Folate receptor targeted NIR cleavable liposomal delivery system augment penetration and therapeutic efficacy in breast cancer.

BACKGROUND: Liposomes are predominantly used sorts of nanocarriers for active a targeted delivery through surface functionalization using targeting ligand. The folate receptors are overexpressed in various cancers including breast cancer and because of its binding aptitude specifically to folate receptors, folic acid became the attractive ligand. METHODS: In this research, we have developed a folate and Poly-l-Lysine conjugate and coated this conjugate onto the liposomes. The prepared liposomes were characterized using DLS, FTIR, NMR, SEM, TEM, XRD, AFM, stability and drug release studies. Furthermore, in vitro studies were carried out on FR overexpressed breast cancer cell line. RESULTS: The FA-LUT-ABC-Lip have diameter of 183 ± 3.17 nm with positive surface charge +33.65 ± 3 mV and the drug release studies confirm the NIR responsive payload cleavage. The coated formulation (in presence of NIR light) effectively reduced the IC50 values and kills breast cancer cells through FR mediated internalization and accelerated drug release. Moreover, LUT Formulation shows anticancer effect due to significant inhibition of cell migration and proliferation by regulating VEGF expression and induced apoptosis through the caspase-3 up-regulation. CONCLUSION: It is evident from the in vitro studies that the formulation was found to be very effective and can be explored for triggered and targeted delivery of the substances through active targeting. GENERAL SIGNIFICANCE: Combining receptor mediated drug delivery with triggered release aid in more amounts of drug reaching the target site and achieving enhanced therapeutic activity.

Design, characterization and evaluation of a new 99mTc-labeled folate derivative with affinity towards folate receptor.

Folate receptors (FRs) are known to be over-expressed in several human malignancies and therefore serve as an important target for small radiolabeled folate derivatives for non-invasive imaging of tumor, which is an important tool for future treatment recourse. In the present article, we report the synthesis of a new 99mTc-labeled radiotracer for the aforementioned application following the well-established 99mTc-'4+1' chemistry. Formation of the desired [99mTc]Tc-complex with >95% radiochemical purity was confirmed by radio-HPLC and its structure was ascertained by characterizing a natural rhenium analogue of the said complex. Although the ligand exhibited a weaker affinity towards FRs compared to native folic acid (IC50 8.09 µM vs 29.46 nM), the 99mTc-labeled complex was found to bind folate receptor-positive KB cells with high specificity (∼90%). Similar studies in a folate receptor negative cell line viz. A549 further corroborated the receptor-specificity of the synthesized complex. In vivo studies in KB tumor xenograft showed moderate uptake of ∼2.6% upto 3 h post-injection with high specificity (∼80%). The favorable features observed warrant further screening of the current design towards achieving an improved molecular probe for the said application.

Anti-tumor Effect of Folate-Binding Protein: In Vitro and In Vivo Studies.

Folate receptor (FR) overexpression in a wide range of solid tumors provides an opportunity to develop novel, targeted cancer therapeutics. In this study, we investigated whether prebinding the chemotherapeutic methotrexate (MTX) to folate-binding protein (FBP), the soluble form of FR, would enable the protein to serve as a targeted therapeutic vector, enhancing uptake into tumor cells and improving therapeutic efficacy. In an in vivo study, using an FR-overexpressing KB xenograft model in SCID mice, modest improvement in inhibiting tumor growth was observed for the MTX/FBP mixtures as compared to saline control and free MTX. Surprisingly, FBP alone inhibited tumor growth compared to saline control, free MTX, and FBP/MTX. In order to better understand this effect, we investigated the cytotoxicity of micromolar concentrations of FBP in vitro using the KB, HeLa, and A549 cancer cell lines. Our results revealed concentration-dependent apoptosis (24 h; 10-50 µM) in all three cell lines accompanied by a time- and concentration-dependent reduction (6, 12, and 24 h; 10-50 µM) in metabolic activity and compromised cell plasma membrane integrity. This study demonstrates an apoptosis pathway for cytotoxicity of FBP, an endogenous serum protein, in cancer cell lines with widely varying levels of FR expression. Furthermore, in vivo tumor growth suppression for xenograft KB tumors in SCID mice was observed. These studies suggest novel strategies for the elimination of cancer cells employing endogenous, serum transport proteins.

