Folate receptor alpha expression in low-grade serous ovarian cancer: Exploring new therapeutic possibilities.

OBJECTIVE: Mirvetuximab soravtansine may be a potentially effective therapeutic option for ovarian low-grade serous carcinoma (LGSC), but the prevalence of folate receptor alpha (FRα) overexpression in this tumor type is unknown. We sought to characterize FRα expression in LGSC and its association with clinical and molecular features. METHODS: FRα immunohistochemistry was performed on a tissue microarray comprised of 89 LGSCs and 42 ovarian serous borderline tumors (SBTs). Clinical tumor-normal panel-based sequencing was performed on 78 LGSCs. Associations between FRα-high status and clinicopathologic characteristics and survival outcomes were examined. RESULTS: Of 89 LGSCs, 36 (40%) were FRα-high (≥75% of viable tumor cells exhibiting moderate-to-strong membranous expression). Of 9 patients with LGSC and samples from different timepoints, 4 (44%) had discordant results, with conversion from FRα-negative to FRα-high in 3 (33%) cases. There was no association between FRα-high status with age, race, or progression-free/overall survival. A MAPK pathway genetic alteration, most commonly involving KRAS (n = 23), was present in 45 (58%) LGSCs. Those lacking MAPK pathway alterations were more likely to be FRα-high compared to MAPK-altered LGSCs (61% vs 20%, p < 0.001). In SBTs, FRα-high expression was associated with high-risk (micropapillary) histology and/or subsequent LGSC recurrence compared to conventional SBTs without malignant recurrence (53% vs 9%, p = 0.008). CONCLUSIONS: Future studies of FRα-directed therapy in patients with LGSC are warranted. Discordant FRα status at recurrence suggests potential benefit for retesting. A biomarker-driven approach to direct treatment selection in LGSC is recommended. As high FRα expression is more common amongst tumors lacking MAPK pathway genetic alterations, FRα testing to determine eligibility for mirvetuximab soravtansine therapy is particularly recommended for this subgroup.

Vaccination with folate receptor-alpha peptides in patients with ovarian cancer following response to platinum-based therapy: A randomized, multicenter clinical trial.

OBJECTIVE: Folate receptor alpha (FRα) is overexpressed on >90% of high-grade epithelial ovarian cancers (EOC). Targeting FRα with antibody-drug conjugates has proven utility in the platinum-resistant setting. It is also a potential therapeutic target for immuno-oncologic agents, such as peptide vaccines that work primarily via adaptive and humoral immunity. We tested the hypothesis that FRα peptide immunization could improve outcomes in patients with EOC following response to platinum-based therapy. METHODS: We conducted a randomized, double-blind, multicenter, phase II study to evaluate the safety and efficacy of TPIV200 (a multi-epitope FRα peptide vaccine admixed with GM-CSF) versus GM-CSF alone in 120 women who did not have disease progression after at least 4 cycles of first-line platinum-based therapy. Patients were vaccinated intradermally once every 4 weeks up to 6 times, followed by a boosting period of 6 vaccinations at 12-week intervals. Primary endpoints included safety, tolerability, and progression free survival (PFS). RESULTS: At study termination with a median follow-up of 15.2 months (range 1.2-28.4 months), 68 of 119 intention-to-treat patients had disease progression (55% in TPIV200 + GM-CSF arm and 59% in GM-CSF alone arm). The median PFS was 11.1 months (95% CI 8.3-16.6 months) with no significant difference between the treatment groups (10.9 months with TPIV200 + GM-CSF versus 11.1 months with GM-CSF, HR, 0.85; upper 90% CI 1.17]. No patient experienced a ≥ grade 3 drug-related adverse event. CONCLUSION: TPIV200 was well tolerated but was not associated with improved PFS. Additional studies are required to uncover potential synergies using multiepitope vaccines targeting FRα. Trial Registration NLM/NCBI Registry, NCT02978222, https://clinicaltrials.gov/search?term=NCT02978222.

Phase 1b study of mirvetuximab soravtansine, a folate receptor alpha (FRα)-targeting antibody-drug conjugate, in combination with carboplatin and bevacizumab in patients with platinum-sensitive ovarian cancer.

