Folic acid inhibits COLO-205 colon cancer cell proliferation through activating the FRα/c-SRC/ERK1/2/NFκB/TP53 pathway: in vitro and in vivo studies

Role of gonadally synthesized steroid hormones in the colorectal cancer microenvironment

Objective

To understand the relationship between steroid hormones synthesized by the gonads and colorectal cancer as well as its tumor microenvironment, in the expectation of providing new ideas in order to detect and treat colorectal cancer.

Methods

Through reviewing the relevant literature at home and abroad, we summarized that androgens promote the growth of colorectal cancer, and estrogens and progesterone help prevent bowel cancer from developing; these three hormones also have a relevant role in the cellular and other non-cellular components of the tumor microenvironment of colorectal cancer.

Conclusion

The current literature suggests that androgens, estrogens, and progesterone are valuable in diagnosing and treating colorectal cancer, and that androgens promote the growth of colorectal cancer whereas estrogens and progesterone inhibit colorectal cancer, and that, in addition, the receptors associated with them are implicated in the modulation of a variety of cellular components of the microenvironment of colorectal cancer.

Uncovering the Hidden Dangers and Molecular Mechanisms of Excess Folate: A Narrative Review

This review delves into the intricate relationship between excess folate (vitamin B9) intake, especially its synthetic form, namely, folic acid, and its implications on health and disease. While folate plays a pivotal role in the one-carbon cycle, which is essential for DNA synthesis, repair, and methylation, concerns arise about its excessive intake. The literature underscores potential deleterious effects, such as an increased risk of carcinogenesis; disruption in DNA methylation; and impacts on embryogenesis, pregnancy outcomes, neurodevelopment, and disease risk. Notably, these consequences stretch beyond the immediate effects, potentially influencing future generations through epigenetic reprogramming. The molecular mechanisms underlying these effects were examined, including altered one-carbon metabolism, the accumulation of unmetabolized folic acid, vitamin-B12-dependent mechanisms, altered methylation patterns, and interactions with critical receptors and signaling pathways. Furthermore, differences in the effects and mechanisms mediated by folic acid compared with natural folate are highlighted. Given the widespread folic acid supplementation, it is imperative to further research its optimal intake levels and the molecular pathways impacted by its excessive intake, ensuring the health and well-being of the global population.

Activation of progesterone receptor is essential for folic acid-regulated cancer cell proliferation and migration

We previously demonstrated that activation of progesterone receptor (PR) is essential for folic acid (FA)-inhibited proliferation in colorectal cancer cell lines. In the present study, we further investigated whether the requirement of PR activation for the FA-regulated cell proliferation and migration is a general phenomenon for all cancer cell lines or specific for colorectal cancer cell lines only. Initially, we examined the expression of PR in various cancer cell lines using Western blot analyses and RT-PCR technique, and then investigated the effects of FA on these cancer cell lines. Our data showed that the effects of FA on proliferation and migration only occurred in the PR positive (+) cancer cell lines, but not the PR negative (-) cancer cell lines, and these effects were abolished by pre-treatment with the PR specific inhibitor, Org 31710. On the other hand, FA significantly reduced the proliferation and migration in the PR (-) cancer cell lines transfected with PR pcDNA. However, FA did not significantly affect the proliferation and migration in the PR-transefected Hep-3B cell line, which does not express endogenous PR and FA receptor (FR). Since we previously showed that FA-regulated proliferation in colorectal and breast cancer cell lines through the cSrc-mediated pathway, we conducted immunoprecipitation assay to demonstrate that PR formed a complex with FR and cSrc, but FR did not directly associate with cSrc. Taken together, these findings suggest that the requirement of PR activation for the FA-regulated cell proliferation and migration is a general phenomenon for all cancer cell lines.

Evaluation of colorectal cancer liver metastases based on liquid biopsy combined with folate receptor– Positive circulating tumor cells and HSP90

Objective

Liver metastasis of colorectal cancer (LMCRC) is a major cause of cancer-related deaths worldwide. We can reduce the mortality rate by discerning the risk of liver metastases in patients with colorectal cancer at an early stage. Hence, we combined the use of folate receptor (FR)–labeled circulating tumor cells (FR+CTCs) and the metastasis-related marker, heat shock protein 90 (HSP90), to screen patients with colorectal cancer and explore the prognostic factors of patients with high expression of FR+CTC and HSP90.

Patients and methods

A retrospective study of 356 patients with measurable colorectal cancer was performed. Negative enrichment and FR-targeted fluorescence quantitative PCR was utilized to detect FR+CTC. An ELISA kit was used to detect HSP90 expression. A timely follow-up study of patients with colorectal cancer was made.

