Tris-assisted one-step fabrication of functional carbon dots for specific folate receptor positive-expressed cancer cell imaging

Specific staining of cancer cells is momentous for cancer research. Nanoprobe with multivalent recognition is emerging as powerful tools for bioimaging, but the nonspecific cell uptake and complex functional modification procedures are still obstacles for specific detection and convenient synthesis. Carbon dots (CDs) with an intrinsic targeting ability, excellent optical properties and biocompatibility acquired from an efficient one-step fabrication procedure were urgently desired in specific cancer cells visualization. Herein, inspired by the interrelationships between interface and biomolecular mechanisms, we suggested that it was possible to construct CDs with the desired characteristics for folate receptor (FR) positive-expressed cancer cell imaging via rich hydroxyl groups Tris-assisted one-step hydrothermal treatment of folate acid (FA) and l-Arginine (L-Arg) precursors. The prepared small-sized F-CDs were equipped with abundant hydroxyl, pterin and negative charge surface, and possessed environmental friendliness, outstanding photostability and biocompatibility. Moreover, F-CDs had an intrinsic FR positive-expressed cancer cell targeting ability without any post-modification of the ligands. Rich hydroxyl groups play a vital role in endowing the optical properties and biological effects of F-CDs. F-CDs could be used as a promising candidate for FR-expressed cancer cell labeling and tracking. In addition, the caveolae-mediated endocytosis pathway of F-CDs was ascertained. More importantly, experimental results confirmed that the combination of physicochemical properties may provide an efficient strategy to overcome non-specific cell uptake interactions for cell labeling. Our strategy put forward a promising alternative to design fluorescent CDs for extensive chemical and biomedical applications.

Folic acid-mediated enhancement of the diagnostic potential of luminescent europium-doped hydroxyapatite nanocrystals for cancer biomaging

Early and accurate cancer diagnosis is crucial for improving patient survival rates. Luminescent nanoparticles have emerged as a promising tool in fluorescence bioimaging for cancer diagnosis. To enhance diagnostic accuracy, ligands promoting endocytosis into cancer cells are commonly incorporated onto nanoparticle surfaces. Folic acid (FA) is one such ligand, known to specifically bind to folate receptors (FR) overexpressed in various cancer cells such as cervical and ovarian carcinoma. Therefore, surface modification of luminescent nanoparticles with FA can enhance both luminescence efficiency and diagnostic accuracy. In this study, luminescent europium-doped hydroxyapatite (EuHAp) nanocrystals were prepared via hydrothermal method and subsequently modified with (3-Aminopropyl)triethoxysilane (APTES) followed by FA to target FR-positive human cervical adenocarcinoma cell line (HeLa) cells. The sequential grafting of APTES and then FA formed a robust covalent linkage between the nanocrystals and FA. Rod-shaped FA-modified EuHAp nanocrystals, approximately 100 nm in size, exhibited emission peaks at 589, 615, and 650 nm upon excitation at 397 nm. Despite a reduction in photoluminescence intensity following FA modification, fluorescence microscopy revealed a remarkable 120-fold increase in intensity compared to unmodified EuHAp, attributed to the enhanced uptake of FA-modified EuHAp. Additionally, confocal microscope observations confirmed the specificity and the internalization of FA-modified EuHAp nanocrystals in HeLa cells. In conclusion, the modification of EuHAp nanocrystals with FA presents a promising strategy to enhance the diagnostic potential of cancer bioimaging probes.

In Vivo Labeling and Detection of Circulating Tumor Cells in Mice Using OTL38

PURPOSE

We recently developed an optical instrument to non-invasively detect fluorescently labeled circulating tumor cells (CTCs) in mice called 'Diffuse in vivo Flow Cytometry' (DiFC). OTL38 is a folate receptor (FR) targeted near-infrared (NIR) contrast agent that is FDA approved for use in fluorescence guided surgery of ovarian and lung cancer. In this work, we investigated the use OTL38 for in vivo labeling and detection of FR + CTCs with DiFC.

PROCEDURES

We tested OTL38 labeling of FR + cancer cell lines (IGROV-1 and L1210A) as well as FR- MM.1S cells in suspensions of Human Peripheral Blood Mononuclear cells (PBMCs) in vitro. We also tested OTL38 labeling and NIR-DIFC detection of FR + L1210A cells in blood circulation in nude mice in vivo.

RESULTS

62% of IGROV-1 and 83% of L1210A were labeled above non-specific background levels in suspensions of PBMCs in vitro compared to only 2% of FR- MM.1S cells. L1210A cells could be labeled with OTL38 directly in circulation in vivo and externally detected using NIR-DiFC in mice with low false positive detection rates.

CONCLUSIONS

This work shows the feasibility of labeling CTCs in vivo with OTL38 and detection with DiFC. Although further refinement of the DiFC instrument and signal processing algorithms and testing with other animal models is needed, this work may eventually pave the way for human use of DiFC.

Electrochemical biosensor based on PAMAM functionalized MXene nanoplatform for detection of folate receptor

The level of folate receptor (FR) has become one of the independent factors for measuring human tumor diseases. The precise quantification of FR is helpful for the early diagnosis and subsequent treatment of tumors. The modification of electrodes is a key issue in ensuring and enhancing the electrochemical biosensing ability. In this study, we in-situ synthesized a nanocomposite material with excellent conductivity and stability by grafting first-generation poly(amidoamine) dendrimers onto the MXene (Ti3C2TX) as the immobilized matrix (PAMAM@MXene). An electrochemical sensor was developed for FR monitor by loading the PAMAM@MXene on screen-printed carbon electrodes (SPCEs). Scanning electron microscopy (SEM) supported the effective synthesis of PAMAM@MXene. Under optimal conditions, the prepared sensor achieved the quantification of FR with a wide range of concentrations from 10 ng/mL to 1000 ng/mL with a detection limit (LOD) of 5.6 ng/mL. It also exhibited satisfactory selectivity, reproducibility, and stability, which provided the possibility for expanding new pathways in the detection of clinical FR.

Targeted delivery and apoptosis induction of CDK-4/6 inhibitor loaded folic acid decorated lipid-polymer hybrid nanoparticles in breast cancer cells

Targeted drug delivery is an advanced approach for active targeting of tumor that can enhance the concentration of the drug at the site of action and reduce the off-target toxicity and non-specific effects of the drug. Folate receptors (FR) are membrane-bound surface proteins, over-expressed in numerous solid tumors, folate and folate conjugates bind to FR with higher affinity. In the present investigation, we fabricated Folic acid (FA) decorated Palbociclib loaded lipid-polymer hybrid nanoparticles (FA-PLPHNPs) using quality by design (QbD) approach and evaluated its anti-cancer activity in folate receptor-positive breast cancer cell lines. 1HNMR, ATR-FTIR spectroscopic techniques confirmed the formation of DSPE-PEG-FA ligand. The optimized FA-PLPHNPs formulation exhibited 143.36 ± 5.24 nm, 0.172 ± 0.004, -16.84 ± 0.27 mV, and 93.12 ± 0.43 % of particle size, PDI, zeta potential and % entrapment efficiency, respectively. The FA-PLPHNPs exhibited an approximately 9, 11-fold reduction in IC50 values than free Palbociclib in MCF-7 and MDA-MB-231 cells at 48 h. The role of FA in targeting breast cancer was studied by means of a receptor-blocking assay, and concluded that FA-PLPHNPs were internalized into MCF-7 and MDA-MB-231 cells by folate receptor-mediated endocytosis. FA-PLPHNPs showed higher anti-cancer efficiency and caused enhanced reactive oxygen species generation, apoptosis (Acridine orange/ ethidium bromide dual staining and Annexin V/PI staining), reduced cell migration, and colony formation. Thus, the fabricated Palbociclib-loaded FA-conjugated lipid polymer hybrid nanoparticles could act as a potential nanocarrier for the treatment of breast cancer.

Folate Receptor Beta Signaling in the Regulation of Macrophage Antimicrobial Immune Response: A Scoping Review

Introduction

Folate, vitamin B9, is a water-soluble vitamin that is essential to cellular proliferation and division. In addition to the reduced folate carrier, eukaryotic cells take up folate through endocytosis mediated by one of two GPI-anchored folate receptors (FRs), FRα or FRβ. Two other isoforms of FR exist, FRγ and FRδ, neither of which support endocytic activities of FR signaling. FRβ is expressed primarily by monocytes and macrophages and highly expressed on activated macrophages. Macrophage expression of FRβ suggests a role for this receptor in modulating function of these immune sentinels, particularly as they engage in inflammatory processes. Despite several studies suggesting that folates can suppress inflammatory responses of macrophages to proinflammatory stimuli, there appears to be a lack of basic research examining the role of FRβ in modulating macrophage responses to microbial sensing. We therefore conducted a scoping review to assess evidence within the published literature addressing the question, "what is known about the extent to which FRβ regulates macrophage responses to sensing, and responding to, microorganisms?".

Methods

As a strategy for the study selection, we queried articles indexed in the research database PubMed and the search engine Google Scholar (up until August 12, 2023), including combinations of the research words: macrophage, folate receptor beta, FOLR2.

Results

We identified 2 relevant articles out of 153 that are worth discussing here, none of which directly addressed our research question.

Conclusion

There is an unmet need to better define the contribution of FRβ to regulating the macrophage response to microbes.

Clinical value of folate receptor-positive circulating tumor cells in patients with esophageal squamous cell carcinomas: a retrospective study

BACKGROUND

The aim of the study is to explore the role of preoperative folate receptor-positive circulating tumor cell (FR+CTC) levels in predicting disease-free survival (DFS) and overall survival (OS) in patients with esophageal squamous cell carcinomas (ESCC).