OBJECTIVE: Evaluate the antitumor activity and safety profile of the triplet combination of mirvetuximab soravtansine (MIRV), carboplatin, and bevacizumab in recurrent, platinum-sensitive ovarian cancer. METHODS: Participants with recurrent, platinum-sensitive epithelial ovarian, fallopian tube, or primary peritoneal cancer (1-2 prior lines of therapy) received MIRV (6 mg/kg adjusted ideal body weight), carboplatin (AUC5), and bevacizumab (15 mg/kg) once every 3 weeks. Carboplatin could be discontinued after 6 cycles per investigator discretion; continuation of MIRV+bevacizumab as maintenance therapy was permitted. Eligibility included folate receptor alpha (FRα) expression by immunohistochemistry (≥50% of cells with ≥2+ intensity; PS2+ scoring); prior bevacizumab was allowed. Tumor response, duration of response (DOR), progression-free survival (PFS), and adverse events (AEs) were assessed. RESULTS: Forty-one participants received triplet therapy, with a median of 6, 12, and 13 cycles of carboplatin, MIRV, and bevacizumab, respectively. The confirmed objective response rate was 83% (9 complete and 25 partial responses). The median DOR was 10.9 months; median PFS was 13.5 months. AEs (any grade) occurred as expected, based on each agent's safety profile; most common were diarrhea (83%), nausea (76%), fatigue (73%), thrombocytopenia (71%), and blurred vision (68%). Most cases were mild to moderate (grade ≤2), except for thrombocytopenia, for which most drug-related discontinuations occurred, and neutropenia. CONCLUSIONS: This triplet regimen (MIRV+carboplatin+bevacizumab) was highly active, with a tolerable AE profile in participants with recurrent, platinum-sensitive, FRα-expressing ovarian cancer. Thrombocytopenia was the primary cause of dose modifications. These outcomes compare favorably to historical data reported for platinum-based chemotherapy plus bevacizumab regimens in similar patient populations.

A phase I study of Mirvetuximab Soravtansine and gemcitabine in patients with FRα-positive recurrent ovarian, primary peritoneal, fallopian tube, or endometrial cancer, or triple negative breast cancer.

OBJECTIVE: Platinum-resistant epithelial ovarian cancer (EOC), recurrent endometrial cancer (EC), and triple negative breast cancer (TNBC) are difficult to treat after failing standard therapies. This phase I study evaluated mirvetuximab soravtansine (MIRV) and gemcitabine in patients with recurrent FRα-positive EOC, EC, or TNBC to determine the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D) (primary endpoint). METHODS: FRα-positive patients with platinum-resistant EOC, EC, or TNBC with ≤4 prior chemotherapy regimens (2 for EC) were enrolled. FRα expression requirement varied among eligible tumors and changed during the study. RESULTS: Twenty patients were enrolled; 17 were evaluable for DLT. Half the patients received ≥3 prior chemotherapy lines. Most EOC and EC patients (78%) were medium (50-74%) or high(75-100%) FRα expressors. TNBC patients were low (25-49%) FRα expressors. The MTD/RP2D was MIRV 6 mg/kg AIBW D1 and gemcitabine 800 mg/m2 IV, D1 and D8, every 21 days (Dose Level [DL] 3), where 5/7 patients demonstrated a partial response (PR) as their best response, including 2 confirmed ovarian responses whose time-to-progression and duration of response were 7.9/5.4 and 8.0/5.7 months respectively. Most common treatment-related adverse events at MTD were anemia and neutropenia (3/7 each, 43%), diarrhea, hypophosphatemia, thrombocytopenia, and leukopenia (2/7 each, 29%). DLTs were thrombocytopenia (DL1), oral mucositis (DL4) and diarrhea (DL4). Nine of 20 patients (45%; 95% CI: 21.1-68.9%) achieved PR as their best response, with 3/20 patients or 15% (95%CI, 0-32.1%) confirmed PR. CONCLUSION: MIRV and gemcitabine demonstrate promising activity in platinum resistant EOC at RP2D, but frequent hematologic toxicities.

