Rho GTPases RhoA and Rac1 mediate effects of dietary folate on metastatic potential of A549 cancer cells through the control of cofilin phosphorylation

Role of apoptosis and autophagy in folic acid-induced cytotoxicity of human breast cancer cells in vitro

Obstacles to the successful treatment of breast cancer patients with chemotherapeutic agents can be overcome with effective new strategies. It is still unclear how folic acid affects the onset and spread of breast cancer. The purpose of this study was to determine how folic acid affected the apoptotic and autophagic pathways of the breast cancer cell lines MCF-7 and MDA-MB-231. In the present study, folic acid was applied to MCF-7 and MDA-MB-231 breast cancer cell lines at different concentrations and for different durations. MTT analysis was used to investigate cytotoxic activity. All groups underwent the Tunel staining procedure to identify apoptosis and the immunofluorescence staining approach to identify the autophagic pathway. 24-hour folic acid values were accepted as the most appropriate cytotoxic dose. In MCF-7, cell cycle arrest was observed in the S phase and MDA-MB-231 G1/G0 phases. When apoptotic TUNEL staining was evaluated in both cell lines, folic acid significantly increased apoptosis. While a significant difference was observed between the groups in terms of Beclin 1 immunoreactivity in the MDA-MB-231 cell line, there was no significant difference in the MCF-7 cell line. In addition, statistical significance was not observed LC3 immunoreactivity in both cell lines. In the study, it was observed that folic acid induced autophagy at the initial stage in the MDA-MB-231 cell line but had no inductive effect in the MCF-7 cell line. In conclusion, our findings showed that folic acid has a potential cytotoxic and therapeutic effect on MCF-7 and MDA-MB-231 breast cancer cell lines.

ERK3 and DGKζ interact to modulate cell motility in lung cancer cells

Extracellular signal-regulated kinase 3 (ERK3) promotes cell migration and tumor metastasis in multiple cancer types, including lung cancer. The extracellular-regulated kinase 3 protein has a unique structure. In addition to the N-terminal kinase domain, ERK3 includes a central conserved in extracellular-regulated kinase 3 and ERK4 (C34) domain and an extended C-terminus. However, relatively little is known regarding the role(s) of the C34 domain. A yeast two-hybrid assay using extracellular-regulated kinase 3 as bait identified diacylglycerol kinase ζ (DGKζ) as a binding partner. DGKζ was shown to promote migration and invasion in some cancer cell types, but its role in lung cancer cells is yet to be described. The interaction of extracellular-regulated kinase 3 and DGKζ was confirmed by co-immunoprecipitation and in vitro binding assays, consistent with their co-localization at the periphery of lung cancer cells. The C34 domain of ERK3 was sufficient for binding to DGKζ, while extracellular-regulated kinase 3 bound to the N-terminal and C1 domains of DGKζ. Surprisingly, in contrast to extracellular-regulated kinase 3, DGKζ suppresses lung cancer cell migration, suggesting DGKζ might inhibit ERK3-mediated cell motility. Indeed, co-overexpression of exogenous DGKζ and extracellular-regulated kinase 3 completely blocked the ability of ERK3 to promote cell migration, but DGKζ did not affect the migration of cells with stable ERK3 knockdown. Furthermore, DGKζ had little effect on cell migration induced by overexpression of an ERK3 mutant missing the C34 domain, suggesting DGKζ requires this domain to prevent ERK3-mediated increase in cell migration. In summary, this study has identified DGKζ as a new binding partner and negative regulator of extracellular-regulated kinase 3 in controlling lung cancer cell migration.

Dietary Folate Deficiency Promotes Lactate Metabolic Disorders to Sensitize Lung Cancer Metastasis through MTOR-Signaling-Mediated Druggable Oncotargets

Lactate metabolism plays a pivotal role in cancers but is often overlooked in lung cancer (LC). Folate deficiency has been linked to lung cancer development, but its impact on lactate metabolism and cancer malignancy is unclear. To investigate this, mice were fed either a folate-deficient (FD) or control diet and intrapleurally implanted with lung cancer cells pre-exposed to FD growth medium. Results showed that FD promoted lactate over-production and the formation of tumor oncospheroids (LCSs) with increased metastatic, migration, and invasion potential. Mice implanted with these cells and fed an FD diet developed hyperlactatemia in blood and lungs. This coincided with increased expression of hexokinase 2 (HK2), lactate dehydrogenase (LDH), and decreased expression of pyruvate dehydrogenase (PDH). Pre-treatment of the FD-LCS-implanted mice with the mTORC1 inhibitor, rapamycin, and the anti-metabolic drug metformin abolished FD/LCS-activated mTORC1 and its targets including HIF1α, HK2, LDH, and monocarboxylate transporters (MCT1 and MCT4), which coincided with the reduction in lactate disorders and prevention of LC metastasis. The findings suggest that dietary FD promotes lactate metabolic disorders that sensitize lung cancer metastasis through mTOR-signaling-mediated targets.

Folylpolyglutamate synthetase mRNA G-quadruplexes regulate its cell protrusion localization and enhance a cancer cell invasive phenotype upon folate repletion

BACKGROUND

Folates are crucial for the biosynthesis of nucleotides and amino acids, essential for cell proliferation and development. Folate deficiency induces DNA damage, developmental defects, and tumorigenicity. The obligatory enzyme folylpolyglutamate synthetase (FPGS) mediates intracellular folate retention via cytosolic and mitochondrial folate polyglutamylation. Our previous paper demonstrated the association of the cytosolic FPGS (cFPGS) with the cytoskeleton and various cell protrusion proteins. Based on these recent findings, the aim of the current study was to investigate the potential role of cFPGS at cell protrusions.

RESULTS

Here we uncovered a central role for two G-quadruplex (GQ) motifs in the 3'UTR of FPGS mediating the localization of cFPGS mRNA and protein at cell protrusions. Using the MBSV6-loop reporter system and fluorescence microscopy, we demonstrate that following folate deprivation, cFPGS mRNA is retained in the endoplasmic reticulum, whereas upon 15 min of folate repletion, this mRNA is rapidly translocated to cell protrusions in a 3'UTR- and actin-dependent manner. The actin dependency of this folate-induced mRNA translocation is shown by treatment with Latrunculin B and inhibitors of the Ras homolog family member A (RhoA) pathway. Upon folate repletion, the FPGS 3'UTR GQs induce an amoeboid/mesenchymal hybrid cell phenotype during migration and invasion through a collagen gel matrix. Targeted disruption of the 3'UTR GQ motifs by introducing point mutations or masking them by antisense oligonucleotides abrogated cell protrusion targeting of cFPGS mRNA.

CONCLUSIONS

Collectively, the GQ motifs within the 3'UTR of FPGS regulate its transcript and protein localization at cell protrusions in response to a folate cue, inducing cancer cell invasive phenotype. These novel findings suggest that the 3'UTR GQ motifs of FPGS constitute an attractive druggable target aimed at inhibition of cancer invasion and metastasis.

Probing Folate-Responsive and Stage-Sensitive Metabolomics and Transcriptional Co-Expression Network Markers to Predict Prognosis of Non-Small Cell Lung Cancer Patients

Tumour metabolomics and transcriptomics co-expression network as related to biological folate alteration and cancer malignancy remains unexplored in human non-small cell lung cancers (NSCLC). To probe the diagnostic biomarkers, tumour and pair lung tissue samples (n = 56) from 97 NSCLC patients were profiled for ultra-performance liquid chromatography tandem mass spectrometry (UPLC/MS/MS)-analysed metabolomics, targeted transcriptionomics, and clinical folate traits. Weighted Gene Co-expression Network Analysis (WGCNA) was performed. Tumour lactate was identified as the top VIP marker to predict advance NSCLC (AUC = 0.765, Sig = 0.017, CI 0.58-0.95). Low folate (LF)-tumours vs. adjacent lungs displayed higher glycolytic index of lactate and glutamine-associated amino acids in enriched biological pathways of amino sugar and glutathione metabolism specific to advance NSCLCs. WGCNA classified the green module for hub serine-navigated glutamine metabolites inversely associated with tumour and RBC folate, which module metabolites co-expressed with a predominant up-regulation of LF-responsive metabolic genes in glucose transport (GLUT1), de no serine synthesis (PHGDH, PSPH, and PSAT1), folate cycle (SHMT1/2 and PCFR), and down-regulation in glutaminolysis (SLC1A5, SLC7A5, GLS, and GLUD1). The LF-responsive WGCNA markers predicted poor survival rates in lung cancer patients, which could aid in optimizing folate intervention for better prognosis of NSCLCs susceptible to folate malnutrition.

