Customizable Porphyrin Platform Enables Folate Receptor PET Imaging Using Copper-64

Folate receptors including folate receptor α (FRα) are overexpressed in up to 90% of ovarian cancers. Ovarian cancers overexpressing FRα often exhibit high degrees of drug resistance and poor outcomes. A porphyrin chassis has been developed that is readily customizable according to the desired targeting properties. Thus, compound O5 includes a free base porphyrin, two water-solubilizing groups that project above and below the macrocycle plane, and a folate targeting moiety. Compound O5 was synthesized (>95% purity) and exhibited aqueous solubility of at least 0.48 mM (1 mg/mL). Radiolabeling of O5 with 64Cu in HEPES buffer at 37 °C gave a molar activity of 1000 μCi/μg (88 MBq/nmol). [64Cu]Cu-O5 was stable in human serum for 24 h. Cell uptake studies showed 535 ± 12% bound/mg [64Cu]Cu-O5 in FRα-positive IGROV1 cells when incubated at 0.04 nM. Subcellular fractionation showed that most radioactivity was associated with the cytoplasmic (39.4 ± 2.7%) and chromatin-bound nuclear (53.0 ± 4.2%) fractions. In mice bearing IGROV1 xenografts, PET imaging studies showed clear tumor uptake of [64Cu]Cu-O5 from 1 to 24 h post injection with a low degree of liver uptake. The tumor standardized uptake value at 24 h post injection was 0.34 ± 0.16 versus 0.06 ± 0.07 in the blocking group. In summary, [64Cu]Cu-O5 was synthesized at high molar activity, was stable in serum, exhibited high binding to FRα-overexpressing cells with high nuclear translocation, and gave uptake that was clearly visible in mouse tumor xenografts.

Exosomal or follicular FNDC3A decreases FOLR1 mRNA abundance and progesterone and lactate synthesis in bovine granulosa cells

In brief

Dairy cattle experience a period of infertility postpartum that is caused in part by the development of IGF1/insulin resistance. This study suggests that an adipokine, FNDC3A, reduces IGF1-dependent glycolysis and may contribute to postpartum infertility.

Abstract

Dairy cows go through a period of subfertility after parturition, triggered in part by a disruption of energy homeostasis. The mobilization of body fat alters the secretion of adipokines, which have been shown to impact ovarian function. Fibronectin type III domain-containing 3A (FNDC3A) is a recently discovered adipokine-myokine, and FNDC3A mRNA abundance in subcutaneous adipose tissue is increased postpartum in cattle. In this study, we hypothesized that FNDC3A may compromise granulosa cell function in cattle and investigated this using a well-established in vitro cell culture model. Here, we demonstrate the presence of FNDC3A protein associated with extracellular vesicles in follicular fluid and in plasma, suggesting an endocrine role for this adipokine. FNDC3A protein and mRNA was also detected in the bovine ovary (cortex, granulosa and theca cells, cumulus, oocyte and corpus luteum). Abundance of FNDC3A mRNA in granulosa cells from small follicles was increased by in vitro treatment with the adipokines leptin and TNF but not by visfatin, resistin, adiponectin, chemerin or IGF1. Addition of recombinant FNDC3A at physiological doses (10 ng/mL) to granulosa cells decreased IGF1-dependent progesterone but not estradiol secretion and IGF1-dependent lactate secretion and abundance of GLUT3 and GLUT4 mRNA. This concentration of FNDC3A increased cell viability, abundance of mRNA encoding a putative receptor FOLR1, and increased phosphorylation of Akt. Collectively, these data suggest that FNDC3A may regulate folliculogenesis in cattle by modulating IGF1-dependent granulosa cell steroidogenesis and glucose metabolism.

Role of folate receptor α in the partial rejuvenation of dentate gyrus cells: Improvement of cognitive function in 21-month-old aged mice

Neuronal aging may be, in part, related to a change in DNA methylation. Thus, methyl donors, like folate and methionine, may play a role in cognitive changes associated to neuronal aging. To test the role of these metabolites, we performed stereotaxic microinjection of these molecules into the dentate gyrus (DG) of aged mice (an average age of 21 month). Folate, but not S-Adenosyl-Methionine (SAM), enhances cognition in aged mice. In the presence of folate, we observed partial rejuvenation of DG cells, characterized by the expression of juvenile genes or reorganization of extracellular matrix. Here, we have also tried to identify the mechanism independent of DNA methylation, that involve folate effects on cognition. Our analyses indicated that folate binds to folate receptor α (FRα) and, upon folate binding, FRα is transported to cell nucleus, where it is acting as transcription factor for expressing genes like SOX2 or GluN2B. In this work, we report that a FRα binding peptide also replicates the folate effect on cognition, in aged mice. Our data suggest that such effect is not sex-dependent. Thus, we propose the use of this peptide to improve cognition since it lacks of folate-mediated side effects. The use of synthetic FRα binding peptides emerge as a future strategy for the study of brain rejuvenation.

Noncanonical function of folate through folate receptor 1 during neural tube formation

Folate supplementation reduces the occurrence of neural tube defects (NTDs), birth defects consisting in the failure of the neural tube to form and close. The mechanisms underlying NTDs and their prevention by folate remain unclear. Here we show that folate receptor 1 (FOLR1) is necessary for the formation of neural tube-like structures in human-cell derived neural organoids. FOLR1 knockdown in neural organoids and in Xenopus laevis embryos leads to NTDs that are rescued by pteroate, a folate precursor that is unable to participate in metabolism. We demonstrate that FOLR1 interacts with and opposes the function of CD2-associated protein, molecule essential for apical endocytosis and turnover of C-cadherin in neural plate cells. In addition, folates increase Ca2+ transient frequency, suggesting that folate and FOLR1 signal intracellularly to regulate neural plate folding. This study identifies a mechanism of action of folate distinct from its vitamin function during neural tube formation.

Developing Folate-Conjugated miR-34a Therapeutic for Prostate Cancer: Challenges and Promises

Prostate cancer (PCa) remains a common cancer with high mortality in men due to its heterogeneity and the emergence of drug resistance. A critical factor contributing to its lethality is the presence of prostate cancer stem cells (PCSCs), which can self-renew, long-term propagate tumors, and mediate treatment resistance. MicroRNA-34a (miR-34a) has shown promise as an anti-PCSC therapeutic by targeting critical molecules involved in cancer stem cell (CSC) survival and functions. Despite extensive efforts, the development of miR-34a therapeutics still faces challenges, including non-specific delivery and delivery-associated toxicity. One emerging delivery approach is ligand-mediated conjugation, aiming to achieve specific delivery of miR-34a to cancer cells, thereby enhancing efficacy while minimizing toxicity. Folate-conjugated miR-34a (folate-miR-34a) has demonstrated promising anti-tumor efficacy in breast and lung cancers by targeting folate receptor α (FOLR1). Here, we first show that miR-34a, a TP53 transcriptional target, is reduced in PCa that harbors TP53 loss or mutations and that miR-34a mimic, when transfected into PCa cells, downregulated multiple miR-34a targets and inhibited cell growth. When exploring the therapeutic potential of folate-miR-34a, we found that folate-miR-34a exhibited impressive inhibitory effects on breast, ovarian, and cervical cancer cells but showed minimal effects on and targeted delivery to PCa cells due to a lack of appreciable expression of FOLR1 in PCa cells. Folate-miR-34a also did not display any apparent effect on PCa cells expressing prostate-specific membrane antigen (PMSA) despite the reported folate's binding capability to PSMA. These results highlight challenges in the specific delivery of folate-miR-34a to PCa due to a lack of target (receptor) expression. Our study offers novel insights into the challenges and promises within the field and casts light on the development of ligand-conjugated miR-34a therapeutics for PCa.

Super-resolution imaging of folate receptor alpha on cell membranes using peptide-based probes

Folate receptor alpha (FRα) is a vital membrane protein which have great association with cancers and involved in various biological processes including folate transport and cell signaling. However, the distribution and organization pattern of FRα on cell membranes remains unclear. Previous studies relied on antibodies to recognize the proteins. However, multivalent crosslinking and large size of antibodies confuse the direct observation to some extent. Fortunately, the emergence of peptide, which are small-sized and monovalent, has supplied us an unprecedented choice. Here, we applied fluorophore-conjugated peptide probe to recognize the FRα and study the distribution pattern of FRα on cell membrane using dSTORM super-resolution imaging technique. FRα were found to organized as clusters on cell surface with different sizes. And they have a higher expression level and formed larger clusters on various cancer cells than normal cells, which hinted that its specific distribution could be utilized for cancer diagnosis. Furthermore, we revealed that the lipid raft and cortical actin as restrictive factors for the FRα clustering, suggesting a potential assembly mechanism insight into FRα clustering on cell membrane. Collectively, our work clarified the morphology distribution and clustered organization of FRα with peptide probes at the nanometer scale, which paves the way for further revealing the relationship between the spatial organization and functions of membranal proteins.

Sensitivity and specificity of folate receptor α-positive circulating tumour cells in gastric cancer

PURPOSE

We aimed to investigate whether folate receptor α (FRα)-positive circulating tumour cells (CTCs) could be used as a noninvasive liquid biopsy approach in gastric cancer (GC).

METHODS

Tissue microarray and bioinformatic analyses were used to evaluate FRα expression in GC. Patients with FRα-positive CTC examinations at our institute between July 2021 and May 2022 were retrospectively evaluated. Receiver operating characteristic curves were used to evaluate the diagnostic performance of FRα-positive CTCs in GC.