Maintenance with mirvetuximab soravtansine plus bevacizumab vs bevacizumab in FRα-high platinum-sensitive ovarian cancer.

At first recurrence, platinum-sensitive ovarian cancer (PSOC) is frequently treated with platinum-based chemotherapy doublets plus bevacizumab, then single-agent bevacizumab. Most patients' disease progresses within a year after chemotherapy, emphasizing the need for novel strategies. Mirvetuximab soravtansine-gynx (MIRV), an antibody-drug conjugate, comprises a folate receptor alpha (FRα)-binding antibody and tubulin-targeting payload (maytansinoid DM4). In FRα-high PSOC, MIRV plus bevacizumab previously showed promising efficacy (objective response rate, 69% [95% CI: 41-89]; median progression-free survival, 13.3 months [95% CI: 8.3-18.3]; median duration of response, 12.9 months [95% CI: 6.5-15.7]) and safety. The Phase III randomized GLORIOSA trial will evaluate MIRV plus bevacizumab vs. bevacizumab alone as maintenance therapy in patients with FRα-high PSOC who did not have disease progression following second-line platinum-based doublet chemotherapy plus bevacizumab.Clinical Trial Registration: ClinicalTrials.gov ID: NCT05445778; GOG.org ID: GOG-3078; ENGOT.ESGO.org ID: ENGOT-ov76.

Most patients with ovarian cancer are initially treated with platinum-based chemotherapy. If the cancer reappears/recurs after more than 6 months following this therapy, it is called platinum-sensitive ovarian cancer (PSOC). Patients with PSOC usually receive additional platinum-based chemotherapy along with bevacizumab, a drug that reduces tumor growth by decreasing its blood supply. If patients improve or are stable on this therapy, they are usually kept on bevacizumab alone for 'maintenance therapy'. Unfortunately, this maintenance therapy does not work long-term in all patients, so better long-term treatments are needed. The GLORIOSA (NCT05445778) clinical trial will compare maintenance therapy with bevacizumab alone to maintenance therapy with bevacizumab plus a drug called mirvetuximab soravtansine-gynx (MIRV) to determine which therapy leads to better results in patients with PSOC. MIRV is made up of an antibody that binds to a specific protein (folate receptor alpha [FRα]) on cancer cells to directly deliver a cancer-killing drug. MIRV received US FDA approval to be used as a therapy for patients with ovarian cancer who are resistant to platinum-based chemotherapy and express high levels of FRα. The GLORIOSA trial will study maintenance therapy with MIRV plus bevacizumab in patients with PSOC who have not had cancer progression after second-line platinum-based chemotherapy plus bevacizumab, and whose cancer expresses high amounts of FRα. The main purpose of this trial is to determine if MIRV plus bevacizumab leads to better patient survival and decreases cancer growth and spread when compared with bevacizumab alone.

Folate Receptor Alpha-A Novel Approach to Cancer Therapy.

Folate receptor α (FR) was discovered many decades ago, along with drugs that target intracellular folate metabolism, such as pemetrexed and methotrexate. Folate is taken up by the cell via this receptor, which also targeted by many cancer agents due to the over-expression of the receptor by cancer cells. FR is a membrane-bound glycosyl-phosphatidylinositol (GPI) anchor glycoprotein encoded by the folate receptor 1 (FOLR1) gene. FR plays a significant role in DNA synthesis, cell proliferation, DNA repair, and intracellular signaling, all of which are essential for tumorigenesis. FR is more prevalent in cancer cells compared to normal tissues, which makes it an excellent target for oncologic therapeutics. FRα is found in many cancer types, including ovarian cancer, non-small-cell lung cancer (NSCLC), and colon cancer. FR is widely used in antibody drug conjugates, small-molecule-drug conjugates, and chimeric antigen-receptor T cells. Current oncolytic therapeutics include mirvetuximab soravtansine, and ongoing clinical trials are underway to investigate chimeric antigen receptor T cells (CAR-T cells) and vaccines. Additionally, FRα has been used in a myriad of other applications, including as a tool in the identification of tumor types, and as a prognostic marker, as a surrogate of chemotherapy resistance. As such, FRα identification has become an essential part of precision medicine.