Folic acid depletion as well as oversupplementation helps in the progression of hepatocarcinogenesis in HepG2 cells

Folate ingestion below and above the physiologic dose has been shown to play a tumorigenic role in certain cancers. Also, excessive folate supplementation after establishment of pre-established lesions led to an advancement in the growth of a few tumors. However, such information has not yet been achieved in the case of HCC. In our study, HepG2 cells were administered with three different concentrations of folic acid i.e. folic acid normal (FN) (2.27 µM), folic acid deficient (FD) (no folic acid), folic acid oversupplementation (FO) (100 µM) for 10 days. Intracellular folate levels were assayed by Elecsys Folate III kit based method. The migratory and invasive abilities were estimated by transwell migration and matrigel invasion methods respectively. FACS was done to evaluate cell viability and apoptosis. Agarose-coated plates were used to access cancer stem cells (CSCs) number. Quantitative RT-PCR and western blotting approaches were used for gene and protein expression of certain tumor suppressor genes (TSGs), respectively. FD cells depicted increased migration, invasion, apoptosis, necrosis and decreased cell viability, CSCs. On the other hand, FO cells showed increased migration, invasion, cell viability and number of CSCs and decreased apoptosis and necrosis. TSGs revealed diminished expression with both FA modulations with respect to FN cells. Thus, FA deficiency as well as abundance enhanced the HCC progression by adapting different mechanisms.

Sex-Specific Metabolic Effects of Dietary Folate Withdrawal in Wild-Type and Aldh1l1 Knockout Mice

ALDH1L1 (10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism, is highly expressed in the liver. It regulates the overall flux of folate-bound one-carbon groups by converting 10-formyltetrahydrofolate to tetrahydrofolate and CO2 in a NADP+-dependent reaction. Our previous study revealed that Aldh1l1 knockout (KO) mice have an altered liver metabotype with metabolic symptoms of folate deficiency when fed a standard chow diet containing 2 ppm folic acid. Here we performed untargeted metabolomic analysis of liver and plasma of KO and wild-type (WT) male and female mice fed for 16 weeks either standard or folate-deficient diet. OPLS-DA, a supervised multivariate technique that was applied to 6595 and 10,678 features for the liver and plasma datasets, respectively, indicated that genotype and diet, alone or in combination, gave distinct metabolic profiles in both types of biospecimens. A more detailed analysis of affected metabolic pathways based on most confidently identified metabolites in the liver and plasma (OL1 and OL2a ontology level) indicated that the dietary folate restriction itself does not fully recapitulate the metabolic effect of the KO. Of note, dietary folate withdrawal enhanced the metabolic perturbations linked to the ALDH1L1 loss only for a subset of metabolites. Importantly, both the ALDH1L1 loss and dietary folate deficiency produced sex-specific metabolic effects.

FMNL2 suppresses cell migration and invasion of breast cancer: a reduction of cytoplasmic p27 via RhoA/LIMK/Cofilin pathway

Formin-like protein 2 (FMNL2) belongs to a highly conserved family of cytoskeletal remodeling proteins that have been reported to be implicated in various actin-dependent physiological and cancer-associated processes. In this study, we mainly investigated the effects of FMNL2 on breast cancer cell migration and invasion, and the underlying mechanisms involved. We found that FMNL2 reduced cell migration and invasion of breast cancer in vitro and in vivo. Further, FMNL2 disrupted actin cytoskeleton rearrangement and hampered the RhoA/LIMK/Cofilin pathway in breast cancer cells. Critically, both Rho inhibitor ZOL and LIMK inhibitor BMS3 significantly abrogated these migration-promoting effects in FMNL2-silencing MDA-MB-231 and BT549 cells. RhoA/LIMK/Cofilin pathway was involved in FMNL2 silencing-induced actin cytoskeleton rearrangement in MDA-MB-231 and BT549 cells. More importantly, cytoplasmic p27 promoted FMNL2-mediated cell migration and invasion through RhoA/LIMK/Cofilin pathway in MCF7 and MDA-MB-231 cells. In addition, the expression and prognosis of FMNL2 were associated with ER in breast cancer. Furthermore, ERα overexpression reduced the protein levels of FMNL2 in breast cancer cells, which were reversed by MG132. In conclusion, FMNL2 suppressed cell migration and invasion of breast cancer by inhibiting RhoA/LIMK/Cofilin pathway through a reduction of cytoplasmic p27. This finding implies that the interference of FMNL2-mediated RhoA/LIMK/Cofilin pathway involving the cytoplasmic p27 may be a promising strategy for ameliorating breast cancer metastasis and prognosis.

Elevated Expression of Gamma-Glutamyl Hydrolase Is Associated With Poor Prognosis and Altered Immune Signature in Uterine Corpus Endometrial Carcinoma

Uterine corpus endometrial carcinoma (UCEC) is a common malignant tumor of the female reproductive system with poor prognosis in advanced, recurrent, and metastatic cases. Identification of reliable molecular markers will help in the development of clinical strategies for early detection, diagnosis, and intervention. Gamma-glutamyl hydrolase (GGH) is a key enzyme in folate metabolism pathway. High expression of GGH is associated with severe clinicopathological features and poor prognosis of several cancers. High GGH expression is also related to cell resistance to antifolate drugs such as methotrexate. In this study we focused on the prognostic value of immunohistochemical GGH expression level in UCEC tissue and RNA-seq data from The Cancer Genome Atlas to establish associations with clinical features and outcomes. Further, we conducted comprehensive bioinformatics analyses to identify and functionally annotate differentially expressed genes (DEGs) associated with UCEC upregulation and assessed the effects of upregulation on immune infiltration. Both GGH mRNA and protein expression levels were elevated in tumor tissues, and higher expression was significantly associated with advanced clinicopathological features and poor prognosis by univariate analysis. Further multivariate analysis identified elevated GGH expression as an independent risk factor for poor outcome. Nomograms including GGH expression yielded a c-index for disease-specific survival prediction of 0.884 (95% confidence interval: 0.861–0.907). A total of 520 DEGs (111 upregulated and 409 downregulated) were identified between high and low GGH expression groups. Analysis using Gene ontology, Kyoto Encyclopedia of Genes and Genomes pathway, Gene set enrichment analysis, and protein‒protein interaction indicated significant associations of altered GGH expression with cell proliferation, immune response, and the occurrence and development of UCEC tumors. Finally, GGH expression level was associated with high Th2 cell and low natural killer CD56bright cell infiltration. Collectively, these findings indicate that GGH drives UCEC progression and could be a useful biomarker for survival prediction as well as a therapeutic target.