RESULTS

FRα was highly expressed and associated with poor prognosis in GC based on public database. Data for 163 patients (20 with benign disease and 143 with GC) were retrospectively collected. FRα-positive CTC levels were significantly higher in the GC group than in the benign disease group (12.15 ± 1.47 FU/3 ml vs. 10.47 ± 1.63 FU/3 ml, P < 0.01). FRα-positive CTC levels were also elevated in GC patients with vessel/neuron invasion or extra-nodal tumour deposits (12.31 ± 1.47 FU/3 ml vs. 11.77 ± 1.38 FU/3 ml, P = 0.037). Areas under the curve of FRα-positive CTC levels for GC and early GC were 0.774 (P < 0.001) and 0.736 (P = 0.005). With a cut-off value of 10.95 FU/3 ml, the Youden indexes for GC and early GC were 0.502 (sensitivity = 85.2% and specificity = 65.0%) and 0.450 (sensitivity = 80.0% and specificity = 65.0%), respectively.

CONCLUSION

FRα-positive CTC detection by noninvasive liquid biopsy is a useful and effective approach for screening of patients with GC.

KEY MESSAGES

Folate receptor overexpression induces toxicity in a diet-dependent manner in C. elegans

Folate receptor (FR) alpha (FOLR1) and beta (FOLR2) are membrane-anchored folate transporters that are expressed at low levels in normal tissues, while their expression is strongly increased in several cancers. Intriguingly, although the function of these receptors in, for example, development and cancer has been studied intensively, their role in aging is still unknown. To address this, we utilized Caenorhabditis elegans, in which FOLR-1 is the sole ortholog of folate receptors. We found that the loss of FOLR-1 does not affect reproduction, physical condition, proteostasis or lifespan, indicating that it is not required for folate transport to maintain health. Interestingly, we found that FOLR-1 is detectably expressed only in uterine-vulval cells, and that the histone-binding protein LIN-53 inhibits its expression in other tissues. Furthermore, whereas knockdown of lin-53 is known to shorten lifespan, we found that the loss of FOLR-1 partially rescues this phenotype, suggesting that elevated folr-1 expression is detrimental for health. Indeed, our data demonstrate that overexpression of folr-1 is toxic, and that this phenotype is dependent on diet. Altogether, this work could serve as a basis for further studies to elucidate the organismal effects of abnormal FR expression in diseases such as cancer.

Folate regulation of planar cell polarity pathway and F-actin through folate receptor alpha

Folate deficiency contribute to neural tube defects (NTDs) which could be rescued by folate supplementation. However, the underlying mechanisms are still not fully understood. Besides, there is considerable controversy concerning the forms of folate used for supplementation. To address this controversy, we prepared culture medium with different forms of folate, folic acid (FA), and 5-methyltetrahydrofolate (5mTHF), at concentrations of 5 μM, 500 nM, 50 nM, and folate free, respectively. Mouse embryonic fibroblasts (MEFs) were treated with different folates continuously for three passages, and cell proliferation and F-actin were monitored. We determined that compared to 5mTHF, FA showed stronger effects on promoting cell proliferation and F-actin formation. We also found that FOLR1 protein level was positively regulated by folate concentration and the non-canonical Wnt/planar cell polarity (PCP) pathway signaling was significantly enriched among different folate conditions in RNA-sequencing analyses. We demonstrated for the first time that FOLR1 could promote the transcription of Vangl2, one of PCP core genes. The transcription of Vangl2 was down-regulated under folate-deficient condition, which resulted in a decrease in PCP activity and F-actin formation. In summary, we identified a distinct advantage of FA in cell proliferation and F-actin formation over 5mTHF, as well as demonstrating that FOLR1 could promote transcription of Vangl2 and provide a new mechanism by which folate deficiency can contribute to the etiology of NTDs.

Discovery of novel tumor-targeted near-infrared probes with 6-substituted pyrrolo[2,3-d]pyrimidines as targeting ligands

Since the overexpression of folate receptors (FRs) in certain types of cancers, a variety of FR-targeted fluorescent probes for tumor detection have been developed. However, the reported probes almost all have the same targeting ligand of folic acid with various fluorophores and/or linkers. In the present study, a series of novel tumor-targeted near-infrared (NIR) molecular fluorescent probes were designed and synthesized based on previously reported 6-substituted pyrrolo[2,3-d]pyrimidine antifolates. All newly synthesized probes showed specific FR binding in vitro, whereas GT-NIR-4 and GT-NIR-5 with a benzene and a thiophene ring, respectively, on the side chain of pyrrolo[2,3-d]pyrimidine exhibited better FR binding affinity than that of GT-NIR-6 with folic acid as targeting ligand. GT-NIR-4 also showed high tumor uptake in KB tumor-bearing mice with good pharmacokinetic properties and biological safety. This work demonstrates the first attempt to replace folic acid with antifolates as targeting ligands for tumor-targeted NIR probes.

Protein-Labeling Fluorescent Probe for Folate Receptor α

GPI-anchored folate receptor α (FRα) is an attractive anticancer drug target and diagnosis marker in fundamental biology and medical research due to its significant expression on many cancer cells. Currently, analyses of FRα expression levels are usually achieved using immunological methods. Due to the continual FRα synthesis and degradation, immunological methods are not suitable for studying real-time dynamic activities of FRα in living cells. In this paper, we introduce a rapid and specific FRα protein-labeling fluorescent probe, FR1, to facilitate the study of the dynamics of expression and degradation processes of endogenous FRα in living cells. With this labeling probe, insights on FRα protein lifetime and shedding from the cell surface can be obtained using fluorescence live-cell imaging and electrophoresis techniques. We revealed that FRα undergoes soluble domain release and endocytosis degradation simultaneously. Imaging results showed that most of the membrane FRα are transported to the lysosomes after 2 h of incubation. Furthermore, we also showed that the secretion of a FRα soluble domain into the environment is most likely accomplished by phospholipase. We believe that this protein-labeling approach can be an important tool for analyzing various dynamic processes involving FRα.

Brain Uptake of Folate Forms in the Presence of Folate Receptor Alpha Antibodies in Young Rats: Folate and Antibody Distribution

In a rat model, following exposure to rat folate receptor alpha antibodies (FRαAb) during gestation, FRαAb accumulates in the placenta and the fetus and blocks folate transport to the fetal brain and produces behavioral deficits in the offspring. These deficits could be prevented with folinic acid. Therefore, we sought to evaluate folate transport to the brain in young rat pups and determine what effect FRαAb has on this process, to better understand the folate receptor autoimmune disorder associated with cerebral folate deficiency (CFD) in autism spectrum disorders (ASD). When injected intraperitoneally (IP), FRαAb localizes to the choroid plexus and blood vessels including the capillaries throughout the brain parenchyma. Biotin-tagged folic acid shows distribution in the white matter tracts in the cerebrum and cerebellum. Since these antibodies can block folate transport to the brain, we orally administered various folate forms to identify the form that is better-absorbed and transported to the brain and is most effective in restoring cerebral folate status in the presence of FRαAb. The three forms of folate, namely folic acid, D,L-folinic acid and levofolinate, are converted to methylfolate while L-methylfolate is absorbed as such and all are efficiently distributed to the brain. However, significantly higher folate concentration is seen in the cerebrum and cerebellum with levofolinate in the presence or absence of FRαAb. Our results in the rat model support testing levofolinate to treat CFD in children with ASD.

A Paternal Methylation Error in the Congenital Hydrocephalic Texas (H-Tx) Rat Is Partially Rescued with Natural Folate Supplements

Folate deficiencies, folate imbalance and associated abnormal methylation are associated with birth defects, developmental delays, neurological conditions and diseases. In the hydrocephalic Texas (H-Tx) rat, 10-formyl tetrahydrofolate dehydrogenase (FDH) is reduced or absent from the CSF and the nuclei of cells in the brain and liver and this is correlated with decreased DNA methylation. In the present study, we tested whether impaired folate metabolism or methylation exists in sexually mature, unaffected H-Tx rats, which may explain the propagation of hydrocephalus in their offspring. We compared normal Sprague Dawley (SD, n = 6) rats with untreated H-Tx (uH-Tx, n = 6 and folate-treated H-Tx (TrH-Tx, n = 4). Structural abnormalities were observed in the testis of uH-Tx rats, with decreased methylation, increased demethylation, and cell death, particularly of sperm. FDH and FRα protein expression was increased in uH-Tx males but not in folate-treated males but tissue folate levels were unchanged. 5-Methylcytosine was significantly reduced in untreated and partially restored in treated individuals, while 5-hydroxymethylcytosine was not significantly changed. Similarly, a decrease in DNA-methyltransferase-1 expression in uH-Tx rats was partially reversed with treatment. The data expose a significant germline methylation error in unaffected adult male H-Tx rats from which hydrocephalic offspring are obtained. Reduced methylation in the testis and sperm was partially recovered by treatment with folate supplements leading us to conclude that this neurological disorder may not be completely eradicated by maternal supplementation alone.

Folate receptor alpha in ovarian cancer tissue and patient serum is associated with disease burden and treatment outcomes

BACKGROUND

Survival rates for ovarian cancer remain poor, and monitoring and prediction of therapeutic response may benefit from additional markers. Ovarian cancers frequently overexpress Folate Receptor alpha (FRα) and the soluble receptor (sFRα) is measurable in blood. Here we investigated sFRα as a potential biomarker.

METHODS

We evaluated sFRα longitudinally, before and during neo-adjuvant, adjuvant and palliative therapies, and tumour FRα expression status by immunohistrochemistry. The impact of free FRα on the efficacy of anti-FRα treatments was evaluated by an antibody-dependent cellular cytotoxicity assay.

