds of new drugs might affect them in terms of being toxic to them.

Everything happening in the company really reflects the development of my career as, first, a cancer cell molecular biologist and then an adult stem cell biologist.

Ann Nguyen:
You're also interested in stem cell kinetics dynamics. How does that relate to 3D cell models and drug toxicity research?

James Sherley:
Yeah so, in the research I described just a moment ago, this sort of critical principal is the idea that our tissues, although they look static, are not. They're turning over constantly. One of the best examples of this in terms of physical architecture, which is what a lot of tissue engineering is concerned with, is the three-dimensional physical structure of tissues and how to mimic that in culture in a way, or in systems that can be used for diagnostics, for drug development, for testing for new drugs.

That feature is what people are focused on, physical architecture, but what's been left out, and which is my interest in this area, is the cell kinetic architecture. That is to say, the cell developmental surface, say the skin, for instance here, that are there today and a couple of months from now, there will be new cells there. Stem cells are in their stem cell compartments. They're dividing, giving life to cells which undergo what are called transit amplifying divisions as they differentiate. Ultimately all those cells stop dividing. They perform their function for some amount of time and then they are lost either through apoptosis by other cells or by just the natural way cells sort of get sloughed off.

That architecture, that kinetic architecture, is probably very important for how tissues function, how differentiation occurs, how they respond to diseases, how diseases emerge, like cancer, because this so-called turnover division or renewal division takes place in pretty much all of our tissues, even in the brain. So what I'm excited about, is coming to this conference, is sort of infusing with the idea that we not only need to worry about physical three-dimensional architecture, we also have to think about the cell-dynamic three-dimensional architecture, the dimension of time, because this constant -- right now, as far as I know, there are no three-dimensional models that I've heard about where one of the features that's incorporated is the turnover of cells in the engineered system.

Ann Nguyen:
Your intriguingly titled presentation on June 11 discusses “When Time Is the Third Dimension: Combining Computer Simulation and Primary Tissue Cell Culture to Identify Tissue Stem Cell-Toxic Drug Candidates”. What's the main theme you'd like to convey?

James Sherley:
I'm coming to a conference where everybody's focused on three-dimensional physical structure and I really don't have any three-dimensional physical structure to talk about. Our work is really focused on cell kinetics, not to mention time. Now, one of the things I recognize is that everybody sort of starts in cell culture and what we call in vitro studies of cells, talking about two-dimensional systems, because that's when cells are growing flat on plastic. Tissue engineers are talking about adding a third dimension -- height, if you will -- so you have something that looks like a tissue, but what's missing again, is the fourth dimension. I decided to have a title that would talk about our third dimension and in the work that's going on at Asymmetrex, the third dimension is time.

What we are currently doing is we develop technology so we can take any primary tissue, put the cells in culture -- no isolation -- just put the associated cells in culture and follow in a two-dimensional format. The third dimension for us is time, so we look at how total cell number in the culture divides over long periods of time and within that information of that total cell number, there is, in fact, component information for what stem cells are doing, what transit amplifying cells are doing and even what differentiated cells are doing.

If one has a good model for describing those underlying components, one can extract them from cell kinetic data, and this has become a very strong technology within Asymmetrex. We are partnering now with a company called AlphaSTAR Corporation, which is a computer simulation company, and we now have a method by which we can grow, in culture, primary human tissues, keep track of how the cell number, that third dimension of time for us, changes over time and we can then take that data and by computer simulation, we can extract from it information about stem cells.

This is one of the first opportunities really to be able to get information about whether stem cells are proliferating, whether they're dividing and producing differentiated cells, or in the case of toxic drugs, whether or not they are being killed by those drugs. I really wanted to say to this group that there is another dimension we need to think about. We call it our third; for them, it would be the fourth. The kinetic architecture, back in tissues in the body, the kinetic architecture is superimposed on the physical 3D architecture and they go hand in hand. Even though we’re looking at events that are taking place in flatland, two dimensions in the cell culture dish, they are in fact quite relevant to what's happening in the third dimension, in tissues, because of the time component.

So I really wanted to have a title that was going to grab everybody's attention about the fact that we're doing something that's really different, but still quite relevant to where tissue engineering is going, if it's going to really reflect, in full capacity, the properties of human tissues.

Ann Nguyen:
Makes sense. Thank you, James, for giving us a glimpse of your contributions so far. It's definitely fascinating work and we'll hopefully see its preclinical impact lead to positive results for future patients. And of course, we're looking forward to your talk in June this year.

That was James Sherley of Asymmetrex. He'll be speaking at the 3D Cellular Models conference at the upcoming World Preclinical Congress, which runs June 10-12 in Boston.

If you'd like to delve into these topics more deeply with him in person, visit www.worldpharmacongress.com for registration information and enter the keycode, “Podcast”. I'm Ann Nguyen. Thanks for listening.