Q&A: Kandice Tanner on applying physics to cancer research

Growing up in Trinidad and Tobago, Kandice Tanner went to a school where she was one of only a dozen girls among 1200 pupils. She had switched from an all-girl school to avoid the distractions of socializing and to take the more advanced math classes offered at the boys’ school. “Being submerged in an all-male environment early on was beneficial to me,” Tanner says. “I felt comfortable with guys, and more important, I knew I could hold my own in a male-dominated environment.”

In 1998 she came to the US to do her undergraduate studies at South Carolina State University, a historically black college and university (HBCU). She went on to earn her PhD in physics at the University of Illinois at Urbana-Champaign in 2006. Her research involved mapping functionality of the mammalian brain. She then spent her postdoctoral years learning biology.

Now Tanner holds a prestigious Stadtman principal investigator post at the National Cancer Institute at the National Institutes of Health in Bethesda, Maryland. She runs a group that uses biophysical tools to probe how physical properties of the tissue microenvironment influence the spread of cancer from its initial location to other parts of the body. (For more on how researchers are employing physical and mathematical approaches to understand the development and spread of cancer, see Physics Today, June 2019, page 26 .)

PT: What made you decide to go into physics?

TANNER: I was good at math, but I also liked languages. In Trinidad we had to select our subjects at age 14. My mother made a deal with me. She said, “Do physics, sciences, and math. And if you really hate it, I will pay for you to do languages later on.” I did it, and I stuck with it.

PT: How did you end up coming to the US?

TANNER: The US embassy held college fairs, and schools from the US would come to recruit students from Trinidad and Tobago. The boys’ school sent us to the fair on a school outing. I met a woman who asked if I was interested in coming to the US. I said “not particularly"—I had already been accepted to the University of the West Indies. But after I told her my SAT scores, she said she would give me a full scholarship. I went home and told my parents, and my mother and I went back the next day. The woman took my information, and two weeks later I got an offer letter from South Carolina State University. So I went there and got a dual degree in electrical engineering and physics.

That was an eye-opener. South Carolina State is an HBCU, which I didn’t know until I came. I now understand why HBCUs were created, but at the time, it just didn’t dawn on me that one would need a school dedicated to one race versus another.

I am glad I went there. Until I came to the US, I hadn’t appreciated that I’d grown up with the luxury of not having to deal with people’s preconceptions about race. When you are treated based on what you do rather than on what you look like, you have more freedom of expression, you are able to contribute more, you are less afraid of what people think of you, and you are less burdened by the idea that people may treat you differently. Those are some of the intangible benefits of not having to identify by what you look like.

In the US, we still have a ways to go . Support of HBCUs is critically needed to ensure both their success and the ability to diversify the workforce.

PT: How did you choose your research group at Urbana-Champaign?

TANNER: First-year graduate students went to seminars to hear about professors’ work and to find out who had money to support students. It was a matching process. I started off in a condensed-matter lab there—I had done an REU [Research Experiences for Undergraduates] when I was an undergraduate and loved the research. But I kept thinking about the biophysics project that my eventual adviser, Enrico Gratton, had presented. So I went to the chair and said I wanted to change groups.

PT: What intrigued you about Gratton’s work?

TANNER: Enrico was looking at the functional relationship between neuronal activation and blood flow in the brain. How do we know what part of the brain is activated? He was using light to do the equivalent of what magnetic resonance imaging does, but on a faster timescale and with high spatial resolution. It fascinated me. And the idea of being able to do this in a living animal caught me. My PhD was done on the brains of living cats. We used broadband near-IR to look at fingerprints of components of the brain—oxyhemoglobin, deoxyhemoglobin, water, and so forth.

The question was, “How do we separate absorption and scattering events in thick tissues to identify changes due to neuronal activation?” The idea was to map the brain with sufficient temporal and spatial resolution to understand cognition.

To further understand our in vivo results, we also performed phantom experiments and simulations, where we would build models to approximate the optical properties of the human brain. There was a period when I would be going to the lab with gallons of 2% milk, which has absorption and scattering properties comparable to the gray matter found in the human brain.

PT: How did you expand beyond your doctoral research?

TANNER: My adviser had two labs. One was in photon migration, where I was for my PhD research. The other was using fluorescence dynamics to look at processes in living cells—for example, how different organelles contribute to cell motility. People came from all over the world to learn fluorescence techniques from him, and I thought it would be stupid not to learn from him while I was there. He moved to the University of California, Irvine, and I moved with him to do a postdoc. I immersed myself in a different type of imaging.