RESULTS

Membrane and/or cytoplasmic FRα staining were observed in 52.7% tumours from 316 ovarian cancer patients with diverse histotypes. Circulating sFRα levels were significantly higher in patients, compared to healthy volunteers, specifically in patients sampled prior to neoadjuvant and palliative treatments. sFRα was associated with FRα cell membrane expression in the tumour. sFRα levels decreased alongside concurrent tumour burden in patients receiving standard therapies. High concentrations of sFRα partly reduced anti-FRα antibody tumour cell killing, an effect overcome by increased antibody doses.

CONCLUSIONS

sFRα may present a non-invasive marker for tumour FRα expression, with the potential for monitoring patient response to treatment. Larger, prospective studies should evaluate FRα for assessing disease burden and response to systemic treatments.

Ultrasmall Folate Receptor Alpha Targeted Enzymatically Cleavable Silica Nanoparticle Drug Conjugates Augment Penetration and Therapeutic Efficacy in Models of Cancer

To address the key challenges in the development of next-generation drug delivery systems (DDS) with desired physicochemical properties to overcome limitations regarding safety, in vivo efficacy, and solid tumor penetration, an ultrasmall folate receptor alpha (FRα) targeted silica nanoparticle (C'Dot) drug conjugate (CDC; or folic acid CDC) was developed. A broad array of methods was employed to screen a panel of CDCs and identify a lead folic acid CDC for clinical development. These included comparing the performance against antibody-drug conjugates (ADCs) in three-dimensional tumor spheroid penetration ability, assessing in vitro/ex vivo cytotoxic efficacy, as well as in vivo therapeutic outcome in multiple cell-line-derived and patient-derived xenograft models. An ultrasmall folic acid CDC, EC112002, was identified as the lead candidate out of >500 folic acid CDC formulations evaluated. Systematic studies demonstrated that the lead formulation, EC112002, exhibited highly specific FRα targeting, multivalent binding properties that would mediate the ability to outcompete endogenous folate in vivo, enzymatic responsive payload cleavage, stability in human plasma, rapid in vivo clearance, and minimal normal organ retention organ distribution in non-tumor-bearing mice. When compared with an anti-FRα-DM4 ADC, EC112002 demonstrated deeper penetration into 3D cell-line-derived tumor spheroids and superior specific cytotoxicity in a panel of 3D patient-derived tumor spheroids, as well as enhanced efficacy in cell-line-derived and patient-derived in vivo tumor xenograft models expressing a range of low to high levels of FRα. With the growing interest in developing clinically translatable, safe, and efficacious DDSs, EC112002 has the potential to address some of the critical limitations of the current systemic drug delivery for cancer management.

A T-cell engaging bispecific antibody with a tumor-selective bivalent folate receptor alpha binding arm for the treatment of ovarian cancer

The use of T-cell engagers (TCEs) to treat solid tumors is challenging, and several have been limited by narrow therapeutic windows due to substantial on-target, off-tumor toxicities due to the expression of low levels of target antigens on healthy tissues. Here, we describe TNB-928B, a fully human TCE that has a bivalent binding arm for folate receptor alpha (FRα) to selectively target FRα overexpressing tumor cells while avoiding the lysis of cells with low levels of FRα expression. The bivalent design of the FRα binding arm confers tumor selectivity due to low-affinity but high-avidity binding to high FRα antigen density cells. TNB-928B induces preferential effector T-cell activation, proliferation, and selective cytotoxic activity on high FRα expressing cells while sparing low FRα expressing cells. In addition, TNB-928B induces minimal cytokine release compared to a positive control TCE containing OKT3. Moreover, TNB-928B exhibits substantial ex vivo tumor cell lysis using endogenous T-cells and robust tumor clearance in vivo, promoting T-cell infiltration and antitumor activity in mouse models of ovarian cancer. TNB-928B exhibits pharmacokinetics similar to conventional antibodies, which are projected to enable favorable administration in humans. TNB-928B is a novel TCE with enhanced safety and specificity for the treatment of ovarian cancer.

Widespread choroid plexus contamination in sampling and profiling of brain tissue

The choroid plexus, a tissue responsible for producing cerebrospinal fluid, is found predominantly in the lateral and fourth ventricles of the brain. This highly vascularized and ciliated tissue is made up of specialized epithelial cells and capillary networks surrounded by connective tissue. Given the complex structure of the choroid plexus, this can potentially result in contamination during routine tissue dissection. Bulk and single-cell RNA sequencing studies, as well as genome-wide in situ hybridization experiments (Allen Brain Atlas), have identified several canonical markers of choroid plexus such as Ttr, Folr1, and Prlr. We used the Ttr gene as a marker to query the Gene Expression Omnibus database for transcriptome studies of brain tissue and identified at least some level of likely choroid contamination in numerous studies that could have potentially confounded data analysis and interpretation. We also analyzed transcriptomic datasets from human samples from Allen Brain Atlas and the Genotype-Tissue Expression (GTEx) database and found abundant choroid contamination, with regions in closer proximity to choroid more likely to be impacted such as hippocampus, cervical spinal cord, substantia nigra, hypothalamus, and amygdala. In addition, analysis of both the Allen Brain Atlas and GTEx datasets for differentially expressed genes between likely "high contamination" and "low contamination" groups revealed a clear enrichment of choroid plexus marker genes and gene ontology pathways characteristic of these ciliated choroid cells. Inclusion of these contaminated samples could result in biological misinterpretation or simply add to the statistical noise and mask true effects. We cannot assert that Ttr or other genes/proteins queried in targeted assays are artifacts from choroid contamination as some of these differentials may be due to true biological effects. However, for studies that have an unequal distribution of choroid contamination among groups, investigators may wish to remove contaminated samples from analyses or incorporate choroid marker gene expression into their statistical modeling. In addition, we suggest that a simple RT-qPCR or western blot for choroid markers would mitigate unintended choroid contamination for any experiment, but particularly for samples intended for more costly omic profiling. This study highlights an unexpected problem for neuroscientists, but it is also quite possible that unintended contamination of adjacent structures occurs during dissections for other tissues but has not been widely recognized.

High Expression of Folate Receptor Alpha (FOLR1) is Associated With Aggressive Tumor Behavior, Poor Response to Chemoradiotherapy, and Worse Survival in Rectal Cancer

Objectives: Recently, molecular medicine targeting Folate Receptor Alpha (FOLR1), which mediates intracellular folate uptake and tumor cell proliferation, has been identified in several malignancies. However, the association between FOLR1 expression and rectal cancer remains unclear. Methods: Immunostaining of FOLR1 was performed on biopsy specimens from 172 rectal cancer patients undergoing preoperative chemoradiotherapy (CRT). FOLR1 expression was measured and divided into low (0+-2+) or high (3+-4+) level. Correlations between FOLR1 status and clinicopathologic features, tumor regression grade, disease-specific survival (DSS), local recurrence-free survival, and metastasis-free survival (MeFS) were analyzed, retrospectively. Results: High FOLR1 expression was significantly associated with advanced post-treatment tumor and nodal status (T3-4; N1-2, P = .001), vascular invasion (P = .042), perineural invasion (P = .012), and poor regression change after CRT (P = .001). In uni- and multi-variable survival analysis, FOLR1 overexpression remained a significant predictor of lower DSS (hazard ratio [HR], 2.328; 95% confidence interval [CI], 1.014-5.344; P = .046) and MeFS (HR, 2.177; 95% CI, 1.000-1.1286; P = .050). Conclusion: These results indicate that high FOLR1 status is associated with aggressive tumor behavior, poor response to CRT, and worse survival. Therefore, FOLR1 expression at initial biopsy may be useful in predicting outcomes and also be a target for the exploration of FOLR1-based therapeutic agents.

Conjugated β-Cyclodextrin Enhances the Affinity of Folic Acid towards FRα: Molecular Dynamics Study

Drug targeting is a progressive area of research with folate receptor alpha (FRα) receiving significant attention as a biological marker in cancer drug delivery. The binding affinity of folic acid (FA) to the FRα active site provides a basis for recognition of FRα. In this study, FA was conjugated to beta-cyclodextrin (βCD) and subjected to in silico analysis (molecular docking and molecular dynamics (MD) simulation (100 ns)) to investigate the affinity and stability for the conjugated system compared to unconjugated and apo systems (ligand free). Docking studies revealed that the conjugated FA bound into the active site of FRα with a docking score (free binding energy < -15 kcal/mol), with a similar binding pose to that of unconjugated FA. Subsequent analyses from molecular dynamics (MD) simulations, root mean square deviation (RMSD), root mean square fluctuation (RMSF), and radius of gyration (Rg) demonstrated that FA and FA-βCDs created more dynamically stable systems with FRα than the apo-FRα system. All systems reached equilibrium with stable RMSD values ranging from 1.9-2.4 Å and the average residual fluctuation values of the FRα backbone atoms for all residues (except for terminal residues ARG8, THR9, THR214, and LEU215) were less than 2.1 Å with a consistent Rg value of around 16.8 Å throughout the MD simulation time (0-100 ns). The conjugation with βCD improved the stability and decreased the mobility of all the residues (except residues 149-151) compared to FA-FRα and apo-FRα systems. Further analysis of H-bonds, binding free energy (MM-PBSA), and per residue decomposition energy revealed that besides APS81, residues HIS20, TRP102, HIS135, TRP138, TRP140, and TRP171 were shown to have more favourable energy contributions in the holo systems than in the apo-FRα system, and these residues might have a direct role in increasing the stability of holo systems.

Folate receptor α increases chemotherapy resistance through stabilizing MDM2 in cooperation with PHB2 that is overcome by MORAb-202 in gastric cancer

BACKGROUND

The main function of folate receptor α (FOLRα) has been considered to mediate intracellular folate uptake and induce tumor cell proliferation. Given the broad spectrum of expression among malignant tumors, including gastric cancer (GC) but not in normal tissue, FOLRα represents an attractive target for tumor-selective drug delivery. However, the efficacy of anti-FOLRα monoclonal antibodies (mAbs) has not been proved so far, with the reason for this failure remaining unclear, raising the need for a better understanding of FOLRα function.