Designing Relevant Preclinical Rodent Models for Studying Links Between Nutrition, Obesity, Metabolism, and Cancer

Diet and nutrition are intricately related to cancer prevention, growth, and treatment response. Preclinical rodent models are a cornerstone to biomedical research and remain instrumental in our understanding of the relationship between cancer and diet and in the development of effective therapeutics. However, the success rate of translating promising findings from the bench to the bedside is suboptimal. Well-designed rodent models will be crucial to improving the impact basic science has on clinical treatment options. This review discusses essential experimental factors to consider when designing a preclinical cancer model with an emphasis on incorporating these models into studies interrogating diet, nutrition, and metabolism. The aims of this review are to (a) provide insight into relevant considerations when designing cancer models for obesity, nutrition, and metabolism research; (b) identify common pitfalls when selecting a rodent model; and (c) discuss strengths and limitations of available preclinical models. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Ceramide synthase 6 mediates sex-specific metabolic response to dietary folic acid in mice

Folic acid-fortified foods and multi-vitamin supplements containing folic acid (FA) are widely used around the world, but the exact mechanisms/metabolic effects of FA are not precisely identified. We have demonstrated that Ceramide Synthase 6 (CerS6) and C_16:0-ceramide mediate response to folate stress in cultured cells. Here we investigated the dietary FA effects on mouse liver metabolome, with a specific focus on sphingolipids, CerS6 and C_16:0-ceramide. Wild-type and CerS6^-/- mice were fed FA-deficient, control, or FA over-supplemented diets for 4 weeks. After dietary treatment, liver concentrations of ceramides, sphingomyelins and hexosylceramides were measured by LC-MS/MS and complemented by untargeted metabolomic characterization of mouse livers. Our study shows that alterations in dietary FA elicit multiple sphingolipid responses mediated by CerS6 in mouse livers. Folic acid-deficient diet elevated C_14:0-, C_18:0- and C_20:0- but not C_16:0-ceramide in WT male and female mice. Additionally, FA over-supplementation increased multiple sphingomyelin species, including total sphingomyelins, in both sexes. Of note, concentrations of C_14:0- and C_16:0-ceramides and hexosylceramides were significantly higher in female livers than in male. The latter were increased by FD diet, with no difference between sexes in total pools of these sphingolipid classes. Untargeted liver metabolomic analysis concurred with the targeted measurements and showed broad effects of dietary FA and CerS6 status on multiple lipid classes including sex-specific effects on phosphatidylethanolamines and diacylglycerols. Our study demonstrates that both dietary FA and CerS6 status exhibit pleiotropic and sex-dependent effects on liver metabolism, including hepatic sphingolipids, diacylglycerols, long chain fatty acids, and phospholipids.

Hhex inhibits cell migration via regulating RHOA/CDC42-CFL1 axis in human lung cancer cells

Background

Hhex(human hematopoietically expressed homeobox), also known as PRH, is originally considered as a transcription factor to regulate gene expression due to its homebox domain. Increasing studies show that Hhex plays a significant role in development, including anterior–posterior axis formation, vascular development and HSCs self-renewal etc. Hhex is linked to many diseases such as cancers, leukemia, and type-2 diabetes. Although Hhex is reported to inhibit cell migration and invasion of breast and prostate epithelial cells by upregulating Endoglin expression, the effect and molecular mechanism for lung cancer cell motility regulation remains elusive.

Methods

Human non-small cell lung cancer cells and HEK293FT cells were used to investigate the molecular mechanism of Hhex regulating lung cancer cell migration by using Western blot, immunoprecipitation, wound-healing scratch assay, laser confocal.

Results

Our data indicated that Hhex could inhibit cell migration and cell protrusion formation in lung cancer cells. In addition, Hhex inhibited CFL1 phosphorylation to keep its F-actin-severing activity. RHOGDIA was involved in Hhex-induced CFL1 phosphorylation regulation. Hhex enhanced RHOGDIA interaction with RHOA/CDC42, thus maintaining RHOA/CDC42 at an inactive form.

Conclusion

Collectively, these data indicate that Hhex inhibited the activation of RHOA/CDC42 by enhancing interaction of RHOGDIA with RHOA/CDC42, and then RHOA/ CDC42-p-CFL1 signaling pathway was blocked. Consequently, the formation of Filopodium and Lamellipodium on the cell surface was suppressed, and thus the ability of lung cancer cells to migrate was decreased accordingly. Our findings show Hhex plays an important role in regulating migration of lung cancer cells and may provide a potential target for lung cancer therapy.

Syndecan-4 in Tumor Cell Motility

Simple Summary

Cell migration is crucial fReaor metastasis formation and a hallmark of malignancy. The primary cause of high mortality among oncology patients is the ability of cancer cells to metastasize. To form metastasis, primary tumor cells must be intrinsically able to move. The transmembrane, heparan sulfate proteoglycan syndecan-4 (SDC4) exhibits multiple functions in signal transduction by regulating Rac1 GTPase activity and consequently actin remodeling, as well as regulating focal adhesion kinase, protein kinase C-alpha and the level of intracellular calcium. By affecting several signaling pathways and biological processes, SDC4 is involved in cell migration under physiological and pathological conditions as well. In this review, we discuss the SDC4-mediated cell migration focusing on the role of SDC4 in tumor cell movement.

Abstract

Syndecan-4 (SDC4) is a ubiquitously expressed, transmembrane proteoglycan bearing heparan sulfate chains. SDC4 is involved in numerous inside-out and outside-in signaling processes, such as binding and sequestration of growth factors and extracellular matrix components, regulation of the activity of the small GTPase Rac1, protein kinase C-alpha, the level of intracellular calcium, or the phosphorylation of focal adhesion kinase. The ability of this proteoglycan to link the extracellular matrix and actin cytoskeleton enables SDC4 to contribute to biological functions like cell adhesion and migration, cell proliferation, cytokinesis, cellular polarity, or mechanotransduction. The multiple roles of SDC4 in tumor pathogenesis and progression has already been demonstrated; therefore, the expression and signaling of SDC4 was investigated in several tumor types. SDC4 influences tumor progression by regulating cell proliferation as well as cell migration by affecting cell-matrix adhesion and several signaling pathways. Here, we summarize the general role of SDC4 in cell migration and tumor cell motility.

Knockout of Putative Tumor Suppressor Aldh1l1 in Mice Reprograms Metabolism to Accelerate Growth of Tumors in a Diethylnitrosamine (DEN) Model of Liver Carcinogenesis

Simple Summary

Cancers often loose the enzyme of folate metabolism ALDH1L1. We proposed that such loss is advantageous for the malignant tumor growth and tested this hypothesis in mice proficient or deficient (gene knockout) in ALDH1L1 expression. Liver cancer in both groups was induced by injection of chemical carcinogen diethylnitrosamine. While the number of tumors observed in ALDH1L1 proficient and deficient mice was similar, tumors grew faster and to a larger size in the knockout mice. We conclude that the ALDH1L1 loss promotes liver tumor growth without affecting tumor initiation or multiplicity. Accelerated growth of tumors lacking the enzyme was linked to several metabolic pathways, which are beneficial for rapid proliferation.

Abstract

Cytosolic 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) is commonly downregulated in human cancers through promoter methylation. We proposed that ALDH1L1 loss promotes malignant tumor growth. Here, we investigated the effect of the Aldh1l1 mouse knockout (Aldh1l1^−/−) on hepatocellular carcinoma using a chemical carcinogenesis model. Fifteen-day-old male Aldh1l1 knockout mice and their wild-type littermate controls (Aldh1l1^+/+) were injected intraperitoneally with 20 μg/g body weight of DEN (diethylnitrosamine). Mice were sacrificed 10, 20, 28, and 36 weeks post-DEN injection, and livers were examined for tumor multiplicity and size. We observed that while tumor multiplicity did not differ between Aldh1l1^−/− and Aldh1l1^+/+ animals, larger tumors grew in Aldh1l1^−/− compared to Aldh1l1^+/+ mice at 28 and 36 weeks. Profound differences between Aldh1l1^−/− and Aldh1l1^+/+ mice in the expression of inflammation-related genes were seen at 10 and 20 weeks. Of note, large tumors from wild-type mice showed a strong decrease of ALDH1L1 protein at 36 weeks. Metabolomic analysis of liver tissues at 20 weeks showed stronger differences in Aldh1l1^+/+ versus Aldh1l1^−/− metabotypes than at 10 weeks, which underscores metabolic pathways that respond to DEN in an ALDH1L1-dependent manner. Our study indicates that Aldh1l1 knockout promoted liver tumor growth without affecting tumor initiation or multiplicity.