Results

Colorectal patients with liver metastases showed high expression of FR+CTCs and HSP90. The diagnostic ability of the combined receiver operating characteristic curve of FR+CTC and HSP90 (area under the curve [AUC]=0.79, sensitivity 70.55%, specificity 92.66%) was significantly greater than that of a single index. The results of timely follow-up of patients showed that the high expression of FR+CTC significantly shortened the median disease-free survival (mDFS) of 36.5 months (95% confidence interval [CI]: 14.13–58.87, Logrank p < 0.0001) compared with the low expression cohort. The mDFS of the HSP90 high-expression cohort was significantly higher than that of the low-expression cohort (Logrank p = 0.0002), mDFS=58.47 months (95% CI: 37.12–79.81, Logrank p < 0.0001). We performed univariate and multivariate analyses to show that FR+CTC and HSP90 were risk factors for the progression of metastatic colorectal cancer (MCRC) disease. We then constructed a high- and low-risk score model of risk factors to evaluate MCRC. The diagnostic sensitivity of the risk model for MCRC was significantly improved (AUC=0.89, sensitivity 85.29%, specificity 81.33%), and the mDFS of patients in a high-risk group increased to 33.28 months (95% CI: 27.24–39.31, Logrank p < 0.0001). The establishment of the model improves the early screening of patients with MCRC.

Conclusion

Patients with colorectal cancer and high expression of FR+CTC and HSP90 are at risk of liver metastasis and this suggests a poor prognosis. Combining the two markers can improve the early screening and diagnosis of LMCRC patients. In addition, combining a multivariate risk model can further assist patients in appropriate stratification and the design of tailored treatment regimens. However, further validation these markers is needed before their routine clinical application.

The efficacy of chemopreventive agents on the incidence of colorectal adenomas: A systematic review and network meta-analysis

Colorectal cancer (CRC) is the fourth most common cancer and third leading cause of cancer-related death worldwide. Use of chemopreventive agents (CPAs) to reduce the incidence of precursor colorectal adenomas could lower the future burden of CRC. Many classes of potential CPAs have been investigated. To identify the most effective CPAs, we conducted a systematic review and a network meta-analysis (NMA). An electronic search was performed through August 2020 to identify all randomized controlled trials (RCTs) assessing the efficacy of CPAs in reducing the incidence of colorectal adenomas at the time of surveillance colonoscopy among patients who had previously undergone polypectomy during an index colonoscopy. In total, 33 RCTs were included in the NMA, which was conducted under a Bayesian inference framework. Random effects models were used with adjustment for follow-up length and control group event rates to yield relative risks (RRs) and 95% credible intervals (CrIs). Our full network consisted of 13 interventions in addition to a placebo arm. Of 20,925 included patients, 7766 had an adenoma. Compared to placebo, the combination of difluoromethylornithine (DFMO) + Sulindac (RR 0.24, CrI 0.10-0.55) demonstrated a protective effect, while aspirin had a RR of 0.77 (CrI 0.60-1.00), celecoxib 800 mg had a RR of 0.56 (CrI 0.31-1.01) and metformin had a RR of 0.56 (CrI 0.22-1.39). Our results suggest that select CPAs may be efficacious in preventing the development of adenomas. Further studies are needed to identify those patients most likely to benefit and the minimum effective dosages of CPAs.

Folic acid supplementation during pregnancy modulates hepatic methyl metabolism and genes expression profile of neonatal lambs of different litter sizes

Maternal folic acid (FA) plays an important role in the fetus development, but it is unknown the response of hepatic metabolism in the offspring from different litter sizes to maternal FA supplementation. In the present study, this was done by feeding the ewes with 0, 16 and 32 mg/(kg·DM) FA supplemented diet during pregnancy and analysing the hepatic one-carbon metabolism-related indices and gene expression in the neonatal lambs of different litter sizes (twins, TW; triplets, TR). Regardless of litter sizes, the concentrations of folate, methionine, S-adenosylmethionine and DNA methyltransferase increased significantly, but homocysteine and S-adenosylhomocysteine decreased in the liver of newborn lambs from ewes whose diet was supplemented with FA. In TW, maternal FA status has little effect on hepatic genes expression profile of newborn lambs, and no significant enriched pathway was found. However, DEG involved in cell proliferation such as CCNA2, CCNB2, CCNE2, CDK1 and BUB1 were significantly enriched when the ewes were supplemented with FA in TR groups. In addition, nucleotide synthesis-related genes such as POLD1, POLD2, MCM4 and MCM5 were enriched markedly in DNA replication and pyrimidine metabolism pathways in triplets when a higher FA ingestion [32 mg/(kg·DM)] was implemented in ewes. This finding demonstrated that the hepatic methyl metabolism in TW and TR newborn lambs was regulated by maternal FA status. The hepatic cell proliferation and nucleotide metabolism related genes in TR were more susceptible to maternal dietary FA supplementation during pregnancy.

Integration of Network Pharmacology and Molecular Docking Technology Reveals the Mechanism of the Therapeutic Effect of Xixin Decoction on Alzheimer's Disease

BACKGROUND

So far, only a few researchers have systematically analyzed the constituents of the traditional Chinese medicine prescription Xixin Decoction (XXD) and its potential mechanism of action in treating Alzheimer's disease (AD). This study aimed to explore the potential mechanism of XXD in the treatment of AD using network pharmacology and molecular docking.