METHODS

Three ml blood samples were prospectively drawn from ESCC patients, and ligand-targeted polymerase chain reaction (LT-PCR) was used for the quantification of FR+CTCs. Other serum indicators were measured by traditional methods. Clinicopathological characteristics were obtained from the hospital medical record system, DFS and OS data were obtained by follow-up. The correlation between clinico-pathological characteristics, DFS, and OS and FR+CTCs were analyzed, respectively. Risk factors potentially affecting DFS and OS were explored by Cox regression analysis.

RESULTS

there were no significant correlations between FR+CTCs and patient age, sex, albumin, pre-albumin, C-reactive protein (CRP), ferritin and CRP/Albumin ratio, tumor size, grade of differentiation, lymph node metastasis, TNM stage, perineural invasion/vessel invasion (all P > 0.05). Nevertheless, preoperative FR+CTCs were an independent prognostic factor for DFS (HR 2.7; 95% CI 1.31-, P = 0.007) and OS (HR 3.37; 95% CI 1.06-, P = 0.04). DFS was significantly shorter for patients with post-operative FR+CTCs ≥ 17.42 FU/3ml compared with patients < 17.42 FU/3ml (P = 0.0012). For OS, it was shorter for patients with FR+CTCs ≥ 17.42 FU/3ml compared with patients < 17.42 FU/3ml, however, the difference did not reach statistical significance (P = 0.51).

CONCLUSIONS

ESCC patients with high FR+CTCs tend to have a worse prognosis. FR+CTCs may monitor the recurrence of cancers in time, accurately assess patient prognosis, and guide clinical decision-making.

TRIAL REGISTRATION

The study was approved by the Sichuan Cancer Hospital & Institute Ethics Committee (No. SCCHEC-02-2022-050).

Evaluation of acute toxicity and in vitro antitumor activity of a novel doxorubicin-loaded folate-coated pH-sensitive liposome

Doxorubicin (DOX) loaded liposomes have been used and studied in the last decades due to the significant decrease in DOX induced cardiac and systemic toxicity relative to administration of free drug. Therefore, new strategies are sought to improve DOX delivery and antitumor activity, while avoiding side effects. Recently, folate-coated pH-sensitive liposomes (SpHL-Fol) have been studied as a tool to enhance cellular uptake and antitumor activity of paclitaxel and DOX in breast cancer cells expressing folate receptor (FR+). However, the elucidation of folate functionalization relevance in DOX-loaded SpHL (SpHL-DOX-Fol) in different cell types (MDA-MB-231, MCF-7, and A549), as well as, the complete safety evaluation, is necessary. To achieve these objectives, SpHL-DOX-Fol was prepared and characterized as previously described. Antitumor activity and acute toxicity were evaluated in vivo through direct comparison of free DOX verses SpHL-DOX, a well-known formulation to reduce DOX cardiotoxicity. The obtained data are crucial to support future translational research. Liposomes showed long-term stability, suitable for biological use. Cellular uptake, cytotoxicity, and percentage of migration inhibition were significantly higher for MDA-MB-231 (FR+) treated with SpHL-DOX-Fol. In addition, SpHL-DOX-Fol demonstrated a decrease in the systemic toxic effects of DOX, mainly in renal and cardiac parameters evaluation, even using a higher dose (20 mg/kg). Collectively these data build the foundation of support demonstrating that SpHL-DOX-Fol could be considered a promising drug delivery strategy for the treatment of FR+ breast tumors.

Prospective validation of tumor folate receptor expression density with the association of pafolacianine fluorescence during intraoperative molecular imaging-guided lung cancer resections

PURPOSE

Pafolacianine, a folate receptor alpha-targeted NIR tracer, has demonstrated clear efficacy in intraoperative molecular imaging-guided (IMI) lung cancer surgery. However, the selection of patients who would benefit from IMI remains challenging given the variability of fluorescence with patient-associated and histopathologic factors. Our goal in this study was to prospectively evaluate whether preoperative FRα/FRβ staining can predict pafolacianine-based fluorescence during real-time lung cancer resections.

METHODS

This was a prospective study conducted between 2018 and 2022 that reviewed core biopsy and intraoperative data from patients with suspected lung cancer. A total of 196 patients were deemed eligible, of whom core biopsies were taken from 38 patients and assessed for FRα and FRβ expression by immunohistochemistry (IHC). All patients underwent infusion of pafolacianine 24 h prior to surgery. Intraoperative fluorescence images were captured with the VisionSense bandpass filter-enabled camera. All histopathologic assessments were performed by a board-certified thoracic pathologist.

RESULTS

Of the 38 patients, 5 (13.1%) were found to have benign lesions (necrotizing granulomatous inflammation, lymphoid aggregates) and 1 had metastatic non-lung nodule. Thirty (81.5%) had malignant lesions, with the vast majority (23, 77.4%) being lung adenocarcinoma (7 (22.5%) SCC). None of the benign tumors (0/5, 0%) exhibited in vivo fluorescence (mean TBR of 1.72), while 95% of the malignant tumors fluoresced (mean TBR of 3.11 ± 0.31) compared to squamous cell carcinoma (1.89 ± 0.29) of the lung and sarcomatous lung metastasis (2.32 ± 0.09) (p < 0.01). The TBR was significantly higher in the malignant tumors (p = 0.009). The median FRα and FRβ staining intensities were both 1.5 for benign tumors, while the FRα and FRβ staining intensities were 3 and 2 for malignant tumors, respectively. Increased FRα expression was significantly associated with the presence of fluorescence (p = 0.01), CONCLUSION: This prospective study sought to determine whether preoperative FRα and FRβ expression on core biopsy IHC correlates with intraoperative fluorescence during pafolacianine-guided surgery. These results, although of small sample size, including limited non-adenocarcinoma cohort, suggest that performing FRα IHC on preoperative core biopsies of adenocarcinomas as compared to squamous cell carcinomas could provide low-cost, clinically useful information for optimal patient selection which should be further explored in advanced clinical trials.

Study of folate-based carbon nanotube drug delivery systems targeted to folate receptor α by molecular dynamic simulations

We designed targeted drug delivery systems containing folate (FOL), the functionalized carbon nanotube (f-CNT) and doxorubicin (DOX), and studied the targeting properties of folate, f-CNT-FOL and DOX/f-CNT-FOL to folate receptor α (FRα). Folate was actively targeted to FRα in molecular dynamics simulations, and the dynamic process, effect of folate receptor evolution, and characteristics were analyzed. On this basis, the f-CNT-FOL and DOX/f-CNT-FOL nano-drug-carrier systems were designed, and the drug delivery process targeted to FRα was studied by 4 times MD simulations. The system evolution and detailed interactions of f-CNT-FOL and DOX/f-CNT-FOL with FRα residues were examined. We found that though the connection of CNT with the FOL could decrease the insertion depth of the pterin of FOL into the pocket of FRα, the loading of drug molecules could reduce this effect. Representative snapshots from the MD simulations were analyzed, showing that the location of DOX on the surface of CNT was constantly changed during the MD simulation, but the surface of the four rings of DOX were almost always parallel to the surface of CNT. The RMSD and RMSF were used to further analyze. The results may provide new insights for the design of novel targeted nano-drug-delivery systems.

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.

Surface-modified nanoparticles of docetaxel for chemotherapy of lung cancer: An intravenous to oral switch

Despite being potent, the marketed formulations of Docetaxel (DX) are associated with numerous side effects and are meant for intravenous administration. Advanced pharmaceutical nanotechnology has a significant potential to facilitate the 'intravenous (i.v) to oral switch'. The present research work deals with the development of an orally administrable, folate-receptor-targeted Nanostructured lipid carriers (NLCs) of DX (FA-DX-NLCs) for facilitating oral chemotherapy of lung cancer while overcoming the bioavailability and toxicity issues. The nanoformulation prepared to employ high-pressure homogenization and lyophilization, was evaluated and statistically analyzed for various in-vitro and in-vivo formulation characteristics. The lyophilized nanoparticles were observed to be spherical with a particle size of 183.4 ± 2.13 (D90), Pdi of 0.358 ± 0.03, % EE of 82.41 ± 2.44, % DL of 4.41 ± 0.54 and a zeta potential of -3.3 ± 0.7 mv. The increased oral in-vivo bioavailability of DX was evident from the plasma-concentration area under the time curve (AUC_0-t), which was ∼ 27-fold greater for FA-DX-NLCs as compared to DX suspension. The orally administered FA-DX-NLCs exhibited excellent antitumor efficacy in a pre-clinical model of lung carcinoma. Tumor staging, histopathology, and immunostaining of the tumors suggested greater anti-proliferative, apoptotic, anti-metastatic, and anti-angiogenic potential as compared to DX-suspension. The pre-clinical toxicity studies affirmed the excellent safety and bio-compatibility of FA-DX-NLCs. The research work presents immense translational potential for switching the DX-based chemotherapy for lung cancer from 'hospital to home.'

Folate Receptor as a Biomarker and Therapeutic Target in Solid Tumors

Folate is a B vitamin necessary for basic biological functions, including rapid cell turnover occurring in cancer cell proliferation. Though the role of folate as a causative versus protective agent in carcinogenesis is debated, several studies have indicated that the folate receptor (FR), notably subtype folate receptor alpha (FRα), could be a viable biomarker for diagnosis, progression, and prognosis. Several cancers, including gastrointestinal, gynecological, breast, lung, and squamous cell head and neck cancers overexpress FR and are currently under investigation to correlate receptor status to disease state. Traditional chemotherapies have included antifolate medications, such as methotrexate and pemetrexed, which generate anticancer activity during the synthesis phase of the cell cycle. Increasingly, the repertoire of pharmacotherapies is expanding to include FR as a target, with a heterogenous pool of directed therapies. Here we discuss the FR, expression and effect in cancer biology, and relevant pharmacologic inhibitors.