A Novel Method of Magnetic Nanoparticles Functionalized with Anti-Folate Receptor Antibody and Methotrexate for Antibody Mediated Targeted Drug Delivery.

Therapeutic effects of anticancer medicines can be improved by targeting the specific receptors on cancer cells. Folate receptor (FR) targeting with antibody (Ab) is an effective tool to deliver anticancer drugs to the cancer cell. In this research project, a novel formulation of targeting drug delivery was designed, and its anticancer effects were analyzed. Folic acid-conjugated magnetic nanoparticles (MNPs) were used for the purification of folate receptors through a novel magnetic affinity purification method. Antibodies against the folate receptors and methotrexate (MTX) were developed and characterized with enzyme-linked immunosorbent assay and Western blot. Targeting nanomedicines (MNP-MTX-FR Ab) were synthesized by engineering the MNP with methotrexate and anti-folate receptor antibody (anti-FR Ab). The cytotoxicity of nanomedicines on HeLa cells was analyzed by calculating the % age cell viability. A fluorescent study was performed with HeLa cells and tumor tissue sections to analyze the binding efficacy and intracellular tracking of synthesized nanomedicines. MNP-MTX-FR Ab demonstrated good cytotoxicity along all the nanocomposites, which confirms that the antibody-coated medicine possesses the potential affinity to destroy cancer cells in the targeted drug delivery process. Immunohistochemical approaches and fluorescent study further confirmed their uptake by FRs on the tumor cells' surface in antibody-mediated endocytosis. The current approach is a useful addition to targeted drug delivery for better management of cancer therapy along with immunotherapy in the future.

Detection of folate receptor-positive circulating tumor cells as a biomarker for diagnosis, prognostication, and therapeutic monitoring in breast cancer.

OBJECTIVES: This study is to explore the clinical significance of folate receptor-positive circulating tumor cells (FR+ CTC) in the early diagnosis and disease progress in patients with breast cancer. METHODS: Folate receptor-positive circulating tumor cells was enriched from peripheral blood of the patients with immunomagnetic separation method and quantitated by folate receptor on the CTC with the ligand-targeted PCR. RESULTS: The levels of FR+ CTC were significantly higher in breast cancer patients compared with healthy controls. Detective rate of FR+ CTC was decreased in 19 of 27 patients underwent the surgery in 2 weeks post-operation compared with pre-operation; statistical analysis showed the difference was significant. We also found that the combination of FR+ CTC, CEA, CA125, and CA153 can significantly improve the diagnostic efficiency for breast cancer. CONCLUSIONS: This study showed the detective rate of FR+ CTC is significantly increased in the patients with breast cancer, and the detective level is associated with disease progress.

Synthesis of biocompatible nanocrystalline cellulose against folate receptors as a novel carrier for targeted delivery of doxorubicin.

We designed amine-functionalized nanocrystalline cellulose grafted folic acid/magnetic nanoparticles (AF-NCC/Fe3O4 NPs) against folate receptors for targeted delivery of doxorubicin (DOX). Toxicity is a major side effect of DOX, damaging vital organs such as the heart, kidney, and liver; for example, it causes dilated cardiomyopathy and hepatotoxicity. Accordingly, we aimed to reduce this adverse effect and increase the targeted delivery of DOX to the right point of cancer cells by using the unique features of cancer cells. The characterizations were approved in each step using Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), zeta potential, and dynamic light scattering (DLS) analysis techniques. Encapsulation efficacy of AF-NCC/Fe3O4 NPs was 99.6%; drug release investigations showed excellent stability in physiological conditions (pH âˆ¼ 7.4) and a high release rate in the low pH condition of cancer environments (pH âˆ¼ 5.0). The hemolysis assay and Masson's trichrome and hematoxylin and eosin (H&E) staining results showed that the nanocarrier was entirely biocompatible. In vitro cell viability study approved that the designed nanocarrier increased the therapeutic effects of DOX on Saos-2 cells. The cellular internalization results displayed a high percentage of uptake within 2 h. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was applied for the evaluation of tumor protein p53 (p53), p21, and Bcl-2-associated X protein (Bax). DOX exerted its effects through DNA damage and oxidative stress that led to p53 upregulation, and p53 inhibited cell cycle progression. This arrest initiated apoptosis and inhibited cell migration. In summary, encapsulating DOX in AF-NCC/Fe3O4 NPs dramatically decreases the toxic effects of this chemotherapeutic agent on vital organs, especially on the heart. This smart nanocarrier increases the delivery of DOX using acid folic on its surface and also enhances the DOX release in the acidic environment of cancer cells. DOX exerts its therapeutic effects by the initiation of apoptosis and inhibition of migration.

