Ligand Binding and Kinetics of Folate Receptor Recycling in Vivo: Impact on Receptor-Mediated Drug Delivery

Abstract

Folate receptor-targeted cancer therapies constitute a promising treatment for the approximately one third of human cancers that overexpress the folate receptor (FR). However, the potencies of all folate-receptor targeted therapies depend on 1) the rate of folate-linked drug conjugate binding to the cancer cell surface, 2) the dose of folate conjugate that will saturate tumor cell surface FR in vivo, 3) the rate of FR internalization, unloading, and recycling back to the tumor cell surface for another round of conjugate uptake, and 4) the residence time of the folate conjugate before its metabolism or release from the cell. Because little information exists on any of these processes, we have undertaken to characterize them on both cancer cells in culture and solid tumors in live mice. We quantitate here the properties of FR saturation, internalization, recycling, and unloading in several cultured cancer cell lines and murine tumor models, and we describe the conditions that should maximize both the potencies and specificities of folate receptor-targeted therapies in vivo.The folate receptor (FR) is a tumor marker that is overexpressed on a variety of human cancers, including cancers of the ovary, kidney, lung, breast, brain, endometrium, and myeloid cells of hematopoietic origin (Leamon et al

In vivo quantitation of rare circulating tumor cells by multiphoton intravital flow cytometry

“…1b, plasma clearance of folate-rhodamine was biphasic, with a rapid phase characterized by a t1 ͞2 of Ϸ3-5 min and comprising 75% of the clearance in anesthetized mice and a slower phase that we attribute to serum protein binding. Because these data are similar to those reported for folate-FITC (22,23), we assume that folate-dye conjugates will generally be rapidly excreted if they are not captured by a FR-expressing cell.…”

Preparation, cytotoxicity, and in vivo antitumor efficacy of ¹¹¹In-labeled modular nanotransporters

“…We have chosen Laemmli SDS-PAGE instead of the usually used instant thin layer chromatography to evaluate the labeling yields, since this method not only provides the data about the percentage of unreacted 111 In that migrates immediately before bromophenol blue on the gel, but also demonstrates the integrity of protein molecule after labeling. cytotoxicity studies 23 HeLa or SK-OV-3 (both FR-positive), 24,25 and A431 or U87MG. wtEGFR (both EGFR-positive) 15 In-NOTA-MNT (0.03-9.5 MBq/mL) or 111 In-EDTA as a control (0.3-9.5 MBq/mL) were added.…”

Efficient polyethylenimine-mediated gene delivery proceeds via a caveolar pathway in HeLa cells

“…The delayed uptake of PEI-Fol(1.1)/DNA complexes is likely due to the slow kinetics of caveolae-mediated uptake. 9,26,27 . To verify that folate-targeted complexes entered cells through folate receptors, a competitive inhibition assay was performed.…”

“…[9][10][11] Notably, these ligands utilize different uptake mechanisms which ultimately result in distinct intracellular processing.…”