Folate binding protein distribution in normal tissues and biological fluids from ovarian carcinoma patients as detected by the monoclonal antibodies MOv18 and MOv19

Targeted treatment of gouty arthritis by biomineralized metallic nanozyme-mediated oxidative stress-mitigating nanotherapy

Gouty arthritis is characterized by chronic deposition of monosodium urate (MSU) crystals in the joints and other tissues, resulting in the production of excess reactive oxygen species (ROS) and proinflammatory cytokines that intensify synovial inflammation. This condition is mainly associated with inflammatory M1 macrophage activation and oxidative stress production. Hence, gout symptoms can often be resolved by eliminating M1 macrophage activation and scavenging oxidative stress in the inflamed areas. Herein, we developed M1-macrophage-targeting biomineralized metallic nanozymes (FALNZs) that deplete oxidative stress and reduce the M1 macrophage levels to mitigate gouty arthritis. Intra-articular injection of the FALNZs targets inflammatory macrophages and suppresses ROS levels in joints with MSU-crystal-induced arthritis. In addition, the FALNZs alleviate joint swelling, inflammatory cytokine production, and pathological features of the joints. Overall, the proposed therapeutic approach is biocompatible and is an effective ROS scavenger for the treatment of gouty pathogenesis.

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.

Role of antibody engineering in generation of derivatives starting from MOv19 MAb: 40 years of biological/therapeutic tools against folate receptor alfa

In the 1980s, we developed and characterized numerous murine monoclonal antibodies (MAbs) directed against human tumor-associated antigens. This mini review is focused on the generation of derivatives of an anti-folate receptor α (FRα) MAbs, named MOv19, exploiting the antibody-engineering progresses in the last 40 years. The FRα location on the luminal surface of proliferating epithelial cells, inaccessible to circulation, versus its over-expression in the entire surface of numerous carcinomas suggested a role for anti-FRα MAbs in the diagnosis and/or treatment of solid tumors. Presently, two MOv19 derivatives are in clinical trials: a chimeric resurfaced version in an antibody-drug conjugate format (SORAYA trial, 2022) and the murine scFv in a second generation chimeric antigen receptor, CAR-T (Phase Ia, 2021). MOv19 and its derivatives could be considered a relevant example that well-characterized anti-tumor murine Mabs and antibody engineering could be combined to generate useful therapeutic tools.

Folate Receptor Alpha is Decreased in Pregnancy Affected with Fetal Neural Tube Defect: A Case Control Study

BACKGROUND

Neural tube defect (NTD) is a multifactorial disorder. Decrease transfer of folate to the developing embryo is one of the etiologies. It could be due to decrease folate receptors resulting in NTD in fetus.

OBJECTIVE

To analyze serum folate receptor alpha (FOLR1) concentration in women having fetus with NTD and compare it with women having normal fetus during and after pregnancy.

MATERIAL AND METHODS

This was a prospective case control study conducted in a tertiary care hospital. Pregnant women with detected isolated NTD in fetus were enrolled as cases and equal number of matched pregnant women without any fetal congenital malformation were recruited as controls. Serum FOLR1 levels were analyzed in cases and controls during pregnancy and 6 weeks after delivery.

RESULTS

Mean serum FOLR1 concentration during pregnancy was 70.5 pg/mL (range: 23.8-98.5 pg/mL) and 103.9 pg/mL (range: 70-110 pg/mL) in cases and controls, respectively. Serum level of FOLR1 was 448.9 pg/mL (range: 133.5-475) and 414.5 pg/mL (range: 269.7-412.5) in cases and controls at 6 weeks postpartum, respectively. There was statistically significant difference (P < 0.001) between cases and control during pregnancy but not in postpartum (P = 0.092). There was significant increase in level of FOLR1 in both cases and control at 6 weeks postpartum as compared to antenatal period.

CONCLUSIONS

Maternal serum FOLR1 is significantly reduced in pregnancy with fetal NTD as compared to normal pregnancy. The level is significantly increased in postpartum period in both groups. FOLR1 level being similar in both groups in postpartum indicates that it is not influenced by the history of fetal NTD.

Perspectives of Methotrexate-Based Radioagents for Application in Nuclear Medicine

Methotrexate is a gold standard among disease modifying antirheumatic drugs and is also extensively used clinically in combination with oncological therapies. Thus, it is not surprising that nuclear medicine found an interest in methotrexate in the search for diagnostic and therapeutic solutions. Numerous folate-related radiopharmaceuticals have been proposed for nuclear medicine purposes; however, methotrexate radioagents represent only a minority. This imbalance results from the fact that methotrexate has significantly weaker affinity for folate receptors than folic acid. Nevertheless, radiolabeled methotrexate agents utilized as a tool for early detection and imaging of inflammation in rheumatoid arthritis patients gave promising results. Similarly, the use of multimodal MTX-release nanosystems may find potential applications in radiosynovectomy and theranostic approaches in folate receptor positive cancers.

Standardization and Optimization of Intraoperative Molecular Imaging for Identifying Primary Pulmonary Adenocarcinomas

PURPOSE

Intraoperative molecular imaging (IMI) is an emerging technology used to locate pulmonary adenocarcinomas and identify positive margins during surgery. Background noise and tissue autofluorescence have been major obstacles. The goal of this study is to optimize the image quality of folate receptor alpha (FRα) targeted IMI for pulmonary adenocarcinomas by modifying emission data.

PROCEDURES

A total of 15 lung cancer patients were enrolled in a pilot study. In the first cohort, FRα upregulation within pulmonary adenocarcinoma tumors was confirmed by analyzing specimens from five pulmonary adenocarcinoma patients with flow cytometry and immunohistochemistry. Next, in a cohort of five additional patients, autofluorescence of intrathoracic structures and tissues was quantified. Lastly, five patients with tumors at various depths from the pleural surface were enrolled and received the FRα-targeted optical contrast agent, EC17. In this final cohort, resected pulmonary adenocarcinomas were imaged at a wide range of fluorescence exposure times (0 to 200 ms), various laser powers, and with unique filter configurations. Tumor-to-noise ratio (TNR) for images was generated using region of interest software.

RESULTS

Pulmonary adenocarcinomas highly express FRα. Significant autofluorescence from native thoracic tissues was found with the highest fluorescent signals at the bronchial stump (547 ± 98, range 423-699), the pulmonary artery (267 ± 64, range 200-374), and cortical bone (266 ± 17, range 243-287). High levels of autofluorescence were appreciated after systemic administration of EC17; however, TNR was improved by altering exposure settings at the time of the imaging. Optimal fluorescent exposure time occurs at 40 ms (25 frames/s).