Redox-Sensitive and Folate-Receptor-Mediated Targeting of Cervical Cancer Cells for Photodynamic Therapy Using Nanophotosensitizers Composed of Chlorin e6-Conjugated ß-Cyclodextrin via Diselenide Linkage.

The aim of this study was to fabricate a reactive oxygen species (ROS)-sensitive and folate-receptor-targeted nanophotosensitizer for the efficient photodynamic therapy (PDT) of cervical carcinoma cells. Chlorin e6 (Ce6) as a model photosensitizer was conjugated with succinyl ß-cyclodextrin via selenocystamine linkages. Folic acid (FA)-poly(ethylene glycol) (PEG) (FA-PEG) conjugates were attached to these conjugates and then FA-PEG-succinyl ß-cyclodextrin-selenocystamine-Ce6 (FAPEGbCDseseCe6) conjugates were synthesized. Nanophotosensitizers of FaPEGbCDseseCe6 conjugates were fabricated using dialysis membrane. Nanophotosensitizers showed spherical shapes with small particle sizes. They were disintegrated in the presence of hydrogen peroxide (H2O2) and particle size distribution changed from monomodal distribution pattern to multimodal pattern. The fluorescence intensity and Ce6 release rate also increased due to the increase in H2O2 concentration, indicating that the nanophotosensitizers displayed ROS sensitivity. The Ce6 uptake ratio, ROS generation and cell cytotoxicity of the nanophotosensitizers were significantly higher than those of the Ce6 itself against HeLa cells in vitro. Furthermore, the nanophotosensitizers showed folate-receptor-specific delivery capacity and phototoxicity. The intracellular delivery of nanophotosensitizers was inhibited by folate receptor blocking, indicating that they have folate-receptor specificity in vitro and in vivo. Nanophotosensitizers showed higher efficiency in inhibition of tumor growth of HeLa cells in vivo compared to Ce6 alone. These results show that nanophotosensitizers of FaPEGbCDseseCe6 conjugates are promising candidates as PDT of cervical cancer.

Composite phospholipid-gold nanoparticles with targeted fragment for tumor imaging.

Gold nanoparticles and their conjugates have significant potential in the field of diagnosis of various diseases due to their SPR, which enhances light scattering and absorption. Conjugates of gold nanoparticles with various ligands can be used for imaging biomolecules or detecting malignant neoplasms at an early stage. This study focuses on the construction of composite (or hybrid) phospholipid-gold nanoparticles using soy phosphatidylcholine and a targeted ligand (folic acid derivative) to attach specific targeting properties. According to the method of dynamic light scattering, the diameter of the obtained nanoparticles was less than 100 nm, the results of the MTT test indicated their moderate cytotoxicity. In vitro and in vivo experiments showed a significant increase in the accumulation of phospholipid-gold nanoparticles with a targeted fragment compared to those without a targeted fragment both in HeLa cells and in a tumor (in BDF mice with an injected LLC tumor). The resulting nanoparticles are suitable for specific delivery into tumor cells and visualization of various malignant neoplasms, including at early stages, due to the increased expression of the folate receptor characteristic of cells of a wide range of tumors.

Preparation and Evaluation of Novel Folate Isonitrile 99mTc Complexes as Potential Tumor Imaging Agents to Target Folate Receptors.