Myo-Inositol as a Key Supporter of Fertility and Physiological Gestation

Pregnancy is a complex process, featuring several necessary changes in women’s physiology. Most women undergo healthy pregnancies; even so, several women experience reduced fertility or pathologies related to the pregnancy. In the last years, researchers investigated several molecules as promoters of fertility. Among all, myo-inositol (myo-ins) represents a safe compound that proved useful in issues related to fertility and pregnancy. In fact, myo-ins participates in several signaling processes, including the pathways of insulin and gonadotropins, and, therefore, it is likely to positively affect fertility. In particular, several clinical trials demonstrate that its administration can have therapeutic effects in infertile women, and that it can also be useful as a preventive treatment during pregnancy. Particularly, myo-ins could prevent the onset of neural tube defects and the occurrence of gestational diabetes mellitus, promoting a trouble-free gestation. Due to the safety and efficiency of myo-ins, such a treatment may also substitute several pharmaceuticals, which are contraindicated in pregnancy.

Metabolic Response of Triple-Negative Breast Cancer to Folate Restriction

Background: Triple-negative breast cancers (TNBCs), accounting for approximately 15% of breast cancers, lack targeted therapy. A hallmark of cancer is metabolic reprogramming, with one-carbon metabolism essential to many processes altered in tumor cells, including nucleotide biosynthesis and antioxidant defenses. We reported that folate deficiency via folic acid (FA) withdrawal in several TNBC cell lines results in heterogenous effects on cell growth, metabolic reprogramming, and mitochondrial impairment. To elucidate underlying drivers of TNBC sensitivity to folate stress, we characterized in vivo and in vitro responses to FA restriction in two TNBC models differing in metastatic potential and innate mitochondrial dysfunction. Methods: Metastatic MDA-MB-231 cells (high mitochondrial dysfunction) and nonmetastatic M-Wnt cells (low mitochondrial dysfunction) were orthotopically injected into mice fed diets with either 2 ppm FA (control), 0 ppm FA, or 12 ppm FA (supplementation; in MDA-MB-231 only). Tumor growth, metabolomics, and metabolic gene expression were assessed. MDA-MB-231 and M-Wnt cells were also grown in media with 0 or 2.2 µM FA; metabolic alterations were assessed by extracellular flux analysis, flow cytometry, and qPCR. Results: Relative to control, dietary FA restriction decreased MDA-MB-231 tumor weight and volume, while FA supplementation minimally increased MDA-MB-231 tumor weight. Metabolic studies in vivo and in vitro using MDA-MB-231 cells showed FA restriction remodeled one-carbon metabolism, nucleotide biosynthesis, and glucose metabolism. In contrast to findings in the MDA-MB-231 model, FA restriction in the M-Wnt model, relative to control, led to accelerated tumor growth, minimal metabolic changes, and modest mitochondrial dysfunction. Increased mitochondrial dysfunction in M-Wnt cells, induced via chloramphenicol, significantly enhanced responsiveness to the cytotoxic effects of FA restriction. Conclusions: Given the lack of targeted treatment options for TNBC, uncovering metabolic vulnerabilities that can be exploited as therapeutic targets is an important goal. Our findings suggest that a major driver of TNBC sensitivity to folate restriction is a high innate level of mitochondrial dysfunction, which can increase dependence on one-carbon metabolism. Thus, folate deprivation or antifolate therapy for TNBCs with metabolic inflexibility due to their elevated levels of mitochondrial dysfunction may represent a novel precision-medicine strategy.

Pin1 Regulates IL-5 Induced Eosinophil Polarization and Migration

Eosinophils become polarized in response to cytokines such IL-5 or eotaxin prior to directional migration. Polarization is preceded by F-actin assembly, but the mechanisms that regulate these events and how the shape change influences cell migration from the peripheral blood into the lung remain unclear. In this study, we show that the prolyl isomerase, Pin1, is required for IL-5-induced Eos polarization and migration. Co-immunoprecipitation and immunofluorescence analysis revealed that Pin1 directly interacts with members of Rho GTPase family. Mouse eosinophils lacking Pin1 or human cells treated with Pin1 inhibitors showed significantly reduced IL-5-induced GTPase activity and cofilin phosphorylation, resulting in reduced F-actin polymerization, cell polarization, and directional migration to chemokines. Our result suggests that Pin1 regulates cytoskeletal re-organization, eosinophil morphology, and cell migration through the modulation of Rho GTPase activity. Targeting Pin1 along with GTPases could provide a new approach to reduce pulmonary Eos accumulation during asthmatic exacerbations.

Downregulation of Rac1/PAK1/LIMK1/cofilin signaling pathway in colon cancer SW620 cells treated with Chlorin e6 photodynamic therapy

BACKGROUND

Colorectal cancer is one of the most common gastrointestinal malignancies. Photodynamic therapy (PDT) is a novel and non-invasive treatment for tumors as PDT features small trauma, good applicability, andaccurate targeting. PDT may also be a potential treatment for colon cancer as itmay may induce suppressive effects on metastatic potential.. However, the molecular mechanism of the Chlorin e6 Photodynamic therapy (Ce6-PDT) inhibiting the migration of human colon cancer SW620 cells remains unclear.

METHODS

Scratch wound healing assay, scanning electron microscope, MTT, immunofluorescence and laser confocal technique were used to investigate the suppressive effects of Ce6-PDT on the SW620 cells migration, pseudopodia, viability and the actin cytoskeleton. The effect of Ce6-PDT on actin-Filaments and signaling molecules of the Rac1/PAK1/LIMK1/cofilin signaling pathway in SW620 cells were examined by western blot analysis. RNA interference (RNAi) technology was used to establish siRNA-Rac1/SW620 cells. The combined effects of Ce6-PDT and RNAi on colon cancer SW620 cells was investigated by the same technology and methods mentioned above to clarify the signal transduction effect of Rac1/PAK1/LIMK1/cofilin signaling pathway in Ce6-PDT caused inhibition of SW620 cell migration.

RESULTS

The healing and migration rate of the SW620 cells was significantly reduced and the cell pseudopodia were reduced or disappeared by Ce6-PDT. The Immunofluorescence and western blot analysis results showed that Ce6-PDT destroy microfilament's original structure and significantly downregulated F-actin protein expression. The Rac1/PAK1/LIMK1/cofilin signaling pathway was downregulated by Ce6-PDT. Furthermore, the RNAi significantly strengthened the effect of Ce6-PDT on colon cancer SW620 cells migration.

CONCLUSIONS

Actin cytoskeleton and protrusions of SW620 cells correlate with its migration ability. Ce6-PDT suppresses SW620 cells migration by downregulating the Rac1/PAK1/LIMK1/cofilin signaling pathway, and its suppressive effect was enhanced by knocking down Rac1 gene expression.

Aldh1l2 knockout mouse metabolomics links the loss of the mitochondrial folate enzyme to deregulation of a lipid metabolism observed in rare human disorder

Background

Mitochondrial folate enzyme ALDH1L2 (aldehyde dehydrogenase 1 family member L2) converts 10-formyltetrahydrofolate to tetrahydrofolate and CO₂ simultaneously producing NADPH. We have recently reported that the lack of the enzyme due to compound heterozygous mutations was associated with neuro-ichthyotic syndrome in a male patient. Here, we address the role of ALDH1L2 in cellular metabolism and highlight the mechanism by which the enzyme regulates lipid oxidation.

Methods

We generated Aldh1l2 knockout (KO) mouse model, characterized its phenotype, tissue histology, and levels of reduced folate pools and applied untargeted metabolomics to determine metabolic changes in the liver, pancreas, and plasma caused by the enzyme loss. We have also used NanoString Mouse Inflammation V2 Code Set to analyze inflammatory gene expression and evaluate the role of ALDH1L2 in the regulation of inflammatory pathways.

Results

Both male and female Aldh1l2 KO mice were viable and did not show an apparent phenotype. However, H&E and Oil Red O staining revealed the accumulation of lipid vesicles localized between the central veins and portal triads in the liver of Aldh1l2^-/- male mice indicating abnormal lipid metabolism. The metabolomic analysis showed vastly changed metabotypes in the liver and plasma in these mice suggesting channeling of fatty acids away from β-oxidation. Specifically, drastically increased plasma acylcarnitine and acylglycine conjugates were indicative of impaired β-oxidation in the liver. Our metabolomics data further showed that mechanistically, the regulation of lipid metabolism by ALDH1L2 is linked to coenzyme A biosynthesis through the following steps. ALDH1L2 enables sufficient NADPH production in mitochondria to maintain high levels of glutathione, which in turn is required to support high levels of cysteine, the coenzyme A precursor. As the final outcome, the deregulation of lipid metabolism due to ALDH1L2 loss led to decreased ATP levels in mitochondria.

