Folic acid induces cell type-specific changes in the transcriptome of breast cancer cell lines: a proof-of-concept study

The Role of Folic Acid in DNA Methylation and Breast Cancer

Folate and folic acid (FA) are two forms of vitamin B9, a B-complex nutrient essential for the human body. Folate is the natural form of vitamin B9 and is found in foods such as citrus fruits, leafy green vegetables, and beans. In contrast, FA is the synthetic form and is commonly found in supplements and added to fortified foods. The metabolism of folate and FA plays a crucial role in DNA synthesis and methylation; therefore, understanding the mechanism through which a decrease in folate and FA consumption affects the development of breast cancer (BC) is important. DNA hypermethylation can inhibit the transcription of tumor suppressor genes, while DNA hypomethylation may have the same effect and activate oncogene transcription. However, some genetic variants exist, such as rs1801133 and rs1801131 in the MTHFR gene and rs1051266 in the RFC gene. The MTHFR gene encodes an enzyme that facilitates the utilization of folate to support essential bodily functions, while the RFC gene is responsible for transporting folate into cells and acts as an anion exchanger. Both genes intervene in the transport and absorption of FA and are related to an increased risk of cancer. Studies investigating the relationship between FA and BC often rely on in vitro and in vivo models; however, the findings may not fully translate to humans due to significant physiological and metabolic differences across species. This article explores how changes in FA metabolism due to malabsorption defects, a deficient diet or genetic variants may impact methylation processes and their relationship with BC.

Folate-assisted targeted photocytotoxicity of red-light-activable iron(III) complex co-functionalized gold nanoconjugates (Fe@FA-AuNPs) against HeLa and triple-negative MDA-MB-231 cancer cells

Photo-redox chemistry resulting from ligand to metal charge transfer in red-light-activable iron(III) complexes could be a potent strategic tool for next-generation photochemotherapeutic applications. Herein, we developed an iron(III) complex and folate co-functionalized gold nanoconjugate (Fe@FA-AuNPs) and thoroughly characterized it with NMR, ESI MS, UV-visible, EPR, EDX, XPS, powder X-ray diffraction, TEM and DLS studies. There was a remarkable shift in the SPR band of AuNPs to 680 nm, and singlet oxygen (1O2) and hydroxyl radicals were potently generated upon red-light activation, which were probed by UV-visible and EPR spectroscopic assays. Cellular uptake studies of the nanoconjugate (Fe@FA-AuNPs) revealed significantly higher uptake in folate(+) cancer cells (HeLa and MDA-MB-231) than folate(-) (A549) cancer cells or normal cells (HPL1D), indicating the targeting potential of the nanoconjugate. Confocal imaging indicated primarily mitochondrial localization. The IC50 values of the nanoconjugate determined from a cell viability assay in HeLa, MDA-MB-231, and A549 cells were 27.83, 39.91, and 69.54 μg mL-1, respectively in red light, while in the dark the values were >200 μg mL-1; the photocytotoxicity was correlated with the cellular uptake of the nanoconjugate. The nanocomposite exhibited similar photocytotoxicity (IC50 in red light, 37.35 ± 8.29 μg mL-1 and IC50 in the dark, >200 μg mL-1). Mechanistic studies revealed that intracellular generation of ROS upon red-light activation led to apoptosis in HeLa cells. Scratch-wound-healing assays indicated the inhibition of the migration of MDA-MB-231 cells treated with the nanoconjugate and upon photo-activation. Overall, the nanoconjugate has emerged as a potent tool for next-generation photo-chemotherapeutics in the clinical arena of targeted cancer therapy.

Folate-depletion alters mouse trophoblast stem cell regulation in vitro

Maternal folate deficiency increases risk of congenital malformations, yet its effect on placenta development is unclear. Here, we investigated how folate-depleted culture medium affects the developmental potential of mouse trophoblast stem cells (TSCs). When cultured in stem cell conditions, TSC viability was unaffected by folate depletion, but ectopic differentiation of trophoblast cell subtypes occurred. When cultured in conditions that promote differentiation, folate-depleted TSCs were driven towards a syncytiotrophoblast cell fate potentially at the expense of other lineages. Additionally, trophoblast giant cell nuclei were small implicating folate in the regulation of endoreduplication. Therefore, dietary folate intake likely promotes trophoblast development.