CONCLUSIONS

Exposure properties can be manipulated to maximize TNR thus allowing for successful intraoperative detection of pulmonary adenocarcinomas during surgery. Optimization of the conditions for intraoperative molecular imaging sets the stage for future clinical trials utilizing targeted IMI techniques which can aid the surgeon at the time of cancer resection.

Targeting folate receptor alpha for cancer treatment

Promising targeted treatments and immunotherapy strategies in oncology and advancements in our understanding of molecular pathways that underpin cancer development have reignited interest in the tumor-associated antigen Folate Receptor alpha (FRα). FRα is a glycosylphosphatidylinositol (GPI)-anchored membrane protein. Its overexpression in tumors such as ovarian, breast and lung cancers, low and restricted distribution in normal tissues, alongside emerging insights into tumor-promoting functions and association of expression with patient prognosis, together render FRα an attractive therapeutic target. In this review, we summarize the role of FRα in cancer development, we consider FRα as a potential diagnostic and prognostic tool, and we discuss different targeted treatment approaches with a specific focus on monoclonal antibodies. Renewed attention to FRα may point to novel individualized treatment approaches to improve the clinical management of patient groups that do not adequately benefit from current conventional therapies.

Thyroid dysfunction in children with autism spectrum disorder is associated with folate receptor α autoimmune disorder

Folate receptor α (FRα) autoantibodies (FRAAs) are prevalent in autism spectrum disorder (ASD). FRAAs disrupt folate transport across the blood-brain barrier by binding to the FRα. Thyroid dysfunction is frequently found in children with ASD. We measured blocking and binding FRAAs and thyroid-stimulating hormone (TSH), free thyroxine (T4) (FT4), total triiodothyronine (T3) (TT3), reverse T3 (rT3), thyroid-releasing hormone (TRH) and other metabolites in 87 children with ASD, 84 of whom also underwent behaviour and cognition testing and in 42 of whom FRAAs, TSH and FT4 were measured at two time points. To better understand the significance of the FRα in relation to thyroid development, we examined FRα expression on prenatal and postnatal thyroid. TSH, TT3 and rT3 were above the normal range in 7%, 33% and 51% of the participants and TRH was below the normal range in 13% of the participants. FT4 was rarely outside the normal range. TSH concentration was positively and the FT4/TSH, TT3/TSH and rT3/TSH ratios were inversely related to blocking FRAA titres. On repeated measurements, changes in TSH and FT4/TSH ratio were found to correspond to changes in blocking FRAA titres. TSH and the FT4/TSH, TT3/TSH and rT3/TSH ratios were related to irritability on the Aberrant Behavior Checklist and several scales of the Social Responsiveness Scale (SRS), whereas TT3 was associated with SRS subscales and TRH was related to Vineland Adaptive Behavior Scale subscales. The thyroid showed significant FRα expression during the early prenatal period, although expression decreased significantly in later gestation and postnatal thyroid tissue. The results of the present study suggest that thyroid dysfunction in ASD may be related to blocking FRAA. The high expression of FRα in the early foetal thyroid suggests that foetal and neonatal exposure to maternal FRAAs could affect the development of the thyroid and may contribute to the pathology in ASD.

Cationic folate-mediated liposomal delivery of bis-arylidene oxindole induces efficient melanoma tumor regression

The folate receptor (FR) is a well-validated and common target for cancer due to its high over-expression in many different cancer cells.

Folate receptor targeted three-layered micelles and hydrogels for gene delivery to activated macrophages

New folic acid (FA) coupled three layered micelles (3LM) were designed to encapsulate DNA, and their application as delivery system that specifically targets activated macrophages was investigated for new treatment options in rheumatoid arthritis (RA). FA coupled poly(l-lactide)-b-poly(ethylene glycol) (FA-PEG-PLLA) was synthesized via the NHS-ester activated/amine coupling method. Fluorescein labeled folic acid was used for flow cytometric detection of the expression of functional folic receptor β in LPS-activated and resting macrophages. FA coupled 3LM were formulated in a two-step procedure and characterized regarding hydrodynamic diameters and zeta potentials. The presence of the targeting ligand was shown not to increase the size of the 3LM compared to their non-targeted counterparts. Targeted and non-targeted 3LM were used in vitro to optimize uptake conditions in the RAW 264.7 macrophage cell line. The amount of FA coupled polymer in the final formulation was found to be optimal at 75% FA-PEG-PLLA and 25% PLLA-PEG-PLLA. Subsequently, transgene expression in vitro in RAW 264.7 cells and ex vivo in primary activated and resting mouse macrophages was determined as a function of FR-mediated internalization of 3LM encapsulating GFP expressing plasmid. FR-overexpressing activated cells, as successfully identified by internalization of FA-fluorescein, showed significantly higher GFP expression in vitro and ex vivo than resting macrophages with only a basal level of FR expression. Lastly, injectable hydrogels as depot formulation were formed by stereocomplexation, and their degradation, DNA release profiles, and dissociation into intact 3LM were found to be beneficial for potential in vivo application. Our findings confirm that FA-3LM are taken up by activated macrophages via folate receptor mediated endocytosis and that their hydrogels release intact 3LM for efficient transfection of primary macrophages. Therefore, FA-3LM could become a promising delivery system for receptor-mediated drug or gene delivery and novel therapy for rheumatoid arthritis in an in situ forming gel formulation.

Role of the folate receptor in ovarian cancer treatment: evidence, mechanism, and clinical implications

Folate can be transported into the cell by the reduced folate carrier (RFC), the proton-coupled folate transporter (PCFT), or the folate receptor (FR), of which various isoforms exist. While the RFC and PCFT are expressed by many normal cells, the FR is present only in a small proportion of normal tissues. In these tissues, the FR expression level is often low and restricted to the apical surface of polarized epithelial cells. In contrast, FR is expressed on the blood-accessible basal and lateral membranes of many types of epithelial cancer. Considering that FR is expressed in few nonmalignant cell types on luminal membranes generally not accessible for molecules transported in the blood, FR is considered a promising antitumor target. As FR expression seems associated with tumor progression and prognosis, anticancer therapies targeting FR are currently being developed, such as farletuzumab (Morphotek, Exton, PA, USA), IMGN853 (ImmunoGen, Waltham, MA, USA), vintafolide, and EC1456 (both Endocyte Inc., West Lafayette, IN, USA). FR expression could be used as a response-predictive biomarker for these treatments. The ability to identify patients and treat them with an effective therapy based on the known expression of the tumor marker would, indeed, be the next step in predictive medicine for these patients. This review summarizes the role of FR in ovarian cancer and the value of FR as a prognostic biomarker for ovarian cancer and a response-predictive biomarker for folate-targeted therapeutics.