Folate receptor-targeted near-infrared photodynamic therapy for folate receptor-overexpressing tumors

BACKGROUND

Photodynamic therapy (PDT) is a minimally invasive form of cancer therapy, and the development of a novel photosensitizer (PS) with optimal properties is important for enhancing PDT efficacy. Folate receptor (FR) membrane protein is frequently overexpressed in 40% of human cancer and a good candidate for tumor-specific targeting. Specific active targeting of PS to FR can be achieved by conjugation with the folate moiety. A folate-linked, near-infrared (NIR)-sensitive probe, folate-Si-rhodamine-1 (FolateSiR-1), was previously developed and is expected to be applicable to NIR-PDT.

AIM

To investigate the therapeutic efficacy of NIR-PDT induced by FolateSiR-1, a FR-targeted PS, in preclinical cancer models.

METHODS

FolateSiR-1 was developed by conjugating a folate moiety to the Si-rhodamine derivative through a negatively charged tripeptide linker. FR expression in the designated cell lines was examined by western blotting (WB). The selective binding of FolateSiR-1 to FR was confirmed in FR overexpressing KB cells (FR+) and tumors by fluorescence microscopy and in vivo fluorescence imaging. Low FR expressing OVCAR-3 and A4 cell lines were used as negative controls (FR-). The NIR light (635 ± 3 nm)-induced phototoxic effect of FolateSiR-1 was evaluated by cell viability imaging assays. The time-dependent distribution of FolateSiR-1 and its specific accumulation in KB tumors was determined using in vivo longitudinal fluorescence imaging. The PDT effect of FolateSiR-1 was evaluated in KB tumor-bearing mice divided into four experimental groups: (1) FolateSiR-1 (100 μmol/L) alone; (2) FolateSiR-1 (100 μmol/L) followed by NIR irradiation (50 J/cm²); (3) NIR irradiation (50 J/cm²) alone; and (4) no treatment. Tumor volume measurement and immunohistochemical (IHC) and histological examinations of the tumors were performed to analyze the effect of PDT.

RESULTS

High FR expression was observed in the KB cells by WB, but not in the OVCAR-3 and A4 cells. Substantial FR-specific binding of FolateSiR-1 was observed by in vitro and in vivo fluorescence imaging. Cell viability imaging assays showed that NIR-PDT induced cell death in KB cells. In vivo longitudinal fluorescence imaging showed rapid peak accumulation of FolateSiR-1 in the KB tumors 2 h after injection. In vivo PDT conducted at this time point caused tumor growth delay. The relative tumor volumes in the PDT group were significantly reduced compared to those in the other groups [5.81 ± 1.74 (NIR-PDT) vs 12.24 ± 2.48 (Folate-SiR-1), vs 11.84 ± 3.67 (IR), vs 12.98 ± 2.78 (Untreated), at Day 16, P < 0.05]. IHC analysis revealed reduced proliferation marker Ki-67-positive cells in the PDT treated tumors, and hematoxylin-eosin staining revealed features of necrotic- and apoptotic cell death.

CONCLUSION

FolateSiR-1 has potential for use in PDT, and FR-targeted NIR-PDT may open a new effective strategy for the treatment of FR-overexpressing tumors.

Novel localization of folate transport systems in the murine central nervous system

BACKGROUND

Folates are a family of B9 vitamins that serve as one-carbon donors critical to biosynthetic processes required for the development and function of the central nervous system (CNS) in mammals. Folate transport is mediated by three highly specific systems: (1) folate receptor alpha (FRα; FOLR1/Folr1), (2) the reduced folate-carrier (RFC; SLC19A1/Slc19a1) and (3) the proton-coupled folate transporter (PCFT; SLC46A1/Slc46a1). Folate transport into and out of the CNS occurs at the blood-cerebrospinal fluid barrier (BCSFB), mediated by FRα and PCFT. Impairment of folate transport at the BCSFB results in cerebral folate deficiency in infants characterized by severe neurological deficiencies and seizures. In contrast to the BCSFB, CNS folate transport at other brain barriers and brain parenchymal cells has not been extensively investigated. The aim of this study is to characterize folate transport systems in the murine CNS at several known barriers encompassing the BCSFB, arachnoid barrier (AB), blood-brain barrier (BBB) and parenchymal cells (astrocytes, microglia, neurons).

METHODS

Applying immunohistochemistry, localization of folate transport systems (RFC, PCFT, FRα) was examined at CNS barriers and parenchymal sites in wildtype (C57BL6/N) mice. Subcellular localization of the folate transport systems was further assessed in an in vitro model of the mouse AB. Gene and protein expression was analyzed in several in vitro models of brain barriers and parenchyma by qPCR and western blot analysis.

RESULTS

RFC, PCFT, and FRα expression was localized within the BCSFB and BBB consistent with previous reports. Only RFC and PCFT expression was detected at the AB. Varied levels of RFC and PCFT expression were detected in neuronal and glial cells.

CONCLUSIONS

Localization of RFC and PCFT within the AB, described here for the first time, suggest that AB may contribute to folate transport between the peripheral circulation and the CSF. RFC and PCFT expression observed in astrocytes and microglia is consistent with the role that one or both of these transporters may play in delivering folates into cells within brain parenchyma. These studies provide insights into mechanisms of folate transport in the CNS and may enhance our understanding of the critical role folates play in neurodevelopment and in the development of novel treatment strategies for disorders of brain folate deficiency due to impaired transporter function.

Microvesicle-camouflaged biomimetic nanoparticles encapsulating a metal-organic framework for targeted rheumatoid arthritis therapy

Background

Methotrexate (MTX) has been highlighted for Rheumatoid arthritis (RA) treatment, however, MTX does not accumulate well at inflamed sites, and long-term administration in high doses leads to severe side effects. In this study, a novel anti-RA nanoparticle complex was designed and constructed, which could improve the targeted accumulation in inflamed joints and reduce side effects.

Results

Here, we prepared a pH-sensitive biomimetic drug delivery system based on macrophage-derived microvesicle (MV)-coated zeolitic imidazolate framework-8 nanoparticles that encapsulated the drug methotrexate (hereafter MV/MTX@ZIF-8). The MV/MTX@ZIF-8 nanoparticles were further modified with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[folate (polyethylene glycol)-2000] (hereafter FPD/MV/MTX@ZIF-8) to exploit the high affinity of folate receptor β for folic acid on the surface of activated macrophages in RA. MTX@ZIF-8 nanoparticles showed high DLE (~ 70%) and EE (~ 82%). In vitro study showed that effective drug release in an acidic environment could be achieved. Further, we confirmed the activated macrophage could uptake much more FPD/MV/MTX@ZIF-8 than inactivated cells. In vivo biodistribution experiment displayed FPD/MV/MTX@ZIF-8 nanoparticles showed the longest circulation time and best joint targeting. Furthermore, pharmacodynamic experiments confirmed that FPD/MV/MTX@ZIF-8 showed sufficient therapeutic efficacy and safety to explore clinical applications.

Conclusions

This study provides a novel approach for the development of biocompatible drug-encapsulating nanomaterials based on MV-coated metal-organic frameworks for effective RA treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01447-0.

Folate derivatives, 5-methyltetrahydrofolate and 10-formyltetrahydrofolate, protect BEAS-2B cells from high glucose-induced oxidative stress and inflammation

Folate (vitamin B₉) and its biologically active derivatives are well-known antioxidant molecules protecting cells from oxidative degradation. The presence of high glucose, often found in diabetic patients, causes oxidative stress resulting in cellular stress and inflammatory injury. Cells in organs such as the lung are highly prone to inflammation, and various protective mechanisms exist to prevent the progressive disorders arising from inflammation. In the present study, the synthetic form of folate, i.e. folic acid, and active forms of folate, i.e. 5-methyltetrahydrofolate and 10-formyltetrahydrofolate, were evaluated for their antioxidant and antiinflammatory potential against high glucose (50 mM)–mediated oxidative stress and inflammation in BEAS-2B cells, an immortalised bronchial epithelial cell line. High glucose treatment showed a 67% reduction in the viability of BEAS-2B cells, which was restored to the viability levels seen in control cultures by the addition of active folate derivatives to the culture media. The DCFH-DA fluorometric assay was performed for oxidative stress detection. The high glucose–treated cells showed a significantly higher fluorescence intensity (1.81- and 3.8-fold for microplate assay and microscopic observation, respectively), which was normalised to control levels on supplementation with active folate derivatives. The proinflammatory NF-κB p50 protein expression in the active folate derivative–supplemented high glucose–treated cells was significantly lower compared to the folic acid treatment. In support of these findings, in silico microarray GENVESTIGATOR database analysis showed that in bronchiolar small airway epithelial cells exposed to inflammatory condition, folate utilization pathway genes are largely downregulated. However, the folate-binding protein gene, which encodes to the folate receptor 1 (FOLR1), is significantly upregulated, suggesting a high demand for folate by these cells  in inflammatory situations. Supplementation of the active folate derivatives 5-methyltetrahydrofolate and 10-formyltetrahydrofolate resulted in significantly higher protection over the folic acid from high glucose–induced oxidative stress and inflammation. Therefore, the biologically active folate derivatives could be a suitable alternative over the folic acid for alleviating inflammatory injury-causing oxidative stress.

The role of folate receptor-positive circulating tumor cell analysis in the diagnosis of colorectal cancer: a retrospective cohort study

OBJECTIVE

To explore the application value of folate receptor-positive circulating tumor cell analysis (FR⁺-CTC analysis) in the diagnosis of colorectal cancer (CRC).

METHODS

Clinical data of CRC patients and healthy subjects admitted to our hospital from January 2019 to October 2019 were retrospectively collected. CTC result and serological and pathological outcomes of the study patients were collected and analyzed. Receiver operating characteristic curve (ROC curve) was drawn.

RESULTS

The CTC levels of cancer patients (9.34 ± 3.53 FU/3 ml) were significantly higher than those of healthy subjects (7.00 ± 2.33 FU/3 ml). CTC levels could be related to cancer stage and metastasis in patients. ROC curves were drawn and the area under the ROC curve (AUC) was 0.702. The cutoff value was determined to be 8.87 FU/3 ml. At this cutoff value, the sensitivity and specificity of FR⁺-CTC analysis in the diagnosis of colorectal cancer were 61.8% and 82.6%, respectively. The diagnostic efficiency of FR⁺-CTCs in advanced CRC was significantly higher than that in the early stage. And the cutoff value of early and advanced stage CRC was determined to be 9.66 FU/3 ml.