METHODS

The distribution of FOLRα in GC cells was evaluated by immunohistochemistry. The impacts of FOLRα expression on the survival of GC patients and GC cell lines were examined with the Gene Expression Omnibus database and by siRNA of FOLRα. RNA-sequencing and Microarray analysis was conducted to identify the function of FOLRα. Proteins that interact with FOLRα were identified with shotgun LC-MS/MS. The antitumor efficacy of the anti-FOLRα mAb farletuzumab as well as the antibody-drug conjugate (ADC) consists of the farletuzumab and the tublin-depolymerizing agent eribulin (MORAb-202) was evaluated both in vitro and in vivo.

RESULTS

FOLRα was detected both at the cell membrane and in the cytoplasm. Shorter overall survival was associated with FOLRα expression in GC patients, whereas reduction of FOLRα attenuated cell proliferation without inducing cell death in GC cell lines. Transcriptomic and proteomic examinations revealed that the FOLRα-expressing cancer cells possess a mechanism of chemotherapy resistance supported by MDM2, and FOLRα indirectly regulates it through a chaperone protein prohibitin2 (PHB2). Although reduction of FOLRα brought about vulnerability for oxaliplatin by diminishing MDM2 expression, farletuzumab did not suppress the MDM2-mediated chemoresistance and cell proliferation in GC cells. On the other hand, MORAb-202 showed significant antitumor efficacy.

CONCLUSIONS

The ADC could be a more reasonable choice than mAb as a targeting agent for the FOLRα-expressing tumor.

Diagnostic accuracy of novel folate receptor-mediated staining solution detection (FRD) for CIN2+: A systematic review and meta analysis

BACKGROUND

Early detection and diagnosis of high-grade cervical intraepithelial neoplasia grade 2 or higher (CIN2+) is critical for a good prognosis and appropriate treatment. The chief aim of our study was to evaluate the diagnostic performance of folate receptor-mediated staining solution detection (FRD) for CIN2+.

METHODS

We conducted a systematic review and meta-analysis by searching the PubMed and EMBASE databases for studies published until May 2020, which assessed the diagnostic accuracy of FRD, human papilloma virus (HPV) testing, and ThinPrep cytology test (TCT) for the detection of CIN2+. Bivariate models were used to compare the diagnostic performance of FRD, HPV, and TCT.

RESULTS

Six studies involving 2817 patients were included in this meta-analysis. The pooled specificity of FRD was higher than that of HPV and TCT for detecting CIN2+ (0.65, 0.12, and 0.39, respectively). The summary area under the receiver operating characteristic curve values using FRD, HPV, and TCT for detecting CIN2+ were 0.79, 0.95, and 0.77, respectively, indicating that FRD was superior to TCT. The diagnostic odds ratios of FRD, HPV, and TCT were 6 (95% CI: 5-7), 3 (95% CI: 2-5), and 3 (95% CI: 2-4), respectively, demonstrating that FRD had good diagnostic accuracy.

CONCLUSION

FRD showed good diagnostic accuracy and higher specificity than HPV and TCT for detecting CIN2+. Based on our results, we propose that FRD could be a candidate for cervical screening, especially in underdeveloped countries.

Folate transporter dynamics and therapy with classic and tumor-targeted antifolates

There are three major folate uptake systems in human tissues and tumors, including the reduced folate carrier (RFC), folate receptors (FRs) and proton-coupled folate transporter (PCFT). We studied the functional interrelationships among these systems for the novel tumor-targeted antifolates AGF94 (transported by PCFT and FRs but not RFC) and AGF102 (selective for FRs) versus the classic antifolates pemetrexed, methotrexate and PT523 (variously transported by FRs, PCFT and RFC). We engineered HeLa cell models to express FRα or RFC under control of a tetracycline-inducible promoter with or without constitutive PCFT. We showed that cellular accumulations of extracellular folates were determined by the type and levels of the major folate transporters, with PCFT and RFC prevailing over FRα, depending on expression levels and pH. Based on patterns of cell proliferation in the presence of the inhibitors, we established transport redundancy for RFC and PCFT in pemetrexed uptake, and for PCFT and FRα in AGF94 uptake; uptake by PCFT predominated for pemetrexed and FRα for AGF94. For methotrexate and PT523, uptake by RFC predominated even in the presence of PCFT or FRα. For both classic (methotrexate, PT523) and FRα-targeted (AGF102) antifolates, anti-proliferative activities were antagonized by PCFT, likely due to its robust activity in mediating folate accumulation. Collectively, our findings describe a previously unrecognized interplay among the major folate transport systems that depends on transporter levels and extracellular pH, and that determines their contributions to the uptake and anti-tumor efficacies of targeted and untargeted antifolates.

Multimodal image-guided folic acid targeted Ag-based quantum dots for the combination of selective methotrexate delivery and photothermal therapy

Multifunctional quantum dots (QDs) with photothermal therapy (PTT) potential loaded with an anticancer drug and labelled with a targeting agent can be highly effective nano-agents for tumour specific, image-guided PTT/chemo combination therapy of cancer. Ag-chalcogenides are promising QDs with good biocompatibility. Ag₂S QDs are popular theranostic agents for imaging in near-infrared with PTT potential. However, theranostic applications of AgInS2 QDs emitting in the visible region and its PTT potential need to be explored. Here, we first present a simple synthesis of small, glutathione (GSH) coated AgInS₂ QDs with peak emission at 634 nm, 21% quantum yield, and excellent long-term stability without an inorganic shell. Ag2S-GSH QDs emitting in the near-infrared region (peak emission = 822 nm) were also produced. Both QDs were tagged with folic acid (FA) and conjugated with methotrexate (MTX). About 3-fold higher internalization of FA-tagged QDs by folate-receptor (FR) overexpressing HeLa cells than HT29 and A549 cells was observed. Delivery of MTX by QD-FA-MTX reduced the IC50 of the drug from 10 μg/mL to 2.5-5 μg/mL. MTX release was triggered at acidic pH, which was further enhanced with local temperature increase created by laser irradiation. Irradiation of AgInS₂-GSH QDs at 640 nm (300 mW) for 10 min, caused about 10 °C temperature increase but did not cause any thermal ablation of cells. On the other hand, Ag₂S-GSH-FA based PTT effectively and selectively killed HeLa cells with 10 min 808 nm laser irradiation via mostly necrosis with an IC₅₀ of 5 μg Ag/mL. Under the same conditions, IC₅₀ of MTX was reduced to 0.21 μg/mL if Ag₂S-GSH-FA.

Identification of folate receptor α (FRα) binding oligopeptides and their evaluation for targeted virotherapy applications

Oncolytic virotherapies (OV) based on human adenoviral (HAdV) vectors hold significant promise for the treatment of advanced ovarian cancers where local, intraperitoneal delivery to tumour metastases is feasible, bypassing many complexities associated with intravascular delivery. The efficacy of HAdV-C5-based OV is hampered by a lack of tumour selectivity, where the primary receptor, hCAR, is commonly downregulated during malignant transformation. Conversely, folate receptor alpha (FRα) is highly expressed on ovarian cancer cells, providing a compelling target for tumour selective delivery of virotherapies. Here, we identify high-affinity FRα-binding oligopeptides for genetic incorporation into HAdV-C5 vectors. Biopanning identified a 12-mer linear peptide, DWSSWVYRDPQT, and two 7-mer cysteine-constrained peptides, CIGNSNTLC and CTVRTSAEC that bound FRα in the context of the phage particle. Synthesised lead peptide, CTVRTSAEC, bound specifically to FRα and could be competitively inhibited with folic acid. To assess the capacity of the elucidated FRα-binding oligopeptides to target OV to FRα, we genetically incorporated the peptides into the HAdV-C5 fiber-knob HI loop including in vectors genetically ablated for hCAR interactions. Unfortunately, the recombinant vectors failed to efficiently target transduction via FRα due to defective intracellular trafficking following entry via FRα, indicating that whilst the peptides identified may have potential for applications for targeted drug delivery, they require additional refinement for targeted virotherapy applications.

Exploiting the folate receptor α in oncology

Folate receptor α (FRα) came into focus as an anticancer target many decades after the successful development of drugs targeting intracellular folate metabolism, such as methotrexate and pemetrexed. Binding to FRα is one of several methods by which folate is taken up by cells; however, this receptor is an attractive anticancer drug target owing to the overexpression of FRα in a range of solid tumours, including ovarian, lung and breast cancers. Furthermore, using FRα to better localize effective anticancer therapies to their target tumours using platforms such as antibody-drug conjugates, small-molecule drug conjugates, radioimmunoconjugates and, more recently, chimeric antigen receptor T cells could further improve the outcomes of patients with FRα-overexpressing cancers. FRα can also be harnessed for predictive biomarker research. Moreover, imaging FRα radiologically or in real time during surgery can lead to improved functional imaging and surgical outcomes, respectively. In this Review, we describe the current status of research into FRα in cancer, including data from several late-phase clinical trials involving FRα-targeted therapies, and the use of new technologies to develop FRα-targeted agents with improved therapeutic indices.