METHODS

The compounds of XXD were searched within the Traditional Chinese Medicine System Pharmacology Database (TCMSP) and the Traditional Chinese Medicine Integrated Database (TCMID) databases. Overlapping AD-related targets obtained from the two databases and the predicted targets of XXD obtained from SwissTargetPrediction platform were imported into the STRING database to build PPI networks including hub targets; Cytoscape software was used to construct the herb-compound-target network while its plug-in CytoNCA was used to screen the main active compounds of XXD. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses explored the core biological mechanism and pathways via the Metascape platform. In addition, we used AutoDock Vina and PyMOL software to investigate the molecular docking of main compounds to hub targets.

RESULTS

We determined 114 active compounds, 973 drug targets, and 973 disease targets. However, intersection analysis screened out 208 shared targets.Protein-protein interaction (PPI) network identified 9 hub targets. The hub targets were found to be majorly enriched in several biological processes (positive regulation of kinase activity, positive regulation of cell death, regulation of MAPK cascade, trans-synaptic signaling, synaptic signaling, etc.) and the relevant pathways of Alzheimer's disease, including neuroactive ligand-receptor interaction, dopaminergic synapse, serotonergic synapse, and the MAPK signaling pathway, etc. The pathway-target-compound network of XXD for treating AD was then constructed. 8 hub targets exhibited good binding activity with 9 main active compounds of XXD in molecular docking.

CONCLUSION

In this study, we found multi-compound-multi-target-multi-pathway regulation to reveal the mechanism of XXD for treating AD based on network pharmacology and molecular docking. XXD may play a therapeutic role through regulating the Alzheimer's disease pathway, its downstream PI3K/Akt signaling pathway or the MAPK signaling pathway, thereby treating AD. This provides new insights for further experiments on the pharmacological effects of XXD.

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

Simple Summary

Folic acid (FA) participates in DNA synthesis and in DNA methylation; hence, it has a dual role in established neoplasms. We aimed to observe this phenomenon on FA-treated colorectal cancer cell lines (HT-29, SW480). Our results demonstrated that the maintenance processes, namely cell proliferation, cell viability, and DNA repair, were altered in HT-29 cells for short-term FA supplementation, while genetic and epigenetic regulations of SW480 cells were also affected. Despite the fact that FA is a precursor molecule in methyl donor formation, DNA methylation alterations were observed in both directions, primarily influencing the pathways of carcinogenesis. Moreover, behind the great number of differentially expressed genes, other FA-related effects than promoter methylation were suspected. All of our results point beyond the attributes related to FA so far. The different response of the two cell lines is worth considering in clinical practice to facilitate the effectiveness of therapy in the case of tumor heterogeneity.

Abstract

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.

Emerging roles for folate receptor FOLR1 in signaling and cancer

Folates are B vitamins that function in one-carbon metabolism. Folate receptors are one of three major types of folate transporters. The folate receptors FOLR1 and FOLR2 are overexpressed in multiple cancers. The overexpression of FOLR1 is often associated with increased cancer progression and poor patient prognosis. There is emerging evidence that FOLR1 is involved in signaling pathways that are independent of one-carbon metabolism. Recent publications implicate a direct role of FOLR1 in three signaling pathways: JAK-STAT3, ERK1/2, and as a transcription factor. Six other signaling pathways have been proposed to include FOLR1, but these currently lack sufficient data to infer a direct signaling role for FOLR1. We discuss the data that support noncanonical roles for FOLR1, and its limitations.

Perspective: The High-Folate-Low-Vitamin B-12 Interaction Is a Novel Cause of Vitamin B-12 Depletion with a Specific Etiology-A Hypothesis

Vitamin B-12 is a water-soluble vitamin that plays important roles in intermediary metabolism. Vitamin B-12 deficiency has many identifiable causes, including autoimmune and other gastrointestinal malabsorption disorders, dietary deficiency, and congenital defects in genes that are involved in vitamin B-12 trafficking and functions. Another putative cause of vitamin B-12 deficiency is the high-folate-low vitamin B-12 interaction, first suspected as the cause for observed relapse and exacerbation of the neurological symptoms in patients with pernicious anemia who were prescribed high oral doses of folic acid. We propose that this interaction is real and represents a novel cause of vitamin B-12 depletion with specific etiology. We hypothesize that excessive intake of folic acid depletes serum holotranscobalamin (holoTC), thereby decreasing active vitamin B-12 in the circulation and limiting its availability for tissues. This effect is specific for holoTC and does not affect holohaptocorrin, the inert form of serum vitamin B-12. Depletion of holoTC by folic acid in individuals with already low vitamin B-12 status further compromises the availability of vitamin B-12 coenzymes to their respective enzymes, and consequently a more pronounced state of biochemical deficiency. This hypothesis is drawn from evidence of observational and intervention studies of vitamin B-12-deficient patients and epidemiological cohorts. The evidence also suggests that, in a depleted state, vitamin B-12 is diverted to the hematopoietic system or the kidney. This most likely reflects a selective response of tissues expressing folate receptors with high affinity for unmetabolized folic acid (UMFA; e.g., hematopoietic progenitors and renal tubules) compared with those tissues (e.g., liver) that only express the reduced folate carrier, which is universally expressed but has poor affinity for UMFA. The biochemical and physiological mechanisms underlying this interaction require elucidation to clarify its potential public health significance.