Immunotherapy for ovarian cancer

OPINION STATEMENT

All work referenced herein relates to treatment of epithelial ovarian carcinomas, as their treatment differs from ovarian germ cell cancers and other rare ovarian cancers, the treatments of which are addressed elsewhere. Fallopian tube cancers and primary peritoneal adenocarcinomatosis are also generally treated as epithelial ovarian cancers. The standard of care initial treatment of advanced stage epithelial ovarian cancer is optimal debulking surgery as feasible plus chemotherapy with a platinum plus a taxane agent. If this front-line approach fails, as it too often the case, several FDA-approved agents are available for salvage therapy. However, because no second-line therapy for advanced-stage epithelial ovarian cancer is typically curative, we prefer referral to clinical trials as logistically feasible, even if it means referring patients outside our system. Immune therapy has a sound theoretical basis for treating carcinomas generally, and for treating ovarian cancer in particular. Advances in understanding the immunopathogenic basis of ovarian cancer, and the immunopathologic basis for prior failures of immunotherapy for it and other carcinomas promises to afford novel treatment approaches with potential for significant efficacy, and reduced toxicities compared with cytotoxic agents. Thus, referral to early phase immunotherapy trials for ovarian cancer patients that fail conventional treatment merits consideration.

Synthesis of a novel, sequentially active-targeted drug delivery nanoplatform for breast cancer therapy

Breast cancer is the leading cause of cancer deaths among women. Paclitaxel (PTX), an important breast cancer medicine, exhibits reduced bioavailability and therapeutic index due to high hydrophobicity and indiscriminate cytotoxicity. PTX encapsulation in one-level active targeting overcomes such barriers, but enhances toxicity to normal tissues with cancer-similar expression profiles. This research attempted to overcome this challenge by increasing selectivity of cancer cell targeting while maintaining an ability to overcome traditional pharmacological barriers. Thus, a multi-core, multi-targeting construct for tumor specific delivery of PTX was fabricated with (i) an inner-core prodrug targeting the cancer-overexpressed cathepsin B through a cathepsin B-cleavable tetrapeptide that conjugates PTX to a poly(amidoamine) dendrimer, and (ii) the encapsulation of this prodrug (PGD) in an outer core of a RES-evading, folate receptor (FR)-targeting liposome. Compared to traditional FR-targeting PTX liposomes, this sequentially active-targeted dendrosome demonstrated better prodrug retention, an increased cytotoxicity to cancer cells (latter being true when FR and cathepsin B activities were both at moderate-to-high levels) and higher tumor reduction. This research may eventually evolve a product platform with reduced systemic toxicity inherent with traditional chemotherapy and localized toxicity inherent to single-target nanoplatforms, thereby allowing for better tolerance of higher therapeutic load in advanced disease states.

Intraoperative molecular imaging can identify lung adenocarcinomas during pulmonary resection

BACKGROUND

More than 80,000 people undergo resection of a pulmonary tumor each year, and the only method to determine if the tumor is malignant is histologic analysis. We propose that a targeted molecular contrast agent could bind lung adenocarcinomas, which could be identified using real-time optical imaging at the time of surgery.

METHODS

Fifty patients with a biopsy-proven lung adenocarcinoma were enrolled. Before surgery, patients were systemically administered 0.1 mg/kg of a fluorescent folate receptor alpha (FRα)-targeted molecular contrast agent by intravenous infusion. During surgery, tumors were imaged in situ and ex vivo, after the lung parenchyma was dissected to directly expose the tumor to the imaging system.

RESULTS

Tumors ranged from 0.3 to 7.5 cm (mean: 2.6 cm), and 46 of 50 (92%) lung adenocarcinomas were fluorescent. No false uptake occurred, and in 2 cases, intraoperative imaging revealed tumor metastases (3 mm and 6 mm) that were not recognized preoperatively. Four adenocarcinomas were not fluorescent, and immunohistochemistry showed that these adenocarcinomas did not express FRα. Tumor fluorescence was independent of nodule size, uptake of 2-deoxy-2-((18)F)fluoro-D-glucose, histology, and tumor differentiation. Molecular imaging could identify only 7 of the 50 adenocarcinomas in situ in the patient without bisection. The most important predictor of the success of molecular imaging in locating the tumor in situ was the distance of the nodule from the pleural surface.

CONCLUSIONS

Intraoperative molecular imaging with a targeted contrast agent can identify lung adenocarcinomas, and this technology is currently useful in patients with subpleural tumors, irrespective of size. With further refinements, this tool may prove useful in locating adenocarcinomas that are deeper in the lung parenchyma, in lymph nodes, and at pleural and resection margins.

Design and structure activity relationship of tumor-homing histone deacetylase inhibitors conjugated to folic and pteroic acids

Histone deacetylase (HDAC) inhibition has recently emerged as a novel therapeutic approach for the treatment of various pathological conditions including cancer. Currently, two HDAC inhibitors (HDACi) – Vorinostat and Romidepsin – have been approved for the treatment of cutaneous T-cell lymphoma. However, HDACi remain ineffective against solid tumors and are associated with adverse events including cardiotoxicity. Targeted delivery may enhance the therapeutic indices of HDACi and enable them to be efficacious against solid tumors. We showed herein that morphing of folic and pteroic acids into the surface recognition group of HDACi results in hydroxamate and benzamide HDACi which derived tumor homing by targeting folate receptor (FR), a receptor commonly overexpressed in solid tumors. We observed a correlation between the potency of HDAC1 inhibition and cytotoxicity as only the potent pteroate hydroxamates, 11d and 11e, displayed antiproliferative activity against two representative FR-expression cancer cells. Our observation further supports the previous results which suggest that for a drug to be successfully targeted using the FR, it must be extremely potent against its primary target as the FR has a low delivery efficiency.