CONCLUSION

FR⁺-CTC analysis has high potential in recurrence diagnosis and decision of adjuvant chemotherapy for CRC.

Design and evaluation of folate-modified liposomes for pulmonary administration in lung cancer therapy

Pulmonary drug administration for the treatment of lung cancer is useful because the drug is directly delivered to the lung tissues with minimal invasiveness and higher efficiency compared to other conventional methods. However, it is critical to enhance drug accumulation in the lung cancer tissues to achieve sufficient therapeutic efficacy. The submicron-sized liposome (ssLip) preparation is one of the most promising approaches to enhance drug accumulation in the lungs; however, ssLips prepared for conventional inhalation do not have tumour selectivity. Therefore, in this study, we prepared folate (FA)-modified ssLip (FA-ssLip) to enhance drug accumulation in folate receptor (FR)-expressing lung cancer cells, and evaluated its physicochemical properties and potential as a drug carrier in pulmonary administration. In addition, we prepared rapamycin (RM-an autophagy-inducing anticancer drug)-loaded FA-ssLip (RM/FA-ssLip) and investigated its anti-tumour effect. FA-ssLip showed excellent nanoparticle properties with submicron size (approximately 120 nm) and high lung accumulation in lung cancer mouse model-bearing LL2 cells-a mouse Lewis lung carcinoma cell line. RM/FA-ssLip showed significant cytotoxic activity in FR-expressing cancer cells. In addition, pulmonary administration of RM/FA-ssLip extended the survival of LL2 cell tumour-bearing mice. Taken together, our results suggest the potential of FA-ssLip as a pulmonary drug carrier for the efficient treatment of lung cancer.

Methotrexate-loaded folic acid of solid-phase synthesis conjugated gold nanoparticles targeted treatment for rheumatoid arthritis

PURPOSE

Methotrexate (MTX) is a first-line drug for rheumatoid arthritis (RA). Targeting of MTX to inflamed joints is essential to the prevention of potential toxicity and improving therapeutic effects. Gold nanoparticles (GNPs) are characterized by controllable particle sizes and good biocompatibilities, therefore, they are promising drug delivery systems. We aimed at developing a GNPs drug delivery system incorporating MTX and folic acid (FA) with strong efficacies against RA.

METHODS

MTX-Cys-FA was synthesized through solid-phase organic synthesis. Then, it was coupled with sulfhydryl groups in GNPs, thereby successfully preparing a GNPs/MTX-Cys-FA nanoconjugate with targeting properties. Physical and chemical techniques were used to characterize it. Moreover, we conducted its stability, release, pharmacokinetics, biodistribution and cell cytotoxicity, cell uptake, cell migration, as well as its therapeutic effect on CIA rats. The histopathology was conducted to investigate anti-RA effects of GNPs/MTX-Cys-FA nanoconjugates.

RESULTS

The GNPs/MTX-Cys-FA nanoconjugate exhibited a spherical appearance, had a particle size of 103.06 nm, a zeta potential of -33.68 mV, drug loading capacity of 11.04 %, and an encapsulation efficiency of 73.61%. Cytotoxicity experiments revealed that GNPs had good biocompatibilities while GNPs/MTX-Cys-FA exhibited excellent drug-delivery abilities. Cell uptake and migration experiment showed that nanoconjugates containing FA by LPS activated mouse mononuclear macrophages (RAW264.7) was significantly increased, and they exerted significant inhibitory effects on human fibroblast-like synoviocytes (HFLS) of RA (p<0.01). In addition, the nanoconjugate prolonged blood circulation time of MTX in collagen-induced arthritis (CIA) rats (p<0.01), enhanced MTX accumulation in inflamed joints (p<0.01), enhanced their therapeutic effects (p<0.01), and reduced toxicity to major organs (p<0.01).

CONCLUSION

GNPs/MTX-Cys-FA nanoconjugates provide effective approaches for RA targeted therapeutic strategies.

Fluorescence Labeling of Circulating Tumor Cells with a Folate Receptor-Targeted Molecular Probe for Diffuse In Vivo Flow Cytometry

PURPOSE

We recently developed a new instrument called "diffuse in vivo flow cytometry" (DiFC) for enumeration of rare fluorescently labeled circulating tumor cells (CTCs) in small animals without drawing blood samples. Until now, we have used cell lines that express fluorescent proteins or were pre-labeled with a fluorescent dye ex vivo. In this work, we investigated the use of a folate receptor (FR)-targeted fluorescence molecular probe for in vivo labeling of FR+ CTCs for DiFC.

PROCEDURES

We used EC-17, a FITC-folic acid conjugate that has been used in clinical trials for fluorescence-guided surgery. We studied the affinity of EC-17 for FR+ L1210A and KB cancer cells. We also tested FR- MM.1S cells. We tested the labeling specificity in cells in culture in vitro and in whole blood. We also studied the detectability of labeled cells in mice in vivo with DiFC.

RESULTS

EC-17 showed a high affinity for FR+ L1210A and KB cells in vitro. In whole blood, 85.4 % of L1210A and 80.9 % of KB cells were labeled above non-specific background with EC-17, and negligible binding to FR- MM.1S cells was observed. In addition, EC-17-labeled CTCs were readily detectable in circulation in mice with DiFC.

CONCLUSIONS

This work demonstrates the feasibility of labeling CTCs with a cell-surface receptor-targeted probe for DiFC, greatly expanding the potential utility of the method for pre-clinical animal models. Because DiFC uses diffuse light, this method could be also used to enumerate CTCs in larger animal models and potentially even in humans.

Selenofolate inhibits the proliferation of IGROV1 cancer cells independently from folate receptor alpha

Cancer is one of the main causes of human mortality worldwide and novel chemotherapeutics are required due to the limitations of conventional cancer therapies. For example, using redox selenium compounds as novel chemotherapeutics seem to be very promising. The objective of this study was to explore if folate could be used as a carrier to deliver a newly synthesised selenium derivative selenofolate into cancer cells. Particularly, the cytotoxic effects of this selenofolate compound were investigated in a variety of cancer cell types including lung, liver, and cervical cancers and specifically IGROV1 cells. Our results showed that selenofolate inhibits the growth of cancer cells in-vitro. However, despite the expectations, folate receptor alpha (FRα) was not involved in the transportation of selenofolate compound into the cells i.e. growth inhibition was independent of FRα, suggesting that multiple transporters (e.g. reduced folate carrier-1) are possibly involved in the delivery and internalisation of folate in IGROV1 cells. Additionally, selenofolate did not exert cell death through apoptosis. Instead, anti-proliferative activity showed to be the main cause of growth inhibition of selenolofate in the IGROV1 cell line. In conclusion, selenofolate inhibits the growth of cancer cells and thus, may be explored further as a potential chemotherapeutic agent.

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 and characterization of folic acid conjugated sulfated polysaccharides on NK cell activation and cellular uptake in HeLa cells

In this study, the sulfated polysaccharide (SP) of Codium fragile was conjugated to folic acid (SP-FA). FT-IR and ¹H NMR techniques revealed the occurrence of esterification reaction between the hydroxyl group of SP and the γ-carboxyl group of FA that confirming the SP-FA conjugation. SP and SP-FA did not show any direct toxicity on NK cells and HeLa cells. However, the treatment of SP and SP-FA enhance the NK cells cytotoxicity against HeLa cells by the upregulation of IFN-γ, TNF-α, perforin, and Granzyme-B. Moreover, NK cells activation was stimulated through NF-кB and MAPK pathways. The binding capacity studies exposed the targeting ability of HeLa cells by folate receptor (FR) which was assessed by a confocal quantitative image cytometer analysis. These results indicate that SP-FA could be used as selective drug delivery systems for targeting FR-overexpressed cancer cells with less toxicity.

Efficacy and tolerability of folate-aminopterin therapy in a rat focal model of multiple sclerosis

BACKGROUND

Activated macrophages in the experimental model of multiple sclerosis (MS) express folate receptor-β (FR-β), representing a promising target for the treatment of MS. Here, we both evaluated the efficacy of a novel folate-aminopterin construct (EC2319) in a rat focal model of multiple sclerosis (MS) and investigated the utility of ⁶⁸Ga-labeled 1,4,7-triazacyclononane-1,4,7-triacetic acid-conjugated folate (⁶⁸Ga-FOL) for assessing inflammatory lesions. In addition, we investigated whether FR-β is expressed in the brain of patients with MS.

METHODS

Focal delayed-type hypersensitivity experimental autoimmune encephalomyelitis (fDTH-EAE) was induced in 40 Lewis rats; 20 healthy Lewis rats were used as controls. Rats were divided into six groups according to the duration of disease (control, acute, or chronic) and intervention (vehicle versus EC2319). ⁶⁸Ga-FOL analyses, histology, and immunofluorescence of the brain were performed to evaluate the efficacy of subcutaneously administered EC2319 on lesion development. Immunofluorescence was used to assess FR-β expression in postmortem brain samples from 5 patients with MS and 5 healthy controls.

RESULTS

Immunofluorescence and histological analyses revealed significant reductions in FR-β expression (P < 0.05) and lesion size (P < 0.01), as well as improved inducible nitric oxide synthase/mannose receptor C type 1 ratios (P < 0.01) in macrophages and microglia during the chronic but not acute phase of fDTH-EAE in EC2319-treated rats. The uptake of IV-injected ⁶⁸Ga-FOL in the brain was low and did not differ between the groups, but the in vitro binding of ⁶⁸Ga-FOL was significantly lower in EC2319-treated rats (P < 0.01). FR-β positivity was observed in chronically active lesions and in normal-appearing white matter in MS brain samples.