I was also thinking deeply about what I wanted to do on my own. We had a fruitful collaboration with a biology lab, and I had an epiphany. You can build all the sexy instruments you want, you can have all the analysis and algorithms, but the reality was that we relied on the biologists to make samples for us. So I thought that if I wanted to do this level of exciting research, I could either rely heavily on collaborators or I could learn to do it myself.

I did a postdoc in Mina Bissell’s biology lab at Berkeley. I literally followed a graduate student and a postdoc around. I learned how to culture cells, do 3D culture assays, cloning, immunostaining, western blots. They taught me everything. Now when my students and postdocs are doing things, I have a deeper understanding of their experiments.

PT: Why did you go to NIH?

TANNER: A physics department may or may not be appreciative of some of the interdisciplinary aspects of what I do. And if publishing in Physical Review Letters is the standard for obtaining tenure, then such a department would not be helpful for me. I wanted to focus as much as possible on science, and I thought that at NIH I could bridge the fields of physics and biology and be successful.

PT: How did you know to think of those things at that early stage of your career?

TANNER: Enrico was very transparent, and early on he talked to me about tenure. He also warned that people would try to “minority hire” me. He said, “If someone wants you to do a Skype interview, be careful"—they may do that so they can say they interviewed and tried to find a minority candidate. Sure enough, some schools started to call me in my third year of graduate school. I was not close to graduating. Because he had warned me, I didn’t respond. I had a “woke” adviser before the expression “woke” existed. I simply had the right mentors.

PT: Were you already doing cancer research before you got the appointment as a Stadtman investigator at NIH?

TANNER: You didn’t have to work in cancer to be a Stadtman investigator—they just wanted people with good ideas. In Mina’s lab I did normal epithelial biology in hopes of understanding what may go awry in diseased phenotypes. On the surface that may not seem cancer related, but the questions really came down to what governs normal tissue homeostasis, and then what key steps drive malignant transformation. So my idea was to take what we already understood from normal cells to understand strategies tumor cells might use to form a new lesion during metastasis.

PT: What is your group investigating?

TANNER: After tumor cells leave their original site, a first step in metastasis, they have to adapt to both the mechanical and chemical cues in a new environment. We built an optical tweezers setup and use it to steer beads around tissues in zebrafish. By looking at the displacement of the beads, we can learn about the mechanical properties of the tissue.

One project we are especially excited about is using zebrafish to model aspects of human metastasis. We introduce human tumor cells into the fish and look at the early stages of organ colonization. This is easier to see in fish than in mice, because fish are smaller and light scattering is less pronounced. And it turns out that metastasis occurs in the same organs in mammalian systems and zebrafish. We have found that there are physical properties of the microenvironment that regulate the early stage of metastatic selectivity. Now we are building on that; we want to understand the cues, shift the colonization, understand what governs organ targeting that will be relevant to human diseases.

PT: What do you like most, and least, about being at NIH?

TANNER: You get a fixed amount of money, which gives you flexibility to plan—assuming Congress passes a budget or a continuing resolution. That’s one of the benefits. And I was surprised at how collaborative the institute is. When I first got there, my new freezer broke down. Because I was so new, the freezer was not yet connected to the remote alarm, and the cells I brought from Berkeley died. I sent out an email to everyone in the building saying I needed cells and materials. Practically before I could hit “send,” people replied with offers of help. And you see those types of emails frequently. A bit later, I was vacillating between working with mice or with zebrafish. I knew I had to go in vivo. I picked up the phone and called a senior director. We talked for 45 minutes, and she sent someone over the next day to offer advice. I enjoy those aspects of NIH.

The challenge comes down to things we have no control over. We’ve had around six government shutdowns. That is always very frustrating, because it’s actually illegal to work when there is no funding. You lose time preparing to shut down, and then you lose time as you start back up. If you have postdocs or trainees, they can’t work on experiments or on paper revisions. And new people can’t start.

PT: Where do you see yourself in 5 or 10 years?

TANNER: For now I am focused on my scientific goals. I’d like to flesh out the question of how cells sense their environment. It is fascinating to me how cells interpret cues that may be physical or chemical to make cell fate decisions. Can a physical cue override a chemical cue? If so, in what regime would this be applicable? Can we delineate a hierarchy for the cues that cells sense?

PT: Are you interested in going back to Trinidad and Tobago?

TANNER: I’d like to host high school or university students or participate in a joint program. I feel strongly that I need to remember where I came from.