Folate receptor alpha is widely expressed and a potential therapeutic target in uterine and ovarian carcinosarcoma.

OBJECTIVE: Folate receptor alpha (FRα), which is expressed in various cancers, is a potential therapeutic target. However, its expression and clinical significance in uterine (UCS) and ovarian carcinosarcoma (OCS) remain to be elucidated. METHODS: This retrospective study included patients with gynecologic carcinosarcoma who underwent primary surgery between 1997 and 2019 at our institution. Immunohistochemical staining of surgical FFPE specimens was performed for FRα and HER2. FRα was evaluated using the H-score and the 4-tired scoring system (0 to 3+). Subsequently, FRα expression (≥5% of tumor cells with ≥1+ intensity) and FRα-high (score 2+ and 3+) were evaluated. HER2 was scored according to the modified ASCO/CAP criteria. The association between FRα-high and clinicopathological features, HER2 expression, and survival was assessed in UCS. RESULTS: A total of 120 patients with UCS and nine patients with OCS were included. In UCS, FRα expression was observed in all patients, whereas FRα-high status was present in 20% of patients. Among HER2-negative UCS, 34% exhibited FRα-high. No significant association was observed between clinicopathological characteristics and FRα status. During the follow-up period (median 34.5 mo), FRα-high was not strongly associated with progression, free survival, and overall survival. All the OCS tumor specimens showed FRα-high expression. CONCLUSIONS: FRα expression was observed in all the UCS and OCS specimens, including HER2-negative UCS patients. This widespread FRα expression suggests that FRα-targeted therapies may hold promise for the treatment for gynecologic carcinosarcoma. However, in uterine carcinosarcoma, no significant relationship was observed between FRα expression and clinicopathological features or prognosis.

Safety and efficacy of mirvetuximab soravtansine, a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), in combination with bevacizumab in patients with platinum-resistant ovarian cancer.

PURPOSE: Evaluate the antitumor activity and safety profile of the combination of mirvetuximab soravtansine and bevacizumab in patients with platinum-resistant ovarian cancer. METHODS: Patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer, whose most recent platinum-free interval was ≤6 months, were administered mirvetuximab soravtansine (6 mg/kg adjusted ideal body weight) and bevacizumab (15 mg/kg), intravenously, once every 3 weeks. Eligibility included FRα expression by immunohistochemistry (IHC; ≥25% of cells with ≥2+ intensity). Prior bevacizumab and/or PARP inhibitor (PARPi) treatment were permitted. The primary endpoint was confirmed objective response rate (ORR). Secondary endpoints included duration of response (DOR), progression-free survival (PFS), and safety. RESULTS: Ninety-four patients received combination treatment with mirvetuximab soravtansine and bevacizumab. Median age was 62 years (range, 39-81). Fifty-two percent had ≥3 prior therapies; 59% had prior bevacizumab; and 27% had prior PARPi. ORR was 44% (95% CI 33, 54) with 5 complete responses, median DOR 9.7 months (95% CI 6.9, 14.1), and median PFS 8.2 months (95% CI 6.8, 10.0). Treatment-related adverse events were consistent with the profiles of each agent, with the most common being blurred vision (all grades 57%; grade 3, 1%), diarrhea (54%; grade 3, 1%), and nausea (51%; grade 3, 1%). CONCLUSION: The mirvetuximab soravtansine plus bevacizumab doublet is an active and well-tolerated regimen in patients with FRα-expressing platinum-resistant ovarian cancer. Promising activity was observed for patients regardless of level of FRα expression or prior bevacizumab. These data underscore the potential for mirvetuximab soravtansine as the combination partner of choice for bevacizumab in this setting.

Antibody-drug conjugate MORAb-202 exhibits long-lasting antitumor efficacy in TNBC PDx models.

