Pteroyl-gamma-glutamate-cysteine synthesis and its application in folate receptor-mediated cancer cell targeting using folate-tethered liposomes.
Cell membrane-associated folate receptors are selectively overexpressed in certain human tumors. The high affinity of folic acid for folate receptors provides a unique opportunity to use folic acid as a targeting ligand to deliver chemotherapeutic agents to cancer cells. Folate-tethered liposomes bearing pteroyl-gamma-glutamate-cysteine-polyethylene glycol (PEG)-distearoylphosphatidylethanolamine (DSPE) as the targeting component are under investigation as mediators of drug and gene delivery to cancer cells that overexpress folate receptors. Pteroyl-gamma-glutamate-cysteine synthesis is one of the crucial starting steps in the preparation of pteroyl-gamma-glutamate-cysteine-PEG-DSPE. However, published methods for the synthesis of pteroyl-gamma-glutamate-cysteine provide low yields and are not easily reproducible. Therefore, we developed a modified synthetic method for the removal of the N(10)-trifluoroacetyl group after cleavage/deprotection that is reliable, is easily reproducible, and has high yield (38%) compared with an unreliable yield of 3-20% with the earlier methods. Folate-tethered liposomes containing calcein or doxorubicin were prepared using pteroyl-gamma-glutamate-cysteine-PEG-DSPE as the targeting component along with nontargeted liposomes with PEG-DSPE. The results of the uptake of calcein and cytotoxicity of doxorubicin in human cervical cancer HeLa-IU(1) cells and human colon cancer Caco-2 cells demonstrated that folate-tethered liposomes were efficient in selective delivery to cancer cells overexpressing folate receptors. The improvement in yield of the targeting component can significantly facilitate "scale up" of folate receptor-mediated liposomal cancer therapy to the preclinical and clinical levels of investigations.
Zhang
Yonghua
Y
Division of Hematology-Oncology, Department of Medicine, Indiana University School of Medicine, Indianapolis 46202, USA.
Guo
Lili
L
Roeske
Roger W
RW
Antony
Aśok C
AC
Jayaram
Hiremagalur N
HN
D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000378:metabolism*; D004317:Doxorubicin / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D011092:Polyethylene Glycols / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*
D002352:Carrier Proteins; D005452:Fluoresceins; D058973:Folate Receptors, GPI-Anchored; D008081:Liposomes; D010714:Phosphatidylethanolamines; D011956:Receptors, Cell Surface; C038089:1,2-distearoylphosphatidylethanolamine; D011092:Polyethylene Glycols; D004317:Doxorubicin; D005492:Folic Acid; D003545:Cysteine; C007740:fluorexon