CONCLUSIONS

EC2319 was well tolerated and attenuated inflammation and lesion development in a rat model of a chronic progressive form of MS. Human MS patients have FR-β-positive cells in chronically active plaques, which suggests that these results may have translational relevance.

Folic acid-appended galactoxyloglucan-capped iron oxide nanoparticles as a biocompatible nanotheranostic agent for tumor-targeted delivery of doxorubicin

Iron oxide nanoparticles (IONPs) are employed as MRI contrast agents and as effective drug delivery vehicles. However, the limited solubility and biodegradability of these nanoparticles need to be improved for safer biomedical applications. In an attempt to improve the bottlenecks associated with IONPs, the current study focuses on the synthesis of folic acid conjugated, galactoxyloglucan-iron oxide nanoparticles (FAPIONPs), for the loading and controlled release of the encapsulated chemotherapeutic agent doxorubicin (DOX). The as-designed DOX@FAPIONPs induced a dose-dependent increase in cytotoxicity in folate receptor-positive cells through a caspase-mediated programmed cell death pathway while bare DOX demonstrated a non-targeted toxicity profile. Using LC-MS/MS analysis, several major biological processes altered in treated cells, from which, cell cycle, cellular function and maintenance were the most affected. Detailed toxicity studies in healthy mice indicated the absence of any major side effects while bare drugs created substantial organ pathology. Gadolinium-based contrast agents have a risk of adverse effects, including nephrogenic systemic fibrosis overcome by the administration of DOX@FAPIONPs in xenograft mice model. Tumor-targeted biodistribution pattern with a favorable DOX pharmacokinetics will be the driving factor behind the appealing tumor reduction capacity and increased survival benefits demonstrated on solid tumor-bearing mice.

Surface-engineered nanostructured lipid carrier systems for synergistic combination oncotherapy of non-small cell lung cancer

Nanoparticle-aided combination chemotherapy offers several advantages like ratiometric drug delivery, dose reduction, multi-targeted therapy, synergism, and overcoming multi-drug resistance. The current research was instigated to facilitate targeted and ratiometric co-delivery of docetaxel (DT) and curcumin (CR) through the development of folate (FA)-appended nanostructured lipid carriers (NLCs), i.e., FA-DTCR-NLCs to lung cancer cells. The FA-DTCR-NLCs were formulated by employing a scaleable and solvent-free high-pressure homogenization approach. The FA-DTCR-NLCs were evaluated for in vitro and in vivo characteristics using suitable analytical and statistical techniques. The FA-DTCR-NLCs demonstrated physicochemical properties and particokinetics suitable for targeted, ratiometric co-delivery of the anticancer agents. This was further affirmed by significantly better in vivo relative bioavailability of DT (24.85 fold) with FA-DTCR-NLCs as compared with Taxotere^® (p < 0.05) and cell line studies. A significant tumor regression was observed from the results of tumor staging in a murine model of lung carcinoma (p < 0.05). Immunostaining of the tumor sections with tumor differentiation biomarkers suggested considerably higher apoptotic, anti-proliferative, anti-angiogenic, and anti-metastatic potential of FA-DTCR-NLCs compared with Taxotere^®. In vivo toxicity assessment of the FA-DTCR-NLCs demonstrated a noteworthy reduction in DT associated side effects. The in vitro and in vivo pre-clinical findings prove the therapeutic and safety pre-eminence of FA-DTCR-NLCs for the treatment of NSCLC.

A Bibliometric analysis of folate receptor research

BACKGROUND

The objective of this study was to conduct a bibliometric analysis of the entire field of folate receptor research. Folate receptor is expressed on a wide variety of cancers and certain immune cells.

METHODS

A Web of Science search was performed on folate receptor or folate binding protein (1969-to June 28, 2019). The following information was examined: publications per year, overall citations, top 10 authors, top 10 institutions, top 10 cited articles, top 10 countries, co-author collaborations and key areas of research.

RESULTS

In total, 3248 documents for folate receptor or folate binding protein were retrieved for the study years outlined in the methods section search query. The range was 1 per year in 1969 to 264 for the last full year studied (2018). A total of 123,720 citations for the 3248 documents retrieved represented a mean citation rate per article of 38.09 and range of 1667 citations (range 0 to 1667). Researchers in 71 countries authored publications analyzed in this study. The US was the leader in publications and had the highest ranking institution. The top 10 articles have been cited 7270 times during the time frame of this study. The top cited article had an average citation rate of 110 citations per year. Network maps revealed considerable co-authorship among several of the top 10 authors.

CONCLUSION

Our study presents several important insights into the features and impact of folate receptor research. To our knowledge, this is the first bibliometric analysis of folate receptor.

Promising potential of [177Lu]Lu-DOTA-folate to enhance tumor response to immunotherapy-a preclinical study using a syngeneic breast cancer model

PURPOSE

It was previously demonstrated that radiation effects can enhance the therapy outcome of immune checkpoint inhibitors. In this study, a syngeneic breast tumor mouse model was used to investigate the effect of [¹⁷⁷Lu]Lu-DOTA-folate as an immune stimulus to enhance anti-CTLA-4 immunotherapy.

METHODS

In vitro and in vivo studies were performed to characterize NF9006 breast tumor cells with regard to folate receptor (FR) expression and the possibility of tumor targeting using [¹⁷⁷Lu]Lu-DOTA-folate. A preclinical therapy study was performed over 70 days with NF9006 tumor-bearing mice that received vehicle only (group A); [¹⁷⁷Lu]Lu-DOTA-folate (5 MBq; 3.5 Gy absorbed tumor dose; group B); anti-CTLA-4 antibody (3 × 200 μg; group C), or both agents (group D). The mice were monitored regarding tumor growth over time and signs indicating adverse events of the treatment.

RESULTS

[¹⁷⁷Lu]Lu-DOTA-folate bound specifically to NF9006 tumor cells and tissue in vitro and accumulated in NF9006 tumors in vivo. The treatment with [¹⁷⁷Lu]Lu-DOTA-folate or an anti-CTLA-4 antibody had only a minor effect on NF9006 tumor growth and did not substantially increase the median survival time of mice (23 day and 19 days, respectively) as compared with untreated controls (12 days). [¹⁷⁷Lu]Lu-DOTA-folate sensitized, however, the tumors to anti-CTLA-4 immunotherapy, which became obvious by reduced tumor growth and, hence, a significantly improved median survival time of mice (> 70 days). No obvious signs of adverse effects were observed in treated mice as compared with untreated controls.

CONCLUSION

Application of [¹⁷⁷Lu]Lu-DOTA-folate had a positive effect on the therapy outcome of anti-CTLA-4 immunotherapy. The results of this study may open new perspectives for future clinical translation of folate radioconjugates.

Preclinical evaluation of 5-methyltetrahydrofolate-based radioconjugates-new perspectives for folate receptor-targeted radionuclide therapy

Purpose

The folate receptor (FR) is frequently overexpressed in a variety of tumor types and, hence, an interesting target for radionuclide therapy. The aim of this study was to evaluate a new class of albumin-binding radioconjugates comprising 5-methyltetrahydrofolate (5-MTHF) as a targeting agent and to compare their properties with those of the previously established folic acid-based [¹⁷⁷Lu]Lu-OxFol-1.

Methods

[¹⁷⁷Lu]Lu-6R-RedFol-1 and [¹⁷⁷Lu]Lu-6S-RedFol-1 were investigated in vitro using FR-positive KB tumor cells. Biodistribution studies were performed in KB tumor-bearing mice, and the areas under the curve (AUC_{0 → 120h}) were determined for the uptake in tumors and kidneys. [¹⁷⁷Lu]Lu-6R-RedFol-1 was compared with [¹⁷⁷Lu]Lu-OxFol-1 in a therapy study over 8 weeks using KB tumor-bearing mice.

Results

Both radioconjugates demonstrated similar in vitro properties as [¹⁷⁷Lu]Lu-OxFol-1; however, the tumor uptake of [¹⁷⁷Lu]Lu-6R-RedFol-1 and [¹⁷⁷Lu]Lu-6S-RedFol-1 was significantly increased in comparison with [¹⁷⁷Lu]Lu-OxFol-1. In the case of [¹⁷⁷Lu]Lu-6S-RedFol-1, also the kidney uptake was increased; however, renal retention of [¹⁷⁷Lu]Lu-6R-RedFol-1 was similar to that of [¹⁷⁷Lu]Lu-OxFol-1. This led to an almost 4-fold increased tumor-to-kidney AUC_{0 → 120h} ratio of [¹⁷⁷Lu]Lu-6R-RedFol-1 as compared with [¹⁷⁷Lu]Lu-6S-RedFol-1 and [¹⁷⁷Lu]Lu-OxFol-1. At equal activity, the therapeutic effect of [¹⁷⁷Lu]Lu-6R-RedFol-1 was better than that of [¹⁷⁷Lu]Lu-OxFol-1, reflected by a slower tumor growth and, consequently, an increased median survival time (49 days vs. 34 days).

Conclusion

This study demonstrated the promising potential of 5-MTHF-based radioconjugates for FR-targeting. Application of [¹⁷⁷Lu]Lu-6R-RedFol-1 resulted in unprecedentedly high tumor-to-kidney ratios and, as a consequence, a superior therapeutic effect as compared with [¹⁷⁷Lu]Lu-OxFol-1. These findings, together with the absence of early side effects, make [¹⁷⁷Lu]Lu-6R-RedFol-1 attractive in view of a future clinical translation.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-04980-y) contains supplementary material, which is available to authorized users.

Intraoperative Molecular Imaging Utilizing a Folate Receptor-Targeted Near-Infrared Probe Can Identify Macroscopic Gastric Adenocarcinomas

PURPOSE

Current methods of assessing disease burden in gastric adenocarcinoma are imperfect. Improved visualization during surgery with intraoperative molecular imaging (IMI) could improve gastric adenocarcinoma staging and guide surgical decision-making. The goal of this study was to evaluate if IMI with a folate receptor-targeted near-infrared fluorescent agent, OTL38, could identify gastric adenocarcinomas during surgery.