Cell-Surface Proteomics Identifies Differences in Signaling and Adhesion Protein Expression between Naive and Primed Human Pluripotent Stem Cells

Naive and primed human pluripotent stem cells (hPSC) provide valuable models to study cellular and molecular developmental processes. The lack of detailed information about cell-surface protein expression in these two pluripotent cell types prevents an understanding of how the cells communicate and interact with their microenvironments. Here, we used plasma membrane profiling to directly measure cell-surface protein expression in naive and primed hPSC. This unbiased approach quantified over 1,700 plasma membrane proteins, including those involved in cell adhesion, signaling, and cell interactions. Notably, multiple cytokine receptors upstream of JAK-STAT signaling were more abundant in naive hPSC. In addition, functional experiments showed that FOLR1 and SUSD2 proteins are highly expressed at the cell surface in naive hPSC but are not required to establish human naive pluripotency. This study provides a comprehensive stem cell proteomic resource that uncovers differences in signaling pathway activity and has identified new markers to define human pluripotent states.

Folate receptor alpha targeted delivery of artemether to breast cancer cells with folate-decorated human serum albumin nanoparticles

The pharmaceutical application of artemether (ARM) as an anticancer natural agent is hampered due to its poor solubility and bioavailability. In the present study, ARM was encapsulated in human serum albumin nanoparticles (HSA NPs) via desolvation method led to improvement of the water solubility by 50 folds. In further, folate-decorated ARM-HSA NPs (F-ARM-HSA NPs) were developed to enhance targeted delivery to folate receptor alpha (FRα)-overexpressing breast cancer cells. The hydrodynamic diameter and the zeta potential value of F-ARM-HSA NPs were 198 ± 11.22 nm and -23 ± 0.88 mV, respectively. Fluorescent microscopy demonstrated an enhanced cellular uptake of F-ARM-HSA NPs by high FRα-expressing MDA-MB-231 breast cancer cells compared to low FRα-expressing SK-BR-3 breast cancer cells. Cytotoxicity assay revealed a small significant difference between cytotoxicity effect of targeted and non-targeted NPs in SK-BR-3 cells. However, in MDA-MB-231 cells due to FRα-mediated endocytosis, the F-conjugated NPs had less inhibitory concentration (IC50) value (19.82 μg/mL) and higher cytotoxicity after 72 h compared to non-targeted ARM-HSA NPs. Flow cytometry analysis indicated a more potent drug-induced apoptosis rather than necrosis. The results suggest that our novel F-ARM-HSA NPs are likely to be recommended as a promising candidate for combination therapy of FRα-overexpressing breast cancer cells.

Clinicopathological and immunohistochemical characteristics of breast cancer patients from Northeast India with special reference to triple negative breast cancer: A prospective study

BACKGROUND

Molecular pathogenesis of Triple-negative breast cancer (TNBC) is inconclusively documented from resource limited countries and hence there is a lack of available targeted therapy for clinical interventions. Compared to other breast cancer subtypes, TNBC is more aggressive, higher recurrence rate, and higher prevalence in younger premenopausal women. Sporadic literature indicates predominance of TNBC in all reported breast cancer cases from Northeast India.

AIM

This study was conducted to evaluate the candidature of panel of key molecular markers involved in the development and progression of TNBC for prognosis and futuristic tailored targeted therapy.

MATERIALS AND METHODS

We analyzed the clinicopathological characterized and immunohistochemically screened the differential expression of key molecular markers involved in the development and progression of in TNBC cases vis-a-vis non-TNBC and autopsy-based control samples.

RESULTS

TNBC tends to display at an early reproductive age and is more aggressive in nature. Further, the differential expression of 2 specific markers viz., epidermal growth factor receptor (EGFR) and FolR1 was higher in TNBC cases compared to controls and non-TNBC (both in terms of susceptibility and specificity), clinical staging in TNBC cases (severity) and mortality (outcome). Although Ki67 and vascular endothelial growth factor expression also correlated with severity and outcome of the disease but their differences in non-TNBC cases were not significantly differentiable compared to TNBC.

CONCLUSIONS

The study indicates that EGFR and FolR1 could serve as useful biomarkers to determine TNBC prognosis. Further studies will be needed to evaluate EGFR and Folate pathways in order to screen out the molecular targets which may be meaningfully used for clinical stratification, intervention, and treatment.

Aqueous stable Pd nanoparticles/covalent organic framework nanocomposite: an efficient nanoenzyme for colorimetric detection and multicolor imaging of cancer cells

Accurate, sensitive detection of cancer cells from clinical fluids is helpful for screening and early diagnosis of tumors. Here, we develop a facile approach for in situ growth of palladium nanoparticles in an aqueous stable carboxymethyl cellulose-modified covalent organic framework hydrogel (named Pd NPs/CMC-COF-LZU1). The resulting nanocomposite has been proven to show superior catalytic performance for the transformation of N-butyl-4-NHAlloc-1,8-naphthalimide (NNPH) into N-butyl-4-amido-1,8-naphthalimide (NPH), indicated by significant changes in both color and fluorescence. Based on these features, the designed nanocomposite was used as a signal transducer to develop a colorimetric assay and multicolor imaging for accurate and sensitive detection of cancer cells. The transformation of NNPH into NPH enabled the detection system to perform multicolor imaging of HeLa cells. By using folic acid (FA) as a recognition element, a total of 100 cancer cells (HeLa) can be distinguished in 1 mL culture medium with 10% FBS. We envision that these COF-based composite materials (Pd NPs/CMC-COF-LZU1) have tremendous potential applications in biotechnology and biological sciences.

microRNA-29b inhibits cell growth and promotes sensitivity to oxaliplatin in colon cancer by targeting FOLR1

The present study was aimed to explore the functional role of microRNA (miR)-29b in colon cancer, as well as underlying mechanisms. Expressions of miR-29b and folate receptor 1 (FOLR1) were measured in both human colon tumor samples and cell lines. Colon cancer cell lines SW480 and SW620 were transfected with miR-29b mimic, antisense oligonucleotides (ASO)-miR-29b, small interfering (siRNA) against FOLR1 (si-FOLR1), or corresponding negative controls (NCs), and then were incubated with or without oxaliplatin (L-OHP). Thereafter, cell viability, cytotoxicity, cell apoptosis, and expression of FOLR1, ATP Binding Cassette Subfamily G Member 2 (ABCG2) and p-glycoprotein (p-gp) were analyzed. We found that miR-29b was significantly decreased, while FOLR1 was statistically elevated in colon cancer samples and cell lines compared to the nontumor samples and nontumourigenic immortalized human colon epithelial cell line FHC. Overexpression of miR-29b markedly inhibited cell viability, promoted sensitivity to L-OHP, stimulated cell apoptosis (all p < .05), and decreased the levels of ABCG2 and p-gp in cancer cells, whereas suppression of miR-29b showed contrary results. Moreover, we observed that FOLR1 was a direct target of miR-29b and was negatively regulated by miR-29b. In addition, the findings revealed that the effects of FOLR1 inhibition on cell viability, sensitivity to L-OHP, cell apoptosis, and the levels of ABCG2 and p-gp were similar to overexpression of miR-29b. Taken together, our study suggests that miR-29b inhibits cell growth and promotes sensitivity to L-OHP in colon cancer by targeting FOLR1.

Clinical Application of Folate Receptor-Mediated Staining Solution Detection in Cervical Cancer Screening

OBJECTIVE

Cervical cancer is the fourth most deadly women's cancer worldwide, and regular screening is essential to lower mortality rates. The folate receptor-mediated staining solution detection (FRD) has been suggested to be a rapid and cost-effective screening method. We aim to evaluate the validity of FRD testing in cervical cancer screening.

METHODS

A total of 207 participants were enrolled in the study. The validity of screening by FRD, cytology screening, and a HPV test were compared using histopathology as the gold standard. Sensitivity, specificity, positive predictive value, negative predictive value, Kappa value, positive likelihood ratio, negative likelihood ratio, percent agreement, and positive detection rates were compared among the three screening methods.

RESULTS

83(40.1%) participants were diagnosed as NILM, 50(24.15%) were diagnosed as CIN1, and 74(35.74%) were diagnosed as CIN2+. For CIN2+, the detection rates for the FRD, cytology screening, and HPV were 75.68%, 82.09% and 93.22%, respectively. For CIN2+, the sensitivity of HPV testing (93.22%) was significantly higher than that of cytology screening (82.09%) and FRD (75.68%), while the specificity of FRD (63.91%) was higher than that of cytology screening (35.34%) and HPV test (7.56%). The percent agreement and Kappa value of FRD were significantly higher than those of the cytology screening and HPV test. In HPV-HC2+ and ASCUS patients, FRD was associated with a lower false positive rate compared to other screening methods.

CONCLUSION

Our study indicates that FRD has a good sensitivity and high specificity in cervical cancer screening, and could be a rapid, valid and cost-effective screening test.

Hybrid micelles containing methotrexate-conjugated polymer and co-loaded with microRNA-124 for rheumatoid arthritis therapy

Purpose: Methotrexate (MTX) is a first-line drug for rheumatoid arthritis (RA)therapy. However, MTX monotherapy often results in irreversible joint damage due to its slow onset of action and long duration. microRNA-124 (miR-124) has shown direct bone protection activity against RA. A co-delivery system for MTX and microRNA combination may provide therapeutic synergy. Methods: Methotrexate-conjugated polymer hybrid micelles (M-PHMs) were prepared by self-assembly of two functional amphiphilic polymers (MTX-PEI-LA and mPEG-LA) at an optimized weight ratio. Incorporation of microRNA was achieved through electrostatic interactions between microRNA and cationic polymer MTX-PEI-LA. Cellular uptake, endosome escape, biodistribution, and therapeutic efficacy of M-PHMs/miR-124 complexes were investigated and evaluated in RAW264.7 cells and a rat adjuvant-induced arthritis (AIA) model. Results: M-PHMs/miR-124 complexes exhibited folate receptor-mediated uptake in activated RAW264.7 cells. miR-124 was able to escape from the endosome and down-regulate nuclear factor of activated T cells cytoplasmic1 (NFATc1). M-PHMs/miR-124 complexes accumulated in inflamed joints of AIA rats and showed superior therapeutic efficacy through both anti-inflammatory effect and direct bone protective effect. Combination of miR-124 and MTX in these micelles induced disease remission. Conclusions: M-PHMs/miR-124 was highly effective against RA through therapeutic synergy. Additional studies are warranted to further investigate its therapeutic potential and delineate its mechanisms of action.