Chimeric antigen receptor T Cells with dissociated signaling domains exhibit focused antitumor activity with reduced potential for toxicity in vivo

Adoptive immunotherapy using T lymphocytes genetically modified to express a chimeric antigen receptor (CAR-T) holds considerable promise for the treatment of cancer. However, CAR-based therapies may involve on-target toxicity against normal tissues expressing low amounts of the targeted tumor-associated antigen (TAA). To specify T cells for robust effector function that is selective for tumor but not normal tissue, we developed a trans-signaling CAR strategy, whereby T-cell activation signal 1 (CD3z) is physically dissociated from costimulatory signal 2 (CD28) in two CARs of differing antigen specificity: mesothelin and a-folate receptor (FRa). Human T cells were genetically modified to coexpress signal 1 (anti-Meso scFv-CD3z) and signal 2 (anti-FRa scFv-CD28) CARs in trans. Trans-signaling CAR-T cells showed weak cytokine secretion against target cells expressing only one TAA in vitro, similar to first-generation CAR-T cells bearing CD3z only, but showed enhanced cytokine secretion upon encountering natural or engineered tumor cells coexpressing both antigens, equivalent to that of second-generation CAR-T cells with dual signaling in cis. CAR-T cells with dual specificity also showed potent anticancer activity and persistence in vivo, which was superior to first-generation CAR-T cells and equivalent to second-generation CARs. Importantly, second-generation CAR-T cells exhibited potent activity against cells expressing mesothelin alone, recapitulating normal tissue, whereas trans-signaling CAR-T cells did not. Thus, a dual specificity, trans-signaling CAR approach can potentiate the therapeutic efficacy of CAR-T cells against cancer while minimizing parallel reactivity against normal tissues bearing single antigen.

Immunotherapy targeting folate receptor induces cell death associated with autophagy in ovarian cancer

PURPOSE

Cancer cells are highly dependent on folate metabolism, making them susceptible to drugs that inhibit folate receptor activities. Targeting overexpressed folate receptor alpha (FRα) in cancer cells offers a therapeutic opportunity. We investigated the functional mechanisms of MORAB-003 (farletuzumab), a humanized mAb against FRα, in ovarian cancer models.

EXPERIMENTAL DESIGN

We first examined FRα expression in an array of human ovarian cancer cell lines and then assessed the in vivo effect of MORAB-003 on tumor growth and progression in several orthotopic mouse models of ovarian cancer derived from these cell lines. Molecular mechanisms of tumor cell death induced by MORAB-003 were investigated by cDNA and protein expression profiling analysis. Mechanistic studies were performed to determine the role of autophagy in MORAB-003-induced cell death.

RESULTS

MORAB-003 significantly decreased tumor growth in the high-FRα IGROV1 and SKOV3ip1 models but not in the low-FRα A2780 model. MORAB-003 reduced proliferation, but had no significant effect on apoptosis. Protein expression and cDNA microarray analyses showed that MORAB-003 regulated an array of autophagy-related genes. It also significantly increased expression of LC3 isoform II and enriched autophagic vacuolization. Blocking autophagy with hydroxychloroquine or bafilomycin A1 reversed the growth inhibition induced by MORAB-003. In addition, alteration of FOLR1 gene copy number significantly correlated with shorter disease-free survival in patients with ovarian serous cancer.

CONCLUSIONS

MORAB-003 displays prominent antitumor activity in ovarian cancer models expressing FRα at high levels. Blockade of folate receptor by MORAB-003 induced sustained autophagy and suppressed cell proliferation.

Farletuzumab in lung cancer

Folate is essential for proliferating cells and folate transport pathways and folate-dependent metabolic processes show promise as targets for anti-neoplastic therapy. Folate receptor α (FOLR1), a folate transporter, is an attractive target for anti-neoplastic therapy due to its high affinity for folate, restricted range of expression in normal tissue and differential over-expression in malignant tissue. FOLR1 is expressed in non-small cell lung cancer, with a higher expression in adenocarcinoma compared with squamous cell carcinoma. Farletuzumab is a monoclonal antibody targeting FOLR1 which in pre-clinical studies led to cytotoxicity of FOLR1-expressing cells, inhibited tumor growth in animal models and showed limited reactivity with normal tissue. In phase I/II trials, farletuzumab was well tolerated as a single-agent and in combination, without additive toxicity with chemotherapy. An ongoing phase II, double blind, placebo-controlled study is evaluating farletuzumab in patients with FOLR1 expressing metastatic adenocarcinoma of lung.

Characterization of the human folate receptor alpha via novel antibody-based probes

Folate receptor alpha (FRA) is a cell surface protein whose aberrant expression in malignant cells has resulted in its pursuit as a therapeutic target and marker for diagnosis of cancer. The development of immune-based reagents that can reproducibly detect FRA from patient tissue processed by varying methods has been difficult due to the complex post-translational structure of the protein whereby most reagents developed to date are highly structure-sensitive and have resulted in equivocal expression results across independent studies. The aim of the present study was to generate novel monoclonal antibodies (mAbs) using modified full length FRA protein as immunogen in order to develop a panel of mAbs to various, non-overlapping epitopes that may serve as diagnostic reagents able to robustly detect FRA-positive disease. Here we report the development of a panel of FRA-specific mAbs that are able to specifically detect FRA using an array of diagnostic platforms and methods. In addition, the methods used to develop these mAbs and their diverse binding properties provide additional information on the three dimensional structure of FRA in its native cell surface configuration.

Serous ovarian carcinoma patients with high alpha-folate receptor had reducing survival and cytotoxic chemo-response

The alpha-folate receptor (α-FR) is highly-expressed in various non-mucinous tumors of epithelial origin, including ovarian carcinoma. The aim of this study was to investigate the relationship between alpha-folate receptor (α-FR) and the clinico-pathologic features and outcomes of serous ovarian carcinoma patients and the possible mechanism of α-FR to chemo-resistance. Therefore, semi-quantitative reverse-transcription polymerase chain reactions for α-FR expression were performed in the 91 specimens of serous ovarian carcinomas. The expression of α-FR in each ovarian cancer tissue specimen was defined as the ratio of density of α-FR to density of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In vitro apoptotic experiments were tested in the original OVCAR-3 tumor cells and various OVCAR-3 α-FR-transfectants. Patients with an increased α-FR expression level had poorer responses to chemotherapy (per α-FR expression level increase: odds ratio (OR): 8.97 (95% confidence interval (CI): 1.40-57.36), p = 0.021). An increased α-FR expression level was an independently poor prognostic factor for disease free interval (DFI) (per α-FR expression level increase: hazard ratio (HR): 2.45 (95% CI: 1.16-5.18), p = 0.02) and had a negative impact on overall survival (OS) of these serous ovarian cancer patients (per α-FR expression level increase: HR: 3.6 (95% CI: 0.93-13.29), p = 0.03) by multivariate analyses. α-FR inhibited cytotoxic drug-induced apoptosis in our in vitro apoptotic assays. α-FR could induce chemo-resistance via regulating the expression of apoptosis-related molecules, Bcl-2 and Bax. Therefore, α-FR can be a potential biomarker for the prediction of chemotherapeutic responses and clinical prognosis. It also could be the target of ovarian cancer treatment.