PROCEDURES

Five patients were enrolled in an IMI clinical trial. Patients received a folate receptor-targeted near-infrared dye (OTL38) 1.5-6 h prior to surgery. During staging laparoscopy and gastric resection, IMI was utilized to identify the primary tumor and any fluorescent lymph nodes. Resected tumors were analyzed for folate receptor alpha (FRα) and CD68 expression using immunohistochemistry. Microscopic OTL38 accumulation was examined with immunofluorescence.

RESULTS

Four out of five patients underwent total or subtotal gastrectomy; one had a staging laparoscopy only. All four patients who underwent gastric resection had invasive gastric adenocarcinoma; three had fluorescent tumors, mean tumor to background ratio (TBR) 4.1 ± 2.9. The one patient with a non-fluorescent tumor had a T1a tumor with two 0.4 cm tumor foci within a larger polyp. In each case with a fluorescent tumor, the fluorescence was evident from the exterior of the stomach. Two of the fluorescent tumors had modest FRα expression and no CD68 expression. One fluorescent tumor had high CD68 expression and no FRα expression.

CONCLUSIONS

Intraoperative molecular imaging of gastric adenocarcinoma with OTL38 is feasible. Further studies should evaluate the clinical utility of this technique.

Targeted bioimaging and sensing of folate receptor-positive cancer cells using folic acid-conjugated sulfur-doped graphene quantum dots

For the first time is reported a facile in situ synthesis of folic acid-conjugated sulfur-doped graphene quantum dots (FA-SGQDs) through simple pyrolysis of citric acid (CA), 3-mercaptopropionic acid (MPA), and FA. The as-prepared FA-SGQDs were extensively characterized to confirm the synthesis and incidence of FA molecule on the surface of SGQDs through advanced characterization techniques. Upon excitation at 370-nm wavelength, FA-SGQDs exhibited blue fluorescence with an emission band at 455 nm. While exhibiting relatively high quantum yield (~ 78%), favorable biocompatibility, excellent photostability, and desirable optical properties, the FA-SGQDs showed suitability as a fluorescent nanoprobe to distinguish the folate receptor (FR)-positive and FR-negative cancer cells. The experimental studies revealed that FA-SGQDs aptly entered into FR-positive cancer cells via a non-immunogenic FR-mediated endocytosis process. Additionally, the FA-SGQDs exhibited excellent free radical scavenging activity. Hence, these FA-SGQDs hold high promise to serve as efficient fluorescent nanoprobes for the pre-diagnosis of cancer through targeted bioimaging and other pertinent biological studies. Graphical abstract.

Cu-In-S/ZnS@carboxymethylcellulose supramolecular structures: Fluorescent nanoarchitectures for targeted-theranostics of cancer cells

Although the field of oncology nanomedicine has shown indisputable progress in recent years, cancer remains one of the most lethal diseases, where the early diagnosis plays a pivotal role in the patient's prognosis and therapy. Herein, we report for the first time, the synthesis of biocompatible nanostructures composed of Cu-In-S and Cu-In-S/ZnS nanoparticles functionalized with carboxymethylcellulose biopolymer produced by a green aqueous process. These inorganic-organic colloidal nanohybrids developed supramolecular architectures stabilized by chemical functional groups of the polysaccharide shell with the fluorescent semiconductor nanocrystal core, which were extensively characterized by several morphological and spectroscopical techniques. Moreover, these nanoconjugates were covalently bonded with folic acid via amide bonds and electrostatically conjugated with the anticancer drug, producing functionalized supramolecular nanostructures. They demonstrated nanotheranostics properties for bioimaging and drug delivery vectorization effective for killing breast cancer cells in vitro. These hybrids offer a new nanoplatform using fluorescent polysaccharide-drug conjugates for cancer theranostics applications.

Folate-appended cyclodextrin improves the intratumoral accumulation of existing boron compounds

In this study, the tumor accumulation and antitumor effect of folate-modified cyclodextrin (ND201) purified with folate receptor (FR) connotated with BSH were examined. ND201 and BSH were stably bound in blood, and the mixing ratio 1:1 was most efficient. ND-BSH showed higher boron concentration (38.5 ppm) than BSH alone (11.25 ppm). The maximum ND-BSH tumor/blood ratio was also markedly higher (6.58) than that of BSH alone (1.04). ND-BSH showed a significant antitumor effect compared with BSH after neutron irradiation.

Design, synthesis and biological evaluation of novel pyrrolo[2,3-d]pyrimidine as tumor-targeting agents with selectivity for tumor uptake by high affinity folate receptors over the reduced folate carrier

Tumor-targeted 6-substituted pyrrolo[2,3-d]pyrimidine benzoyl compounds based on 2 were isosterically modified at the 4-carbon bridge by replacing the vicinal (C11) carbon by heteroatoms N (4), O (5) or S (6), or with an N-substituted formyl (7), trifluoroacetyl (8) or acetyl (9). Replacement with sulfur (6) afforded the most potent KB tumor cell inhibitor, ~6-fold better than the parent 2. In addition, 6 retained tumor transport selectivity via folate receptor (FR) α and -β over the ubiquitous reduced folate carrier (RFC). FRα-mediated cell inhibition for 6 was generally equivalent to 2, while the FRβ-mediated activity was improved by 16-fold over 2. N (4) and O (5) substitutions afforded similar tumor cell inhibitions as 2, with selectivity for FRα and -β over RFC. The N-substituted analogs 7-9 also preserved transport selectivity for FRα and -β over RFC. For FRα-expressing CHO cells, potencies were in the order of 8 > 7 > 9. Whereas 8 and 9 showed similar results with FRβ-expressing CHO cells, 7 was ~16-fold more active than 2. By nucleoside rescue experiments, all the compounds inhibited de novo purine biosynthesis, likely at the step catalyzed by glycinamide ribonucleotide formyltransferase. Thus, heteroatom replacements of the CH₂ in the bridge of 2 afford analogs with increased tumor cell inhibition that could provide advantages over 2, as well as tumor transport selectivity over clinically used antifolates including methotrexate and pemetrexed.

Radiation dosimetry of 18F-AzaFol: A first in-human use of a folate receptor PET tracer

Background

The folate receptor alpha (FRα) is an interesting target for imaging and therapy of different cancers. We present the first in-human radiation dosimetry and radiation safety results acquired within a prospective, multicentric trial (NCT03242993) evaluating the ¹⁸F-AzaFol (3′-aza-2′-[¹⁸F]fluorofolic acid) as the first clinically assessed PET tracer targeting the FRα.

Material and methods

Six eligible patients presented a histologically confirmed adenocarcinoma of the lung with measurable lesions (≥ 10 mm according to RECIST 1.1). TOF-PET images were acquired at 3, 11, 18, 30, 40, 50, and 60 min after the intravenous injection of 327 MBq (range 299–399 MBq) of ¹⁸F-AzaFol to establish dosimetry. Organ absorbed doses (AD), tumor AD, and patient effective doses (E) were assessed using the OLINDA/EXM v.2.0 software and compared with pre-clinical results.

Results

No serious related adverse events were observed. The highest AD were in the liver, the kidneys, the urinary bladder, and the spleen (51.9, 45.8, 39.1, and 35.4 μGy/MBq, respectively). Estimated patient and gender-averaged E were 18.0 ± 2.6 and 19.7 ± 1.4 μSv/MBq, respectively. E in-human exceeded the value of 14.0 μSv/MBq extrapolated from pre-clinical data. Average tumor AD was 34.8 μGy/MBq (range 13.6–60.5 μGy/MBq).

Conclusions

¹⁸F-Azafol is a PET agent with favorable dosimetric properties and a reasonable radiation dose burden for patients which merits further evaluation to assess its performance.

Trial registration

ClinicalTrial.gov, NCT03242993, posted on August 8, 2017

Formulation and characterization of folate receptor-targeted PEGylated liposome encapsulating bioactive compounds from Kappaphycus alvarezii for cancer therapy

This study aimed to formulate and characterize the folate receptor-targeted PEGylated liposome encapsulating bioactive compounds from Kappaphycus alvarezii to enhance the anticancer activity. Twenty valued bioactive compounds (3-hydroxy benzoicacid, gallicacid, chlorogenicacid, cinnamicacid, artemiseole, hydrazine carbothioamide, etc.,) are confirmed from methanol extract of K. alvarezii using analytical techniques like HPLC and GC-MS. The delivery of bioactive compounds of K. alvarezii via naturally overexpressed folate receptor (FR) to FR-positive breast cancer cells was studied. FR targeted PEGylated liposome was constructed by modified thin-film hydration technique using FA-PEG-DSPE/cholesterol/DSPC (5:40:55) and bioactive compounds of K. alvarezii was encapsulated. Their morphology, size, shape, physiological stability and drug release kinetics were studied. The study reports of K. alvarezii extract-encapsulated PEGylated liposome showed spherical shaped particles with amorphous in nature. The mean diameter of K. alvarezii extract-encapsulated PEGylated and FA-conjugated PEGylated liposomes was found to be 110 ± 6 nm and 140 ± 5 nm, respectively. Based on the stability studies, it could be confirmed that FA-conjugated PEGylated liposome was highly stable in various physiological buffer medium. FA-conjugated PEGylated liposome can steadily release the bioactive compounds of K. alvarezii extract in acidic medium (pH 5.4). MTT assay demonstrated the concentration-dependent cytotoxicity against MCF-7 cells after 24 h with IC₅₀ of 81 µg/mL. Also, PEGylated liposome enhanced the delivery of K. alvarezii extract in MCF-7 cells. After treatment, typical apoptotic morphology of condensed nuclei and distorted membrane bodies was picturized. Additionally, PEGylated liposome targets the mitochondria of MCF-7 cells and significantly increased the level of ROS and contributes to the damage of mitochondrial transmembrane potential. Hence, PEGylated liposome could positively deliver the bioactive compounds of K. alvarezii extract into FR-positive breast cancer cells (MCF-7) and exhibit great potential in anticancer therapy.