Suboptimal folic acid exposure rewires oncogenic metabolism and proteomics signatures to mediate human breast cancer malignancy

Whether treatment with folic acid (FA) affects human breast cancer positively or negatively remains unclear. We subjected human MCF-7 cells, a human breast cancer cell line, to suboptimal FA at low levels (10 nM; LF) and high levels (50 μM; HF) and investigated the molecular mechanisms underlying their effects through metabolic flux and systematic proteomics analyses. The data indicated that LF induced and HF aggravated 2-fold higher mitochondrial toxicity in terms of suppressed oxidative respiration, increased fermented glycolysis, and enhanced anchorage-independent oncospheroid formation. Quantitative proteomics and Gene Ontology enrichment analysis were used to profile LF- and HF-altered proteins involved in metabolism, apoptosis, and malignancy pathways. Through STRING analysis, we identified a connection network between LF- and HF-altered proteins with mTOR. Rapamycin-induced blockage of mTOR complex 1 (mTORC1) signaling, which regulates metabolism, differentially inhibited LF- and HF-modulated protein signatures of mitochondrial NADH dehydrogenase ubiquinone flavoprotein 2, mitochondrial glutathione peroxidase 4, kynureninase, and alpha-crystallin B chain as well as programmed cell death 5 in transcript levels; it subsequently diminished apoptosis and oncospheroid formation in LF/HF-exposed cells. Taken together, our data indicate that suboptimal FA treatment rewired oncogenic metabolism and mTORC1-mediated proteomics signatures to promote breast cancer development.

Different Serum, Different Protein Corona! The Impact of the Serum Source on Cellular Targeting of Folic Acid-Modified Chitosan-Based Nanoparticles

The nanoparticle (NP) protein corona represents an interface between biological components and NPs, dictating their cellular interaction and biological fate. To assess the success of cellular targeting, NPs modified with targeting ligands are incubated with target cells in serum-free culture medium or in the presence of fetal bovine serum (FBS). In the former, the role of the corona is overlooked, and in the latter, the effects of a corona that does not represent the one forming in humans nor the respective disease state are considered. Via proteomic analysis, we demonstrate how the difference in the composition of FBS, sera from healthy human volunteers, and breast cancer patients (BrCr Pt) results in the formation of completely different protein coronas around the same NP. Successful in vitro targeting of breast cancer cells was only observed when NPs were incubated with target cells in the presence of BrCr Pt sera only. In such cases, the success of targeting was not attributed to the targeting ligand itself, but to the adsorption of specific serum proteins that facilitate NP uptake by cancer cells in the presence of BrCr Pt sera. This work therefore demonstrates how the serum source affects the reliability of in vitro experiments assessing NP-cell interactions and the consequent success or failure of active targeting and may in fact indicate an additional reason for the limited clinical success of drug targeting by NPs in cancer.

Folic Acid Treatment Directly Influences the Genetic and Epigenetic Regulation along with the Associated Cellular Maintenance Processes of HT-29 and SW480 Colorectal Cancer Cell Lines

Folic acid (FA) is a synthetic form of vitamin B9, generally used as a nutritional supplement and an adjunctive medication in cancer therapy. FA is involved in genetic and epigenetic regulation; therefore, it has a dual modulatory role in established neoplasms. We aimed to investigate the effect of short-term (72 h) FA supplementation on colorectal cancer; hence, HT-29 and SW480 cells were exposed to different FA concentrations (0, 100, 10,000 ng/mL). HT-29 cell proliferation and viability levels elevated after 100 ng/mL but decreased for 10,000 ng/mL FA. Additionally, a significant (p ≤ 0.05) improvement of genomic stability was detected in HT-29 cells with micronucleus scoring and comet assay. Conversely, the FA treatment did not alter these parameters in SW480 samples. RRBS results highlighted that DNA methylation changes were bidirectional in both cells, mainly affecting carcinogenesis-related pathways. Based on the microarray analysis, promoter methylation status was in accordance with FA-induced expression alterations of 27 genes. Our study demonstrates that the FA effect was highly dependent on the cell type, which can be attributed to the distinct molecular background and the different expression of proliferation- and DNA-repair-associated genes (YWHAZ, HES1, STAT3, CCL2). Moreover, new aspects of FA-regulated DNA methylation and consecutive gene expression were revealed.

