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

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

Predict the Progression of Cervical Intraepithelial Neoplasia by a Novel Marker Folate Combine with FRα, p16 and Ki-67

Purpose

To study the expression of serum folate and red blood cell (RBC) folate, folate receptor α (FRα), p^16INK4a (p16), and Ki-67 at different levels of cervical intraepithelial neoplasia (CIN) and then analyze their role in the progression of CIN and their value as an early warning indicator of CIN progression.

Patients and methods

We randomly collected the data of patients at the Department of Gynecology in Guangxi Medical University Affiliated Cancer Hospital from January 2016 to December 2018: Normal controls (149 cases), CIN1 (150 cases), CIN2 (100 cases), and CIN3 (101 cases). [Ethical approval by Ethics Committee of the Second Hospital of Shanxi Medical University. (2013) No. (001–1)]. The expression of serum folate and RBC folate was detected by the chemiluminescence method, while the expression of FRα, p16, and Ki-67 was detected by Streptavidin-Perosidase (SP) immunohistochemistry.

Results

There was no statistically significant difference in serum folate levels between different grades of CIN (P=0.784), but the RBC folate levels were statistically significant (P=0.015), and there was a negative correlation between RBC folate levels and CIN lesion grades (P<0.05). The FRα, p16, and Ki-67 levels in the CIN group were significantly different from those in the normal control group (P <0.01), and a positive correlation was found (P <0.01); FRα positivity (P=0.000), Ki-67 positivity (P=0.000), and low-level RBC folate (P=0.000) were independent risk factors for the progression of CIN; these indicators were combined to establish a random forest (RF) model in which the Ki-67+FRα model was used as the early warning model of CIN progression.

Conclusion

RBC folate, FRα, p16, and Ki-67 can be used as valuable clinical test indicators for predicting the progression of CIN; the combined detection model of Ki-67+FRα can be used as an early warning model for predicting the progression of CIN.

Redox-Sensitive and Folate-Receptor-Mediated Targeting of Cervical Cancer Cells for Photodynamic Therapy Using Nanophotosensitizers Composed of Chlorin e6-Conjugated β-Cyclodextrin via Diselenide Linkage

The aim of this study was to fabricate a reactive oxygen species (ROS)-sensitive and folate-receptor-targeted nanophotosensitizer for the efficient photodynamic therapy (PDT) of cervical carcinoma cells. Chlorin e6 (Ce6) as a model photosensitizer was conjugated with succinyl β-cyclodextrin via selenocystamine linkages. Folic acid (FA)-poly(ethylene glycol) (PEG) (FA-PEG) conjugates were attached to these conjugates and then FA-PEG-succinyl β-cyclodextrin-selenocystamine-Ce6 (FAPEGbCDseseCe6) conjugates were synthesized. Nanophotosensitizers of FaPEGbCDseseCe6 conjugates were fabricated using dialysis membrane. Nanophotosensitizers showed spherical shapes with small particle sizes. They were disintegrated in the presence of hydrogen peroxide (H₂O₂) and particle size distribution changed from monomodal distribution pattern to multimodal pattern. The fluorescence intensity and Ce6 release rate also increased due to the increase in H₂O₂ concentration, indicating that the nanophotosensitizers displayed ROS sensitivity. The Ce6 uptake ratio, ROS generation and cell cytotoxicity of the nanophotosensitizers were significantly higher than those of the Ce6 itself against HeLa cells in vitro. Furthermore, the nanophotosensitizers showed folate-receptor-specific delivery capacity and phototoxicity. The intracellular delivery of nanophotosensitizers was inhibited by folate receptor blocking, indicating that they have folate-receptor specificity in vitro and in vivo. Nanophotosensitizers showed higher efficiency in inhibition of tumor growth of HeLa cells in vivo compared to Ce6 alone. These results show that nanophotosensitizers of FaPEGbCDseseCe6 conjugates are promising candidates as PDT of cervical cancer.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Evaluation of folate receptor-mediated tumor detection as a triage tool in cervical cancer screening

OBJECTIVE

To evaluate the efficacy of folate receptor-mediated tumor detection (FRD) for identifying high-grade intraepithelial squamous lesions (HSIL) in the triage of women who are positive for human papillomavirus (HPV), and those with cytology findings of atypical squamous cells of undetermined significance (ASCUS).