In order to seek novel technetium-99m folate receptor-targeting agents, two folate derivatives (CN5FA and CNPFA) were synthesized and radiolabeled to obtain [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA complexes, which exhibited high radiochemical purity (>95%) without purification, hydrophilicity, and good stability in vitro. The KB cell competitive binding experiments indicated that [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA had specificity to folate receptor. Biodistribution studies in KB tumor-bearing mice illustrated that [99mTc]Tc-CN5FA and [99mTc]Tc-CNPFA had specific tumor uptake. Compared with [99mTc]Tc-CN5FA, the tumor/muscle ratios of [99mTc]Tc-CNPFA were higher, resulting in a better SPECT/CT imaging background. According to the results, the two 99mTc complexes have potential as tumor imaging agents to target folate receptors.

A Novel Folic Acid Receptor-Targeted Drug Delivery System Based on Curcumin-Loaded ß-Cyclodextrin Nanoparticles for Cancer Treatment.

PURPOSE: A novel folate receptor-targeted ß-cyclodextrin (ß-CD) drug delivery vehicle was constructed to improve the bioavailability, biosafety, and drug loading capacity of curcumin. Controlled release and targeted delivery was achieved by modifying the nanoparticles with folic acid (FA). METHODS: Folate-conjugated ß-CD-polycaprolactone block copolymers were synthesized and characterized. Curcumin-loaded nanoparticles (FA-Cur-NPs) were structured by self-assembly. The physicochemical properties, stability, release behavior and tumor-targeting ability of the fabricated nanoparticles were studied. RESULTS: The average particle size and drug loading of FA-Cur-NPs was 151.8 nm and 20.27%, respectively. Moreover, the FA-Cur-NPs exhibited good stability in vitro for 72 h. The drug release profiles showed that curcumin from FA-Cur-NPs was released significantly faster in a pH 6.4 phosphate buffered solution (PBS) than in pH 7.4, indicating that curcumin can be enriched around the tumor site compared with normal cells. Additionally, the internalization of FA-Cur-NPs was aided by FA receptor-mediated endocytosis, and its cytotoxicity was proportional to the cellular uptake efficiency. Furthermore, in vivo studies confirmed that FA-Cur-NPs exhibited marked accumulation in the tumor site and excellent antitumor activity. CONCLUSION: These findings suggest that FA-Cur-NPs are a promising approach for improving cancer therapy through active targeting and controllable release.

Janus-Type Mesoporous Silica Nanoparticles for Sequential Tumoral Cell and Mitochondria Targeting.

The development of nanoparticles has provided a powerful weapon in the fight against cancer due to the discovery of their selective accumulation in tumoral tissues, known as enhanced permeation and retention (EPR) effect (Peer et al, Nat Nanotechnol 2:751-760, 2007). Tumoral tissues require afastformation of blood vessels to sustain this rapid growth.

Advancements in folate receptor targeting for anti-cancer therapy: A small molecule-drug conjugate approach.

Targeted delivery combined with controlled release of drugs has a crucial role in future of personalized medicine. The majority of cancer drugs are intended to interfere with one or more cellular events. Anticancer agents can also be toxic to healthy cells, as healthy cells may also need to proliferate and avoid apoptosis. The focus of this review covers the principles, advantages, drawbacks and summarize criteria that must be met for design of small molecule-drug conjugates (SMDCs) to achieve the desired therapeutic potency with minimal toxicity. SMDCs are composed of a targeting ligand, a releasable bridge, a spacer, and a therapeutic payload. We summarize the criteria for the effective design that influences the selection of tumor specific receptor and optimum elements in the design of SMDCs. We also discuss the criteria for selecting the optimal therapeutic drug payload, spacer and linker. The linker chemistries and cleavage strategies are also discussed. Finally, we review the folate receptor targeting SMDCs that are in preclinical development and in clinical trials.

Preparation of FA-targeted magnetic nanocomposites co-loading TFPI-2 plasmid and cis-platinum and its targeted therapy effects on nasopharyngeal carcinoma.

