Blog

Functional Characterization of Circulating Tumor Cells

We recently published a paper in PLoS One (go here) about functional characterization of prostate circulating tumor cells.  This work was the product of many people’s efforts, including Erica, Jason, Jim, and Steven in our group–Erica did chip design and fab and SOP development, Jason did initial surface chemistry characterization and capture experiments, Jim did CFD analysis, and Steven characterized prostate cell adhesion parameters.

The point of this paper was to show that we can capture prostate circulating tumor cells by use of a prostate-specific (rather than pan-epithelial) antibody–this is important because the antibodies to epithelial markers (e.g., EpCAM) may suffer when cells undergo epithelial-to-mesenchymal transition as part of the metastatic process.  Also, we showed that we can characterize cells functionally, meaning that we see how the living cells

A circulating prostate cancer cell stained to show the nucleus (upper left), tubulin (upper right), and PSMA (lower left). The bundled tubulin seen at upper right is indicative of drug-target engagement when taxane chemotherapy is used.

respond to their environment, in contrast to the (much more common) enumeration of cells or characterization of genetic material.

We are now looking forward to applying these techniques in clinical trials, with the hopes of proving that functional characterization on microdevices is a better way of predicting which patient should be on which chemotherapy regimen.

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243rd ACS National Meeting

Recently I attended the 243rd ACS National Meeting in San Diego, California, from March 25th to 29th. While there, I gave an oral presentation describing my recent progress in the dielectric measurement of algal lipid content as part of the “Challenges in Algal Biofuels: Biochemistry, Lipid Extraction and Analysis” session.

As described in the algae project page, we are developing a method to rapidly measure the lipid content of algae cells in suspension using dielectric spectroscopy. The ability to measure lipid content in real time will improve the productivity of algal biofuel feedstocks by allowing algae growers to respond to changing environmental conditions and even utilize   environmental stresses like nitrogen starvation to increase lipid output. In this presentation, I described our initial dielectric characterization of algae with a range of lipid contents.

The algal biofuel session was an excellent overview of recent progress in algal biofuel production. Presentation topics included FTIR (Fourier transform infrared) spectroscopy of algae samples, methods for avoiding culture contamination during industrial production, and programs to train the future algal biofuel workforce. Outside of the algal biofuels session, Prof. Carolyn Bertozzi from UC Berkeley gave a fascinating keynote lecture on Bio-orthogonal functional groups for labeling sugars and proteins inside of living systems. Other highlights included a presentation on whispering-gallery mode arrays for extremely sensitive detection of biomolecules, a number of presentations on processes converting algal biomass to biofuels, a poster on exploiting spherical aberrations for rapid autocorrelation of lasers, and a poster by by Pat Coller from Oak Ridge National Lab on chemical reactions resulting from the merger of microscale water droplets. Overall, attending and presenting at the ACS meeting was a rewarding experience which I plan to repeat in the future.

Interstitial flow and tumor cell migration

I’m a graduate student in Professor Roger Kamm’s Mechanobiology Lab in the Department of Mechanical Engineering at MIT. I was an undergraduate researcher in Prof. Kirby’s lab, and I graduated from Cornell in 2008. Recently, we reported on the role of interstitial flow on tumor cell migration. Some of this work was inspired by the things I learned in Prof. Kirby’s lab and it relates to some of Prof. Kirby’s ongoing work, so I thought I’d give an update on the work and some of the things going on here at MIT. 

Early in the metastatic process, cells migrate away from the primary tumor before entering the systemic vasculature to be carried to other parts of the body. Metastases cause the majority of cancer-related fatalities, so preventing cells form leaving the primary tumor could render the cancer more treatable. Consequently, understanding how tumor cells migrate and what stimuli influence how they migrate could provide insight into the development of new cancer therapies.

Cells reside within the extracellular matrix (ECM) in tissues, and the ECM is bathed in a fluid that serves as the transport medium for soluble molecules. When a cancer cell migrates, it moves through the ECM. However, the ECM and surrounding interstitial fluid are not static. Osmotic and hydrostatic pressure gradients across the ECM drive fluid flow around cells, transporting soluble molecules and imparting fluid stresses on the cells. Inspired by some of the work from the Swartz group at EPFL, we thought interstitial flow might alter the physiochemical microenvironment of tumor cells and give some signals to direct migrating cells toward the vasculature.

