Retrieval Technique Simplifies Cancer Protein Research

Dr. W. Andy Tao, an assistant professor of biochemistry at Purdue University (West Lafayette, IN, USA), reported that these specific proteins, called phosphoproteins, can be mapped and examined so that investigators can find ways to suppress the processes that lead to cancer. But first, those few proteins must be picked out of a sea of thousands of others.

Dr. Tao developed and patented the polymer-based metal-ion affinity capture (PolyMAC) method. The synthetic nanopolymer isolates proteins and peptides that have undergone a process called phosphorylation that is highly associated with cancer, and a patented technique allows the retrieval of those proteins. Obtaining the information on these proteins is important for studying how to inhibit the processes that lead to cancer.

"You really want to capture these particular proteins, but there are so many different types of proteins around them,” said Dr. Tao, whose findings were published in July 2010 the early online version of the journal Molecular & Cellular Proteomics. "The target proteins are a thousand times lower in amount than other proteins. They are difficult to study without the capturing step.”

Normal cells grow, divide, and ultimately die. However, cancer cells continue to grow and do not die. Dr. Tao noted that phosphorylation--in which a type of enzyme called a kinase attaches to and catalyzes a protein on a cell--is believed in many cases to be responsible for creating cancer cells. Dr. Tao's nanopolymer is water-soluble and has titanium ions on its surface, which bind with phosphorylated proteins and peptides contained in a solution. The polymer also has a chemical group attached that is reactive and attached to small beads, which allow researchers to retrieve the polymers. "Once you put the nanopolymer in the solution, you have to retrieve them, so we put a handle on the polymer so we can grab on to it and fish it out of the solution,” Dr. Tao stated.

In laboratory tests, the nanopolymer and retrieval technique isolated approximately twice as many proteins that had been phosphorylated by an enzyme highly expressed in certain leukemia cells but absent in metastatic breast cancer cells.

Dr. Tao is now looking for ways to get the polymer and technique into wider use to aid in the development of new cancer drugs. "This technique is very useful and can be used widely in research for cancer as well as infectious diseases,” Dr. Tao concluded.

A US$1 million U.S. National Institutes of Health (Bethesda, MD, USA) grant under the American Reinvestment and Recovery Act paid for a mass spectrometer Dr. Tao utilizes to analyze and map the proteins he recovers using his nanopolymer and retrieval technique.

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