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.

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.

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.

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.

Cancer-associated fibroblasts induce sorafenib resistance of hepatocellular carcinoma cells through CXCL12/FOLR1.

BACKGROUND: Due to the high drug resistance of hepatocellular carcinoma (HCC), sorafenib has limited efficacy in the treatment of advanced HCC. Cancer-associated fibroblasts (CAFs) play an important regulatory role in the induction of chemoresistance. This study aimed to clarify the mechanism underlying CAF-mediated resistance to sorafenib in HCC. METHODS: Immunohistochemistry and immunofluorescence showed that the activation of CAFs was enhanced in HCC tissues. CAFs and paracancerous normal fibroblasts (NFs) were isolated from the cancer and paracancerous tissues of HCC, respectively. Cell cloning assays, ELISAs, and flow cytometry were used to detect whether CAFs induced sorafenib resistance in HCC cells via CXCL12. Western blotting and qPCR showed that CXCL12 induces sorafenib resistance in HCC cells by upregulating FOLR1. We investigated whether FOLR1 was the target molecule of CAFs regulating sorafenib resistance in HCC cells by querying gene expression data for human HCC specimens from the GEO database. RESULTS: High levels of activated CAFs were present in HCC tissues but not in paracancerous tissues. CAFs decreased the sensitivity of HCC cells to sorafenib. We found that CAFs secrete CXCL12, which upregulates FOLR1 in HCC cells to induce sorafenib resistance. CONCLUSIONS: CAFs induce sorafenib resistance in HCC cells through CXCL12/FOLR1.

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.

Folate Receptor Targeted Photodynamic Therapy: A Novel Way to Stimulate Anti-Tumor Immune Response in Intraperitoneal Ovarian Cancer.

Photodynamic therapy (PDT) has shown improvements in cancer treatment and in the induction of a proper anti-tumor immune response. However, current photosensitizers (PS) lack tumor specificity, resulting in reduced efficacy and side effects in patients with intraperitoneal ovarian cancer (OC). In order to target peritoneal metastases of OC, which overexpress folate receptor (FRα) in 80% of cases, we proposed a targeted PDT using a PS coupled with folic acid. Herein, we applied this targeted PDT in an in vivo mouse model of peritoneal ovarian carcinomatosis. The efficacy of the treatment was evaluated in mice without and with human peripheral blood mononuclear cell (PBMC) reconstitution. When mice were reconstituted, using a fractionized PDT protocol led to a significantly higher decrease in the tumor growth than that obtained in the non-reconstituted mice (p = 0.0469). Simultaneously, an immune response was reflected by an increase in NK cells, and both CD4+ and CD8+ T cells were activated. A promotion in cytokines IFNγ and TNFα and an inhibition in cytokines TGFß, IL-8, and IL-10 was also noticed. Our work showed that a fractionized FRα-targeted PDT protocol is effective for the treatment of OC and goes beyond local induction of tumor cell death, with the promotion of a subsequent anti-tumor response.

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.

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.

Recent advances in using folate receptor 1 (FOLR1) for cancer diagnosis and treatment, with an emphasis on cancers that affect women.

A glycosylphosphatidylinositol (GPI)-anchored glycoprotein called the folate receptor 1 (FOLR1) facilitates the transportation of folate by mediating receptor-mediated endocytosis in response to ligand binding. While FOLR1 expression is typically restricted to the apical surfaces of the epithelium in the lung, kidney, and choroid plexus in healthy people, it is overexpressed in a number of solid tumours, including high-grade osteosarcoma, breast cancer, ovarian cancer, and non-small cell lung cancer. As a result, FOLR1 has become an attractive target for cancer detection and therapy, particularly for cancers that affect women. A number of methods have been developed to target FOLR1 in cancer therapy, including the development of FOLR1-targeted imaging agents for cancer diagnosis and the use of folate conjugates to deliver cytotoxic agents to cancer cells that overexpress FOLR1. Therefore, we focus on the most recent developments in employing FOLR1 for cancer diagnosis and treatment in this review, particularly with regard to cancers that affect women.

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.

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.

High expression of folate receptor alpha is associated with poor prognosis in patients with cervical cancer.

OBJECTIVE: Folate receptor α (FRα) is a membrane protein expressed in various solid tumors but has limited expression in normal cells. Therefore, FRα is an attractive target for cancer treatment. This study aimed to investigate the relationship between FRα expression and the clinicopathological characteristics and survivals of cervical cancer. METHODS: This retrospective study included patients with cervical cancer who underwent primary surgery between 2000 and 2020 at our institution. Immunohistochemical staining of FRα was performed using an anti-folate-binding protein/FBP antibody. FRα-positive staining was defined as ≥5% of tumor staining and FRα-high as ≥50% tumor staining with ≥2+ intensity. The association between FRα expression and survival was assessed using multivariate Cox regression analysis, adjusting for established prognostic factors. RESULTS: Overall, 123 patients were identified, and 140 tumor samples, including 17 paired primary and metastatic samples, were evaluated. As histological types, 67 patients had squamous cell carcinoma (SCC), and 56 patients had non-SCC. All primary tumors were FRα-positive. High FRα expression was observed in 25% of the cases and differed according to histology (SCC vs. non-SCC, 14.9% vs. 37.5%, p=0.004). FRα expression was significantly higher in metastatic tumors than in primary (170 [IQR, 140-205] vs. 125 [IQR, 110-150], p=0.0006). High FRα expression was significantly associated with worse overall survival (hazard ratio, 6.73; 95% confidence interval, 2.21-20.53; p=0.001). CONCLUSION: In cervical cancer, FRα expression was elevated in metastatic tumors and high expression was associated with a worse prognosis. Our study supports the development of FRα-targeted therapy for advanced cervical cancer.

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.