Biomaterial Database

A fast chemoenzymatic synthesis of [11C]-N5,N10-methylenetetrahydrofolate as a potential PET tracer for proliferating cells. 2012

Muhammad Saeed, and Timothy J Tewson, and Colbin E Erdahl, and Amnon Kohen

Department of Chemistry, University of Iowa, IA 52242, USA.

BACKGROUND Thymidylate synthase and folate receptors are well-developed targets of cancer therapy. Discovery of a simple and fast method for the conversion of 11CH3Ito[11C]-formaldehyde (11CH2O) encouraged us to label the co-factor of this enzyme. Preliminary studies conducted on cell lines have demonstrated a preferential uptake of [11-14C]-(R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (14CH2H4folate) by cancerous cell vs. normal cells from the same organ (Saeed M., Sheff D. and Kohen A. Novel positron emission tomography tracer distinguishes normal from cancerous cells. J Biol Chem 2011;286:33872-33878), pointing out 11CH2H4folate as a positron emission tomography (PET) tracer for cancer imaging. Herein we report the synthesis of 11CH2H4folate, which may serve as a potential PET tracer. METHODS In a remotely controlled module, methyl iodide (11CH3I) was bubbled into a reaction vial containing trimethylamine N-oxide in N,N-Dimethylformamide (DMF) and heated to 70°C for 2 min. Formaldehyde (11CH2O) formed after the completion of reaction was then mixed with a solution of freshly prepared tetrahydrofolate (H4folate) by using a fast chemoenzymatic approach to accomplish synthesis of 11CH2H4folate. Purification of the product was carried out by loading the crude reaction mixture on a SAX cartridge, washing with water to remove unbound impurities and finally eluting with a saline solution. RESULTS The synthesis and purification of 11CH2H4folate were completed within 5 min. High-performance liquid chromatography analysis of the product after SAX purification indicates that more than 90% of the radioactivity that was retained on the SAX cartridge was in 11CH2H4folate, with minor (<10%) radioactivity due to unreacted 11CH2O. CONCLUSIONS We present a fast (∼5 min) synthesis and purification of 11CH2H4folate as a potential PET tracer. The final product is received in physiologically compatible buffer (100 mM sodium phosphate, pH 7.0 containing 500 mM NaCl) and ready for use in vivo.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D011849	Radioactive Tracers	Radioactive substances added in minute amounts to the reacting elements or compounds in a chemical process and traced through the process by appropriate detection methods, e.g., Geiger counter. Compounds containing tracers are often said to be tagged or labeled. (Hawley's Condensed Chemical Dictionary, 12th ed)	Radioactive Tracer,Radionuclide Tracer,Radionuclide Tracers,Tracer, Radioactive,Tracer, Radionuclide,Tracers, Radioactive,Tracers, Radionuclide
D002250	Carbon Radioisotopes	Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.	Radioisotopes, Carbon
D005492	Folic Acid	A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (POACEAE). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.	Pteroylglutamic Acid,Vitamin M,Folacin,Folate,Folic Acid, (D)-Isomer,Folic Acid, (DL)-Isomer,Folic Acid, Calcium Salt (1:1),Folic Acid, Monopotassium Salt,Folic Acid, Monosodium Salt,Folic Acid, Potassium Salt,Folic Acid, Sodium Salt,Folvite,Vitamin B9,B9, Vitamin
D005557	Formaldehyde	A highly reactive aldehyde gas formed by oxidation or incomplete combustion of hydrocarbons. In solution, it has a wide range of uses: in the manufacture of resins and textiles, as a disinfectant, and as a laboratory fixative or preservative. Formaldehyde solution (formalin) is considered a hazardous compound, and its vapor toxic. (From Reynolds, Martindale The Extra Pharmacopoeia, 30th ed, p717)	Formalin,Formol,Methanal,Oxomethane
D013763	Tetrahydrofolates	Compounds based on 5,6,7,8-tetrahydrofolate.
D013940	Thymidylate Synthase	An enzyme of the transferase class that catalyzes the reaction 5,10-methylenetetrahydrofolate and dUMP to dihydrofolate and dTMP in the synthesis of thymidine triphosphate. (From Dorland, 27th ed) EC 2.1.1.45.	Thymidylate Synthetase,Synthase, Thymidylate,Synthetase, Thymidylate
D049109	Cell Proliferation	All of the processes involved in increasing CELL NUMBER including CELL DIVISION.	Cell Growth in Number,Cellular Proliferation,Cell Multiplication,Cell Number Growth,Growth, Cell Number,Multiplication, Cell,Number Growth, Cell,Proliferation, Cell,Proliferation, Cellular
D049268	Positron-Emission Tomography	An imaging technique using compounds labelled with short-lived positron-emitting radionuclides (such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18) to measure cell metabolism. It has been useful in study of soft tissues such as CANCER; CARDIOVASCULAR SYSTEM; and brain. SINGLE-PHOTON EMISSION-COMPUTED TOMOGRAPHY is closely related to positron emission tomography, but uses isotopes with longer half-lives and resolution is lower.	PET Imaging,PET Scan,Positron-Emission Tomography Imaging,Tomography, Positron-Emission,Imaging, PET,Imaging, Positron-Emission Tomography,PET Imagings,PET Scans,Positron Emission Tomography,Positron Emission Tomography Imaging,Positron-Emission Tomography Imagings,Scan, PET,Tomography Imaging, Positron-Emission,Tomography, Positron Emission
D060326	Chemistry Techniques, Synthetic	Methods used for the chemical synthesis of compounds. Included under this heading are laboratory methods used to synthesize a variety of chemicals and drugs.	Inorganic Synthesis,Inorganic Synthesis Methods,Inorganic Synthesis Techniques,Methods of Inorganic Synthesis,Methods of Organic Synthesis,Methods of Peptide Synthesis,Organic Synthesis,Organic Synthesis Methods,Organic Synthesis Techniques,Peptide Synthesis Methods,Peptide Synthesis Techniques,Peptide Synthesis, Synthetic,Synthetic Chemistry Techniques,Synthetic Peptide Synthesis,Chemistry Technique, Synthetic,Inorganic Syntheses,Inorganic Synthesis Method,Inorganic Synthesis Technique,Method, Inorganic Synthesis,Method, Organic Synthesis,Method, Peptide Synthesis,Methods, Inorganic Synthesis,Methods, Organic Synthesis,Methods, Peptide Synthesis,Organic Syntheses,Organic Synthesis Technique,Peptide Syntheses, Synthetic,Peptide Synthesis Method,Peptide Synthesis Technique,Syntheses, Inorganic,Syntheses, Organic,Syntheses, Synthetic Peptide,Synthesis Method, Inorganic,Synthesis Method, Peptide,Synthesis Methods, Inorganic,Synthesis Methods, Peptide,Synthesis Technique, Inorganic,Synthesis Technique, Organic,Synthesis Technique, Peptide,Synthesis Techniques, Inorganic,Synthesis Techniques, Organic,Synthesis Techniques, Peptide,Synthesis, Inorganic,Synthesis, Organic,Synthesis, Synthetic Peptide,Synthetic Chemistry Technique,Synthetic Peptide Syntheses,Technique, Inorganic Synthesis,Technique, Organic Synthesis,Technique, Peptide Synthesis,Technique, Synthetic Chemistry,Techniques, Inorganic Synthesis,Techniques, Organic Synthesis,Techniques, Peptide Synthesis,Techniques, Synthetic Chemistry