Folic Acid-Functionalized Nanomedicine: Folic Acid Conjugated Copolymer and Folate Receptor Interactions Disrupt Receptor Functionality Resulting in Dual Therapeutic Anti-Cancer Potential in Breast and Prostate Cancer

We have previously reported on a functionalized folic acid (FA) conjugated poly(styrene-alt-maleic anhydride) (SMA) via biological linker 2,4-diaminobutyric acid (DABA) (FA-DABA-SMA) copolymer. This biocompatible nanocopolymer self-assembles in a pH-dependent manner, providing stimuli responsiveness, active targeting, and extended release of hydrophobic chemotherapeutic agents and effectively penetrates the inner core of 3-dimensional cancer spheroid models. The empty FA-DABA-SMA decreased tumor spheroid volume, revealing a previously unknown mechanism of action. Here, we investigated the potential mechanism of the small (20 kDa) and large (350 kDa) FA-DABA-SMA empty copolymers affecting the folic acid receptor alpha (FRα) signaling properties in breast and prostate cancer cell lines. Microscopic imaging, immunocytochemistry, flow cytometry, Caspase 3/7 apoptosis assays, Incucyte live cell tracking, the scratch wound assay, the water-soluble tetrazolium salt-1 (WST-1) cell viability assay, morphologic changes, and Western blot for the expression levels of FRα on the cell surface were used on MDA MB-231 and MCF-7 breast and DU-145 prostate cancer cell lines. The findings indicate that FA-DABA-SMA increases FRα expression levels in breast MDA MB-231 cancer cells and then disrupts FR signaling by reducing HES1 and NOTCH1 protein expression levels. Also, FA-DABA-SMA induces apoptosis and further causes a change in the MDA MB-231 cells' morphology and significantly reduces their ability to migrate in a scratch wound assay. Collectively, these findings provide a novel insight into the functionalized FA-DABA-SMA copolymer. The 350 and 20 kDa copolymers actively target FRα to initialize internationalization. However, only the large size and sheet-shaped 350 kDa copolymers disrupt FRα signaling. The significance of these novel findings reveals that the copolymer's intracellular activity is critically dependent on the size and structural shape. This report offers novel therapeutic insight into a dual mechanism of the FA-DABA-SMA copolymer for its therapeutic potential to treat cancer.

Doxorubicin delivery by magnetic nanotheranostics enhances the cell death in chemoresistant colorectal cancer-derived cells

Colorectal cancer (CRC) is a major cause of cancer death with a high probability of treatment failure. Doxorubicin (DOXO) is an efficient antitumor drug; however, most CRC cells show resistance to its effects. Magnetic nanoparticles (MNPs) are potential cancer management tools that can serve as diagnostic agents and also can optimize and personalize treatments. This work aims to evaluate the aptitude of magnetic nanotheranostics composed of magnetite (Fe₃O₄) nanoparticles coated with folic acid intended to the sustained release of DOXO. The administration of DOXO by means of these MNPs resulted in the enhancement of cell death respect to the free drug administration. Chromatin compaction and cytoplasmic protrusions were observed. Mitochondrial transmembrane potential disruption and increased PARP protein cleavage confirmed apoptosis. The nanosystem was also tested as a vectoring tool by exposing it to the stimuli of a static magnetic field in vitro. CRC-related magnetic nanotechnology still remains in pre-clinical trials. In this context, this contribution expands the knowledge of the behavior of MNPs in contact with in vitro models and proposes the nanodevices studied here as potential theranostic agents for the monitoring of the progress of CRC and the evolution of its treatment.

Knowledge gaps in understanding the metabolic and clinical effects of excess folates/folic acid: a summary, and perspectives, from an NIH workshop

Folate, an essential nutrient found naturally in foods in a reduced form, is present in dietary supplements and fortified foods in an oxidized synthetic form (folic acid). There is widespread agreement that maintaining adequate folate status is critical to prevent diseases due to folate inadequacy (e.g., anemia, birth defects, and cancer). However, there are concerns of potential adverse effects of excess folic acid intake and/or elevated folate status, with the original concern focused on exacerbation of clinical effects of vitamin B-12 deficiency and its role in neurocognitive health. More recently, animal and observational studies have suggested potential adverse effects on cancer risk, birth outcomes, and other diseases. Observations indicating adverse effects from excess folic acid intake, elevated folate status, and unmetabolized folic acid (UMFA) remain inconclusive; the data do not provide the evidence needed to affect public health recommendations. Moreover, strong biological and mechanistic premises connecting elevated folic acid intake, UMFA, and/or high folate status to adverse health outcomes are lacking. However, the body of evidence on potential adverse health outcomes indicates the need for comprehensive research to clarify these issues and bridge knowledge gaps. Three key research questions encompass the additional research needed to establish whether high folic acid or total folate intake contributes to disease risk. 1) Does UMFA affect biological pathways leading to adverse health effects? 2) Does elevated folate status resulting from any form of folate intake affect vitamin B-12 function and its roles in sustaining health? 3) Does elevated folate intake, regardless of form, affect biological pathways leading to adverse health effects other than those linked to vitamin B-12 function? This article summarizes the proceedings of an August 2019 NIH expert workshop focused on addressing these research areas.