Tumor suppression via diverting intracellular sialylation with multifunctional nanoparticles

Sialylation plays an important role in tumor-related physiological processes. Therefore, intervention of sialylation has great potential to explore new paths for tumor therapy. In view of the immune modulation of sialic acid (SA) on tumors, this work designs a multifunctional mesoporous silica nanoparticle (MFMSN) to divert intracellular sialylation for tumor suppression. The galactose groups covered on MFMSN act as sialylation substrates to bind intracellular SAs competitively, which inhibits the SA expression on the tumor cell surface. The diverted intracellular sialylation can be visualized on living cells and in vivo by specifically binding the sialylated galactose with a phenylboronic acid labeled ssDNA probe released from the pore of MFMSN to induce DNA strand displacement, which recovers the fluorescence of the dsDNA probe covered on MFMSN surface. The diverting of sialylation efficiently suppresses tumor growth in mice, demonstrating the great potential of the designed strategy for revealing SA-related biological processes and clinical cancer therapy.

Multifunctional nanoparticles are designed to divert intracellular sialylation, which can suppress tumor growth and be visualized.

In Vivo Efficacy and Toxicity of Curcumin Nanoparticles in Breast Cancer Treatment: A Systematic Review

Breast cancer is one of the most prevalent types of malignant tumors in the world, resulting in a high incidence of death. The development of new molecules and technologies aiming to apply more effective and safer therapy strategies has been intensively explored to overcome this situation. The association of nanoparticles with known antitumor compounds (including plant-derived molecules such as curcumin) has been considered an effective approach to enhance tumor growth suppression and reduce adverse effects. Therefore, the objective of this systematic review was to summarize published data regarding evaluations about efficacy and toxicity of curcumin nanoparticles (Cur-NPs) in in vivo models of breast cancer. The search was carried out in the databases: CINAHL, Cochrane, LILACS, Embase, FSTA, MEDLINE, ProQuest, BSV regional portal, PubMed, ScienceDirect, Scopus, and Web of Science. Studies that evaluated tumor growth in in vivo models of breast cancer and showed outcomes related to Cur-NP treatment (without association with other antitumor molecules) were included. Of the 528 initially gathered studies, 26 met the inclusion criteria. These studies showed that a wide variety of NP platforms have been used to deliver curcumin (e.g., micelles, polymeric, lipid-based, metallic). Attachment of poly(ethylene glycol) chains (PEG) and active targeting moieties were also evaluated. Cur-NPs significantly reduced tumor volume/weight, inhibited cancer cell proliferation, and increased tumor apoptosis and necrosis. Decreases in cancer stem cell population and angiogenesis were also reported. All the studies that evaluated toxicity considered Cur-NP treatment to be safe regarding hematological/biochemical markers, damage to major organs, and/or weight loss. These effects were observed in different in vivo models of breast cancer (e.g., estrogen receptor-positive, triple-negative, chemically induced) showing better outcomes when compared to treatments with free curcumin or negative controls. This systematic review supports the proposal that Cur-NP is an effective and safe therapeutic approach in in vivo models of breast cancer, reinforcing the currently available evidence that it should be further analyzed in clinical trials for breast cancer treatments.

SLC46A1 Haplotype with Predicted Functional Impact has Prognostic Value in Breast Carcinoma

BACKGROUND AND OBJECTIVE

Membrane solute carrier transporters play an important role in the transport of a wide spectrum of substrates including anticancer drugs and cancer-related physiological substrates. This study aimed to assess the prognostic relevance of gene expression and genetic variability of selected solute carrier transporters in breast cancer.

