Lani
03-13-2006, 11:15 PM
Penn Researchers Develop New Test To Detect Rare Proteins in Blood [University of Pennsylvania Health System]
(Philadelphia, PA) - Researchers at the University of Pennsylvania School of Medicine have developed a paradigm-shifting method for detecting small amounts of proteins in the blood. Applications of this method will make discerning low-abundance molecules associated with cancers (such as breast cancer), Alzheimer's disease, prion diseases, and possibly psychiatric diseases relatively easy and more accurate compared with the current methodology, including the widely used ELISA (enzyme-linked immunoadsorbent assay).
ELISA is a common immune-system-based assay that uses enzymes linked to an antibody or antigen as a marker for picking out specific proteins. For example, it is used as a diagnostic test to determine exposure to infectious agents, such as HIV, by identifying antibodies present in a blood sample.
The sensitivity of detecting molecules by the new method, called FACTT, short for Florescent Amplification Catalyzed by T7-polymerase Technique, is five orders of magnitude (100,000 times) greater than that of ELISA, the Penn researchers found.
Senior author Mark I. Greene MD, PhD, the John Eckman Professor of Medical Science, Hongtao Zhang, PhD research specialist; Xin Cheng, PhD, research investigator, and Mark Richter, a research technician in Greene's lab, report their findings in the advanced online publication of Nature Medicine.
"The current ELISA tests can only detect proteins when they are in high abundance," says Zhang. "But the problem is that many of the functional proteins - those that have a role in determining your health - exist in very low amounts until diseases are apparent and cannot be detected or measured at early stages of medical pathology. It was important to develop a technique that can detect these rare molecules to detect abnormalities at an early stage."
The FACTT technology uses a different enzyme amplification system so quantitative signals can be obtained from even a few protein molecules compared to ELISA. "The technology is remarkably adaptable to any protein and can be performed in an automated format," notes Greene. He states that the technology will soon be robotized so as to be able to screen for many rare disease-causing proteins using tiny amounts of blood. "It is even possible that one could screen for multiple diseases at the same time and produce a precise accounting of whether disease-causing molecules are present at an early time when disease can be readily treated," adds Greene.
Greene also noted that the FACTT technology represents the further evolution of an earlier approach that was developed in collaboration with Professor of Pharmacology James Eberwine, PhD, also from Penn. The earlier technique employed radioisotopes.
Development of a test for the cancer marker Her2/neu
The researchers compared detection of Her2/neu in the blood between ELISA and FACTT. Her2/neu proteins were in fact first identified by the Greene laboratory in the early 1980s, and the Her2/neu gene was found by other scientists to be overexpressed in breast cancer. Her2/neu is normally a low-abundance molecule that becomes overexpressed in more than 30 percent of primary breast, ovarian, and pancreatic tumors. Part of the Her2/neu molecule is shed from the surface of tumor cells and has been detected in the blood of breast-cancer patients. Higher blood concentrations of Her2/neu correlate with a lower response rate to chemotherapy and shorter survival time after relapse.
The Greene lab developed mouse models that carry cancer cells overexpressing Her2/neu. When these cells are implanted into animals they form tumors exactly like breast tumors in humans. Using ELISA, the researchers could not detect Her2/neu from mouse blood until the tumors reached an inoperable size, but with the new FACTT technology they could detect Her2/Neu in some mice when tumors were barely visible and within two days of implantation. These results indicate that it is possible to detect tumors at very early stages so that tumor emergence or reoccurrence can be rapidly treated or even prevented.
Greene's laboratory established many of the principles of targeted therapy for Her2/neu tumors and the prototype antibodies that led to the development of Herceptin, a similar antibody molecule that was created by Genentech. The Greene laboratory also previously showed that early treatment of Her2/neu tumors with targeted monoclonal antibodies in animal models led to far more significant prevention of tumor growth as well as tumor emergence and reoccurrence.
Greene stresses that early treatment is far more effective than treating advanced tumors with the same antibodies. Recent clinical trials support the notion that early treatment prevents tumor reoccurrence in women with breast tumors. FACTT technology represents a way to couple early diagnosis with early treatment to prevent tumor emergence.