The antibody-drug conjugate (ADC) MORAb-202, consisting of farletuzumab paired with a cathepsin B-cleavable linker and eribulin, targets folate receptor alpha (FRA), which is frequently overexpressed in various tumor types. MORAb-202 was highly cytotoxic to FRA-positive cells in vitro, with limited off-target killing of FRA-negative cells. Furthermore, MORAb-202 showed a clear in vitro bystander cytotoxic effect in coculture with FRA-positive/negative cells. In vivo antitumor efficacy studies of MORAb-202 were conducted with a single administration of MORAb-202 in triple-negative breast cancer (TNBC) patient-derived xenograft (PDx) models expressing low and high levels of FRA. MORAb-202 exhibited durable efficacy proportional to tumor FRA expression. Toxicology studies (Q3Wx2) in nonhuman primates suggested that the major observed toxicity of MORAb-202 is hematologic toxicity. Overall, these findings support the concept that MORAb-202 represents a promising investigational ADC for the treatment of TNBC patients.

Phase III, randomized trial of mirvetuximab soravtansine versus chemotherapy in patients with platinum-resistant ovarian cancer: primary analysis of FORWARD I.

BACKGROUND: Mirvetuximab soravtansine (MIRV) is an antibody-drug conjugate comprising a folate receptor alpha (FRα)-binding antibody, cleavable linker, and the maytansinoid DM4, a potent tubulin-targeting agent. The randomized, open-label, phase III study FORWARD I compared MIRV and investigator's choice chemotherapy in patients with platinum-resistant epithelial ovarian cancer (EOC). PATIENTS AND METHODS: Eligible patients with 1-3 prior lines of therapy and whose tumors were positive for FRα expression were randomly assigned, in a 2 : 1 ratio, to receive MIRV (6 mg/kg, adjusted ideal body weight) or chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary endpoint was progression-free survival [PFS, Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, blinded independent central review] in the intention-to-treat (ITT) population and in the prespecified FRα high population. RESULTS: A total of 366 patients were randomized; 243 received MIRV and 109 received chemotherapy. The primary endpoint, PFS, did not reach statistical significance in either the ITT [hazard ratio (HR), 0.98, P = 0.897] or the FRα high population (HR, 0.69, P = 0.049). Superior outcomes for MIRV over chemotherapy were observed in all secondary endpoints in the FRα high population including improved objective response rate (24% versus 10%), CA-125 responses (53% versus 25%), and patient-reported outcomes (27% versus 13%). Fewer treatment-related grade 3 or higher adverse events (25.1% versus 44.0%), and fewer events leading to dose reduction (19.8% versus 30.3%) and treatment discontinuation (4.5% versus 8.3%) were seen with MIRV compared with chemotherapy. CONCLUSIONS: In patients with platinum-resistant EOC, MIRV did not result in a significant improvement in PFS compared with chemotherapy. Secondary endpoints consistently favored MIRV, particularly in patients with high FRα expression. MIRV showed a differentiated and more manageable safety profile than chemotherapy.

Fourth-generation chimeric antigen receptor T cells targeting folate receptor alpha antigen expressed on breast cancer cells for adoptive T cell therapy.

PURPOSE: Treatment of breast cancer (BC) by standard methods is effective in the early stage, but ineffective in the advanced stage of disease. To develop an adoptive T cell therapy for advanced and severe BC, we generated fourth-generation chimeric antigen receptor (CAR) T cells targeting folate receptor alpha antigen (FRα) expressed on BC cells, and preclinically evaluated their anti-BC activities. METHODS: The fourth-generation FRα-CAR T cells containing extracellular FRα-specific single-chain variable fragment (scFv) and three intracellular costimulatory domains (CD28, 4-1BB, and CD27) linked to CD3ζ were generated using a lentiviral system, and then were evaluated for their anti-BC activities in two-dimensional and three-dimensional (spheroid) cultures. RESULTS: When our fourth-generation FRα-CAR T cells were cocultured with FRα-expressing MDA-MB-231 BC cell line at an effector to target ratio of 20:1, these CAR T cells specifically lysed 88.7 ± 10.6% of the target cells. Interestingly, the cytotoxic lysis of FRα-CAR T cells was more pronounced in target cells with higher surface FRα expression. This specific cytotoxicity of the CAR T cells was not observed when cocultured with FRα-negative MCF10A normal breast-like cell line at the same ratio (34.3 ± 4.7%). When they were cocultured with MDA-MD-231 spheroid, the FRα-CAR T cells exhibited antitumor activity marked with spheroid size reduction and breakage. CONCLUSION: This proof-of-concept study thus shows the feasibility of using these fourth-generation FRα-CAR T cells for adoptive T cell therapy in BC.