Augmented cytotoxic effects of paclitaxel by curcumin induced overexpression of folate receptor-α for enhanced targeted drug delivery in HeLa cells

BACKGROUND

New targeted therapies are intended to minimize the toxic effects and maximize destruction of tumor cells. Folate is a membrane-bound receptor that plays a vital role in the uptake of anti-folate molecules aimed for efficient drug delivery of anti-folate drugs.

PURPOSE

The present study is aimed at the modulation of the expression of folate receptor by curcumin that enhances the intake, cytotoxicity and anticancer effects of paclitaxel in HeLa cells.

MATERIALS AND METHODS

HeLa cells were pretreated with curcumin and treated with paclitaxel. We measured the cell viability, uptake of radiolabelled folic acid and paclitaxel, Folate receptor -alpha (FR-α) protein expression by immunocytochemistry and western blot and FR-α mRNA expression by qualitative and quantitative analysis.

RESULTS

This study shows that curcumin (10 - 50 µM) causes significantly increased cytotoxicity in a dose and time dependent manner. It also enhances the intake of radiolabeled folic acid and paclitaxel 3-4 folds in HeLa cells. The pretreatment of HeLa cells with curcumin shows statistically significant of cell death by paclitaxel. The quantitative RT-PCR demonstrates the expression of FR- α mRNA upon curcumin treatment. Furthermore, immunochemistry and western blotting analysis proved that curcumin enhances expression the FR- α in HeLa cells.

CONCLUSION

Our study proved that the molecular mechanism of curcumin enhances the upregulation of FR - α mRNA and protein expression in HeLa cells. Therefore, a combination of curcumin and paclitaxel at less concentration may be a targeting strategy for FR-targeted drug delivery providing a better therapeutic intervention of cancer.

Green synthesis of multifunctional PEG-carboxylate π back-bonded gold nanoconjugates for breast cancer treatment

BACKGROUND

Surface functionalization of gold nanoparticles (AuNPs) has emerged as a promising field of research with enormous biomedical applications. The folate (FA)-attached polymer-gold nanoconjugates play vital role in targeting the cancer cells.

METHODS

AuNPs were synthesized by using di- or tri-carboxylate-polyethylene glycol (PEG) polymers, including citrate-PEG (CPEG), malate-PEG (MAP), and tartrate-PEG (TAP), as a reducing and stabilizing agent. After synthesis of polymer-AuNPs, the freely available hydroxyl and carboxylate groups of CPEG, MAP, and TAP were used to attach a cancer cell-targeting agent, FA, via a 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxy succinimide coupling reaction to obtain FA-CPEG-AuNP, FA-MAP-AuNP, and FA-TAP-AuNP nanocon-jugates, respectively. The 5-fluorouracil (5FU) was attached to π back-bonded carbonyl oxygens of the nanoconjugates, and the in vitro drug release profile was studied by high pressure liquid chromatography. Biocompatibility profiles of the FA-CPEG-AuNP, FA-MAP-AuNP, and FA-TAP-AuNP nanoconjugates were investigated using adult human dermal fibroblasts. Anti-breast cancer activity of 5FU-loaded nanoconjugates was investigated using MCF-7 breast cancer cells.

RESULTS

X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy analyses confirmed that AuNPs attached to CPEG, MAP, or TAP via the formation of π back bonding between AuNPs and the ester carbonyl group. The π back-bonded nanoconjugates exhibited sustained release of 5FU up to 27 days. FA-MAP-AuNPs exhibited an IC50 at 5 µg/mL, while FA-CPEG-AuNPs and FA-TAP-AuNPs showed the IC50 at 100 µg/mL toward MCF-7 cancer cells.

CONCLUSION

The developed polymer π back-bonded multifunctional gold nanoconjugates could be used as a potential drug delivery system for targeting MCF-7 cancer cells.

Preclinical investigation of folate receptor-targeted nanoparticles for photodynamic therapy of malignant pleural mesothelioma

Photodynamic therapy (PDT) following lung-sparing extended pleurectomy for malignant pleural mesothelioma (MPM) has been investigated as a potential means to kill residual microscopic cells. High expression levels of folate receptor 1 (FOLR1) have been reported in MPM; therefore, targeting FOLR1 has been considered a novel potential strategy. The present study developed FOLR1‑targeting porphyrin-lipid nanoparticles (folate-porphysomes, FP) for the treatment of PDT. Furthermore, inhibition of activated epidermal growth factor (EGFR)-associated survival pathways enhance PDT efficacy. In the present study, these approaches were combined; FP-based PDT was used together with an EGFR-tyrosine kinase inhibitor (EGFR-TKI). The frequency of FOLR1 and EGFR expression in MPM was analyzed using tissue microarrays. Confocal microscopy and a cell viability assay were performed to confirm the specificity of FOLR1‑targeting cellular uptake and photocytotoxicity in vitro. In vivo fluorescence activation and therapeutic efficacy were subsequently examined. The effects of EGFR-TKI were also assessed in vitro. The in vivo combined antitumor effect of EGFR-TKI and FP-PDT was then evaluated. The results revealed that FOLR1 and EGFR were expressed in 79 and 89% of MPM samples, respectively. In addition, intracellular uptake of FP corresponded well with FOLR1 expression. When MPM cells were incubated with FP and then irradiated at 671 nm, there was significant in vitro cell death, which was inhibited in the presence of free folic acid, thus suggesting the specificity of FPs. FOLR1 targeting resulted in disassembly of the porphysomes and subsequent fluorescence activation in intrathoracic disseminated MPM tumors, as demonstrated by ex vivo tissue imaging. FP-PDT resulted in significant cellular damage and apoptosis in vivo. Furthermore, the combination of pretreatment with EGFR-TKI and FP-PDT induced a marked improvement of treatment responses. In conclusion, FP-based PDT induced selective destruction of MPM cells based on FOLR1 targeting, and pretreatment with EGFR-TKI further enhanced the therapeutic response.

Anti-Folate Receptor Alpha-Directed Antibody Therapies Restrict the Growth of Triple-negative Breast Cancer

Purpose: Highly aggressive triple-negative breast cancers (TNBCs) lack validated therapeutic targets and have high risk of metastatic disease. Folate receptor alpha (FRα) is a central mediator of cell growth regulation that could serve as an important target for cancer therapy.Experimental Design: We evaluated FRα expression in breast cancers by genomic (n = 3,414) and IHC (n = 323) analyses and its association with clinical parameters and outcomes. We measured the functional contributions of FRα in TNBC biology by RNA interference and the antitumor functions of an antibody recognizing FRα (MOv18-IgG1), in vitro, and in human TNBC xenograft models.Results: FRα is overexpressed in significant proportions of aggressive basal like/TNBC tumors, and in postneoadjuvant chemotherapy-residual disease associated with a high risk of relapse. Expression is associated with worse overall survival. TNBCs show dysregulated expression of thymidylate synthase, folate hydrolase 1, and methylenetetrahydrofolate reductase, involved in folate metabolism. RNA interference to deplete FRα decreased Src and ERK signaling and resulted in reduction of cell growth. An anti-FRα antibody (MOv18-IgG1) conjugated with a Src inhibitor significantly restricted TNBC xenograft growth. Moreover, MOv18-IgG1 triggered immune-dependent cancer cell death in vitro by human volunteer and breast cancer patient immune cells, and significantly restricted orthotopic and patient-derived xenograft growth.Conclusions: FRα is overexpressed in high-grade TNBC and postchemotherapy residual tumors. It participates in cancer cell signaling and presents a promising target for therapeutic strategies such as ADCs, or passive immunotherapy priming Fc-mediated antitumor immune cell responses. Clin Cancer Res; 24(20); 5098-111. ©2018 AACR.

Down-regulation of placental folate transporters in intrauterine growth restriction

Folate deficiency in pregnancy is associated with neural tube defects, restricted fetal growth and fetal programming of diseases later in life. Fetal folate availability is dependent on maternal folate levels and placental folate transport capacity, mediated by two key transporters, Folate Receptor-α and Reduced Folate Carrier (RFC). We tested the hypothesis that intrauterine growth restriction (IUGR) is associated with decreased folate transporter expression and activity in isolated syncytiotrophoblast microvillous plasma membranes (MVM). Women with pregnancies complicated by IUGR (birth weight <3rd percentile, mean birth weight 1804±110 g, gestational age 35.7±0.61 weeks, n=25) and women delivering an appropriately-for gestational age infant (control group, birth weight 25th-75th centile, mean birth weight 2493±216 g, gestational age 33.9±0.95 weeks, n=19) were recruited and placentas were collected at delivery. MVM was isolated and folate transporter protein expression was measured using Western blot and transporter activity was determined using radiolabelled methyltetrahydrofolic acid and rapid filtration. Whereas the expression of FR-α was unaffected, MVM RFC protein expression was significantly decreased in the IUGR group (-34%, P<.05). IUGR MVM had a significantly lower folate uptake compared to the control group (-38%, P<.05). In conclusion, placental folate transport capacity is decreased in IUGR, which may contribute to the restricted fetal growth and intrauterine programming of childhood and adult disease. These findings suggest that continuation of folate supplementation in the second and third trimester is of particular importance in pregnancies complicated by IUGR.