In order to test this hypothesis, we developed a microfluidic system that allows stable and repeatable flow to be applied to cancer cells embedded within an artificial ECM. We found that interstitial flow does influence the direction in which cells migrate. Surprisingly, we found that in certain conditions, cells migrated upstream, against the flow. We hypothesize that the fluid stresses imparted on cells provide the stimulus for upstream migration, and we have some preliminary evidence to support this hypothesis. However, much more work needs to be done before we can be sure what mechanism might cause the cells to migrate upstream. Our paper in PNAS can be found here:

http://www.pnas.org/content/108/27/11115.short

We’re currently running follow-up experiments to investigate how gradients in fluid pressure across a cell might guide the direction in which a cell migrates. A key part to these experiments is to design experimental platforms that allow precise control over the cell’s microenvironment. Similar to some of Prof. Kirby’s experimental approaches, we use microfluidics as a tool for precisely controlling the concentrations of molecules and the physical forces that a cell experiences. Microfluidics enabled our observation of the effect of interstitial flow on tumor cell migration, and we hope future, improved designs will allow us to investigate the mechanotransduction mechanism by which cells respond to fluid flow. 

New grant to study pancreatic cancer

We recently got NIH approval for a new grant to study pancreatic cancer. This work involves using our GEDI device on the blood of pancreatic cancer patients to try to learn about how pancreatic cancer spreads during early disease.

Pancreatic cancer is the fourth leading cause of death due to cancer in the United States, killing an estimated 35,000 people in 2009. The 5-year survival rate for patients diagnosed with pancreatic cancer is very low–5% or so. A primary driver of this is that close to 80% of patients with pancreatic cancer have metastatic disease upon diagnosis. Almost all patients eventually develop disseminated metastatic disease as a cause of death. This suggests that pancreatic cancer spreads early, and small metastases spread before pancreatic tumors can be detected with current techniques and removed. We hope that we can learn about this process by detecting pancreatic cells in the blood of cancer patients.

This work is in close collaboration with Dr. Andrew Rhim and Dr. Ben Stanger at University of Pennsylvania Medical Center. Their work (to be featured in the Jan 20 2012 issue of Cell) shows that, in mice, pancreas cells can be found in the blood even before the mice develop what we would call cancer. This result is important because it indicates that the spread of pancreatic cancer may start very early in the development of the disease.

The funded work will allow us to show that our GEDI microfluidic device can capture the cells that lead to spread of pancreatic cancer in humans, and allow us to study those cells in detail.

Smith wins Poster Merit Award at 2010 GRC on Microfluidics

I recently attended the 2011 Gordon Research Conference on the Physics and Chemistry of Microfluidics in Waterville Valley, NH.  I presented a poster on “Transport and collision dynamics in GEDI cell capture microdevices” at both the Gordon Research Seminar, organized and run by students and preceding the conference, and at the Gordon Research Conference itself.  I’m pleased to announce that my poster was one of four selected during the Conference to receive a Poster Merit Award, along with a small prize sponsored by Cambridge University Press. A copy of the poster is available on my website.

Smith wins Best Poster Award at the 2010 ASME-IMECE

I presented a poster on “Circulating tumor cell collision dynamics in geometrically enhanced differential immunocapture (GEDI) microdevices” at the 2010 American Society of Mechanical Engineers (ASME) International Mechanical Engineering Congress & Exposition (IMECE) in Vancouver.  I’m excited to report that I was honored with the Best Poster Award among the those presented at the Student Poster Symposium.

Smith presents particle collision dynamics simulations at the 10th NY Complex Matter Workshop

I presented recent work by myselfJason Gleghorn, and Brian Kirby on “Particle collision dynamics in geometrically enhanced differential immunocapture microdevices” at the 10th New York Complex Matter Workshop. We detail numerical simulations and analytical models that predict the collision modes of particles during low Reynolds number flows in microfluidic obstacle arrays, which is important for designing rare cell capture devices that use the obstacles as an antibody-coated capture surface.