Heterocyclic Substitutions Greatly Improve Affinity and Stability of Folic Acid towards FRα. an In Silico Insight.

Folate receptor alpha (FRα) is known as a biological marker for many cancers due to its overexpression in cancerous epithelial tissue. The folic acid (FA) binding affinity to the FRα active site provides a basis for designing more specific targets for FRα. Heterocyclic rings have been shown to interact with many receptors and are important to the metabolism and biological processes within the body. Nineteen FA analogs with substitution with various heterocyclic rings were designed to have higher affinity toward FRα. Molecular docking was used to study the binding affinity of designed analogs compared to FA, methotrexate (MTX), and pemetrexed (PTX). Out of 19 FA analogs, analogs with a tetrazole ring (FOL03) and benzothiophene ring (FOL08) showed the most negative binding energy and were able to interact with ASP81 and SER174 through hydrogen bonds and hydrophobic interactions with amino acids of the active site. Hence, 100 ns molecular dynamics (MD) simulations were carried out for FOL03, FOL08 compared to FA, MTX, and PTX. The root mean square deviation (RMSD) and root mean square fluctuation (RMSF) of FOL03 and FOL08 showed an apparent convergence similar to that of FA, and both of them entered the binding pocket (active site) from the pteridine part, while the glutamic part was stuck at the FRα pocket entrance during the MD simulations. Molecular mechanics Poisson-Boltzmann surface accessible (MM-PBSA) and H-bond analysis revealed that FOL03 and FOL08 created more negative free binding and electrostatic energy compared to FA and PTX, and both formed stronger H-bond interactions with ASP81 than FA with excellent H-bond profiles that led them to become bound tightly in the pocket. In addition, pocket volume calculations showed that the volumes of active site for FOL03 and FOL08 inside the FRα pocket were smaller than the FA-FRα system, indicating strong interactions between the protein active site residues with these new FA analogs compared to FA during the MD simulations.

Conjugated ß-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 (ßCD) 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-ßCDs 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 ßCD 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-appended cyclodextrin carrier targets ovarian cancer cells expressing the proton-coupled folate transporter.

Folate receptor alpha (FRα) is overexpressed in >80% of epithelial ovarian cancer (EOC). Accordingly, folate is attracting attention as a targeting ligand for EOC. For EOC patients, paclitaxel (PTX) is generally used as a first-line chemotherapeutic agent in combination with platinum-based drugs. Cyclodextrin (CyD) is a potential new formulation vehicle for PTX that could replace Cremophor-EL, a traditional formulation vehicle that causes significant side effects, including neutropenia. Several years ago, folate-appended ß-CyD (Fol-c1 -ß-CyD) was developed as an FRα-targeting drug carrier, but its efficacy as a treatment for EOC remains to be determined. In this study, we assessed the antitumor activity of PTX in Fol-c1 -ß-CyD (PTX/Fol-c1 -ß-CyD) in EOC-derived cell lines. We found that PTX/Fol-c1 -ß-CyD killed not only FRα-expressing cells but also FRα-negative cells. In the FRα-negative A2780 cells, knockdown of proton-coupled folate transporter (PCFT) significantly decreased the cytotoxicity of PTX/Fol-c1 -ß-CyD, whereas knockdown of FRα did not. By contrast, knockdown of either FRα or proton-coupled folate transporter (PCFT) decreased the cytotoxicity of PTX/Fol-c1 -ß-CyD in FRα-expressing SK-OV-3 cells. Furthermore, the cytotoxicity of PTX/Fol-c1 -ß-CyD in A2780 cells was increased at acidic pH, and this increase was suppressed by PCFT inhibitor. In mice intraperitoneally inoculated with FRα-expressing or PCFT-expressing EOC cells, intraperitoneal administration of PTX/Fol-c1 -ß-CyD significantly suppressed the growth of both types of EOC cells relative to PTX alone, without inducing a significant change in the neutrophil/white blood cell ratio. Our data suggest that Fol-c1 -ß-CyD targets not only FRα but also PCFT, and can efficiently deliver anticancer drugs to EOC cells in the peritoneal cavity.