Nanoparticles carrying fingolimod and methotrexate enables targeted induction of apoptosis and immobilization of invasive thyroid cancer

Metastatic tumors are the main cause of cancer-related death, as the invading cancer cells disrupt normal functions of distant organs and are nearly impossible to eradicate by traditional cancer therapeutics. This is of special concern when the cancer has created multiple metastases and extensive surgery would be too dangerous to execute. Therefore, combination chemotherapy is often the selected treatment form. However, drug cocktails often have severe adverse effects on healthy cells, whereby the development of targeted drug delivery could minimize side-effects of drugs and increase the efficacy of the combination therapy. In this study, we utilized the folate antagonist methotrexate (MTX) as targeting ligand conjugated onto mesoporous silica nanoparticles (MSNs) for selective eradication of folate receptor-expressing invasive thyroid cancer cells. The MSNs was subsequently loaded with the drug fingolimod (FTY720), which has previously been shown to efficiently inhibit proliferation and invasion of aggressive thyroid cancer cells. To assess the efficiency of our carrier system, comprehensive in vitro methods were employed; including flow cytometry, confocal microscopy, viability assays, invasion assay, and label-free imaging techniques. The in vitro results show that MTX-conjugated and FTY720-loaded MSNs potently attenuated both the proliferation and invasion of the cancerous thyroid cells while keeping the off-target effects in normal thyroid cells reasonably low. For a more physiologically relevant in vivo approach we utilized the chick chorioallantoic membrane (CAM) assay, showing decreased invasive behavior of the thyroid derived xenografts and an increased necrotic phenotype compared to tumors that received the free drug cocktail. Thus, the developed multidrug-loaded MSNs effectively induced apoptosis and immobilization of invasive thyroid cancer cells, and could potentially be used as a carrier system for targeted drug delivery for the treatment of diverse forms of aggressive cancers that expresses folate receptors.

Tumor-Targeted Dendrimer Nanoparticles for Combinatorial Delivery of siRNA and Chemotherapy for Cancer Treatment

In current cancer therapy, the combined targeted delivery of treatments is an important method to enhance the therapeutic efficiency and reduce adverse side effects. Dendrimer-based nanoparticles have received considerable attention for multifunctional therapeutic delivery. In this chapter, we describe the methods for encapsulating the chemotherapeutic drug, cisplatin (CDDP), and human antigen R (HuR)-targeted siRNA into dendrimer nanoparticles for folate receptor-targeted delivery. We discuss the methodologies for physical and biological characterization of synthesized multifunctional (Den-PEI-CDDP-HuR-FA) nanoparticles in detail. Physical characterization includes size and charge determination, drug encapsulation and release kinetics, ligand conjugation, etc., and functional characterization involves testing of the nanoparticles for receptor-specific uptake and cytotoxicity on human lung cancer and normal cells. The protocol provided is geared to provide the readers an overview of developing multifunctional dendrimer-based nanoparticles. However, based on the individual's objective and the type of combinatorial drugs to deliver, the protocol may need modifications in achieving maximal efficacy.

Folate receptor-targeted positron emission tomography of experimental autoimmune encephalomyelitis in rats

BACKGROUND

Folate receptor-β (FR-β) is a cell surface receptor that is significantly upregulated on activated macrophages during inflammation and provides a potential target for folate-based therapeutic and diagnostic agents. FR-β expression in central nervous system inflammation remains relatively unexplored. Therefore, we used focally induced acute and chronic phases of experimental autoimmune encephalomyelitis (EAE) to study patterns of FR-β expression and evaluated its potential as an in vivo imaging target.

METHODS

Focal EAE was induced in rats using heat-killed Bacillus Calmette-Guérin followed by activation with complete Freund's adjuvant supplemented with Mycobacterium tuberculosis. The rats were assessed with magnetic resonance imaging and positron emission tomography/computed tomography (PET/CT) at acute (14 days) and chronic (90 days) phases of inflammation. The animals were finally sacrificed for ex vivo autoradiography of their brains. PET studies were performed using FR-β-targeting aluminum [¹⁸F]fluoride-labeled 1,4,7-triazacyclononane-1,4,7-triacetic acid conjugated folate ([¹⁸F]AlF-NOTA-folate, ¹⁸F-FOL) and 18 kDa translocator protein (TSPO)-targeting N-acetyl-N-(2-[¹¹C]methoxybenzyl)-2-phenoxy-5-pyridinamine (¹¹C-PBR28). Post-mortem immunohistochemistry was performed using anti-FR-β, anti-cluster of differentiation 68 (anti-CD68), anti-inducible nitric oxide synthase (anti-iNOS), and anti-mannose receptor C-type 1 (anti-MRC-1) antibodies. The specificity of ¹⁸F-FOL binding was verified using in vitro brain sections with folate glucosamine used as a blocking agent.

RESULTS

Immunohistochemical evaluation of focal EAE lesions demonstrated anti-FR-β positive cells at the lesion border in both acute and chronic phases of inflammation. We found that anti-FR-β correlated with anti-CD68 and anti-MRC-1 immunohistochemistry; for MRC-1, the correlation was most prominent in the chronic phase of inflammation. Both ¹⁸F-FOL and ¹¹C-PBR28 radiotracers bound to the EAE lesions. Autoradiography studies verified that this binding took place in areas of anti-FR-β positivity. A blocking assay using folate glucosamine further verified the tracer's specificity. In the chronic phase of EAE, the lesion-to-background ratio of ¹⁸F-FOL was significantly higher than that of ¹¹C-PBR28 (P = 0.016).

CONCLUSION

Our EAE results imply that FR-β may be a useful target for in vivo imaging of multiple sclerosis-related immunopathology. FR-β-targeted PET imaging with ¹⁸F-FOL may facilitate the monitoring of lesion development and complement the information obtained from TSPO imaging by bringing more specificity to the PET imaging armamentarium for neuroinflammation.

Folate-conjugated nanovehicles: Strategies for cancer therapy

Cancer theranostics represents a strategy that aims at combining diagnosis with therapy through the simultaneous imaging and targeted delivery of therapeutics to cancer cells. Recently, the folate receptor alpha has emerged as an attractive theranostic target due to its overexpression in multiple solid tumors and its great functional versatility. In fact, it can be incorporated into folate-conjugated nano-systems for imaging and drug delivery. Hence, it can be used along the line of personalized clinical strategies as both an imaging tool and a delivery method ensuring the selective transport of treatments to tumor cells, thus highlighting its theranostic qualities. In this review, we will explore these theranostic characteristics in detail and assess their clinical potential. We will also discuss the technological advances that have allowed the design of sophisticated folate-based nanocarriers harboring various chemical properties and suited for the transport of various therapeutic agents.

Discovery of amide-bridged pyrrolo[2,3-d]pyrimidines as tumor targeted classical antifolates with selective uptake by folate receptor α and inhibition of de novo purine nucleotide biosynthesis

We previously showed that classical 6-substituted pyrrolo[2,3-d]pyrimidine antifolates bind to folate receptor (FR) α and the target purine biosynthetic enzyme glycinamide ribonucleotide formyltransferase (GARFTase) with different cis and trans conformations. In this study, we designed novel analogs of this series with an amide moiety in the bridge region that can adopt both the cis and trans lowest energy conformations. This provides entropic benefit, by restricting the number of side-chain conformations of the unbound ligand to those most likely to promote binding to FRα and the target enzyme required for antitumor activity. NMR of the most active compound 7 showed both cis and trans amide bridge conformations in ~1:1 ratio. The bridge amide group in the best docked poses of 7 in the crystal structures of FRα and GARFTase adopted both cis and trans conformations, with the lowest energy conformations predicted by Maestro and evidenced by NMR within 1 kcal/mol. Compound 7 showed ~3-fold increased inhibition of FRα-expressing cells over its non-restricted parent analog 1 and was selectively internalized by FRα over the reduced folate carrier (RFC), resulting in significant in vitro antitumor activity toward FRα-expressing KB human tumor cells. Antitumor activity of 7 was abolished by treating cells with adenosine but was incompletely protected by 5-aminoimidazole-4-carboxamide (AICA) at higher drug concentrations, suggesting GARFTase and AICA ribonucleotide formyltransferase (AICARFTase) in de novo purine biosynthesis as the likely intracellular targets. GARFTase inhibition by compound 7 was confirmed by an in situ cell-based activity assay. Our results identify a "first-in-class" classical antifolate with a novel amide linkage between the scaffold and the side chain aryl L-glutamate that affords exclusive selectivity for transport via FRα over RFC and antitumor activity resulting from inhibition of GARFTase and likely AICARFTase. Compound 7 offers significant advantages over clinically used inhibitors of this class that are transported by the ubiquitous RFC, resulting in dose-limiting toxicities.

Oligo-guanidyl targeted bioconjugates forming rod shaped polyplexes as a new nanoplatform for oligonucleotide delivery

Novel bioconjugates (Agm₆-M-PEG-FA) for active oligonucleotide (ON) delivery have been developed by conjugating a cationic oligo-guanidyl star-like shaped "head" (Agm₆-M) to a polymeric "tail" (PEG) terminating with folic acid (FA) as targeting agent or methoxy group (Agm₆-M-PEG-FA and Agm₆-M-PEG-OCH₃, respectively). Gel electrophoresis showed that the bioconjugates completely associated with ONs at 3 nitrogen/phosphate (N/P) ratio. Studies performed with folate receptor (FR)-overexpressing HeLa cells, showed that optimal cell up-take was obtained with the 75:25 w/w Agm₆-M-PEG-OCH₃:Agm₆-M-PEG-FA mixture. Dynamic light scattering and transmission electron microscopy showed that the polyplexes had size <80 nm with narrow polydispersity and rod-shaped morphology. The polyplexes were stable for several hours in plasma while ON was released in the presence of heparin concentration 16-times higher than the physiological one. The polyplexes displayed negligible cytotoxicity, hemolysis and low pro-inflammatory TNF-α release. Studies performed with FR-overexpressing HeLa and MDA-MB-231 cells using siRac1 revealed that the folated polyplexes caused significantly higher gene silencing (86.1 ± 9.6%) and inhibition of cell migration (40%) than the non-folated polyplexes obtained with Agm₆-M-PEG-OCH₃ only. Although cytofluorimetric analyses showed similar cell uptake for both folated and non-folated polyplexes, confocal, TEM and competition studies showed that the folated polyplexes were taken-up by lysosome escaping caveolin-mediated pathway with final polyplex localization within cytosol, while non-folated polyplexes were preferentially taken-up via clathrin-mediated pathway to localize in the lysosomes. Finally, preliminary in vivo studies carried out in mice revealed that the folated polyplexes dispose in the tumor mass.

