Physics Methods Aid Cancer Research

By Calla Cofield

Physicists are assisting in the fight against cancer in a variety of ways, as illustrated by two examples recently presented during the APS March Meeting. Krastan Blagoev, director of the Physics of Living Systems program for the National Science Foundation (NSF), is applying theoretical physics knowledge to the analysis of clinical cancer data and is working on a program to bring these two areas together. Lydia Sohn, at the University of California, Berkeley, is developing new techniques for cancer detection and imaging, while studying the fundamental mechanics of cancer cells.

The National Cancer Institute (NCI) has already invested in bringing physicists together with cancer researchers. In 2009, the NCI established 12 Physical Sciences Oncology Centers at major institutions throughout the U.S.

During a press conference at the meeting, Sohn showed reporters images that looked vaguely like shots of the night sky: speckles of light scattered against a dark blue background – a vast frontier to be explored. In this case, those bits of light are fluorescent markers attached to a particular type of biomarker called CCR7, which appears on the surface of breast cancer cells. CCR7 is of interest to cancer researchers because its high expression is associated with lower survival rates among patients. Sohn and her group are the first to attempt to map the spatial distribution of those markers on the surface of breast cancer cells.

To individually image the receptors, Sohn and her group used a technique called STORM (stochastic optical reconstruction microscopy). STORM allows the user to stack images of the same sample area and reconstruct them into a 2-D or 3-D image with nanoscale resolution.

Sohn and her group would like to find out how mechanical forces and chemical cues change the spatial distribution of markers like CCR7, and eventually, understand how their presence is linked to patient survival rates.
Sohn completed her Ph.D. at Harvard on superconductivity. She said her background and training have proved valuable as she pursues the grand challenge of fighting cancer.

“...I think what we’re bringing in is a very…quantitative way of looking at things. In the end, the biologists still know how to do it best, but physicists bring new and innovative things to the table,” she said.
Krastan Blagoev, director of the Physics of Living Systems program at NSF,  is a theoretical physicist working on cancer via the clinic.

Blagoev is also a theoretical condensed matter physicist by training. Speaking on behalf of himself, he argued that theoretical physicists can not only be helpful, but might even be necessary to unearth the driving forces behind cancerous tumor growth.

Blagoev and colleague, Tito Fojo, a medical oncologist in the Center for Cancer Research at the NCI, are analyzing data from clinical trials in oncology to study tumor growth.

Exponential tumor growth suggests that the cancer cells are dividing more like embryonic stem cells, into two new cells that survive long-term and continue to divide. The indication – a faster rate of tumor cell production–is grim. It is these “dividing cancer cells” as Blagoev labels them, which would need to be targeted with new therapies.

The next step in evaluating this theory is to show that this exponential growth occurs across all patients. Blagoev said he had found a technique to rescale patient data into a single analysis. Theoretical physicists specialize in the analysis of complex systems and can provide unprecedented expertise in data analysis. Blagoev also believes that because of the complexity of cancer– the incredible variety of cells that can arise even in one patient – that a physics approach might help identify more fundamental drivers behind cancer behavior.

“This idea of creating simple theories is the essence of physics,” said Blagoev. “I think that what physics can bring here is to try and find common things rather than the differences between different cancers. We sort of have to forget about the details and look at the forest.”

Blagoev wants to start a program that will join theoretical physicists with clinical cancer researchers and oncologists to share ideas and develop project proposals.

“It seems to me, based on my experience and what I know of the work of others, that there is a big need for theoretical physicists to enter the labs of clinical oncologists to work with them, and look at the data that’s never been published, but that’s available in their labs. We’re looking for people who would be interested to come for 5 or 6 days and actually spend 8 to 10 hours a day working with colleagues from the other field to develop ideas,” said Blagoev. “In my experience, when clinical oncologists work with theoretical physicists, I think they understand the power of quantitative thinking in terms of simple models. And they see the value this can have to cancer research.”

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