The artistic masterpiece above, reminiscent of a stained glass window, is the work of Michael Angelo—no, not the famous 16th Century Italian artist, but a 21st Century physician-scientist who’s out to develop a better way of looking at what’s going on inside solid tumors. Called multiplexed ion beam imaging (MIBI), Angelo’s experimental method may someday give clinicians the power to analyze up to 100 different proteins in a single tumor sample.
In this image, Angelo used MIBI to analyze a human breast tumor sample for nine proteins simultaneously—each protein stained with an antibody tagged with a metal reporter. Six of the nine proteins are illustrated here. The subpopulation of cells that are positive for three proteins often used to guide breast cancer treatment (estrogen receptor a, progesterone receptor, Ki-67) have yellow nuclei, while aqua marks the nuclei of another group of cells that’s positive for only two of the proteins (estrogen receptor a, progesterone receptor). In the membrane and cytoplasmic regions of the cell, red indicates actin, blue indicates vimentin, which is a protein associated with highly aggressive tumors, and the green is E-cadherin, which is expressed at lower levels in rapidly growing tumors than in less aggressive ones. Taken together, such “multi-dimensional” information on the types and amounts of proteins in a patient’s tumor sample may give oncologists a clearer idea of how quickly that tumor is growing and which types of treatments may work best for that particular patient. It also shows dramatically how much heterogeneity is present in a group of breast cancer cells that would have appeared identical by less sophisticated methods.
Angelo got the idea for MIBI during his pathology residency at University of California San Francisco. While learning to process tissue biopsies, he discovered that pathology techniques had changed little over the years: samples were sliced into thin sections, stained, and viewed under the microscope. The staining could reveal the level of one telltale protein at a time. That led to the tedious process of removing the sample, staining for another protein, and looking through the microscope again. Newer imaging techniques used fluorescently labeled antibodies. But that, too, had limitations. Only three different antibodies could be used at once before the fluorescent colors would overlap and blur.
To solve this problem, Angelo decided to label the antibodies with unique metallic elements, each of which has its own distinctive atomic weight. As a finely focused ion beam scans an antibody, it blasts off the metal atoms and sweeps them into a detector that identifies the metal by its unique weight and also measures its quantity in the cell. This approach has the potential to visualize up to 100 proteins at once in a single cancer cell without spectral overlap. So far, Angelo has reached 10 labels at once , and plans to do even more as he uses a NIH Director’s 2014 Early Independence Award to set up his own lab at Stanford University in Palo Alto, CA.
As MIBI and its analytical power advance, Angelo would like to apply the technology to study some of the tens of thousands of stored breast cancer specimens. The hope is two-fold. First, this study may provide a more complete picture of the distinctive protein patterns, or signatures, of normal breast tissue, ductal carcinoma in situ (a common non-invasive form of breast cancer that is contained within the lining of the milk ducts), and invasive breast cancers. Secondly, this work may provide clues to help clinicians to match such signatures with the most effective treatments for breast cancer patients.
 Multiplexed ion beam imaging of human breast tumors. Angelo M, Bendall SC, Finck R, Hale MB, Hitzman C, Borowsky AD, Levenson RM, Lowe JB, Liu SD, Zhao S, Natkunam Y, Nolan GP. Nat Med. 2014 Apr;20(4):436-42.
Michael Angelo, Stanford University, Predictive signatures in breast cancer using multiplexed ion beam imaging