Nanoscale Proteomic Analysis of Oncoproteins in Hematopoietic Cancers
Dean Felsher, MD, PhD, Stanford University
So the objective of our DoD grant proposal was to develop a new technology that would
allow us in real-time to measure the therapeutic response of drugs for cancer. And, what we
specifically wanted to do, was be able to measure proteins and changes in proteins that
were the targets of specific therapeutics.
So, my research program is devoted to figuring out how oncogenes cause cancer and whether
or not shutting down oncogenes could be used to treat cancer. And what we reasoned is that,
there will be some cases where if you turn off that oncogene, the cancer will completely
go away. And the idea that this could happen is coined "oncogene addiction." This has been
referred to as an Achilles heel of cancer.
But in order to do that and make therapies, you need to be able to have drugs that target
oncogenes, and be able to measure whether or not that particular therapy is actually
able to turn off that oncogene. And you'd like to be able to do this in many different
points during patients' care. So we developed a new technology called the nanoscale immuno-assay
for exactly this purpose. And the technology allows you to use very, very small amounts
of material—25 cells, 4 nanoliters of material—then that material is homogenized and passed through
a capillary tube, and the different proteins including the oncoproteins, are now separated
based on their charge. And then using antibodies, we can actually detect very specific proteins
we're interested in, like the MIC oncoprotein and the BCL2 oncoprotein, and the technology
is highly sensitive and very, very quantitative.
And so our reasoning was, with this super powerful technology, we should be able to
then measure in a patient, before and after they get a specific therapy, a response in
their proteins, a phosphorylation response. The tumor would have a specific pattern, and
in response to therapy that pattern would change for a particular oncoprotein that will
tell you whether or not the drug was actually working in the patient.
We had a clinical study where we were giving a drug called Atorvastatin to patients with
lymphoma. And we put a needle into their lymphoma before they received this drug, and we put
a needle into the lymphoma 8 days after they had received this drug, and we measured two
oncoproteins, STAT5 and STAT3. Using this technology, we can measure a phosphorylation
of STAT5 and STAT3 very quantitatively, exactly where expected, and in response to this drug
you can see that now you no longer detect the phosphorylated versions of these proteins.
Now this technology is very sensitive at detecting patterns that distinguish also cancer cells
from normal cells. And this shows an example in a solid tumor, where we measured an oncoprotein
called ERK. And you can see that there's these distinct phosphorylated forms of ERK. They're
not very abundant but they're present. But if you look in the adjacent normal tissue,
you do not see any of these phosphorylated forms. So this potentially could be used as
a way of telling whether or not a tumor mass is a cancer versus just normal tissue. And
this shows the quantification of a specific phosphorylated form of ERK, very high in tumor,
extremely low in non-tumor.
So, this nanoscale technology allows us to predict therapies that are useful to treat
cancer; it can also be used to distinguish normal cells from cancer cells, and it allows
you in real-time to measure how therapies are working, and this enables you to detect
very quickly after giving a therapeutic whether or not a drug is having its intended benefit.
We're now applying this technology in many other clinical circumstances. We initially
proposed in our work for the DoD to look at hematologic cancers, but we're now looking
at many different solid tumors.
What's also exciting is the work we've done has been so interesting to other colleagues
at Stanford, they're using this same technology to measure therapeutic response not just in
cancer, but also in many other diseases, such as heart disease and diabetes and infectious
disease. All of this was stimulated from one grant that came from the DoD.