Conclusions

The ALDH1L2 function is important for CoA-dependent pathways including β-oxidation, TCA cycle, and bile acid biosynthesis. The role of ALDH1L2 in the lipid metabolism explains why the loss of this enzyme is associated with neuro-cutaneous diseases. On a broader scale, our study links folate metabolism to the regulation of lipid homeostasis and the energy balance in the cell.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-020-00291-3.

High CO2 Levels Impair Lung Wound Healing

Delayed lung repair leads to alveolopleural fistulae, which are a major cause of morbidity after lung resections. We have reported that intrapleural hypercapnia is associated with delayed lung repair after lung resection. Here, we provide new evidence that hypercapnia delays wound closure of both large airway and alveolar epithelial cell monolayers because of inhibition of epithelial cell migration. Cell migration and airway epithelial wound closure were dependent on Rac1-GTPase activation, which was suppressed by hypercapnia directly through the upregulation of AMP kinase and indirectly through inhibition of injury-induced NF-κB-mediated CXCL12 (pleural CXC motif chemokine 12) release, respectively. Both these pathways were independently suppressed, because dominant negative AMP kinase rescued the effects of hypercapnia on Rac1-GTPase in uninjured resting cells, whereas proteasomal inhibition reversed the NF-κB-mediated CXCL12 release during injury. Constitutive overexpression of Rac1-GTPase rescued the effects of hypercapnia on both pathways as well as on wound healing. Similarly, exogenous recombinant CXCL12 reversed the effects of hypercapnia through Rac1-GTPase activation by its receptor, CXCR4. Moreover, CXCL12 transgenic murine recipients of orthotopic tracheal transplantation were protected from hypercapnia-induced inhibition of tracheal epithelial cell migration and wound repair. In patients undergoing lobectomy, we found inverse correlation between intrapleural carbon dioxide and pleural CXCL12 levels as well as between CXCL12 levels and alveolopleural leak. Accordingly, we provide first evidence that high carbon dioxide levels impair lung repair by inhibiting epithelial cell migration through two distinct pathways, which can be restored by recombinant CXCL12.

Effects of folic acid withdrawal on transcriptomic profiles in murine triple-negative breast cancer cell lines

We have previously shown that withdrawal of folic acid led to metabolic reprogramming and a less aggressive phenotype in a mouse cell model of triple-negative breast cancer (TNBC). Herein, we evaluate the effects of folic acid withdrawal on transcriptomic profiles in these cells. Murine cell lines were originally derived from a pool of spontaneous mammary tumors grown in MMTV-Wnt1 transgenic mice. Based on their differential molecular characteristics and metastatic potential, these cell lines were previously characterized as non-metastatic epithelial (E-Wnt), non-metastatic mesenchymal (M-Wnt) and metastatic mesenchymal (metM-Wnt^liver) cells. Using custom two-color 180K Agilent microarrays, we have determined gene expression profiles for three biological replicates of each subtype kept on standard medium (2.2 μM folic acid) or folic acid-free medium for 72 h. The analyses revealed that more genes were differentially expressed upon folic acid withdrawal in M-Wnt cells (1884 genes; Benjamini-Hochberg-adjusted P-value <0.05) compared to E-Wnt and metM-Wnt^liver cells (108 and 222 genes, respectively). Pathway analysis has identified that type I interferon signaling was strongly affected by folic acid withdrawal, with interferon-responsive genes consistently being upregulated upon folic acid withdrawal in M-Wnt cells. Of note, repressed interferon signaling has been established as one of the characteristics of aggressive human TNBC, and hence reactivation of this pathway may be a promising therapeutic approach. Overall, while our study indicates that the response to folic acid withdrawal varies by molecular subtype and cellular phenotype, it also underscores the necessity to further investigate one-carbon metabolism as a potential therapeutic means in the treatment of advanced TNBC.

Folate pathways mediating the effects of ethanol in tumorigenesis

Folate and alcohol are dietary factors affecting the risk of cancer development in humans. The interaction between folate status and alcohol consumption in carcinogenesis involves multiple mechanisms. Alcoholism is typically associated with folate deficiency due to reduced dietary folate intake. Heavy alcohol consumption also decreases folate absorption, enhances urinary folate excretion and inhibits enzymes pivotal for one-carbon metabolism. While folate metabolism is involved in several key biochemical pathways, aberrant DNA methylation, due to the deficiency of methyl donors, is considered as a common downstream target of the folate-mediated effects of ethanol. The negative effects of low intakes of nutrients that provide dietary methyl groups, with high intakes of alcohol are additive in general. For example, low methionine, low-folate diets coupled with alcohol consumption could increase the risk for colorectal cancer in men. To counteract the negative effects of alcohol consumption, increased intake of nutrients, such as folate, providing dietary methyl groups is generally recommended. Here mechanisms involving dietary folate and folate metabolism in cancer disease, as well as links between these mechanisms and alcohol effects, are discussed. These mechanisms include direct effects on folate pathways and indirect mediation by oxidative stress, hypoxia, and microRNAs.

Inhibitory effects of ceramide kinase on Rac1 activation, lamellipodium formation, cell migration, and metastasis of A549 lung cancer cells

Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P), a bioactive sphingolipid. Since the mechanisms responsible for regulating the proliferation and migration/metastasis of cancer cells by the CerK/C1P pathway remain unclear, we conducted the present study. The knockdown of CerK in A549 lung and MCF-7 breast cancer cells (shCerK cells) increased the formation of lamellipodia, which are membrane protrusions coupled with cell migration. Mouse embryonic fibroblasts prepared from CerK-null mice also showed an enhanced formation of lamellipodia. The overexpression of CerK inhibited lamellipodium formation in A549 cells. The knockdown of CerK increased the number of cells having lamellipodia with Rac1 and the levels of active Rac1-GTP form, whereas the overexpression of CerK decreased them. CerK was located in lamellipodia after the epidermal growth factor treatment, indicating that CerK functioned there to inhibit Rac1. The migration of A549 cells was negatively regulated by CerK. An intravenous injection of A549-shCerK cells into nude mice resulted in markedly stronger metastatic responses in the lungs than an injection of control cells. The in vitro growth of A549 cells and in vivo expansion after the injection into mouse flanks were not affected by the CerK knockdown. These results suggest that the activation of CerK/C1P pathway has inhibitory roles on lamellipodium formation, migration, and metastasis of A549 lung cancer cells.

Cytosolic 10-formyltetrahydrofolate dehydrogenase regulates glycine metabolism in mouse liver

ALDH1L1 (10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism highly expressed in liver, metabolizes 10-formyltetrahydrofolate to produce tetrahydrofolate (THF). This reaction might have a regulatory function towards reduced folate pools, de novo purine biosynthesis, and the flux of folate-bound methyl groups. To understand the role of the enzyme in cellular metabolism, Aldh1l1^−/− mice were generated using an ES cell clone (C57BL/6N background) from KOMP repository. Though Aldh1l1^−/− mice were viable and did not have an apparent phenotype, metabolomic analysis indicated that they had metabolic signs of folate deficiency. Specifically, the intermediate of the histidine degradation pathway and a marker of folate deficiency, formiminoglutamate, was increased more than 15-fold in livers of Aldh1l1^−/− mice. At the same time, blood folate levels were not changed and the total folate pool in the liver was decreased by only 20%. A two-fold decrease in glycine and a strong drop in glycine conjugates, a likely result of glycine shortage, were also observed in Aldh1l1^−/− mice. Our study indicates that in the absence of ALDH1L1 enzyme, 10-formyl-THF cannot be efficiently metabolized in the liver. This leads to the decrease in THF causing reduced generation of glycine from serine and impaired histidine degradation, two pathways strictly dependent on THF.