The majority of patients diagnosed with nasopharyngeal carcinoma (NPC) present with advanced-stage disease. The main treatment for these patients is concurrent chemoradiotherapy, which has various side effects. To improve the therapeutic effects and reduce the side effects of NPC chemoradiotherapy, we constructed a multifunctional folic acid (FA)-targeted magnetic nanocomposite codelivering tissue factor pathway inhibitor-2 (TFPI-2) and cisplatin (CDDP). This novel nanocomposite (FA-MNP/CDDP/TFPI-2) was obtained by amidation and electrostatic adsorption between FA-methoxypolyethylene glycol-polyethyleneimine (FA-MPEG-PEI) containing the TFPI-2 plasmid and magnetic nanoparticles modified by aldehyde sodium alginate loaded with CDDP. Transmission electron microscopy (TEM) images showed that the size of the individual magnetite particle core was approximately 11.5 nm. The structure and composition of the nanocomposites were identified and examined by 1H nuclear magnetic resonance (NMR) spectroscopy and ultraviolet (UV) spectrophotometry. The fluorescence analysis, Prussian blue iron staining, magnetic resonance (MR) imaging and whole-body fluorescence imaging results demonstrated that FA-MNP/CDDP/TFPI-2 showed high gene transfection efficiency and could target tumor cells via folate receptor (FR)-mediated delivery. The codelivery analysis showed that the obtained FA-MNP/CDDP/TFPI-2 composite could cause significantly more apoptosis than treatment with CDDP or TFPI-2 alone. The results showed that the FA-MNP/CDDP/TFPI-2 composites were successfully synthesized and indicated to be a specific molecular target for the FR with significant inhibitory effects on the growth of HNE-1 cells.

Polymeric Encapsulation of a Ru(II)-Based Photosensitizer for Folate-Targeted Photodynamic Therapy of Drug Resistant Cancers.

The currently used photodynamic therapy (PDT) photosensitizers (PSs) are generally associated with a poor cancer cell selectivity, which is responsible for some undesirable side effects. To overcome these problems, there is an urgent need for a selective drug delivery system for PDT PSs. Herein, the encapsulation of a promising Ru(II) polypyridine complex in a polymer with terminal folate groups to form nanoparticles is presented. While the Ru(II) complex itself has a cytotoxic effect in the dark, the encapsulation is able to overcome this drawback. Upon light exposure, the nanoparticles were found to be highly phototoxic in 2D monolayer cells as well as 3D multicellular tumor spheroids upon 480 or 595 nm irradiation. Importantly, the nanoparticles demonstrated a high selectivity for cancerous cells over noncancerous cells and were found to be active in drug resistant cancer cells lines, indicating that they are able to overcome drug resistances.

Discovery of 6-substituted thieno[2,3-d]pyrimidine analogs as dual inhibitors of glycinamide ribonucleotide formyltransferase and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase in de novo purine nucleotide biosynthesis in folate receptor expressing human tumors.

We discovered 6-substituted thieno[2,3-d]pyrimidine compounds (3-9) with 3-4 bridge carbons and side-chain thiophene or furan rings for dual targeting one-carbon (C1) metabolism in folate receptor- (FR) expressing cancers. Synthesis involved nine steps starting from the bromo-aryl carboxylate. From patterns of growth inhibition toward Chinese hamster ovary cells expressing FRα or FRß, the proton-coupled folate transporter or reduced folate carrier, specificity for uptake by FRs was confirmed. Anti-proliferative activities were demonstrated toward FRα-expressing KB tumor cells and NCI-IGROV1 ovarian cancer cells. Inhibition of de novo purine biosynthesis at both 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase and glycinamide ribonucleotide formyltransferase (GARFTase) was confirmed by metabolite rescue, metabolomics and enzyme assays. X-ray crystallographic structures were obtained with compounds 3-5 and human GARFTase. Our studies identify first-in-class C1 inhibitors with selective uptake by FRs and dual inhibition of enzyme targets in de novo purine biosynthesis, resulting in anti-tumor activity. This series affords an exciting new platform for selective multi-targeted anti-tumor agents.