Regulation of Src Family Kinases during Colorectal Cancer Development and Its Clinical Implications

Src family kinases (SFKs) are non-receptor kinases that play a critical role in the pathogenesis of colorectal cancer (CRC). The expression and activity of SFKs are upregulated in patients with CRC. Activation of SFKs promotes CRC cell proliferation, metastases to other organs and chemoresistance, as well as the formation of cancer stem cells (CSCs). The enhanced expression level of Src is associated with decreased survival in patients with CRC. Src-mediated regulation of CRC progression involves various membrane receptors, modulators, and suppressors, which regulate Src activation and its downstream targets through various mechanisms. This review provides an overview of the current understanding of the correlations between Src and CRC progression, with a special focus on cancer cell proliferation, invasion, metastasis and chemoresistance, and formation of CSCs. Additionally, this review discusses preclinical and clinical strategies to improve the therapeutic efficacy of drugs targeting Src for treating patients with CRC.

Androgen receptor activation reduces the endothelial cell proliferation through activating the cSrc/AKT/p38/ERK/NFκB-mediated pathway

The effect of androgen on angiogenesis has been documented. However, its underlying molecular mechanisms have not been well illustrated. Here, we show that treatment with an androgen receptor (AR) agonist, metribolone (R1881; 0.05-5 nM), or dihydrotestosterone (DHT; 0.5-2 nM), concentration- and time-dependently inhibited proliferation in human umbilical venous endothelial cells (HUVEC). This inhibitory effect was confirmed in human microvascular endothelial cells (HMEC-1). Flow cytometric analysis demonstrated that R1881 induced G0/G1 phase cell cycle arrest in HUVEC. Blockade of the AR activity by pre-treatment with an AR antagonist, hydroxyflutamide (HF), or knockdown of AR expression using the shRNA technique abolished the R1881-induced HUVEC proliferation inhibition, suggesting that AR activation can inhibit endothelial cell proliferation. We further investigated the signaling pathway contributing to the proliferation inhibition induced by AR activation. Our data suggest that R1881 reduced the proliferation rate of HUVEC through activating the AR/cSrc/AKT/p38/ERK/NFκB pathway, subsequently up-regulating p53 expression, which in turn increased the levels of p21 and p27 protein, hence decreasing the activities of cyclin-dependent kinase 2 (CDK2) and CDK4, and finally reduced the cell proliferation rate. An extra-nuclear pathway involved in the proliferation inhibition induced by AR activation in vascular endothelial cells was confirmed by showing that membrane-impermeable testosterone-bovine serum albumin (BSA) treatment significantly increased the levels of p53, p27 and p21 protein and reduced cell proliferation. These data highlight the underlying molecular mechanisms by which AR activation induced proliferation inhibition in vascular endothelial cells.

The contribution of dietary and plasma folate and cobalamin to levels of angiopoietin-1, angiopoietin-2 and Tie-2 receptors depend on vascular endothelial growth factor status of primary breast cancer patients

The aim of this study was to determine the association of dietary folate and cobalamin with plasma levels of Angiopoietins (ANG), vascular endothelial growth factor-C (VEGF-C) and tyrosine kinase receptor-2 (Tie-2) of primary breast cancer patients. Women (n = 177), aged 30 to 75 years diagnosed with breast cancer were recruited from an ongoing case series study. Dietary intake of nutrients was estimated by using a validated food frequency questionnaire. Enzyme-linked immunosorbent assay was applied to measure biomarkers. MCF-7 cell cultures were supplemented with folic acid (0–40 μM) for 24 h to measure cell viability and fold change of expression by the real-time reverse transcriptase-polymerase chain reaction. Structural equation modeling was applied to analyze the structural relationships between the measured variables of nutrients and Angiopoietins. Dietary intake of folate and cobalamin showed a significant inverse correlation with plasma ANG-1 and ANG-2 (P < 0.05), particularly in subjects with estrogen-receptor positive tumors or low plasma VEGF-C. Plasma folate was positively associated with the ratio of ANG-1/ANG-2 (P < 0.05). Residual intake levels of total cobalamin were inversely associated with plasma ANG-1 when plasma stratum of VEGF-C was high (P < 0.05). Structural equation modeling identified a significant inverse contribution of folate profiles on the latent variable of Angiopoietins (coefficient β = −0.99, P < 0.05). Folic acid treatment resulted in dose-dependent down-regulations on ANGPT1 and ANGPT1/ANGPT2 ratio but VEGF and ANGPT2/VEGF were upregulated at folic acid >20 μM. Studying the contributing role of dietary folate to pro-angiogenic biomarkers in breast cancer patients can infer the preventive role of folate in the ANGs/VEGF-C-dependent cascade of tumor metastasis. By contrast, high concentrations of folic acid in vitro supported VEGF-C-dependent ANGPT2 overexpression might potentiate micro-lymphatic vessel development to support malignant cell dissemination.