Tissue microarray analysis reveals that cofilin expression is a poor prognostic factor in juvenile nasopharyngeal angiofibroma

BACKGROUND

Juvenile nasopharyngeal angiofibroma (JNA) has a high recurrence rate after surgery. Cofilin overexpression is associated with increased tumor cell metastasis, and progression of various human cancers. However, studies on cofilin expression in JNA are rare. The purpose of this study was to investigate the expression and localization of cofilin in a tissue microarray (TMA) of JNA specimens. In addition, we also analyzed its correlation with clinicopathological features and recurrence.

METHODS

Immunohistochemistry was performed to detect cofilin expression in a TMA of samples from 70 JNA patients and 10 control subjects. The association between clinicopathological variables and cofilin immunostaining was analyzed using Pearson's chi-square test. Kaplan-Meier survival analysis was used to calculate the disease-free survival rate, and investigate the effect of cofilin expression on time to recurrence (TTR) in JNA patients. The Cox regression model was used for multivariate survival analysis.

RESULTS

Cofilin was detected in irregular smooth muscle cells, pericytes, less differentiated stromal cells, and plump cells, but not in inactive fibroblasts and mature vascular endothelial cells of JNA specimens. The presence of cofilin in JNA was correlated with tumor stage (p = 0.012) and volume of intraoperative hemorrhage (p < 0.001). JNA patients with high cofilin expression had a higher recurrence rate than those with low cofilin expression (p = 0.012). Cofilin expression and patient's age were significant predictors of TTR, and cofilin was a better predictor for disease recurrence (area under the receiver operating curve [AUROC; 0.711; p = 0.005) than other clinicopathological features.

CONCLUSION

Cofilin is an independent prognostic marker for JNA patients who have undergone surgical treatment and may represent a novel therapeutic target for extensive JNA.

Relationship between p-cofilin and cisplatin resistance in patients with ovarian cancer and the role of p-cofilin in prognosis

OBJECTIVE

This study aims to determine the correlation between p-cofilin expression and cisplatin resistance in patients with ovarian cancer, and also to investigate the role of p-cofilin in prognosis.

PATIENTS AND METHODS

The ovarian cancer cell line A2780/DDP resistant to cisplatin was prepared. The cell resistance to cisplatin was measured via MTT assay. The cell invasion capacity was identified via Transwell assay. The mRNA expression and protein level was evaluated via semi-quantitative PCR and Western blot, respectively. The tumor tissues of patients with cisplatin-resistant ovarian cancer were collected. The relationship between prognosis and p-cofilin expression was analyzed.

RESULTS

The growth rate of A2780 was similar to that of A2780/DDP. The sensitivity of A2780 to cisplatin was significantly higher than that of A2780/DDP (p< 0.01). The migration capacity of A2780/DDP was significantly increased compared to that of A2780 (p< 0.01), indicating that the cisplatin-resistant cell lines were successfully constructed. Both CFL1 mRNA level and p-cofilin level in A2780/DDP was significantly higher than that in A2780 (p< 0.01). The p-cofilin level in cancer tissues in patients with cisplatin-resistant ovarian cancer was significantly higher than that in patients with cisplatin-sensitive ovarian cancer (p< 0.01). The cisplatin resistance was positively correlated with the p-cofilin expression level (r= 0.802, p= 0.023). The survival time of patients with normal or low level of p-cofilin was significantly longer than that of patients with high expression.

CONCLUSION

The cisplatin resistance of ovarian cancer is closely related to the expression level of p-cofilin, which affects the prognosis of patients with ovarian cancer.

Proteomic Investigation of Malignant Major Salivary Gland Tumors

The purpose of this study was to define the proteome profile of fine needle aspiration (FNA) samples of malignant major salivary gland tumors (MSGT) compared to benign counterparts, and to evaluate potential clinical correlations and future applications. Patients affected by MSGT (n = 20), pleomorphic adenoma (PA) (n = 37) and Warthin's tumor (WT) (n = 14) were enrolled. Demographic, clinical and histopathological data were registered for all patients. FNA samples were processed to obtain the protein extracts. Protein separation was obtained by two-dimensional electrophoresis (2-DE) and proteins were identified by mass spectrometry. Western blot analysis was performed to validate the 2-DE results. Statistical differences between groups were calculated by the Mann-Whitney U test for non-normal data. Spearman's rank correlation coefficient was calculated to evaluate correlations among suggested protein biomarkers and clinical parameters. Twelve and 27 differentially expressed spots were found for MSGT versus PA and MSGT versus WT, respectively. Among these, annexin-5, cofilin-1, peptidyl-prolyl-cis-trans-isomerase-A and F-actin-capping-alpha-1 were able to differentiate MSGT from PA, WT, and healthy samples. Moreover, STRING analysis suggested cofilin-1 as a key node of protein interactions. Some of the overexpressed proteins are related to some clinical factors of our cohort, such as survival and outcome. Our results suggest potential protein biomarkers of MSGT, which could allow for more appropriate treatment plans, as well as shedding light on the molecular pathways involved.

Triptolide Inhibits Breast Cancer Cell Metastasis Through Inducing the Expression of miR-146a, a Negative Regulator of Rho GTPase

Triptolide, an extract of Tripterygium wilfordii, has been shown to have a potent anticancer activity. In the present study, it was found that triptolide could effectively induce apoptosis and inhibit proliferation and invasion in malignant MDA-MB-231 breast cancer cells. The study focused on its effect on inhibiting invasion, which has not been extensively reported to date. We predicted that triptolide may change invasion activity via microRNAs (miRNAs), which have been recognized as important regulators of gene expression. miRNAome variation in MDA-MB-231 cells with or without triptolide treatment demonstrated that miR-146a was upregulated following treatment with triptolide. Our previous studies have shown that miR-146a can inhibit migration and invasion by targeting RhoA in breast cancer. This time, we found that miR-146a can target Rac1, another key member of the Rho GTPase family. Luciferase reporter containing Rac1 3′-UTR was constructed to prove this hypothesis. In addition, following treatment with triptolide, the expression of RhoA and Rac1 was found to be decreased. These results indicated that triptolide exerts its anti-invasion activity through a miRNA-mediated mechanism, which indirectly regulates the expression of Rho GTPase. Triptolide combined with miR-146a could improve the effect of triptolide treatment on breast cancer.

Mechanistic insights into Nav1.7-dependent regulation of rat prostate cancer cell invasiveness revealed by toxin probes and proteomic analysis

Voltage-gated sodium channels are involved in tumor metastasis, as potentiating or attenuating their activities affects the migration and invasion process of tumor cells. In the present study, we tested the effect of two peptide toxins, JZTX-I and HNTX-III which function as Nav1.7 activator and inhibitor, respectively, on the migration and invasion ability of prostate cancer (PCa) cell line Mat-LyLu. These two peptides showed opposite effects, and subsequently a comparative proteomic analysis characterized 64 differentially expressed membrane proteins from the JZTX-I- and HNTX-III-treated groups. Among these, 15 proteins were down-regulated and 49 proteins were up-regulated in the HNTX-III group. Bioinformatic analysis showed eight proteins are cytoskeleton proteins or related regulators, which might play important roles in the metastasis of Mat-LyLu cells. The altered expressions of four of these proteins, fascin, muskelin, annexin A2, and cofilin-1, were validated by western blot analysis. Further function network analysis of these proteins revealed that the Rho family GTPases RhoA and Rac1 might be of particular importance for the rat PCa cell invasion. Pharmacological data revealed that JZTX-I and HNTX-III could modulate the Rho signaling pathway in a Nav1.7-dependent manner. In summary, this study suggests that the Nav1.7-dependent regulation of Rho GTPase activity plays a vital role in Mat-LyLu cell migration and invasion and provides new insights into the treatment of PCa.

