Project Overview

The Problem: Diagnostics Require Tools for Massively Multiplexed Analysis

Diagnosing a disease is most difficult at the early stages, where therapeutic intervention is most effective and least devastating. A patient's sample contains many different cells, each of which can be distinguished and identified by the biomarkers (proteins, genes and small molecules) that comprise the cell’s biochemical signature. Groundbreaking research in leukemia has advanced the belief that a particular disease may be sustained by only a small fraction of the diseased cells ("cancer stem cells" in the case of cancer), and is thus particularly difficult to detect and treat. The biomarker signature also reflects biochemical processes within the cells that determine cell activity and fate. Accordingly, the capability to measure the full signature of biomarkers at the same time for individual cells provides an opportunity for improved understanding of cell genesis and for the development of drugs to treat the disease.

Enormous progress is being made on the identification of diagnostic biomarker signatures and the understanding of biomarker interactions. Unfortunately, there are few analytical tools capable of recognizing these signatures, and these have serious limitations for detecting many biomarkers in a single analysis. Current single cell diagnostic technologies are based on the detection of fluorescent emission from tagged reagents that specifically recognize the biomarkers. While up to 10 detection channels can be monitored simultaneously, the approach is limited by poor resolution. This results in signal overlap and large errors when biomarkers are present over a wide range of concentrations. There is a clear need for a new technology that will provide for the simultaneous quantitative and independent determination of many (up to 100) biomarkers in individual cells, especially where that analysis can be performed at high speed so that 1000 or more cells can be analyzed per second.

The Solution: Mass Cytometer and Element Tags

An innovative solution to this challenge is being developed. Our approach takes advantage of the high resolution of mass spectrometry to distinguish biologically-rare metal atoms that replace the fluorescent dyes in current use. A new generation of diagnostic reagents that bind different metals to biomarkers is being developed. These “tagging metals” are detected with high sensitivity and resolution, and in a quantitative manner, by a prototype flow cytometer. This instrument introduces individual cells at a rapid rate, up to 1000 cells per second, to a multichannel mass spectrometer analyzer.

Schematic of the concept of the Mass Cytometer. A cell contains many thousands of proteins. It is reasonable to expect that a cell of interest has certain protein "markers" that distinguish that type of cell from other cells in the sample (perhaps by the presence or the concentration or the ratio of the marker proteins). An affinity product (antibody or aptamer) that has been tagged with a specific element binds to the protein marker. When the cell is introduced into the ICP, it is atomized and ionized. The elemental composition of the cell, including the tagged affinity products that are bound to the protein markers, is measured. The presence and intensity of the signals corresponding to the tags on the affinity products indicates the presence of the biomarkers on that cell. The distribution and concomitance of those signals can be used to confirm that the cell was sampled; if the markers have been appropriately selected, the measurement could be diagnostic.

The Future: Defining a New Standard in Diagnostics

The feasibility of this new technology has been demonstrated. [Click here to read about our Genome Canada Applied Human Health (AHH) project]. We are currently transforming the complex research prototype instrument and the reagents required for its operation into an engineering prototype that will be converted to a commercial instrument for widespread diagnostic and research use.

In addition to enabling genomics and proteomics researchers to achieve a vast improvement in the depth and range of cellular analysis, this project will provide a diagnostic tool that will define the new standard-of-care benchmark in hospitals, clinics and research departments world-wide. The success of this project will lead to healthcare savings for Canadians and others worldwide, resulting from first-time-correct diagnosis and consequent reduction in adverse drug reactions.