DHFR/TYMS are positive regulators of glioma cell growth and modulate chemo-sensitivity to temozolomide

Glioma is one of the most lethal malignancies and molecular regulators driving gliomagenesis are incompletely understood. Although temozolomide (TMZ) has been applied for malignant gliomas as a canonical chemotherapy, the treatment of glioma still remains limited due to frequently developed resistance to TMZ. Therefore, promising strategies that sensitize glioma cells to temozolomide are overwhelming to develop. Here we found that the expression of dihydrofolate reductase (DHFR) and thymidylate synthetase (TYMS), which played an essential role in folate metabolism and several types of tumors, were up-regulated in both human glioma tissues and cell lines, and overexpression of DHFR/TYMS promoted the proliferation of glioma cells. Notably, inhibition of DHFR/TYMS by pemetrexed exhibited synergistic anti-glioma activity with TMZ in both cell lines and U251 xenografts, which suggested potential combined chemotherapy for glioma. Mechanistically, the synergistic effect of inhibition of DHFR/TYMS with TMZ was due to activated AMPK and subsequently suppressed mTOR signaling pathway. Taken together, these findings identify an uncharacterized role of DHFR/TYMS in glioma growth and TMZ sensitivity mediated by AMPK-mTOR signal pathway, and provide a prospective approach for improving the anti-tumor activity of TMZ in glioma.

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 cells2019;37:1441–1454

Anti-Tumor Effects of Vitamin B2, B6 and B9 in Promonocytic Lymphoma Cells

Chronic inflammation can lead to tumour initiation and progression. Vitamin B complex has the ability to regulate the immune response and, therefore, inflammation but many of the mechanistic and molecular processes involved in this regulation are still not fully understood. This study sought to determine some of these processes by studying the effects of vitamin B2 (riboflavin) B6 (pyridoxine) and B9 (folic acid) on un-differentiated pro-monocytic lymphoma cells in regard to their ability to alter the proliferation, migration, apoptosis, cytokines and expression levels of programmed death ligand 1. We show that vitamin B2, B6 and B9, on pro-monocytic lymphoma cells exerted an anti-tumorigenic effect. This data could form the basis for future studies in using vitamin B supplementation to reduce cancer cell growth in vivo.

Folic acid modifies the shape of epithelial cells during morphogenesis via a Folr1 and MLCK dependent mechanism

Folic acid supplementation can prevent neural tube defects, but the specific molecular mechanisms by which it does have not been elucidated. During neural plate morphogenesis, epithelial cell apical constriction cooperates with other events to drive tissue-bending, and when defective, can result in neural tube defects. A Rho-kinase deficient binding mutant of the apical constriction regulating protein, Shroom3 (Shroom3^R1838C), is one of only a handful of mouse mutant lines with neural tube defects that can be rescued by folic acid supplementation. This provided a unique opportunity to probe the functional rescue of a protein linked to neural tube development by folic acid. Utilizing an epithelial cell culture model of apical constriction, it was observed that treatment with exogenous folic acid, as well as co-expression of the folic acid receptor Folr1, can rescue the function of the Rho-kinase binding deficient mutant of Shroom3 in vitro It was also determined that the rescuing ability of folic acid is RhoA and Rho-kinase independent but myosin light chain kinase (MLCK) and Src-kinase dependent. Inhibition of Rho-kinase-dependent apical constriction in chick embryo neural epithelium was also observed to be rescued by exogenous folic acid and that treatment with folic acid is accompanied by elevated activated myosin light chain and MLCK. Furthermore, doubly heterozygous mouse embryos lacking one copy each of Shroom3 and Folr1 exhibit a low rate of neural tube defects and also have lower levels of activated myosin light chain and MLCK. These studies suggest a novel mechanism by which folic acid modifies epithelial cell shape during morphogenesis, shedding light onto how folic acid may prevent neural tube defects.

Folic acid inhibits colorectal cancer cell migration

We recently showed that folic acid (FA) could decrease the proliferation rate of colorectal cancer cells in vitro and reduce the volume of COLO-205 tumor in vivo. Since cancer cell proliferation and migration are two major events during cancer development, we further examined whether FA could also affect the migration of colorectal cancer cells. Transwell invasion assays demonstrated that FA reduced the invasion ability of colorectal cancer cell lines, COLO-205, LoVo and HT-29. Using COLO-205 as a cell model, we further delineated the molecular mechanism underlying FA-inhibited colorectal cancer cell invasion. Western blot analyses showed that FA (10 μM) activated cSrc, ERK1/2, NFκB, and p27 at serine 10 (Ser10), and up-regulated p53, p27, and KIS protein. Subcellular fractionation illustrated that FA treatment increased cytosolic translocation of p27, formation of the p27-RhoA complex, and RhoA degradation. The FA-induced migration inhibition in COLO-205 was abolished by blockade of the cSrc or ERK1/2 activity, knockdown of p27 or KIS using the siRNA technique, or over-expression of a constitutive active RhoA cDNA. Our results suggest that FA up-regulated p27 through increasing the cSrc/ERK1/2/NFκB/p53-mediated pathway. In the nucleus, FA up-regulated KIS, which in turn increased p27 phosphorylation at serine 10 (Ser10), subsequently resulting in cytosolic translocation of p27 and forming the p27-RhoA complex, thereby causing RhoA degradation, and eventually inhibited COLO-205 cell migration. Together with our previous findings suggest that FA reduced colorectal cancer development through inhibiting colorectal cancer cell proliferation and migration.