A Carrier-Free Folate Receptor-Targeted Ursolic Acid/Methotrexate Nanodelivery System for Synergetic Anticancer Therapy.

PURPOSE: To avoid undefined metabolic mechanisms and to eliminate potential side effects of traditional nanocarriers, new green carriers are urgently needed in cancer treatment. Carrier-free nanoparticles (NPs) based on ursolic acid (UA) have attracted significant attention, but the UA NPs targeting the folate receptor have never been explored. We designed a novel self-assembled UA-Methotrexate (MTX) NPs targeting the folate-receptor and its synergetic anticancer activity was studied in vitro and in vivo. METHODS: UA-MTX NPs were prepared using the solvent precipitation method. Characterization of the UA-MTX NPs preparation was performed using a size analyzer, transmission electron microscopy, and UV-vis spectrophotometry. The in vitro pH-responsive drug release capability of UA-MTX NPs was tested at different pH values. The UA-MTX NPs targeting of folates was determined by comparing the endocytosis rates of cell lines with low or overexpression of the folate receptor (A549 and MCF-7 cells). The cytotoxicity and cell apoptosis of UA-MTX NPs were also studied to determine the in vitro synergistic effects. Combination chemotherapy of UA-MTX NPs in vivo was evaluated using MCF-7 xenografted tumor models. RESULTS: Compared with free UA or MTX, the water solubility of UA-MTX NPs improved significantly. Drug-release from the UA-MTX NPs was faster at pH 5.0 than pH 7.4, suggesting MTX-UA NPs could rapidly release MTX in the acidic conditions of the tumor microenvironment. Confocal laser scanning microscopy revealed the excellent folate receptor targeting of UA-MTX NPs in MCF-7 cells. Cytotoxicity and cell apoptosis results demonstrated greater antiproliferative capacity of UA-MTX NPs than that of free drug in folate receptor overexpressing MCF-7 cells. Anticancer effects in vivo suggested MTX-UA NPs exhibited good biological safety and could enhance antitumor efficacy due to the combination therapy. CONCLUSION: Our findings indicate that the UA-MTX NPs targeting folate-receptors is an efficient strategy for combination chemotherapy.

Smart Fluorescent Probe Strategy for Precision Targeting Hypoxic Tumor.

Both nitroreductase and the folate receptor are highly expressed in hypoxic tumors. The folate receptor is a potential target for tumors, and nitroreductase can selectively turn on the fluorescence of probes by reducing the nitro group to an amino group. Karan et al. (Karana, S., Cho, M., Lee, H., Lee, H., Park, H., Sundararajan, M., Sessler, J., and Hong, K. Near-infrared fluorescent probe activated by nitroreductase for in vitro and in vivo hypoxic tumor detection. J. Med. Chem. 2021) developed a near-infrared fluorescent probe for hypoxia tumor imaging analysis in vitro and in vivo using folate as the targeting site. This promising strategy may promote advances in precision diagnosis and treatment models of malignant tumors. This Viewpoint looks ahead to new possibilities rendered by their studies.

Identification of a PET Radiotracer for Imaging of the Folate Receptor-α: A Potential Tool to Select Patients for Targeted Tumor Therapy.

