David Rimm on the value of Imaging Mass Cytometry for immunology applications at Yale

Take a moment to remember your favorite painting, a classic that brings you comfort and fills you with introspective thought. Something like Starry Night by van Gogh or Guernica by Picasso. Now imagine that instead of showing the full image, we break it all down inch by inch, pixel by pixel into a collection of dots grouped by color. Does knowing that 80% of Starry Night is blue or that 10% of Guernica is white convey the same message as seeing the image as the artist intended? Even though all the colors are represented, the work of art disappears in the absence of spatial organization. For David L. Rimm, MD, PhD, Professor of Pathology and of Medicine at the Yale School of Medicine, spatial information brings everything together for a better understanding of the cellular environment. That is the power of imaging in scientific studies. The new Hyperion™ Imaging System brings together imaging with proven CyTOF^® technology, pushing highly multiplexed immunohistochemistry-based imaging to the forefront of translational research. Rimm and colleagues are leading the way.

Recognizing early potential

Rimm’s familiarity with highly multiplexed imaging technology began in 2014 when he was writing a commentary on two groundbreaking Nature papers on novel imaging methods. Based on two different techniques, the publications coalesced on the same theme: the need for higher-order imaging technology using metal-tagged antibodies. Rimm recalled that the techniques “were similar approaches but they had some subtle differences in the mechanism.” Rimm recognized the value of these techniques and saw this as the future path for his lab. He saw great potential in the Hyperion Imaging System, where a precisely directed laser beam collects biological samples stained with metal-tagged antibodies and CyTOF technology enables the detection of different metal tags based on mass rather than on wavelength, which is the basis of relatively low-plex immunofluorescence.

For Rimm, this highly multiplexed imaging technology, Imaging Mass Cytometry™, represents the future of pathology-based studies. “A key current clinical problem in pathology,” said Rimm, “is the ability to define levels of protein in tissue so that we are maintaining the spatial information and the localization of different cell types.”

He added, “Research in my lab is related to biomarkers that either predict outcome or response to therapy or to a drug. I see the Hyperion Imaging System as a valuable discovery tool that can provide information about which molecules are most important to predict response to therapy. It gives you information that few other tools can provide: the ability to look at 30 different things at once yet maintain the two dimensional spatial information, giving us the power to discriminate biology beyond a single point measurement.”

Developing biomarker signatures

Rimm’s lab focused on applying Imaging Mass Cytometry technology to two innovative initiatives. The first was discerning key signaling pathways regulating biological effects of targeted therapies in breast cancer. Using banked samples from cancer patients treated with trastuzumab (Herceptin®), Rimm’s group simultaneously analyzed the expression levels of 17 protein markers using Imaging Mass Cytometry. By concurrently staining with a multitude of markers, he said, we can examine “the signaling molecules themselves, the receptors and the molecules in the signaling cascade that occur after the receptors are bound.”

For the second effort, they used Imaging Mass Cytometry to better understand the tumor microenvironment of lung cancer, with a particular emphasis on tumor infiltrating immune cells. This project used Imaging Mass Cytometry to develop a protein-based signature associated with patient response to therapy, with an ultimate goal to more precisely tailor therapy for cancer patients receiving immunotherapy.

The Hyperion Imaging System requires relatively small quantities of tissue to detect large numbers of proteins while maintaining spatial context. This is a key benefit when analyzing small biopsies or relatively rare or precious specimens. Rimm’s training set of tissues for the Herceptin study consisted of tumors from more than 61 patients.

Examining 17 markers simultaneously offered the advantage of identifying a wide variety of cells and activation states without the need for serial sections. Speaking to this point, Rimm said that when using serial sections, it’s unclear if the markers are actually in the same cell. It’s then necessary to take a population approach comparing expression of markers 100 µm apart. Imaging Mass Cytometry on the Hyperion Imaging System provides “unequivocal evidence that they are in the same cell, because they co-localize to the same pixel.”

Looking ahead

For Rimm, the real power of this technique will come from uncovering unanticipated correlations between large numbers of protein markers and patient outcome. Imaging Mass Cytometry enables simultaneous analysis of large numbers of protein markers to more efficiently discover new predictive signatures composed of smaller numbers of markers that may ultimately have clinical utility.

Scientists can also use Imaging Mass Cytometry to identify relevant biomarkers of disease progression and to better understand how cancer arises. When faced with the complexities of a heterogeneous disease state, looking at as many markers as possible can create insightful results that could ultimately lead to improved prognosis and therapies—and by extension improved care for cancer patients.

Going forward, Rimm hopes that Imaging Mass Cytometry will “enable us to answer key biological questions.” Moving away from the one-dimensional data of mass cytometry experiments into two or three-dimensional spatial data will advance future biological exploration. With a sense of reserved excitement, Rimm said he believes that “we’re just at the very beginning of finding out what the Hyperion Imaging System can do.”