Serous ovarian carcinoma patients with high alpha-folate receptor had reducing survival and cytotoxic chemo-response

The alpha-folate receptor (α-FR) is highly-expressed in various non-mucinous tumors of epithelial origin, including ovarian carcinoma. The aim of this study was to investigate the relationship between alpha-folate receptor (α-FR) and the clinico-pathologic features and outcomes of serous ovarian carcinoma patients and the possible mechanism of α-FR to chemo-resistance. Therefore, semi-quantitative reverse-transcription polymerase chain reactions for α-FR expression were performed in the 91 specimens of serous ovarian carcinomas. The expression of α-FR in each ovarian cancer tissue specimen was defined as the ratio of density of α-FR to density of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In vitro apoptotic experiments were tested in the original OVCAR-3 tumor cells and various OVCAR-3 α-FR-transfectants. Patients with an increased α-FR expression level had poorer responses to chemotherapy (per α-FR expression level increase: odds ratio (OR): 8.97 (95% confidence interval (CI): 1.40-57.36), p = 0.021). An increased α-FR expression level was an independently poor prognostic factor for disease free interval (DFI) (per α-FR expression level increase: hazard ratio (HR): 2.45 (95% CI: 1.16-5.18), p = 0.02) and had a negative impact on overall survival (OS) of these serous ovarian cancer patients (per α-FR expression level increase: HR: 3.6 (95% CI: 0.93-13.29), p = 0.03) by multivariate analyses. α-FR inhibited cytotoxic drug-induced apoptosis in our in vitro apoptotic assays. α-FR could induce chemo-resistance via regulating the expression of apoptosis-related molecules, Bcl-2 and Bax. Therefore, α-FR can be a potential biomarker for the prediction of chemotherapeutic responses and clinical prognosis. It also could be the target of ovarian cancer treatment.

Serous ovarian carcinoma patients with high alpha-folate receptor had reducing survival and cytotoxic chemo-response

The alpha-folate receptor (α-FR) is highly-expressed in various non-mucinous tumors of epithelial origin, including ovarian carcinoma. The aim of this study was to investigate the relationship between alpha-folate receptor (α-FR) and the clinico-pathologic features and outcomes of serous ovarian carcinoma patients and the possible mechanism of α-FR to chemo-resistance. Therefore, semi-quantitative reverse-transcription polymerase chain reactions for α-FR expression were performed in the 91 specimens of serous ovarian carcinomas. The expression of α-FR in each ovarian cancer tissue specimen was defined as the ratio of density of α-FR to density of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In vitro apoptotic experiments were tested in the original OVCAR-3 tumor cells and various OVCAR-3 α-FR-transfectants. Patients with an increased α-FR expression level had poorer responses to chemotherapy (per α-FR expression level increase: odds ratio (OR): 8.97 (95% confidence interval (CI): 1.40-57.36), p = 0.021). An increased α-FR expression level was an independently poor prognostic factor for disease free interval (DFI) (per α-FR expression level increase: hazard ratio (HR): 2.45 (95% CI: 1.16-5.18), p = 0.02) and had a negative impact on overall survival (OS) of these serous ovarian cancer patients (per α-FR expression level increase: HR: 3.6 (95% CI: 0.93-13.29), p = 0.03) by multivariate analyses. α-FR inhibited cytotoxic drug-induced apoptosis in our in vitro apoptotic assays. α-FR could induce chemo-resistance via regulating the expression of apoptosis-related molecules, Bcl-2 and Bax. Therefore, α-FR can be a potential biomarker for the prediction of chemotherapeutic responses and clinical prognosis. It also could be the target of ovarian cancer treatment.

Enhancing the specificity of T-cell cultures for adoptive immunotherapy of cancer

Adoptive immunotherapy is a promising approach for the treatment of cancer; however, autoimmunity against normal tissue can be a serious complication of this therapy. We hypothesized that T-cell cultures responding maximally only when engaging two antigens would be more specific for tumor cells, and less active against normal cells, as long as the tumor expressed both antigens, while normal cells expressed only one of the antigens. A model system was developed consisting of cell lines expressing either folate binding protein or erbB-2, representing ‘normal’ tissue, and cells expressing both antigens representing tumor tissue. Human T-cell cultures were produced using two chimeric antigen receptor vectors (‘dual transduced’), or using a single chimeric antigen receptor vector (monospecific). Dual-transduced T cells responded less against ‘normal’ cells compared with tumor cells. This relatively simple procedure produced T-cell cultures that were as active against a tumor as the monospecific cultures used traditionally, but had lower activity against model normal cells.

Ascites regression and survival increase in mice bearing advanced-stage human ovarian carcinomas and repeatedly treated intraperitoneally with CpG-ODN

Tumor cell growth, even in advanced stages of ovarian cancer, is nearly always restricted to the peritoneal cavity; therefore, repeated intraperitoneal injections of oligodeoxynucleotides containing dinucleotides with unmethylated CpG motifs (CpG-ODN) recruiting and activating innate effector cells throughout the abdominal cavity to the tumor site might control tumor cell growth and ascites formation. After a single CpG-ODN treatment, in IGROV-1 ovarian tumor ascites-bearing athymic mice, the number of tumor cells declined rapidly and markedly, and ascites volumes declined shortly after treatment (5 h), increasing thereafter at a slower rate than in controls. When administered every 7 days for 4 weeks, CpG-ODN had only a marginal effect on survival time, whereas administration 5 days/wk for 3 or 4 weeks led to a significantly increased survival time as compared with controls (P<0.005) and completely controlled ascites growth without apparent toxicity, although a disorganization of lymphoid organs was observed. Bio-plex assay of cytokine levels in peritoneal fluid of ascites-bearing mice after CpG-ODN treatment revealed an increase in interleukin (IL)-6, IL-10, IL-12, and interferon-gamma at 24 hours, which returned to control mice levels at 48 to 96 hours, whereas the high levels of angiogenic factors remained unchanged. Depletion of natural killer or monocytes/macrophages only slightly influenced the CpG-ODN-induced reduction of ascites tumor cells, indicating that the antitumor activity might not be related to a specific cell/cytokine but rather to the repertoire of cells and cytokines accumulated in the peritoneal cavity. Thus, our data suggest a relevant role for repeated activation of cells and cytokines of innate immunity in the therapy of ovarian cancer patients with malignant ascites.