Loss of ALDH1L1 folate enzyme confers a selective metabolic advantage for tumor progression

ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase) is the enzyme in folate metabolism commonly downregulated in human cancers. One of the mechanisms of the enzyme downregulation is methylation of the promoter of the ALDH1L1 gene. Recent studies underscored ALDH1L1 as a candidate tumor suppressor and potential marker of aggressive cancers. In agreement with the ALDH1L1 loss in cancer, its re-expression leads to inhibition of proliferation and to apoptosis, but also affects migration and invasion of cancer cells through a specific folate-dependent mechanism involved in invasive phenotype. A growing body of literature evaluated the prognostic value of ALDH1L1 expression for cancer disease, the regulatory role of the enzyme in cellular proliferation, and associated metabolic and signaling cellular responses. Overall, there is a strong indication that the ALDH1L1 silencing provides metabolic advantage for tumor progression at a later stage when unlimited proliferation and enhanced motility become critical processes for the tumor expansion. Whether the ALDH1L1 loss is involved in tumor initiation is still an open question.

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.

Metabolic Phenotype of Wild-Type and As3mt-Knockout C57BL/6J Mice Exposed to Inorganic Arsenic: The Role of Dietary Fat and Folate Intake

BACKGROUND

Inorganic arsenic (iAs) is a diabetogen. Interindividual differences in iAs metabolism have been linked to susceptibility to diabetes in iAs-exposed populations. Dietary folate intake has been shown to influence iAs metabolism, but to our knowledge its role in iAs-associated diabetes has not been studied.

OBJECTIVE

The goal of this study was to assess how folate intake, combined with low-fat (LFD) and high-fat diets (HFD), affects the metabolism and diabetogenic effects of iAs in wild-type (WT) mice and in As3mt-knockout (KO) mice that have limited capacity for iAs detoxification.

METHODS

Male and female WT and KO mice were exposed to 0 or [Formula: see text] iAs in drinking water. Mice were fed the LFD containing [Formula: see text] or [Formula: see text] folate for 24 weeks, followed by the HFD with the same folate levels for 13 weeks. Metabolic phenotype and iAs metabolism were examined before and after switching to the HFD.

RESULTS

iAs exposure had little effect on the phenotype of mice fed LFD regardless of folate intake. High folate intake stimulated iAs metabolism, but only in WT females. KO mice accumulated more fat than WT mice and were insulin resistant, with males more insulin resistant than females despite similar %fat mass. Feeding the HFD increased adiposity and insulin resistance in all mice. However, iAs-exposed male and female WT mice with low folate intake were more insulin resistant than unexposed controls. High folate intake alleviated insulin resistance in both sexes, but stimulated iAs metabolism only in female mice.

CONCLUSIONS

Exposure to [Formula: see text] iAs in drinking water resulted in insulin resistance in WT mice only when combined with a HFD and low folate intake. The protective effect of high folate intake may be independent of iAs metabolism, at least in male mice. KO mice were more prone to developing insulin resistance, possibly due to the accumulation of iAs in tissues. https://doi.org/10.1289/EHP3951.

Cucurbitacin E Inhibits Proliferation and Migration of Intestinal Epithelial Cells via Activating Cofilin

The proliferation and migration of intestinal epithelial cell is important to the barrier integrity of intestinal epithelium. Cucurbitacin E (CuE) is one of the tetracyclic triterpenoids extracted from the cucurbitaceae that has been shown to inhibit cancer cell growth, tumor angiogenesis and inflammatory response. Nevertheless, the role of Cucurbitacin E in regulating the proliferation and migration of intestinal epithelial cells remain unclear. In this study, the human intestinal epithelial cell line Caco-2 was treated with CuE and the effects of CuE on cell cycle, proliferation, migration and actin dynamics in Caco-2 cells were investigated successively. We found that CuE significantly inhibited the cell proliferation and migration, inducing the cell cycle arrest in G2/M phase and disrupting the actin dynamic balance in Caco-2 cells. Finally, we showed that CuE inhibited cofilin phosphorylation by suppressing the phosphorylation of both LIM kinase (LIMK)1 and LIMK2 in vitro, resulting in the activation of cofilin, which is closely associated with cell proliferation and migration. Therefore, our studies provided the first evidence that CuE inhibited the proliferation and migration of intestinal epithelial cells via activating cofilin, and CuE is a potential candidate in intestinal disease therapy.

CD74 interacts with CD44 and enhances tumorigenesis and metastasis via RHOA-mediated cofilin phosphorylation in human breast cancer cells

CD74, also known as Ii, was initially considered to participate primarily in antigen presentation. Subsequent studies have shown that CD74 is highly expressed in various types of tumor cells and has multiple roles in a variety of biological processes. CD74 is thought to promote breast cancer metastasis, but the molecular mechanism remains elusive. In the present study, our results showed that CD74 was more highly expressed on the membrane and in the cytoplasm of breast cancer tissues than in control breast tissues. Consistently, CD74 downregulation reduced MDA-MB-231 cell invasion and migration and suppressed protrusions in breast cancer cells. Moreover, CD74 overexpression promoted the phosphorylation of the actin-severing protein cofilin (CFL1), resulting in actin polymerization in breast cancer cells. CD44 was required for the up-regulation of CFL1 phosphorylation by CD74 because CD44 knockdown downregulated CD74-induced CFL1 phosphorylation, while CD74 overexpression could not rescue CFL1 phosphorylation. Moreover, RHOA is necessary for CFL1 phosphorylation and cell migration induced by CD74 in breast cancer cells. Our findings highlight the critical role of CD74 in breast cancer metastasis. New drugs and antibodies targeting CD74 may be effective strategies for breast cancer therapy.

FPPS mediates TGF-β1-induced non-small cell lung cancer cell invasion and the EMT process via the RhoA/Rock1 pathway

Farnesyl pyrophosphate synthase (FPPS), a key enzyme in the mevalonate pathway, was recently shown to play a role in cancer progression. However, its role in non-small cell lung cancer (NSCLC) metastasis and the underlying mechanism remain unclear. In this study, FPPS expression was significantly correlated with TNM stage, and metastasis. Inhibition or knockdown of FPPS blocked TGF-β1-induced cell invasion and epithelial-to-mesenchymal transition (EMT) process. FPPS expression of FPPS was induced by TGF-β1 and FPPS promoted cell invasion and EMT via the RhoA/Rock1 pathway. In conclusion, FPPS mediates TGF-β1-induced lung cancer cell invasion and EMT via the RhoA/Rock1 pathway. These findings suggest new treatment strategies to reduce mortality associated with metastasis in patients with NSCLC.

shRNA-induced silencing of Ras-related C3 botulinum toxin substrate 1 inhibits the proliferation of colon cancer cells through upregulation of BAD and downregulation of cyclin D1

Ras-related C3 botulinum toxin substrate 1 (RAC1) is a member of the Rho family of small GTPases. Recent studies have reported that RAC1 serves an important role in colon cancer cell proliferation. The present study aimed to investigate the effects of RAC1 knockdown on cell proliferation, cell cycle progression and apoptosis of colon cancer cells. Lentivirus-mediated short hairpin RNA (shRNA) was used to knockdown RAC1 expression in colon cancer cell lines, and cell proliferation, apoptosis, cell cycle progression were evaluated by MTT assays and flow cytometry. The differences in mRNAs expression were identified between RAC1-knockdown cells and control cells using a mRNA microarray, following which quantitative PCR (qPCR) and western blot were employed to confirm the results of the mRNA microarray. The proliferative ability of colon cancer cells was significantly decreased following RAC1 knockdown, and RAC1 knockdown increased the apoptotic rate and enhanced cell cycle arrest at G₁ phase in colon cancer cells. In addition, >1,200 known genes were demonstrated to be involved in RAC1-associated tumorigenic functions in SW620 colon cancer cells, as determined by gene chip analysis; these genes were associated with cell proliferation, cell cycle, apoptosis and metastasis. Furthermore, western blot analysis indicated that cyclin D1 was downregulated, whereas B-cell lymphoma 2-associated agonist of cell death (BAD) was upregulated following RAC1 knockdown in colon cancer cells. In conclusion, RAC1 silencing may suppress the proliferation of colon cancer cells by inducing apoptosis and cell cycle arrest. In addition, a large number of genes were revealed to be involved in the process, including BAD, which was upregulated and cyclin D1, which was downregulated. Further studies on these differentially expressed genes may provide a better understanding of the potential roles of RAC1 in colon carcinogenesis.