Localization of Pulmonary Ground-Glass Opacities with Folate Receptor-Targeted Intraoperative Molecular Imaging

PURPOSE

Intraoperative localization and resection of ill-defined pulmonary ground-glass opacities (GGOs) during minimally invasive pulmonary resection is technically challenging. Current preoperative techniques to facilitate localization of GGOs include microcoil and hook wire placement, both of which have logistic limitations, carry safety concerns, and do not help with margin assessment. In this clinical trial, we explored an alternative method involving near-infrared molecular imaging with a folate receptor-targeted agent, OTL38, to improve localization of GGOs and confirmation of resection margins.

METHODS

In a human trial, 20 subjects with pulmonary GGOs who were eligible for video-assisted thoracoscopic surgery (VATS) resection received 0.025 mg/kg of OTL38 before the resection. The primary objectives were to (1) determine whether use of OTL38 allows safe localization of GGOs and assessment of margins during VATS and (2) determine patient, radiographic, and histopathologic variables that predict the amount of fluorescence during near-infrared imaging.

RESULTS

We observed no toxicity. Of the 21 GGOs, 20 accumulated OTL38 and displayed fluorescence upon in situ or back table evaluation. Intraoperatively, near-infrared imaging localized 15 of 21 lesions whereas VATS alone localized 10 of 21 (p = 0.05). The addition of molecular imaging affected care of nine of 21 subjects by improving intraoperative localization (n = 6) and identifying close margins (n = 3). This approach was most effective for subpleural lesions measuring less than 2 cm. For lesions deeper than 1.5 cm from the pleural surface, intraoperative localization using fluorescent feedback was limited.

CONCLUSIONS

This approach provides a safe alternative for intraoperative localization of small, peripherally located pulmonary lesions. In contrast to alternative localization techniques, use of OTL38 also allows confirmation of adequate margins. Future studies will compare this approach to alternative localization techniques in a clinical trial.

A G-protein-coupled chemoattractant receptor recognizes lipopolysaccharide for bacterial phagocytosis

Phagocytes locate microorganisms via chemotaxis and then consume them using phagocytosis. Dictyostelium amoebas are stereotypical phagocytes that prey on diverse bacteria using both processes. However, as typical phagocytic receptors, such as complement receptors or Fcγ receptors, have not been found in Dictyostelium, it remains mysterious how these cells recognize bacteria. Here, we show that a single G-protein-coupled receptor (GPCR), folic acid receptor 1 (fAR1), simultaneously recognizes the chemoattractant folate and the phagocytic cue lipopolysaccharide (LPS), a major component of bacterial surfaces. Cells lacking fAR1 or its cognate G-proteins are defective in chemotaxis toward folate and phagocytosis of Klebsiella aerogenes. Computational simulations combined with experiments show that responses associated with chemotaxis can also promote engulfment of particles coated with chemoattractants. Finally, the extracellular Venus-Flytrap (VFT) domain of fAR1 acts as the binding site for both folate and LPS. Thus, fAR1 represents a new member of the pattern recognition receptors (PRRs) and mediates signaling from both bacterial surfaces and diffusible chemoattractants to reorganize actin for chemotaxis and phagocytosis.

Folate homeostasis in epileptic rats

Folate is involved in metabolic processes and it has been implicated in both aggravation and amelioration of seizures. The aim of the current work was to study the effect of chronic temporal lobe epilepsy (TLE) on the plasma and brain concentrations of folate and on its uptake carriers in the brain - the reduced folate carrier (RFC), folate receptor α (FRα) and proton coupled folate transporter (PCFT). We utilized the rat lithium pilocarpine model for TLE. Approximately two months following status epilepticus, rats with spontaneous recurrent seizures (SRS) were sacrificed for brain and plasma folate concentration analyses and folate uptake carrier expression studies. RT-PCR and western blot analyses were utilized for quantification of folate carriers' mRNAs and proteins, respectively. The distribution of folate carriers in the brain was studied using immunohistochemistry. In the SRS rats we found lower plasma concentrations (10 ± 0.9 in control vs. 6.6 ± 1.6 ng/ml in SRS, P < 0.05), but preserved cortical and increased hippocampal levels of folate (0.5 ± 0.1 in control vs. 0.9 ± 0.2 ng/mg in SRS, P = 0.055). Hippocampus - to - plasma ratio of folate concentration was 3-fold higher in the SRS group, compared with the controls (0.13 ± 0.03 vs. 0.04 ± 0.02, respectively; P < 0.01). mRNA and protein levels of the folate uptake carriers did not differ between SRS rats and controls. However, immunofluorescent staining quantification revealed that the emission intensity of both RFC and FRα was elevated 8-fold and 4-fold, respectively, in hippocampal CA1 neurons of SRS rats, compared to controls (P < 0.01). PCFT was unquantifiable. If corroborated by complementary research in humans, the findings of this study may be utilized clinically for supplemental therapy planning, in imaging the epileptic focus, and for drug delivery into the epileptic brain. Further studies are required for better elucidating the clinical and mechanistic significance of altered folate balances in the epileptic brain.

A Novel Tumor-Specific Agent for Intraoperative Near-Infrared Fluorescence Imaging: A Translational Study in Healthy Volunteers and Patients with Ovarian Cancer

PURPOSE

Completeness of cytoreductive surgery is a key prognostic factor for survival in patients with ovarian cancer. The ability to differentiate clearly between malignant and healthy tissue is essential for achieving complete cytoreduction. Using current approaches, this differentiation is often difficult and can lead to incomplete tumor removal. Near-infrared fluorescence imaging has the potential to improve the detection of malignant tissue during surgery, significantly improving outcome. Here, we report the use of OTL38, a near-infrared (796 nm) fluorescent agent, that binds folate receptor alpha, which is expressed in >90% of epithelial ovarian cancers.

EXPERIMENTAL DESIGN

We first performed a randomized, placebo-controlled study in 30 healthy volunteers. Four single increasing doses of OTL38 were delivered intravenously. At fixed times following drug delivery, tolerability and blood/skin pharmacokinetics were assessed. Next, using the results of the first study, three doses were selected and administered to 12 patients who had epithelial ovarian cancer and were scheduled for cytoreductive surgery. We measured tolerability and blood pharmacokinetics, as well as the ability to detect the tumor using intraoperative fluorescence imaging.

RESULTS

Intravenous infusion of OTL38 in 30 healthy volunteers yielded an optimal dosage range and time window for intraoperative imaging. In 12 patients with ovarian cancer, OTL38 accumulated in folate receptor alpha-positive tumors and metastases, enabling the surgeon to resect an additional 29% of malignant lesions that were not identified previously using inspection and/or palpation.

CONCLUSIONS

This study demonstrates that performing real-time intraoperative near-infrared fluorescence imaging using a tumor-specific agent is feasible and potentially clinically beneficial. Clin Cancer Res; 22(12); 2929-38. ©2016 AACR.

Utilization of targeted near-infrared molecular imaging to improve pulmonary metastasectomy of osteosarcomas

Pulmonary metastasectomy for osteosarcoma provides a select group of patients an opportunity for long-term survival and possible cure. Unfortunately, a complete metastasectomy is challenging due an inability to accurately identify lesions that lay below the threshold of preoperative imaging or intraoperative visual and tactile inspection. Growing evidence suggests that osteosarcomas express a number of unique molecular markers, including the folate receptor alpha. In this case report, we describe the application of a folate receptor-targeted, near-infrared optical contrast agent (OTL38) to improve osteosarcoma localization during minimally invasive pulmonary resection. In addition to localizing preoperatively identified lesions, this technology helped identify additional disease that was undetected on preoperative imaging or with traditional intraoperative techniques. This report marks the first successful utilization of a molecular imaging probe useful for osteosarcomas. This technology may provide a unique approach to improve pulmonary metastasectomy of osteosarcomas.

Identification of a target protein of Hydra actinoporin-like toxin-1 (HALT-1) using GST affinity purification and SILAC-based quantitative proteomics

Hydra actinoporin-like toxin-1 (HALT-1) is a 20.8 kDa pore-forming toxin isolated from Hydra magnipapillata. HALT-1 shares structural similarity with actinoporins, a family that is well known for its haemolytic and cytolytic activity. However, the precise pore-forming mechanism of HALT-1 remains an open question since little is known about the specific target binding for HALT-1. For this reason, a comprehensive proteomic analysis was performed using affinity purification and SILAC-based mass spectrometry to identify potential protein-protein interactions between mammalian HeLa cell surface proteins and HALT-1. A total of 4 mammalian proteins was identified, of which only folate receptor alpha was further verified by ELISA. Our preliminary results highlight an alternative-binding mode of HALT-1 to the human plasma membrane. This is the first evidence showing that HALT-1, an actinoporin-like protein, binds to a membrane protein, the folate receptor alpha. This study would advance our understanding of the molecular basis of toxicity of pore-forming toxins and provide new insights in the production of more potent inhibitors for the toxin-membrane receptor interactions.

