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PHOTON
AND NEUTRON THERAPISTS
The work of Vicente and her team has resulted in advances in the development of two distinct methods for cancer eradication: photodynamic therapy (PDT), which uses light as a drug activator, and neutron capture therapy (NCT), which uses low energy neutrons. Supported by the National Cancer Institute of the National Institutes of Health, Vicente and her team begin by learning as much as possible about the molecular structure of cancer cells they want to target. Then, they design drugs that have structural features and design components complementary to those on the molecules. For example, several of the drugs they have developed bind to low density lipoproteins (LDL), the major carriers of cholesterol in the bloodstream. These lipoproteins are delivered in a non-toxic state to the over-expressed LDL-receptors on the surface of tumor cells, which are internalized in the cell through endocytosis, meaning the cell “eats” the lipoprotein, and distributes it to its organelles. After synthesizing a series of compounds, Vicente and her team evaluate the drugs inside the cells in a culture and then choose the most promising compounds for further study. Because their cells are fluorescent, the team uses fluorescence microscopy and spectroscopy to determine if the drugs were successful at penetrating the cancerous cell and where they are located inside the cell. In a person, the compound is released into the blood stream, finds cancer cells, penetrates the cells’ walls, and is distributed to the cell’s organelles. Using either PDT or NCT, light or low energy neutrons then activate the compound to become toxic, eradicating only that cell. Diode lasers and fiber optics are currently used for light activation of the drugs Vicente is developing. Nuclear reactor cores at the Massachusetts Institute of Technology, Brookhaven National Laboratory, and the University of California at Davis are currently used as sources for neutron capture therapy.
PDT is currently used in the clinic for the treatment of superficial
tumors, such as bladder cancer. There is currently one FDA-approved
drug for PDT treatment and more than 10,000 patients in the last
decade have been successfully treated with it. NCT is being developed
for deeper tumors, such as malignant brain tumors, but there are
no FDA-approved drugs for clinical use. Vicente estimates that
it will take five to 10 years for NCT treatments to be available
for widespread use by the public. |
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Imagine
something as simple as light dramatically minimizing the side
effects of traditional drug cancer treatments. LSU
chemist Graça Vicente is developing new treatment methods
that affect cancerous areas only, instead of the entire body to
eliminate the disease.
The
result is a significant reduction in the side effects to the patient,
because only the affected area is exposed to the toxicity of the
chemical instead of the entire body as in traditional chemotherapy
methods. Also, the reaction takes place from inside the cell instead
of outside the cell as in older therapies.