CX3CL1 involves in breast cancer metastasizing to the spine via the Src/FAK signaling pathway

C-X3-C chemokine ligand 1 (CX3CL1) has been shown to be involved in the development of multiple tumors. Our previous study demonstrated that CX3CL1 may be involved in the process of metastasis of various malignant tumors to the spine, including breast cancer, but the molecular mechanism was still unknown. In the present study, we found that the receptor CX3CR1 was overexpressed in the spinal metastases of breast cancer than in para-tumor tissue. In terms of CX3CL1, it was significantly more expressed in normal spinal cancellous bone than in limbs. However, CX3CR1 was not expressed at a high level in every breast cancer cell compared with the human mammary epithelial cell line MCF-10A. In addition, CX3CL1 did promote the migration and invasion abilities of MDA-MB-231 cells. However, CX3CL1 has no obvious effect on cell growth. Furthermore, CX3CL1 induced chemotaxis of tumor cells via the Src/FAK signaling pathway. The migration index enhanced by CX3CL1 was dramatically declined using Bosutinib and PF-00562271, which are the inhibitors of Src and FAK signaling pathways, respectively. Therefore, CX3CL1 in spinal cancellous bone attracts CX3CR1-expressing tumor cells to the spine and enhances their migration and invasion abilities through the Src/FAK signaling pathway.

Functionalized Folic Acid-Conjugated Amphiphilic Alternating Copolymer Actively Targets 3D Multicellular Tumour Spheroids and Delivers the Hydrophobic Drug to the Inner Core

Engineering of a “smart” drug delivery system to specifically target tumour cells has been at the forefront of cancer research, having been engineered for safer, more efficient and effective use of chemotherapy for the treatment of cancer. However, selective targeting and choosing the right cancer surface biomarker are critical for a targeted treatment to work. Currently, the available delivery systems use a two-dimensional monolayer of cancer cells to test the efficacy of the drug delivery system, but designing a “smart” drug delivery system to be specific for a tumour in vivo and to penetrate the inner core remains a major design challenge. These challenges can be overcome by using a study model that integrates the three-dimensional aspect of a tumour in a culture system. Here, we tested the efficacy of a functionalized folic acid-conjugated amphiphilic alternating copolymer poly(styrene-alt-maleic anhydride) (FA-DABA-SMA) via a biodegradable linker 2,4-diaminobutyric acid (DABA) to specifically target and penetrate the inner core of three-dimensional avascular human pancreatic and breast tumour spheroids in culture. The copolymer was quantitatively analyzed for its hydrophobic drug encapsulation efficiency using three different chemical drug structures with different molecular weights. Their release profiles and tumour targeting properties at various concentrations and pH environments were also characterized. Using the anticancer drug curcumin and two standard clinical chemotherapeutic hydrophobic drugs, paclitaxel and 5-fluorouracil, we tested the ability of FA-DABA-SMA nanoparticles to encapsulate the differently sized drugs and deliver them to kill monolayer pancreatic cancer cells using the WST-1 cell proliferation assay. The findings of this study revealed that the functionalized folic acid-conjugated amphiphilic alternating copolymer shows unique properties as an active “smart” tumor-targeting drug delivery system with the ability to internalize hydrophobic drugs and release the chemotherapeutics for effective killing of cancer cells. The novelty of the study is the first to demonstrate a functionalized “smart” drug delivery system encapsulated with a hydrophobic drug effectively targeting and penetrating the inner core of pancreatic and breast cancer spheroids and reducing their volumes in a dose- and time-dependent manner.

Effects of female sex hormones on folic acid-induced anti-angiogenesis

AIM

Pregnant women have been recommended to take FA daily to prevent birth defects in the brain and spinal cord. We previously showed that folic acid (FA) exerts an anti-angiogenic activity. As angiogenesis is important for endometrial reorganization and embryonic development, there should be some mechanisms to allow the pregnant mother and the foetus to escape from the FA-induced anti-angiogenesis. This study was designed to investigate the effect of female sex hormones on the FA-induced anti-angiogenic activity.

METHODS

The protein levels and protein-protein interaction were examined by Western blot analysis and immunoprecipitation assay respectively. The cell proliferation and migration were examined by MTT assay and wound healing assay respectively. The in vivo angiogenesis was evaluated by Matrigel angiogenesis assay.

RESULTS

In human umbilical venous endothelial cells (HUVEC), FA receptor (FR) formed a complex with progesterone receptor (PR), oestradiol receptor (ER) and cSrc. Pregnancy levels of progesterone (P4) or oestradiol (E2) prevented FA-induced inhibitions of proliferation and migration in HUVEC. Both E2 and P4 prevented the FA-induced anti-angiogenesis in vivo. Moreover, cotreatment with FA and P4 or E2 inhibited the signalling pathways involved in FA-induced inhibitions of proliferation and migration in HUVEC.

CONCLUSION

Female sex hormones interrupt the FA-induced anti-angiogenic action through receptor-receptor interaction.