β-Cyclodextrin coated and folic acid conjugated magnetic halloysite nanotubes for targeting and isolating of cancer cells

The study developed a simple, effective and inexpensive strategy for capturing, enriching and detecting circulating tumor cells (CTCs) by using folic acid (FA) as the targeting molecule instead of antibodies. This work constructed magnetic halloysite nanotubes (MHNTs) coated with biocompatible β-cyclodextrin (CD), and conjugated to FA via a PEG-Ad linker, to specifically capture the FA receptor (FR)-overexpressing cancer cells. The capture efficiencies of MHNTs@β-CD@Ad-PEG-FA for the Skov3, Hela and A549 cancer cells were 96.3%, 97.0% and 95.6% respectively. In addition, the nanoparticles were able to capture very low numbers of the cancer cells (25-500 cells/mL) from PBS and whole blood, as well as selectively capture the cancer cells over normal HEK 293 T cells. Furthermore, the captured cells were viable and grew normally in vitro, indicating the future potential of downstream analyses. This approach can be adapted for different CTCs, once the tumor-specific surface markers are identified and the efficacy of targeting ligands is established. Taken together, FA-conjugated MHNTs nanoparticles are a highly promising tool for isolating CTCs for the diagnosis and treatment of cancer.

Curcumin ameliorates the targeted delivery of methotrexate intercalated montmorillonite clay to cancer cells

Montmorillonite Clay (MMT) is aimed to develop as an orally administrable drug delivery vehicle with enhanced efficacy. Aiming to enhance the therapeutic index of methotrexate, curcumin is concomitantly used with methotrexate in the present study. Being folate antagonist in nature, methotrexate is internalized into cells by folate receptor (FR); which is over-expressed in certain human cancer cells such as cervical carcinoma cells (HeLa). Firstly, montmorillonite Clay (MMT) is organically modified (OMMT) with cetyl trimethyl ammonium bromide (CTAB) and used to intercalate curcumin and methotrexate separately, designated as OMMT-Cur and OMMT-MTX, respectively. XRD pattern demonstrated successful intercalation of therapeutics and an increase in clay interlayer distance facilitated by CTAB. The dissolution kinetics of methotrexate follows Higuchi model for both Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF), while the release kinetics for curcumin fitted into Higuchi model for SGF and Hixson-Crowell model for SIF, respectively. OMMT-MTX are able to discriminate FR-positive HeLa cells from FR-negative breast cancer cells (MCF7); irrespective of alike cellular phenotypes. Further, the pre-treatment of HeLa cells with curcumin improves its sensitivity towards methotrexate causing a greater killing of the Hela cells. Together, the results propose the concomitant use of curcumin and methotrexate for successfully targeting highly invasive FR-positive carcinomas by means of folate receptor using MMTs.

Value of folate receptor-positive circulating tumour cells in the clinical management of indeterminate lung nodules: A non-invasive biomarker for predicting malignancy and tumour invasiveness

Background

Non-invasive lung adenocarcinoma could benefit from limited resection, nonetheless, there is a lack of method to determine preoperative tumour invasiveness. We aimed to investigate whether folate receptor-positive circulating tumour cells (FR⁺-CTCs) in combination with maximum tumour diameter (MTD) determines, before surgery, the invasiveness of small-sized, indeterminate solitary pulmonary nodules (SPNs).

Methods

A total of 382 patients with suspicious lung adenocarcinoma on computed tomography who were expected to undergo lung resection were enrolled in this study at three participating institutes and randomly assigned into training and validation cohorts. Before surgery, 3 mL peripheral blood was collected from all participants. FR⁺-CTCs were analyzed using immunomagnetic leukocyte depletion and quantitated by ligand-targeted PCR method. After surgery, the resected tissues were diagnosed by pathologists according to IASLC/ATS/ERS classification.

Findings

FR⁺-CTC levels in the peripheral blood can differentiate benign from malignant nodules with a sensitivity of 78·6%–82·7% and a specificity of 68·8%–78·4%. Both FR⁺-CTC and MTD are independent predictive indices of invasive tumours for lung adenocarcinoma ≤2 cm based on multivariate analyses. Further, FR⁺-CTC count in combination with MTD can differentiate non-invasive cancers from invasive cancers with a sensitivity of 63·6%–81·8% and a specificity of 71·4%–89·7%.

Interpretation

Detection of FR⁺-CTC is a reliable method to differentiate malignancy of indeterminate SPNs. Combining of FR⁺-CTC count and MTD could possibly enhance preoperative determination of the invasiveness of lung nodules and guide surgeons to select limited lung resection and avoid overtreatment for patients with non-invasive lesions.

Fund

None.

Folate receptor-targeted novel boron compound for boron neutron capture therapy on F98 glioma-bearing rats

Folic acid (FA) has high affinity for the folate receptor (FR), which is limited expressed in normal human tissues, but over-expressed in several tumor cells, including glioblastoma cells. In the present work, a novel pteroyl-closo-dodecaborate conjugate (PBC) was developed, in which the pteroyl group interacts with FR, and the efficacy of boron neutron capture therapy (BNCT) using PBC was investigated. Thus, in vitro and in vivo studies were performed using F98 rat glioma cells and F98 glioma-bearing rats. For the in vivo study, boronophenylalanine (BPA) was intravenously administered, while PBC was administered by convection-enhanced delivery (CED)-a method for direct local drug infusion into the brain of rats. Furthermore, a combination of PBC administered by CED and BPA administered by intravenous (i.v.) injection was also investigated. In the biodistribution experiment, PBC administration at 6 h after CED termination showed the highest cellular boron concentrations (64.6 ± 29.6 µg B/g). Median survival time (MST) of untreated controls was 23.0 days (range 21-24 days). MST of rats administered PBC (CED) followed by neutron irradiation was 31 days (range 26-36 days), which was similar to that of rats administered i.v. BPA (30 days; range 25-37 days). Moreover, the combination group [PBC (CED) and i.v. BPA] showed the longest MST (38 days; range 28-40 days). It is concluded that a significant MST increase was noted in the survival time of the combination group of PBC (CED) and i.v. BPA compared to that in the single-boron agent groups. These findings suggest that the combination use of PBC (CED) has additional effects.

Folate-targeted immunotherapies: Passive and active strategies for cancer

The glycoprotein FRα is a membrane-attached transport protein that is shielded from the immune system in healthy cells. However, it is upregulated in various malignancies, involved in cancer development and is also immunogenic. Furthermore, FRα is a tumor-associated antigen endowed with unique properties, thus rendering it a suitable target for immunotherapeutic development in cancer. Various anti- FRα immunotherapeutic strategies are thus currently being developed and clinically assessed for the treatment of various solid tumors. These approaches include passive anti-FRα immunotherapies, such as monoclonal antibodies, or active immunotherapies, such as CART, folate haptens and vaccines. In this review, we will explore the advances in the field of FRα-based immune therapies and discuss both their successes and shortcomings in the clinical setting.

The folate receptor β as a macrophage-mediated imaging and therapeutic target in rheumatoid arthritis

Macrophages play a key role in the pathophysiology of rheumatoid arthritis (RA). Notably, positive correlations have been reported between synovial macrophage infiltration and disease activity as well as therapy outcome in RA patients. Hence, macrophages can serve as an important target for both imaging disease activity and drug delivery in RA. Folate receptor β (FRβ) is a glycosylphosphatidyl (GPI)-anchored plasma membrane protein being expressed on myeloid cells and activated macrophages. FRβ harbors a nanomolar binding affinity for folic acid allowing this receptor to be exploited for RA disease imaging (e.g., folate-conjugated PET tracers) and therapeutic targeting (e.g., folate antagonists and folate-conjugated drugs). This review provides an overview of these emerging applications in RA by summarizing and discussing properties of FRβ, expression of FRβ in relation to macrophage polarization, FRβ-targeted in vivo imaging modalities, and FRβ-directed drug targeting.

Folate-Decorated Polyamidoamine Dendrimer Nanoparticles for Head and Neck Cancer Gene Therapy

Gene delivery systems have been developed on the basis of dendrimers and many other types of nanoparticle carriers, but few have been developed for head and neck squamous cell carcinomas (HNSCC). Herein, we describe the design and synthesis of fluorescently labeled, folic acid-decorated polyamidoamine (PAMAM) generation 4 (G4) dendrimer conjugates for HNSCC-targeted gene delivery. This delivery system comprises a dendrimer as the carrier that is conjugated with folic acid (FA) as HNSCC targeting moiety and imaging agents fluorescein isothiocyanate (FITC) or IRDye 800CW (NIR) for in vitro trafficking or bioimaging, respectively. By complexing with plasmid or siRNA, G4-FA/plasmid (or siRNA) significantly enhances gene transfection or knockdown efficiency in HNSCC cells. In a mouse xenograft model of HNSCC, this versatile G4-FA vector shows high biocompatibility, tumor targeting, high uptake, and sustained retention, making it a suitable platform for HNSCC gene therapy.