Synthesis and in vitro evaluation of cyclic NGR peptide targeted thermally sensitive liposome

The Asn-Gly-Arg (NGR) motif in both cyclic and linear form has previously been shown to specifically bind to CD13/aminopeptidase N that is selectively overexpressed in tumor vasculature and some tumor cells. However, previous versions of cyclic NGR used a liable disulfide bridge between cysteine residues that may be problematic for liposome targeting due to disulfide bond formation between adjacent peptides on the liposomal surface. In this study, we report the design, synthesis, and characterization of a novel cyclic NGR-containing peptide, cKNGRE, which does not contain a disulfide bridge. cKNGRE was synthesized in good yield and purity and attached to the fluorescent reporter Oregon Green (cKNGRE-OG) and lysolipid-containing temperature sensitive liposomes (LTSLs). The identity of cKNGRE was verified with NMR and mass spectral techniques. In vitro fluorescence microscopy evaluation of cKNGRE-OG demonstrated binding and active uptake by CD13(+) cancer cells and minimal binding to CD13(-) cancer cells. The cKNGRE-OG ligand displayed 3.6-fold greater affinity for CD13(+) cancer cells than a linear NGR-containing peptide. Affinity for CD13(+) cancer cells was similarly improved 10-fold for both the cyclic and linear NGR when presented in a multivalent fashion on the surface of an LTSL. cKNGRE-targeted LTSLs rapidly released (>75% in <4s) doxorubicin at 41.3 degrees C with minimal release at 37 degrees C. These results demonstrate the ability to synthesize a cKNGRE-targeted temperature sensitive liposome that lacks a disulfide bridge and has sufficient binding affinity for biological applications.

The role of folate receptor alpha (FRalpha) in the response of malignant pleural mesothelioma to pemetrexed-containing chemotherapy

Background:

The standard treatment of choice for malignant pleural mesothelioma is chemotherapy with pemetrexed and platinum, but the clinical outcome is poor. This study investigates the response to pemetrexed in a panel of eight mesothelioma cell lines and the clinical outcome for patients treated with pemetrexed in relation to folate receptor alpha (FRα).

Methods:

Cell lines were treated with pemetrexed to determine the concentration that reduced growth to 50% (GI₅₀). FRα expression was determined by western blotting and that of FRα, reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT) by real-time quantitative RT–PCR. Immunohistochemistry for FRα was carried out on 62 paraffin-embedded samples of mesothelioma from patients who were subsequently treated with pemetrexed.

Results:

A wide range of GI₅₀ values was obtained for the cell lines, H2452 cells being the most sensitive (GI₅₀ 22 nM) and RS5 cells having a GI₅₀ value greater than 10 μM. No FRα protein was detected in any cell line, and there was no relationship between sensitivity and expression of folate transporters. FRα was detected in 39% of tumour samples, generally in a small percentage of cells. There was no correlation between the presence of FRα and the outcome of pemetrexed treatment, and no significant difference between histological subtypes.

Conclusion:

Response to treatment with pemetrexed does not depend on the presence of FRα.

Functional folate receptor alpha is elevated in the blood of ovarian cancer patients

BACKGROUND

Despite low incidence, ovarian cancer is the fifth leading cause of cancer deaths and it has the highest mortality rate of all gynecologic malignancies among US women. The mortality rate would be reduced with an early detection marker. The folate receptor alpha (FRalpha) is one logical choice for a biomarker because of its prevalent overexpression in ovarian cancer and its exclusive expression in only a few normal tissues. In prior work, it was observed that patients with ovarian cancer had elevated serum levels of a protein that bound to a FRalpha-specific monoclonal antibody relative to healthy individuals. However, it was not shown that the protein detected was intact functional FRalpha. In the current study, the goal was to determine whether ovarian cancer patients (n = 30) had elevated serum levels of a fully functional intact FRalpha compared to matched healthy controls (n = 30).

METHODOLOGY/PRINCIPAL FINDINGS

FRalpha levels in serum were analyzed by two methods, immunoblotting analysis and a radiolabeled folic acid-based microfiltration binding assay. Using the immunoassay, we observed that levels of FRalpha were higher in serum of ovarian cancer patients as compared to controls. Similar results were also observed using the microfiltration binding assay, which showed that the circulating FRalpha is functional. Importantly, we also found that the levels of FRalpha were comparable between early and advanced stage patients.

CONCLUSIONS

Our results demonstrate that ovarian cancer patients have elevated levels of functional intact FRalpha. These findings support the potential use of circulating FRalpha as a biomarker of early ovarian cancer.

Functional folate receptor alpha is elevated in the blood of ovarian cancer patients

BACKGROUND

Despite low incidence, ovarian cancer is the fifth leading cause of cancer deaths and it has the highest mortality rate of all gynecologic malignancies among US women. The mortality rate would be reduced with an early detection marker. The folate receptor alpha (FRalpha) is one logical choice for a biomarker because of its prevalent overexpression in ovarian cancer and its exclusive expression in only a few normal tissues. In prior work, it was observed that patients with ovarian cancer had elevated serum levels of a protein that bound to a FRalpha-specific monoclonal antibody relative to healthy individuals. However, it was not shown that the protein detected was intact functional FRalpha. In the current study, the goal was to determine whether ovarian cancer patients (n = 30) had elevated serum levels of a fully functional intact FRalpha compared to matched healthy controls (n = 30).

METHODOLOGY/PRINCIPAL FINDINGS

FRalpha levels in serum were analyzed by two methods, immunoblotting analysis and a radiolabeled folic acid-based microfiltration binding assay. Using the immunoassay, we observed that levels of FRalpha were higher in serum of ovarian cancer patients as compared to controls. Similar results were also observed using the microfiltration binding assay, which showed that the circulating FRalpha is functional. Importantly, we also found that the levels of FRalpha were comparable between early and advanced stage patients.

CONCLUSIONS

Our results demonstrate that ovarian cancer patients have elevated levels of functional intact FRalpha. These findings support the potential use of circulating FRalpha as a biomarker of early ovarian cancer.