METHODS

Gene expression was determined by quantitative real-time polymerase chain reaction. All SLC46A1 and SLCO1A2 exons and surrounding non-coding sequences in DNA extracted from the blood of patients with breast cancer (exploratory phase) were analyzed by next-generation sequencing technology. Common variants (minor allele frequency ≥ 5%) with in silico-predicted functional relevance were further analyzed in a large cohort of patients with breast cancer (n = 815) and their prognostic and predictive potential was estimated (validation phase).

RESULTS

A gene expression and bioinformatics analysis suggested SLC46A1 and SLCO1A2 to play a putative role in the prognosis of patients with breast cancer. In total, 135 genetic variants (20 novel) were identified in both genes in the exploratory phase. Of these variants, 130 were non-coding, three missense, and two synonymous. One common variant in SLCO1A2 and four variants in SLC46A1 were predicted to be pathogenic by in silico programs and subsequently validated. A SLC46A1 haplotype block composed of rs2239911-rs2239910-rs8079943 was significantly associated with ERBB2/HER2 status and disease-free survival of hormonally treated patients.

CONCLUSIONS

This study revealed the prognostic value of a SLC46A1 haplotype block for breast cancer that should be further studied.

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 β‐CyD (Fol‐c₁‐β‐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‐β‐CyD (PTX/Fol‐c₁‐β‐CyD) in EOC‐derived cell lines. We found that PTX/Fol‐c₁‐β‐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‐β‐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‐β‐CyD in FRα‐expressing SK‐OV‐3 cells. Furthermore, the cytotoxicity of PTX/Fol‐c₁‐β‐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‐β‐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‐β‐CyD targets not only FRα but also PCFT, and can efficiently deliver anticancer drugs to EOC cells in the peritoneal cavity.

Transgelin Silencing Induces Different Processes in Different Breast Cancer Cell Lines

Transgelin is a protein reported to be a marker of several cancers. However, previous studies have shown both up- and down-regulation of transgelin in tumors when compared with non-tumor tissues and the mechanisms whereby transgelin may affect the development of cancer remain largely unknown. Transgelin is especially abundant in smooth muscle cells and is associated with actin stress fibers. These contractile structures participate in cell motility, adhesion, and the maintenance of cell morphology. Here, the role of transgelin in breast cancer is focused on. Initially, the effects of transgelin on cell migration of the breast cancer cell lines, BT 549 and PMC 42, is studied. Interestingly, transgelin silencing increased the migration of PMC 42 cells, but decreased the migration of BT 549 cells. To clarify these contradictory results, the changes in protein abundances after transgelin silencing in these two cell lines are analyzed using quantitative proteomics. The results confirmed the role of transgelin in the migration of BT 549 cells and suggest the involvement of transgelin in apoptosis and small molecule biochemistry in PMC 42 cells. The context-dependent function of transgelin reflects the different molecular backgrounds of these cell lines, which differ in karyotypes, mutation statuses, and proteome profiles.

Ultrabright fluorescent silica nanoparticles for in vivo targeting of xenografted human tumors and cancer cells in zebrafish

New ultrabright fluorescent silica nanoparticles capable of the fast targeting of epithelial tumors in vivo are presented. The as-synthesized folate-functionalized ultrabright particles of 30-40 nm are 230 times brighter than quantum dots (QD450) and 50% brighter than the polymer dots with similar spectra (excitation 365 nm and emission 486 nm). To decrease non-specific targeting, particles are coated with polyethylene glycol (PEG). We demonstrate the in vivo targeting of xenographic human cervical epithelial tumors (HeLa cells) using zebrafish as a model system. The particles target tumors (and probably even individual HeLa cells) as small as 10-20 microns within 20-30 minutes after blood injection. To demonstrate the advantages of ultrabrightness, we repeated the experiments with similar but 200× less bright particles. Compared to those, ultrabright particles showed ∼3× faster tumor detection and ∼2× higher relative fluorescent contrast of tumors/cancer cells.