Folate Transporters in Placentas from Preterm Newborns and Their Relation to Cord Blood Folate and Vitamin B12 Levels

Folate deficiency during pregnancy has been related to low birth weight, preterm (PT) birth and other health risks in the offspring; however, it is unknown whether prematurity is related to low folate transport through the placenta due to altered expression of specific folate transporters. We determined placental expression (mRNA and protein concentrations by RT-qPCR and WB respectively) of specific folate transporters: RFC, PCFT/HCP1 and FOLR1 in chorionic (fetal) and basal (maternal) plates of placentas of PT pregnancies (PT, 32–36 weeks, n = 51). Term placentas were used as controls (T, 37–41 weeks, n = 47). Folates and vitamin B12 levels were measured by electrochemiluminescence in umbilical cord blood of newborns. FOLR1 mRNA expression was lower and protein concentration higher in PT placentas (both plates) relative to the control group (p <0.05). In addition, gestational age was positively correlated with mRNA expression (Rho = 0.7), and negatively with protein concentration (Rho = -0.7 for chorionic and -0.43 for basal plate). PCFT/HCP1 mRNA was lower in PT placentas, without changes in protein levels. RFC did not differ in PT placentas compared to controls. PT newborns presented higher cord blood folate level (p = 0.049) along with lower vitamin B12 concentration compared to controls (p = 0.037).In conclusion, placental FOLR1 mRNA was positively associated with gestational age. Conversely, FOLR1 protein concentrations along with folate/vitamin B12 ratio in cord blood were negatively associated with gestational age. Placental FOLR1 is likely the main placental folate transporter to the fetus in newborns.

Synthesis and Evaluation of (99m)Tc-Labeled Dimeric Folic Acid for FR-Targeting

The folate receptor (FR) is overexpressed in a wide variety of human tumors. In our study, the multimeric concept was used to synthesize a dimeric folate derivative via a click reaction. The novel folate derivative (HYNIC-D₁-FA₂) was radiolabeled with ^99mTc using tricine and trisodium triphenylphosphine-3,3′,3″-trisulfonate (TPPTS) as coligands (^99mTc-HYNIC-D₁-FA₂) and its in vitro physicochemical properties, ex vivo biodistribution and in vivo micro-SPECT/CT imaging as a potential FR targeted agent were evaluated. It is a hydrophilic compound (log P = −2.52 ± 0.13) with high binding affinity (IC₅₀ = 19.06 nM). Biodistribution in KB tumor-bearing mice showed that ^99mTc-HYNIC-D₁-FA₂ had high uptake in FR overexpressed tumor and kidney at all time-points, and both of them could obviously be inhibited when blocking with free FA in the blocking studies. From the in vivo micro-SPECT/CT imaging results, good tumor uptake of ^99mTc-HYNIC-D₁-FA₂ was observed in KB tumor-bearing mice and it could be blocked obviously. Based on the results, this new radiolabeled dimeric FA tracer might be a promising candidate for FR-targeting imaging with high affinity and selectivity.

Folate receptor-targeted nanoparticle delivery of HuR-RNAi suppresses lung cancer cell proliferation and migration

BACKGROUND

Human antigen R (HuR) is an RNA binding protein that is overexpressed in many human cancers, including lung cancer, and has been shown to regulate the expression of several oncoproteins. Further, HuR overexpression in cancer cells has been associated with poor-prognosis and therapy resistance. Therefore, we hypothesized that targeted inhibition of HuR in cancer cells should suppress several HuR-regulated oncoproteins resulting in an effective anticancer efficacy. To test our hypothesis, in the present study we investigated the efficacy of folate receptor-α (FRA)-targeted DOTAP:Cholesterol lipid nanoparticles carrying HuR siRNA (HuR-FNP) against human lung cancer cells.

RESULTS

The therapeutic efficacy of HuR-FNP was tested in FRA overexpressing human H1299 lung cancer cell line and compared to normal lung fibroblast (CCD16) cells that had low to no FRA expression. Physico-chemical characterization studies showed HuR-FNP particle size was 303.3 nm in diameter and had a positive surface charge (+4.3 mV). Gel retardation and serum stability assays showed that the FNPs were efficiently protected siRNA from rapid degradation. FNP uptake was significantly higher in H1299 cells compared to CCD16 cells indicating a receptor-dose effect. The results of competitive inhibition studies in H1299 cells demonstrated that HuR-FNPs were efficiently internalized via FRA-mediated endocytosis. Biologic studies demonstrated HuR-FNP but not C-FNP (control siRNA) induced G1 phase cell-cycle arrest and apoptosis in H1299 cells resulting in significant growth inhibition. Further, HuR-FNP exhibited significantly higher cytotoxicity against H1299 cells than it did against CCD16 cells. The reduction in H1299 cell viability was correlated with a marked decrease in HuR mRNA and protein expression. Further, reduced expression of HuR-regulated oncoproteins (cyclin D1, cyclin E, and Bcl-2) and increased p27 tumor suppressor protein were observed in HuR-FNP-treated H1299 cells but not in C-FNP-treated cells. Finally, cell migration was significantly inhibited in HuR-FNP-treated H1299 cells compared to C-FNP.

CONCLUSIONS

Our results demonstrate that HuR is a molecular target for lung cancer therapy and its suppression using HuR-FNP produced significant therapeutic efficacy in vitro.

Modular Integration of Upconverting Nanocrystal-Dendrimer Composites for Folate Receptor-Specific NIR Imaging and Light-Triggered Drug Release

Upconversion nanocrystals (UCNs) display near-infrared (NIR)-responsive photoluminescent properties for NIR imaging and drug delivery. The development of effective strategies for UCN integration with other complementary nanostructures for targeting and drug conjugation is highly desirable. This study reports on a core/shell-based theranostic system designed by UCN integration with a folate (FA)-conjugated dendrimer for tumor targeting and with photocaged doxorubicin as a cytotoxic agent. Two types of UCNs (NaYF4:Yb/Er (or Yb/Tm); diameter = ≈50 to 54 nm) are described, each displaying distinct emission properties upon NIR (980 nm) excitation. The UCNs are surface modified through covalent attachment of photocaged doxorubicin (ONB-Dox) and a multivalent FA-conjugated polyamidoamine (PAMAM) dendrimer G5(FA)6 to prepare UCN@(ONB-Dox)(G5FA). Surface plasmon resonance experiments performed with G5(FA)6 dendrimer alone show nanomolar binding avidity (KD = 5.9 × 10(-9) M) to the folate binding protein. This dendrimer binding corresponds with selective binding and uptake of UCN@(ONB-Dox)(G5FA) by FAR-positive KB carcinoma cells in vitro. Furthermore, UCN@(ONB-Dox)(G5FA) treatment of FAR(+) KB cells inhibits cell growth in a light dependent manner. These results validate the utility of modularly integrated UCN-dendrimer nanocomposites for cell type specific NIR imaging and light-controlled drug release, thus serving as a new theranostic system.

Folate Receptor Alpha Immunohistochemistry in Cytology Specimens of Metastatic Breast Carcinoma

BACKGROUND

Folate receptor alpha (FRA) is involved in folate accumulation and utilization, and is expressed in varying proportions in breast, ovary and parotid epithelial cells, among others. FRA overexpression by immunohistochemistry (IHC) has been shown in estrogen/progesterone receptor (ER/PR)-negative carcinoma (40-74%) and in triple-negative breast carcinoma (TNBC; 50-86%) in histological specimens of primary breast cancers. We assessed the feasibility of IHC in detecting FRA expression and its patterns and clinical significance in metastatic TNBC in fine-needle aspiration (FNA) cell blocks (CBs).

MATERIALS AND METHODS

Metastatic breast ductal carcinoma cases were retrospectively immunostained with FRA IHC on FNA CBs. FRA staining was scored qualitatively (+/-), by intensity (0-3) and by staining area (0-100%). Of these metastatic cases, a subset of primary breast carcinoma cases was also immunostained with FRA. The results were correlated with ER, PR and human epidermal growth factor receptor 2 (Her2/Neu) performed by routine IHC.

RESULTS

A total of 40 FNA CBs with metastatic disease were studied, including hormone (ER/PR) positive (n = 5), triple positive (n = 5), Her2/Neu-only positive (n = 5) and TNBC (n = 25). FRA IHC showed immunoreactivity with moderate positivity in only 1 (4%) TNBC. All the remaining 39 cases were negative for FRA expression. Five cases of primary TNBC were stained with FRA IHC and were negative for FRA expression.

CONCLUSIONS

Our data suggest that FRA expression by IHC was rarely associated with ER/PR-negative tumors relative to ER/PR-positive tumors and, more importantly, with TNBC in FNA CBs. This finding may have a clinical significance and prognostic implications in metastatic breast carcinoma. Furthermore, 5 primary TNBC cases did not overexpress FRA by IHC. Hence, antifolate receptor therapies do not appear to be clinically relevant in TNBC based on immunostaining of FNA CBs of metastatic breast cancers.

Gene expression profiling of taxol-resistant nasopharyngeal carcinoma cells with siRNA-mediated FOLR1 downregulation

OBJECTIVES

Our previous study has shown that downregulation of FOLR1 by siRNA partially reversed taxol-resistant phenotype in taxol-resistant nasopharyngeal carcinoma cell lines. We aim to gain further insight into the molecular mechanisms of this process and identify the differentially expressed genes after FOLR1 downregulation.

METHOD

The global gene expression profile was identified and analyzed using the Affymetrix HG-U133 Plus 2.0 array.

RESULTS

There was a significant dysregulation in the global gene expression of the FOLR1-suppressed taxol-resistant nasopharyngeal carcinoma cell lines. There were 41 upregulated genes and 109 downregulated genes. QRT-PCR validation of the selected differentially expressed genes demonstrated there was a good correlation with the microarray analysis. There was a significant deregulation of expression in the apoptosis-related genes such as BIRC3, PRKX, TNFRSF10A and involved in Viral carcinogenesis, MAPK signaling pathways after FOLR1 was downregulated.

CONCLUSION

The suppression of FOLR1 by RNA interference altered gene expression profile of taxol-resistant nasopharyngeal carcinoma cell lines. The apoptosis-related genes and the gene alterations in viral carcinogenesis, MAPK signaling pathways might be important in FOLR1 siRNA-induced taxol-resistant reversal.