METHOD

A secondary analysis of prospectively collected data from 1504 women who had abnormal results during primary cervical cancer screening at 13 hospitals in Beijing, China, between November 2014 and August 2015. The detection accuracy of FRD was evaluated among HPV-positive women and women with ASCUS referred for colposcopy examination.

RESULTS

Among 1338 women with HPV, the percentage coincidence with pathology findings was higher for FRD (66.7%) than for cytology of ASCUS or higher (51.5%). The rate of colposcopy referral for cytology and FRD as a triage tool was 969 (72.4%) and 736 (55.0%), respectively. Thus, 233 (17.4%) fewer women would be referred for colposcopy by FRD. Among 476 women with cytology of ASCUS, the percentage coincidence with pathology findings was higher for FRD (63.4%) than for HPV (35.9%).

CONCLUSION

FRD was found to be a promising triage tool for women who are HPV-positive and those with cytology findings of ASCUS.

FOLR1 was up-regulated in cervical squamous cell carcinoma and correlated with the patients’ progression free survival

Objective The aim of the present work was to evaluate the folate-receptor 1 (FOLR1) expression in cervical squamous cell carcinoma and its clinical significance.

Methods FOLR1 mRNA expression level was detected in the cancer genome atlas (TCGA) database for multiple carcinomas. The FOLR1 mRNA relative expression between tumor tissue and normal cervix tissue of the cervical squamous cell cancer patients was compared by the online data analysis tool of GEPIA. The overall survival (OS) and progression free survival (PFS) between the FOLR1 high and low expression groups were compared by the log-rank test. Thirty one cervical squamous cancer patients and 20 healthy controls were included in and tested for serum FOLR1 protein level detection. Eighty one cervical squamous cell cancer patients who received surgery were included for FOLR1 protein expression detected by immunohistochemistry assay (IHC). The correlation between FOLR1 protein expression and patients’ clinical features was analyzed.

Results FOLR1 mRNA was up-regulated in tumor tissue compared to corresponding normal cervical tissue of cervical squamous cell carcinoma. Top 20 genes interacted with FOLR1 was identified through the network with the edges of 146. UBXN10 (r=0.668, P<0.01) and GBP6 (r-=0.606, P<0.01) were the top 2 genes that most correlated with FOLR1. The serum level of FR-α (FOLR1 coding protein) were 275.50±83.79 and 161.70±66.62 (ng/L) for the cervical cancer and healthy control subjects respectively with significant statistical difference (P<0.05). Using the serum FR-α as serological marker for cervical cancer detection, the diagnostic sensitivity, specificity and AUC were 80.0% (58.40% to 91.93%), 80.65% (63.72% to 90.81%) and 0.85(95%CI:0.74-0.96), respectively. Immunohistochemical assay indicated that of the 81 cancer tissue samples, 45 (55.6%) was FOLR1 protein positive. FOLR1 protein positive expression rate in FIGO stage Ⅲ/Ⅳ was significant higher than in the stage Ⅰ/Ⅱ with statistical difference (P<0.05). The progression free survival (PFS) was significant different between FOLR1 high and low expression group (HR=2.48, 95%CI:1.1-5.58, P=0.023). However, the overall survival (OS) was not statistical different between the two groups (HR=1.34, 95%CI:0.84-2.15, P=0.22).

Conclusion: FOLR1 was up-regulated in both serum and cancer tissue of cervical squamous cell carcinoma which may act as diagnostic and prognostic maker for cervical squamous cell cancer.