The aim of this study was to identify a folate receptor-α (FRα)-selective PET agent potentially suitable for the selection of patients who might profit from FRα-targeted therapies. The 6R and 6S isomers of 18F-aza-5-methyltetrahydrofolate (MTHF) were assessed regarding their binding to FRα and FRß, expressed on cancer and inflammatory cells, respectively, and compared with 18F-AzaFol, the folic acid-based analog. Methods: FR selectivity was investigated using FRα-transfected (RT16) and FRß-transfected (D4) CHO cells. The cell uptake of 18F-folate tracers was investigated, and receptor-binding affinities were determined with the nonradioactive analogs. In vitro autoradiography of the 18F-folate tracers was performed using RT16 and D4 tissue sections. Biodistribution studies and PET/CT imaging of the radiotracers were performed on mice bearing RT16 and D4 xenografts. Results: The uptake of 18F-6R-aza-5-MTHF was high when using RT16 cells (62% ± 10% of added activity) but much lower when using D4 cells (5% ± 2%). The FRα selectivity of 18F-6R-aza-5-MTHF was further demonstrated by its approximately 43-fold higher binding affinity to FRα (half-maximal inhibitory concentration [IC50], 1.8 ± 0.1 nM) than to FRß (IC50, 77 ± 27 nM). The uptake of 18F-6S-aza-5-MTHF and 18F-AzaFol was equal in both cell lines (52%-70%), with similar affinities to FRα (IC50, 2.1 ± 0.4 nM and 0.6 ± 0.3 nM, respectively) and FRß (0.8 ± 0.2 nM and 0.3 ± 0.1 nM, respectively). The autoradiography signal obtained with 18F-6R-aza-5-MTHF was 11-fold more intense for RT16 than for D4 tissue sections. Biodistribution data showed high uptake of 18F-6R-aza-5-MTHF in RT16 xenografts (81% ± 20% injected activity per gram [IA]/g 1 h after injection) but significantly lower accumulation in D4 xenografts (7.3% ± 2.1% IA/g 1 h after injection), which was also visualized using PET. The uptake of 18F-6S-aza-5-MTHF and 18F-AzaFol was similar in RT16 (53% ± 10% IA/g and 45% ± 2% IA/g, respectively) and D4 xenografts (77% ± 10% IA/g and 52% ± 7% IA/g, respectively). Conclusion: This study demonstrated FRα selectivity for 18F-6R-aza-5-MTHF but not for 18F-6S-aza-5-MTHF or 18F-AzaFol. This characteristic, together with its favorable tissue distribution, makes 18F-6R-aza-5-MTHF attractive for clinical translation to enable detection of FRα-positive cancer while preventing undesired accumulation in FRß-expressing inflammatory cells.

Selection of DNA-encoded chemical libraries against endogenous membrane proteins on live cells.

Membrane proteins on the cell surface perform a myriad of biological functions; however, ligand discovery for membrane proteins is highly challenging, because a natural cellular environment is often necessary to maintain protein structure and function. DNA-encoded chemical libraries (DELs) have emerged as a powerful technology for ligand discovery, but they are mainly limited to purified proteins. Here we report a method that can specifically label membrane proteins with a DNA tag, and thereby enable target-specific DEL selections against endogenous membrane proteins on live cells without overexpression or any other genetic manipulation. We demonstrate the generality and performance of this method by screening a 30.42-million-compound DEL against the folate receptor, carbonic anhydrase 12 and the epidermal growth factor receptor on live cells, and identify and validate a series of novel ligands for these targets. Given the high therapeutic significance of membrane proteins and their intractability to traditional high-throughput screening approaches, this method has the potential to facilitate membrane-protein-based drug discovery by harnessing the power of DEL.

Detection of membrane receptors on per tumor cell by nonimmobilized cell capillary electrophoresis and a mathematic model.

Folate receptors (FRs) are a class of valuable therapeutic target which is highly expressed on a variety of cancers. The accurate detection of the expression of FRs in different cells is conducive to improve the accuracy of FR targeted tumor therapy. Herein, a method based on nonimmobilized cell capillary electrophoresis (NICCE) combined with a mathematic model to quantify FRs on each single tumor cell was developed. At first, we studied the interactions between FA and A549, HT-29, HepG2, and U87MG cells by NICCE respectively, and calculated the kinetic parameters (Ka, k', ka, and kd). Next, we established a mathematic model to accurately determine the number of moles of FRs on per A549, HT-29, HepG2, and U87MG cell for the first time, that were (10.44 ± 0.53) × 10-19 mol, (34.32 ± 1.33) × 10-19 mol, (337.14 ± 10.11) × 10-19 mol, and (37.31 ± 2.13) × 10-19 mol. Then, these re-sults were proved to be consistent with the results of enzyme-linked immunosorbent assay (ELISA). Therefore, this method is simple, rapid, sensitive, and without protein separation or purification, which is expected to achieve clinical detection of cell membrane receptor expression level of cell membrane receptors on a single cell, which may be greatly beneficial to further clinical diagnosis and therapy.