[NOTE: For the full article, please follow the supplied link.]
(Philadelphia, PA) - Researchers at the University of Pennsylvania School of Medicine have developed a paradigm-shifting method for detecting small amounts of proteins in the blood. Applications of this method will make discerning low-abundance molecules associated with cancers (such as breast cancer), Alzheimer's disease, prion diseases, and possibly psychiatric diseases relatively easy and more accurate compared with the current methodology, including the widely used ELISA (enzyme-linked immunoadsorbent assay).
ELISA is a common immune-system-based assay that uses enzymes linked to an antibody or antigen as a marker for picking out specific proteins. For example, it is used as a diagnostic test to determine exposure to infectious agents, such as HIV, by identifying antibodies present in a blood sample.
The sensitivity of detecting molecules by the new method, called FACTT, short for Florescent Amplification Catalyzed by T7-polymerase Technique, is five orders of magnitude (100,000 times) greater than that of ELISA, the Penn researchers found.
Senior author Mark I. Greene MD, PhD, the John Eckman Professor of Medical Science, Hongtao Zhang, PhD research specialist; Xin Cheng, PhD, research investigator, and Mark Richter, a research technician in Greene's lab, report their findings in the advanced online publication of Nature Medicine.
"The current ELISA tests can only detect proteins when they are in high abundance," says Zhang. "But the problem is that many of the functional proteins - those that have a role in determining your health - exist in very low amounts until diseases are apparent and cannot be detected or measured at early stages of medical pathology. It was important to develop a technique that can detect these rare molecules to detect abnormalities at an early stage."
The FACTT technology uses a different enzyme amplification system so quantitative signals can be obtained from even a few protein molecules compared to ELISA. "The technology is remarkably adaptable to any protein and can be performed in an automated format," notes Greene. He states that the technology will soon be robotized so as to be able to screen for many rare disease-causing proteins using tiny amounts of blood. "It is even possible that one could screen for multiple diseases at the same time and produce a precise accounting of whether disease-causing molecules are present at an early time when disease can be readily treated," adds Greene.
Greene also noted that the FACTT technology represents the further evolution of an earlier approach that was developed in collaboration with Professor of Pharmacology James Eberwine, PhD, also from Penn. The earlier technique employed radioisotopes.
Development of a test for the cancer marker Her2/neu
The researchers compared detection of Her2/neu in the blood between ELISA and FACTT. Her2/neu proteins were in fact first identified by the Greene laboratory in the early 1980s, and the Her2/neu gene was found by other scientists to be overexpressed in breast cancer. Her2/neu is normally a low-abundance molecule that becomes overexpressed in more than 30 percent of primary breast, ovarian, and pancreatic tumors. Part of the Her2/neu molecule is shed from the surface of tumor cells and has been detected in the blood of breast-cancer patients. Higher blood concentrations of Her2/neu correlate with a lower response rate to chemotherapy and shorter survival time after relapse.
The Greene lab developed mouse models that carry cancer cells overexpressing Her2/neu. When these cells are implanted into animals they form tumors exactly like breast tumors in humans. Using ELISA, the researchers could not detect Her2/neu from mouse blood until the tumors reached an inoperable size, but with the new FACTT technology they could detect Her2/Neu in some mice when tumors were barely visible and within two days of implantation. These results indicate that it is possible to detect tumors at very early stages so that tumor emergence or reoccurrence can be rapidly treated or even prevented.
Greene's laboratory established many of the principles of targeted therapy for Her2/neu tumors and the prototype antibodies that led to the development of Herceptin, a similar antibody molecule that was created by Genentech. The Greene laboratory also previously showed that early treatment of Her2/neu tumors with targeted monoclonal antibodies in animal models led to far more significant prevention of tumor growth as well as tumor emergence and reoccurrence.
Greene stresses that early treatment is far more effective than treating advanced tumors with the same antibodies. Recent clinical trials support the notion that early treatment prevents tumor reoccurrence in women with breast tumors. FACTT technology represents a way to couple early diagnosis with early treatment to prevent tumor emergence.
[NOTE: For the full article, please follow the supplied link.]