Oral findings and its association with prenatal and perinatal factors in newborns

Purpose

This study aimed to determine the frequency of abnormalities in the newborn oral cavity and to evaluate the association with prenatal and perinatal factors.

Methods

This cross-sectional study evaluated 2,216 newborns. Oral findings were assessed in the first 24 hours of life using visual examination. Sex, weight, length, gestational age, and medical disorders at birth were recorded. Maternal demographic and medical information was also obtained.

Results

The most common oral findings were Bohn’s nodules, Epstein’s pearls, and dental lamina cysts. Other intraoral findings included odontogenic cysts, ankyloglossia, and natal teeth, among others. In logistic regression analyses, folic acid consumption during pregnancy was significantly associated with Bohn’s nodules (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.23–2.55; P=0.002), Epstein’s pearls (OR, 1.63; 95% CI, 1.14–2.33; P=0.007), and dental lamina cysts (OR, 1.45; 95% CI, 1.02–2.05; P=0.038). Moreover, preterm births were negatively associated with prevalence of Bohn’s nodules (OR, 0.63; 95% CI, 0.50–0.80; P≤0.0001). Comparison between newborns with and without oral inclusion cysts showed that maternal folic acid and iron intake were significantly different (P<0.05).

Conclusion

Maternal folic acid and iron intake were associated with the prevalence of oral inclusion cysts.

Genetic screening and functional analysis of CASP9 mutations in a Chinese cohort with neural tube defects

AIM

Neural tube defects (NTDs) are birth defects of the nervous system and are the second most frequent cause of birth defects worldwide. The etiology of NTDs is complicated and involves both genetic and environmental factors. CASP9 is an initiator caspase in the intrinsic apoptosis pathway, which in Casp9^-/- mice has been shown to result in NTDs because of decreased apoptosis. The aim of this study was to evaluate the potential genetic contribution of the CASP9 gene in human NTDs.

METHODS

High-throughput sequencing was performed to screen genetic variants of CASP9 genes in 355 NTD cases and 225 matched controls. Apoptosis-relevant assays were performed on transiently transfected E9 neuroepithelial cells or human embryonic kidney 293T cells, to determine the functional characteristics of NTD-specific rare variants under complete or low folic acid (FA) status.

RESULTS

We found significant expression of CASP9 rare variants in NTDs and identified 4 NTD-specific missense variants. Functional assays demonstrated that a p.Y251C variant attenuates apoptosis by reducing CASP9 protein expression and decreasing activity of the intrinsic apoptosis pathway. From this, we conclude that this variant may represent a loss-of-function mutation. A 4-time recurrent p.R191G variant did not affect intrinsic apoptosis in complete medium, while it completely inhibited apoptosis induced by low FA medium.

CONCLUSION

Our findings identify a genetic link for apoptosis in human NTDs and highlight the effect of gene-environment interactions in a complex disease.

Finding the genetic mechanisms of folate deficiency and neural tube defects-Leaving no stone unturned

Neural tube defects (NTDs) occur secondary to failed closure of the neural tube between the third and fourth weeks of gestation. The worldwide incidence ranges from 0.3 to 200 per 10,000 births with the United States of American NTD incidence at around 3-6.3 per 10,000 dependent on race and socioeconomic background. Human NTD incidence has fallen by 35-50% in North America due to mandatory folic acid fortification of enriched cereal grain products since 1998. The US Food and Drug Administration has approved the folic acid fortification of corn masa flour with the goal to further reduce the incidence of NTDs, especially among individuals who are Hispanic. However, the genetic mechanisms determining who will benefit most from folate enrichment of the diet remains unclear despite volumes of literature published on studies of association of genes with functions related to folate metabolism and risk of human NTDs. The advances in omics technologies provides hypothesis-free tools to interrogate every single gene within the genome of NTD affected individuals to discover pathogenic variants and methylation targets throughout the affected genome. By identifying genes with expression regulated by presence of folate through transcriptome profiling studies, the genetic mechanisms leading to human NTDs due to folate deficiency may begin to be more efficiently revealed.