A Phenotypic Switch of Differentiated Glial Cells to Dedifferentiated Cells Is Regulated by Folate Receptor α.

In a previous study, we showed that folate receptor-α (FRα) translocates to the nucleus where it acts as a transcription factor and upregulates Hes1, Oct4, Sox2, and Klf4 genes responsible for pluripotency. Here, we show that acetylation and phosphorylation of FRα favor its nuclear translocation in the presence of folate and can cause a phenotypic switch from differentiated glial cells to dedifferentiated cells. shRNA-FRα mediated knockdown of FRα was used to confirm the role of FRα in dedifferentiation. Ocimum sanctum hydrophilic fraction-1 treatment not only blocks the folate mediated dedifferentiation of glial cells but also promotes redifferentiation of dedifferentiated glial cells, possibly by reducing the nuclear translocation of ~38 kDa FRα and subsequent interaction with chromatin assembly factor-1. Stem Cells 2019;37:1441-1454.

Correlation of folate receptor alpha expression with clinicopathological parameters and outcome in triple negative breast cancer.

Folate receptor alpha (FRα) is a membrane-bound protein with a high affinity for folate, which is necessary for the biosynthesis of amino acids and nucleotide bases. It has been shown to be a potential prognostic and therapeutic target, primarily in lung and ovarian cancer, as well as in breast cancer. The aim of this study was to examine FRα expression in a cohort of patients with triple negative breast cancer (TNBC), in correlation with clinicopathological parameters and prognostic factors. By using polyclonal FRα antibody on archival paraffin blocks immunohistochemistry was performed. To evaluate the expression of FRα, H-score was used, which marks both the proportion of stained cells and the intensity of staining. Statistical analysis correlating FRα expression with clinicopathologic parameters and clinical outcome were performed. FRα was expressed in most of the patients (85%). Significant correlation of expression and histologic grade (Mann Whitney U test, P = 0,03) and type of tumor (P = 0,02), was found. It was noticed that with higher Ki-67 proliferation index values, H-score has lower values (r = -0,284, P = 0,006). Multivariant regression analysis (Cox regression, Stepwise method) showed H-score as a significant predictor for the risk of disease recurrence (OR = 1,005, P = 0,04). No correlation between FRα expression and overall survival (OS) and disease-free survival (DFS) was found. In conclusion, FRα is highly expressed in TNBC, and, given the correlation with clinicopathological parameters, subpopulation of patients could be identified that could be potential targets for new therapeutic perspectives in the treatment of this breast cancer subtype.

Identification of a Folate Receptor-Targeted Near-Infrared Molecular Contrast Agent to Localize Pulmonary Adenocarcinomas.

Non-small cell lung cancer (NSCLC) is the number one cancer killer in the United States. Despite attempted curative surgical resection, nearly 40% of patients succumb to recurrent disease. High recurrence rates may be partially explained by data suggesting that 20% of NSCLC patients harbor synchronous disease that is missed during resection. In this report, we describe the use of a novel folate receptor-targeted near-infrared contrast agent (OTL38) to improve the intraoperative localization of NSCLC during pulmonary resection. Using optical phantoms, fluorescent imaging with OTL38 was associated with less autofluorescence and greater depth of detection compared to traditional optical contrast agents. Next, in in vitro and in vivo NSCLC models, OTL38 reliably localized NSCLC models in a folate receptor-dependent manner. Before testing intraoperative molecular imaging with OTL38 in humans, folate receptor-alpha expression was confirmed to be present in 86% of pulmonary adenocarcinomas upon histopathologic review of 100 human pulmonary resection specimens. Lastly, in a human feasibility study, intraoperative molecular imaging with OTL38 accurately identified 100% of pulmonary adenocarcinomas and allowed for identification of additional subcentimeter neoplastic processes in 30% of subjects. This technology may enhance the surgeon's ability to identify NSCLC during oncologic resection and potentially improve long-term outcomes.