Folic acid inhibits nasopharyngeal cancer cell proliferation and invasion via activation of FRα/ERK1/2/TSLC1 pathway

Folic acid (FA), which is necessary for normal cell division of mammals, has been implicated to be involved in many tumors. Dietary FA intake has been reported to be associated with a lower risk of nasopharyngeal cancer (NPC). However, the molecular mechanisms of FA in NPC cells remain unclear. In the present study, we found that FA treatment dose dependently inhibited the proliferation, invasion and migration of NPC cells, via folate receptor α (FRα). We further found that FA, bound to FRα, induced the activation of MEK/ERK1/2, and increased the expressions of TSLC1 and E-cadherin. Moreover, blocking of ERK1/2 activation attenuated FA-mediated increase in TSLC1 expression. In addition, knockdown of TSLC1 abolished the FA-mediated inhibition of cell proliferation, invasion and migration, and suppressed the FA-mediated increase oinE-cadherin expression in NPC cells. Taken together, our data suggest that FA treatment inhibits NPC cell proliferation and invasion via activation of FRα/ERK1/2/ TSLC1 signaling pathway. Therefore, FA could be explored as a therapeutic drug for the treatment of NPC, and TSLC1 may act as a tumor suppressor in NPC.

High folic acid diet enhances tumour growth in PyMT-induced breast cancer

Background:

The B-vitamin folate is among the most studied bioactive food compound, and a dietary intake meeting the daily requirements has been found to reduce the risk of cancer and cardiovascular diseases as well as preventing neural tube defects during fetal development. Several countries have therefore introduced dietary fortification with folic acid. However, clinical and animal studies suggest that folic acid has a dual role in cancer development.

Methods:

During the period of initial tumour progression, MMTV-PyMT (MMTV-polyoma virus middle T) transgenic mice were fed with normal diet and high folic acid diet.

Results:

We found that PyMT-induced breast tumours highly express the cancer-specific folate receptor (FR), a feature they share with several human epithelial cancers in which expression of FRα correlates with tumour grade. Mice receiving a high folic acid diet displayed a significantly increased tumour volume compared with mice receiving normal diet. In the largest tumours, only found in mice on high folic acid diet, STAT3 was activated. In primary cells from PyMT tumours, STAT3 was activated upon treatment with folic acid in culture.

Conclusions:

Our results offer a novel molecular explanation for folic acid-induced growth of existing tumours.

RIG-I inhibits pancreatic β cell proliferation through competitive binding of activated Src

Nutrition is a necessary condition for cell proliferation, including pancreatic β cells; however, over-nutrition, and the resulting obesity and glucolipotoxicity, is a risk factor for the development of Type 2 diabetes mellitus (DM), and causes inhibition of pancreatic β-cells proliferation and their loss of compensation for insulin resistance. Here, we showed that Retinoic acid (RA)-inducible gene I (RIG-I) responds to nutrient signals and induces loss of β cell mass through G1 cell cycle arrest. Risk factors for type 2 diabetes (e.g., glucolipotoxicity, TNF-α and LPS) activate Src in pancreatic β cells. Elevated RIG-I modulated the interaction of activated Src and STAT3 by competitive binding to STAT3. Elevated RIG-I downregulated the transcription of SKP2, and increased the stability and abundance of P27 protein in a STAT3-dependent manner, which was associated with inhibition of β cell growth elicited by Src. These results supported a role for RIG-I in β cell mass loss under conditions of metabolic surplus and suggested that RIG-I-induced blocking of Src/STAT3 signalling might be involved in G1 phase cycle arrest through the Skp2/P27 pathway in pancreatic β cells.

Progesterone receptor activation is required for folic acid-induced anti-proliferation in colorectal cancer cell lines

Previously, we demonstrated that folic acid (FA) could inhibit proliferation of colorectal cancer cell lines through activating the folate receptor (FR)α/cSrc/ERK1/2/NFκB/p53 pathway and anti-COLO-205 tumor growth in vivo. Since we recently also demonstrated that female sex hormones could affect the FA's action in regulating endothelial cell proliferation and migration, the aim of this study was to investigate the effect of progesterone (P4) on the FA-induced anti-proliferation in colorectal cancer cells. Treatment with FA significantly reduced the proliferation of the P4 receptor (PR)-positive colon cancer cell lines, COLO-205, HT-29 and LoVo, but did not significantly affect the proliferation of the PR-negative colon cancer cell lines, HCT116 and DLD-1. Pre-treatment with Org 31710, a PR specific antagonist, abolished the FA-induced proliferation inhibition and activation in the signaling pathway involved in regulating proliferation inhibition in these PR positive colorectal cancer cell lines. The involvement of PR in the FA-induced activation of cSrc and up-regulations in cell cycle inhibitory proteins (p21, p27 and p53) was confirmed by knock-down of PR expression using the siRNA technique. Importantly, we show direct protein interaction between FR and PR in COLO-205. Moreover, treatment with FA induced PR activation in COLO-205. Taken together, these data suggest that FA induced proliferation inhibition in colon cancer cells through activation of PR. This finding might explain some of the controversies of FA's effects on cancer growth and provide valuable reference for clinical applications of FA in treating colorectal cancer.