Tumor detection using folate receptor-targeted imaging agents

Folate receptors are up-regulated on a variety of human cancers, including cancers of the breast, ovaries, endometrium, lungs, kidneys, colon, brain, and myeloid cells of hematopoietic origin. This over-expression of folate receptors (FR) on cancer tissues can be exploited to target folate-linked imaging and therapeutic agents specifically to FR-expressing tumors, thereby avoiding uptake by most healthy tissues that express few if any FR. Four folate-targeted therapeutic drugs are currently undergoing clinical trials, and several folate-linked chemotherapeutic agents are in late stage preclinical development. However, because not all cancers express FR, and because only FR-expressing cancers respond to FR-targeted therapies, FR-targeted imaging agents have been required to select patients with FR-expressing tumors likely to respond to folate-targeted therapies. This review focuses on recent advances in the use of the vitamin folic acid to target PET agents, gamma-emitters, MRI contrast agents and fluorescent dyes to FR(+) cancers for the purpose of diagnosing and imaging malignant masses with improved specificity and sensitivity.

Embryonic development in the reduced folate carrier knockout mouse is modulated by maternal folate supplementation

BACKGROUND

The reduced folate carrier (RFC1) is a ubiquitously expressed integral membrane protein that mediates delivery of 5-methyltetrahydrofolate into mammalian cells. In this study, embryonic/fetal development is characterized in an RFC1 knockout mouse model in which pregnant dams receive different levels of folate supplementation.

METHODS

RFC1(+/-) males were mated to RFC1(+/-) females, and pregnant dams were treated with vehicle (control) or folic acid (25 or 50 mg/kg) by daily subcutaneous injection (0.1 mL/10 g bwt), beginning on E0.5 and continuing throughout gestation until the time of sacrifice.

RESULTS

Without maternal folate supplementation, RFC1 nullizygous embryos die shortly postimplantation. Supplementation of pregnant dams with 25 mg/kg/day folic acid prolongs survival of mutant embryos until E9.5-E10.5, but they are developmentally delayed relative to wild-type littermates, display a marked absence of erythropoiesis, severe neural tube and limb bud defects, and failure of chorioallantoic fusion. Fgfr2 protein levels are significantly reduced or absent in the extraembryonic membranes of RFC1 nullizygous embryos. Maternal folate supplementation with 50 mg/kg/day results in survival of 22% of RFC1 mutants to E18.5, but they develop with multiple malformations of the eyelids, lungs, heart, and skin.

CONCLUSIONS

High doses of daily maternal folate supplementation during embryonic/fetal development are necessary for early postimplantation embryonic viability of RFC1 nullizygous embryos, and play a critical role in chorioallantoic fusion, erythropoiesis, and proper development of the neural tube, limbs, lungs, heart, and skin.

Flow cytometric method for determining folate receptor expression on ovarian carcinoma cells

The alpha-folate receptor (alpha-FR) is a folate transporter with restricted expression levels in normal tissues. It is over-expressed in several cancers, particularly epithelial carcinomas, including nonmucinous ovarian carcinoma. It offers a novel therapeutic target for selective imaging and cytotoxic agents. Measurement of the receptor could be a valuable tool in selecting patients more likely to respond to new drugs that target the alpha-FR, and monitoring them while on treatment. While tumor samples are often unavailable, a number of patients who relapse develop ascites, which are often rich in tumor cells. We have therefore developed a triple antibody flow cytometric method to assess alpha-FR expression on tumor cells from ascites. An antibody to BerEP4, an epithelial cell marker expressed on >90% ovarian cancers, labeled with fluorescein, and an alpha-FR antibody labeled with antimouse-phycoerythrin have been used to label tumor cells, with a CD45-phycoerythrin-cyanine5 antibody used to exclude white blood cells from the analysis. The method was optimized using human carcinoma cell lines (JEG-3, IGROV-1, and KB cells). Calibrated beads were used to quantify the number of antibodies bound per cell. The triple antibody protocol successfully measured alpha-FR expression levels in cell lines spiked with blood. Tumor cells were obtained from ascites in 25 patients with relapsed ovarian cancer. In each case sufficient cells were harvested to identify an epithelial cell population to estimate the number of binding sites/cell. All the samples contained a single population of BerEP4, alpha-FR positive cells between 5x10(3) and 5x10(5) antibody binding sites/cell. The method can be used to determine the number of anti-alpha-FR antibodies bound per epithelial cell in ascites from patients with ovarian carcinoma. The results obtained were reproducible and the method could be applied to specimens that had been stored at -80 degrees C.

Pemetrexed: biochemical and cellular pharmacology, mechanisms, and clinical applications

Pemetrexed is a new-generation antifolate, approved for the treatment of mesothelioma and non-small cell lung cancer, currently being evaluated for the treatment of a variety of other solid tumors. This review traces the history of antifolates that led to the development of pemetrexed and describes the unique properties of this agent that distinguish it from other antifolates. These include (a) its very rapid conversion to active polyglutamate derivatives in cells that build to high levels and are retained for long intervals to achieve prolonged and potent inhibition of its major target enzyme thymidylate synthase, (b) its high affinity for three folate transporters, and (c) its marked sensitivity to the level of physiologic folates in cells. The latter results in the unique and paradoxical finding that when transport mediated by the major folate transporter (the reduced folate carrier) is impaired, pemetrexed activity is preserved. This is due to concurrent contraction of competing cellular physiologic folates and utilization of a novel second transport carrier for which pemetrexed has high affinity, recently identified as the proton-coupled folate transporter (PCFT). Laboratory studies are reviewed that raise the possibility of new approaches to the use of folic acid supplementation in clinical regimens with pemetrexed.

In vivo antitumor activity of the folate-conjugated pH-sensitive polymeric micelle selectively releasing adriamycin in the intracellular acidic compartments

Cancer treatment efficacy and safety of the environmentally sensitive polymeric micelle drug carriers were significantly increased by optimizing the number of ligands on their surface. These micelles were designed to target the cancerous tumors through the interaction between folate and its receptors that overexpress on the cancer cell membrane while achieving pH-controlled drug release in the intracellular acidic compartments such as endosomes and lysosomes. In order to elucidate the effects of folate on cytotoxicity, biodistribution, anticancer activity, and pharmacological properties, folate concentration on the surface of the micelles was controlled by precise synthesis of two different amphiphilic block copolymers that self-assemble into spherical micelles, folate-poly(ethylene glycol)-poly(aspartate-hydrazone-adriamycin) with gamma-carboxylic acid activated folate and methoxy-poly(ethylene glycol)-poly(aspartate-hydrazone-adriamycin) without folate. It is of significance that, although folate conjugation induced an extremely small change in tumor accumulation of the micelles, folate-conjugated micelles showed lower in vivo toxicity and higher antitumor activity over a broad range of the dosage from 7.50 to 26.21 mg/kg, which was 5-fold broader than free drugs.