Targeted Gene Delivery Therapies for Cervical Cancer

Despite being largely preventable through early vaccination and screening strategies, cervical cancer is the most common type of gynecological malignancy worldwide and constitutes one of the leading causes of cancer deaths in women. Patients with advanced or recurrent disease have a very poor prognosis; hence, novel therapeutic modalities to improve clinical outcomes in cervical malignancy are needed. In this regard, targeted gene delivery therapy is presented as a promising approach, which leads to the development of multiple strategies focused on different aspects. These range from altered gene restoration, immune system potentiation, and oncolytic virotherapy to the use of nanotechnology and the design of improved and enhanced gene delivery systems, among others. In the present manuscript, we review the current progress made in targeted gene delivery therapy for cervical cancer, the advantages and drawbacks and their clinical application. At present, multiple targeted gene delivery systems have been reported with encouraging preclinical results. However, the translation to humans has not yet shown a significant clinical benefit due principally to the lack of efficient vectors. Real efforts are being made to develop new gene delivery systems, to improve tumor targeting and to minimize toxicity in normal tissues.

Metastatic Inhibitory and Radical Scavenging Efficacies of Saponins Extracted from the Brittle Star (Ophiocoma erinaceus)

Echinodermata use saponins in chemical defense against pathogens and predators. The molecular mechanisms of antimetastatic effects of brittle star saponins are still unknown. The present study examined antioxidant capacity and invasive ability in HeLa carcinoma cells exposed to brittle star crude saponins. Discolorating methods with DPPH and ABTS and expression of SOD-2 with RT-PCR were used to estimate the antioxidant activity. The anti-invasive activity of extracted saponins was examined through adhesion of HeLa cells to extracellular matrix, wound healing and evaluation of the mRNA levels of MMP-2 and MMP-9 by real time-PCR. The results showed that extracted saponins had cytotoxicity against cervical cancer cells and ABTS and DPPH scavenging properties with IC50 values of 604.5, 1012 μg/ml, respectively. Further, we found that, in wound healing assay, brittle star saponins could prevent invasion of HeLa cells in a concentration dependent manner. Furthermore, cell adhesion assay demonstrated blockage of cell attachment to extracellular matrix with an IC50 concentration of 16.1μg/ml. The significant dose dependent down regulation of MMP-2 and MMP-9 in treated cells demonstrated that isolated saponins can decline tumor metastasis in vitro. The brittle star saponins remarkably prevented cervical cancer invasion and migration associated with down regulation of matrix metalloproteinase expression. Therefore, saponins could be suggested as an anti-invasive candidate against cervical cancer and an antioxidant as well.

PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells

TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53‐null and p53‐mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo‐like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up‐regulated by cisplatin. PLK2‐phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up‐regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73‐enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.

Consensus reference gene(s) for gene expression studies in human cancers: end of the tunnel visible?

BACKGROUND

Gene expression studies are increasingly used to provide valuable information on the diagnosis and prognosis of human cancers. Also, for in vitro and in vivo experimental cancer models gene expression studies are widely used. The complex algorithms of differential gene expression analyses require normalization of data against a reference or normalizer gene, or a set of such genes. For this purpose, mostly invariant housekeeping genes are used. Unfortunately, however, there are no consensus (housekeeping) genes that serve as reference or normalizer for different human cancers. In fact, scientists have employed a wide range of reference genes across different types of cancer for normalization of gene expression data. As a consequence, comparisons of these data and/or data harmonizations are difficult to perform and challenging. In addition, an inadequate choice for a reference gene may obscure genuine changes and/or result in erroneous gene expression data comparisons.

METHODS

In our effort to highlight the importance of selecting the most appropriate reference gene(s), we have screened the literature for gene expression studies published since the turn of the century on thirteen of the most prevalent human cancers worldwide.

CONCLUSIONS

Based on the analysis of the data at hand, we firstly recommend that in each study the suitability of candidate reference gene(s) should carefully be evaluated in order to yield reliable differential gene expression data. Secondly, we recommend that a combination of PPIA and either GAPDH, ACTB, HPRT and TBP, or appropriate combinations of two or three of these genes, should be employed in future studies, to ensure that results from different studies on different human cancers can be harmonized. This approach will ultimately increase the depth of our understanding of gene expression signatures across human cancers.