IgA Fc-folate conjugate activates and recruits neutrophils to directly target triple-negative breast cancer cells.

PURPOSE: According to the American Cancer Society, 1 in 8 women in the U.S. will develop breast cancer, with triple-negative breast cancer (TNBC) comprising 15-20% of all breast cancer cases. TNBC is an aggressive subtype due to its high metastatic potential and lack of targeted therapy. Recently, folate receptor alpha (FRA) is found to be expressed on 80% of TNBC with high expression correlating with poor prognosis. In this study, we examined whether binding IgA Fc-folate molecules to FRA receptors on TNBC cells can elicit and induce neutrophils (PMNs), by binding their FcαR1 receptors, to destroy TNBC cells. METHODS: FRA was analyzed on TNBC cells and binding assays were performed using 3H-folate. Fc-folate was synthesized by linking Fc fragments of IgA via amine groups to folate. Binding specificity and antibody-dependent cellular cytotoxicity (ADCC) potential of Fc-folate to FcαR1 were confirmed by measuring PMN adhesion and myeloperoxidase (MPO) release in a cell-based ELISA. Fc-folate binding to FRA-expressing TNBC cells inducing PMNs to destroy these cells was determined using 51Cr-release and calcein-labeling assays. RESULTS: Our results demonstrate expression of FRA on TNBC cells at levels consistent with folate binding. Fc-folate binds with high affinity to FRA compared to whole IgA-folate and induces MPO release from PMN when bound to FcαR1. Fc-folate inhibited binding of 3H-folate to TNBC cells and induced significant cell lysis of TNBC cells when incubated in the presence of PMNs. CONCLUSION: These findings support the hypothesis that an IgA Fc-folate conjugate can destroy TNBC cells by eliciting PMN-mediated ADCC.

Review of Immune Therapies Targeting Ovarian Cancer.

OPINION STATEMENT: The rise of immunotherapy is the greatest advance in oncology to occur over the last several years, but applications in gynecologic malignancies lag behind other tumors. The term "immunotherapy" envelops monoclonal antibodies as receptor mediators, including immune checkpoint inhibitors (ICPI), cancer vaccines, and adoptive immunotherapies alone or in combination with other therapeutic approaches. The purpose of this review is to summarize the status of immunotherapy trials in ovarian cancer and to specifically highlight data published in the last 1-2 years.

Folate receptor α is associated with poor clinicopathological perspectives in breast carcinoma.

BACKGROUND: Breast carcinoma is the commonest malignancy in females. Folate is required for the biosynthesis of nucleotide bases, amino acids, and other cellular methylation reactions in proteins and phospholipids. The high affinity folate receptor alpha (FRα) has been shown to be expressed in several kinds of human cancers. METHODS: In this descriptive-analytic study, sections from formalin-fixed paraffin-embedded tissue blocks of 50 cases of invasive ductal breast carcinoma (IDC) as well as 15 cases of non-neoplastic breast specimens were immunohistochemically stained with FRα antibody. Histopathological evaluation for various clinicopathological parameters was done and was correlated with FRα expression. RESULTS: Positive FRα expression was more frequently detected in IDC (64%) compared to non-neoplastic breast specimens (20%). In IDC, Positive FRα expression was significantly associated with high tumor grade (p = 0.007), large tumor size (p < 0.001), high lymph node stage (p = 0.004), presence of angiolymphatic emboli (p = 0.001), presence of perineural invasion (p = 0.001). Significant association between FRα positivity and negative hormone receptors (estrogen and progesterone) (p < 0.001) and triple negative cases (p = 0.0021). CONCLUSION: Our work demonstrates that FRα is over expressed in IDC compared to non-neoplastic breast tissue. Folate receptor α expression was associated with poor clinicopathological perspective. This work suggests that FRα may be an independent prognostic factor and supports the possibility of using FRα-targeted therapies of breast carcinoma. However, our work requires validation on larger cohort with correlation with survival data of patients.