Overexpression of folate binding protein and mesothelin are associated with uterine serous carcinoma

PURPOSE

Folate receptor alpha (FOLR1) is a membrane bound receptor involved in the transport of folate as well as other regulatory cellular processes. The purpose of this study was to examine the expression of FOLR1 in uterine cancers and to identify changes in gene expression that are associated with overexpression of FOLR1.

EXPERIMENTAL DESIGN

Fifty-eight frozen uterine cancer specimens were stained for FOLR1 using immunohistochemistry and results were correlated with transcript expression noted on quantitative PCR. Total RNA from 16 cases of uterine serous carcinoma (USC) was analyzed for gene expression using the Affymetrix HG-U133A and HG-U133B GeneChip set. USCs overexpressing FOLR1 were compared to cancers with an absence of FOLR1 using binary comparison and template matching of data was used to identify genes that correlate with FOLR1 expression. Selected targets from this analysis were evaluated by quantitative PCR as well as in an independent set of USC represented in quadruplicate on a tissue microarray (TMA).

RESULTS

Overexpression of FOLR1 was observed in 11/16 (69%) of USC and 0/10 normal endometrium cases using frozen tissue specimens. Binary comparison between FOLR1 positive and negative cases identified 121 genes altered by 2-fold at p<0.01 of which 45 are well correlated with FOLR1 expression pattern. Using quantitative PCR, both mesothelin (MSLN) and PTGS1 (COX1) were significantly increased in FOLR1 overexpressing tumors (p=0.014 and p=0.006 respectively). TMA confirmed that overexpression of FOLR1 and MSLN respectively occurred in 23/48 (48%) and 17/54 (32%) of pure USC.

CONCLUSION

Both FOLR1 and MSLN are cell surface targets that are co-expressed at high levels in USC and are appealing targets for biologic therapy.

A folic acid-based functionalized surface for biosensor systems

The performance of a biosensor depends largely on its interface with the biological system. This interface imparts a biologically relevant function to the device and provides a measure of specificity towards the biological analyte of interest. This paper documents the choice of folic acid as the functional component of a cantilever sensor to recognize nasopharyngeal (KB) cancer cells. A conjugation chemistry protocol has been outlined to deploy folic acid onto a titanium-coated sensor surface using a silane linker. The presence and biological activity of the sensor was verified by means of an immunospecific (ELISA) procedure. The overall performance of the folic acid-based cantilever sensor was measured using cancerous KB cell-binding experiments.

A phase I study on adoptive immunotherapy using gene-modified T cells for ovarian cancer

PURPOSE

A phase I study was conducted to assess the safety of adoptive immunotherapy using gene-modified autologous T cells for the treatment of metastatic ovarian cancer.

EXPERIMENTAL DESIGN

T cells with reactivity against the ovarian cancer-associated antigen alpha-folate receptor (FR) were generated by genetic modification of autologous T cells with a chimeric gene incorporating an anti-FR single-chain antibody linked to the signaling domain of the Fc receptor gamma chain. Patients were assigned to one of two cohorts in the study. Eight patients in cohort 1 received a dose escalation of T cells in combination with high-dose interleukin-2, and six patients in cohort 2 received dual-specific T cells (reactive with both FR and allogeneic cells) followed by immunization with allogeneic peripheral blood mononuclear cells.

RESULTS

Five patients in cohort 1 experienced some grade 3 to 4 treatment-related toxicity that was probably due to interleukin-2 administration, which could be managed using standard measures. Patients in cohort 2 experienced relatively mild side effects with grade 1 to 2 symptoms. No reduction in tumor burden was seen in any patient. Tracking 111In-labeled adoptively transferred T cells in cohort 1 revealed a lack of specific localization of T cells to tumor except in one patient where some signal was detected in a peritoneal deposit. PCR analysis showed that gene-modified T cells were present in the circulation in large numbers for the first 2 days after transfer, but these quickly declined to be barely detectable 1 month later in most patients. An inhibitory factor developed in the serum of three of six patients tested over the period of treatment, which significantly reduced the ability of gene-modified T cells to respond against FR+ tumor cells.

CONCLUSIONS

Large numbers of gene-modified tumor-reactive T cells can be safely given to patients, but these cells do not persist in large numbers long term. Future studies need to employ strategies to extend T cell persistence. This report is the first to document the use of genetically redirected T cells for the treatment of ovarian cancer.

The role of folate receptor alpha in cancer development, progression and treatment: cause, consequence or innocent bystander?

Folate receptor alpha (FRalpha) is a membrane-bound protein with high affinity for binding and transporting physiologic levels of folate into cells. Folate is a basic component of cell metabolism and DNA synthesis and repair, and rapidly dividing cancer cells have an increased requirement for folate to maintain DNA synthesis, an observation supported by the widespread use of antifolates in cancer chemotherapy. FRalpha levels are high in specific malignant tumors of epithelial origin compared to normal cells, and are positively associated with tumor stage and grade, raising questions of its role in tumor etiology and progression. It has been suggested that FRalpha might confer a growth advantage to the tumor by modulating folate uptake from serum or by generating regulatory signals. Indeed, cell culture studies show that expression of the FRalpha gene, FOLR1, is regulated by extracellular folate depletion, increased homocysteine accumulation, steroid hormone concentrations, interaction with specific transcription factors and cytosolic proteins, and possibly genetic mutations. Whether FRalpha in tumors decreases in vivo among individuals who are folate sufficient, or whether the tumor's machinery sustains FRalpha levels to meet the increased folate demands of the tumor, has not been studied. Consequently, the significance of carrying a FRalpha-positive tumor in the era of folic acid fortification and widespread vitamin supplement use in countries such as Canada and the United States is unknown. Epidemiologic and clinical studies using human tumor specimens are lacking and increasingly needed to understand the role of environmental and genetic influences on FOLR1 expression in tumor etiology and progression. This review summarizes the literature on the complex nature of FOLR1 gene regulation and expression, and suggests future research directions.