Metabolic Reprogramming by Folate Restriction Leads to a Less Aggressive Cancer Phenotype

Folate coenzymes are involved in biochemical reactions of one-carbon transfer, and deficiency of this vitamin impairs cellular proliferation, migration, and survival in many cell types. Here, the effect of folate restriction on mammary cancer was evaluated using three distinct breast cancer subtypes differing in their aggressiveness and metastatic potential: noninvasive basal-like (E-Wnt), invasive but minimally metastatic claudin-low (M-Wnt), and highly metastatic claudin-low (metM-Wnt^liver) cell lines, each derived from the same pool of MMTV-Wnt-1 transgenic mouse mammary tumors. NMR-based metabolomics was used to quantitate 41 major metabolites in cells grown in folate-free medium versus standard medium. Each cell line demonstrated metabolic reprogramming when grown in folate-free medium. In E-Wnt, M-Wnt, and metM-Wnt^liver cells, 12, 29, and 25 metabolites, respectively, were significantly different (P < 0.05 and at least 1.5-fold change). The levels of eight metabolites (aspartate, ATP, creatine, creatine phosphate, formate, serine, taurine and β-alanine) were changed in each folate-restricted cell line. Increased glucose, decreased lactate, and inhibition of glycolysis, cellular proliferation, migration, and invasion occurred in M-Wnt and metM-Wnt^liver cells (but not E-Wnt cells) grown in folate-free versus standard medium. These effects were accompanied by altered levels of several folate-metabolizing enzymes, indicating that the observed metabolic reprogramming may result from both decreased folate availability and altered folate metabolism. These findings reveal that folate restriction results in metabolic and bioenergetic changes and a less aggressive cancer cell phenotype.

IMPLICATIONS

Metabolic reprogramming driven by folate restriction represents a therapeutic target for reducing the burden of breast cancer. Mol Cancer Res; 15(2); 189-200. ©2016 AACR.

Celastrus orbiculatus extract suppresses the epithelial-mesenchymal transition by mediating cytoskeleton rearrangement via inhibition of the Cofilin 1 signaling pathway in human gastric cancer

Celastrus orbiculatus is a traditional medicinal plant used in the anti-inflammatory and analgesic treatment of various diseases. A previous study demonstrated that ethyl acetate extract of C. orbiculatus (COE) exhibited significant antitumor effects. However, studies concerning the effects and mechanism of COE in terms of suppressing the epithelial-mesenchymal transition (EMT) in human gastric adenocarcinoma cells have not been performed at present. The present study hypothesized that COE may inhibit EMT in gastric adenocarcinoma cells by regulating cell cytoskeleton rearrangement. The effect of COE on the viability of AGS cells was detected by MTT assay. An EMT model was induced by transforming growth factor-β1. Cell cytoskeleton staining, laser scanning confocal microscopy and electronic microscopy were used to detect the changes in cell morphology and microstructure of gastric adenocarcinoma cells prior and subsequent to COE treatment. Invasion and migration assays were used to observe the effect of COE on the metastatic ability of AGS cells in vitro. The effect of COE on the expression of Cofilin 1 and EMT biomarkers, including Epithelial-cadherin, Neural-cadherin, Vimentin and matrix metalloproteinases, was examined by western blotting in AGS cells. The correlation between Cofilin 1 and EMT was investigated with immunofluorescence and cytoskeleton staining methods. The results demonstrated that COE may significantly inhibit the process of EMT in AGS cells, and that this was concentration-dependent. In addition, COE significantly downregulated the level of Cofilin 1 in a concentration-dependent manner. In conclusion, these results suggested that Cofilin 1 was directly involved in the process of EMT in AGS cells, and that it served an important function. COE may significantly inhibit EMT in AGS cells, potentially by inhibiting the activation of the Cofilin 1 signaling pathway. The present study may provide a basis for the development of novel anticancer drugs and the development of novel therapeutic strategies, targeting Cofilin 1 protein.

TOP2A, GGH, and PECAM1 are associated with hematogenous, lymph node, and peritoneal recurrence in stage II/III gastric cancer patients enrolled in the ACTS-GC study

Background

To identify factors related to relapse sites, we carried out an exploratory biomarker analysis of data from the Adjuvant Chemotherapy Trial of TS-1 for Gastric Cancer study, which is a randomized, controlled trial comparing postoperative adjuvant S-1 therapy with surgery alone in 1,059 patients with stage II/III gastric cancer.

Patients and Methods

Surgical specimens from 829 patients were retrospectively examined, and 63 genes involved in a variety of biological processes were analyzed by quantitative real-time PCR. Gene expression normalized to reference genes was categorized as lower or higher than the median, and association with relapse sites was analyzed based on 5-year relapse-free survival.

Results

Hematogenous, lymph node, and peritoneal recurrence developed in 72, 105, and 138 of the 829 patients, respectively; hazard ratios were 0.79 (95% confidential interval: 0.54–1.16), 0.51 (0.31–0.82), and 0.60 (0.42–0.84), respectively. Expression of platelet/endothelial cell adhesion molecule 1 (PECAM1) and topoisomerase II alpha (TOP2A) was strongly correlated with hematogenous recurrence and peritoneal recurrence, respectively (false discovery rate = 7.7×10⁻⁵ and 0.002, respectively). Gamma-glutamyl hydrolase (GGH) expression was moderately correlated with lymph node recurrence (false discovery rate = 0.34). Relapse-free survival was worse in patients expressing high levels of PECAM1 (hazard ratio = 2.37, 1.65–3.41), TOP2A (hazard ratio = 2.35, 1.55–3.57), or GGH (hazard ratio = 1.87, 1.13–3.08), respectively. A multivariate analysis revealed that these were stronger independent risk factors than tumor histological type.

Conclusion

In patients with stage II/III gastric cancer, TOP2A, GGH, and PECAM1 levels in primary tumors are linked to high risk of hematogenous, lymph node, and peritoneal recurrence, respectively.

Trp-Asp (WD) Repeat Domain 1 Is Essential for Mouse Peri-implantation Development and Regulates Cofilin Phosphorylation

Trp-Asp (WD) repeat domain 1 (WDR1) is a highly conserved actin-binding protein across all eukaryotes and is involved in numerous actin-based processes by accelerating Cofilin severing actin filament. However, the function and the mechanism of WDR1 in mammalian early development are still largely unclear. We now report that WDR1 is essential for mouse peri-implantation development and regulates Cofilin phosphorylation in mouse cells. The disruption of maternal WDR1 does not obviously affect ovulation and female fertility. However, depletion of zygotic WDR1 results in embryonic lethality at the peri-implantation stage. In WDR1 knock-out cells, we found that WDR1 regulates Cofilin phosphorylation. Interestingly, WDR1 is overdosed to regulate Cofilin phosphorylation in mouse cells. Furthermore, we showed that WDR1 interacts with Lim domain kinase 1 (LIMK1), a well known phosphorylation kinase of Cofilin. Altogether, our results provide new insights into the role and mechanism of WDR1 in physiological conditions.

CXCL16/CXCR6 chemokine signaling mediates breast cancer progression by pERK1/2-dependent mechanisms

Our previous studies demonstrate that CXCL6/CXCR6 chemokine axis induces prostate cancer progression by the AKT/mTOR signaling pathway; however, its role and mechanisms underlying invasiveness and metastasis of breast cancer are yet to be elucidated. In this investigation, CXCR6 protein expression was examined using high-density tissue microarrays and immunohistochemistry. Expression of CXCR6 shows a higher epithelial staining in breast cancer nest site and metastatic lymph node than the normal breast tissue, suggesting that CXCR6 may be involved in breast cancer (BC) development. In vitro and in vivo experiments indicate that overexpression of CXCR6 in BC cells has a marked effect on increasing cell migration, invasion and metastasis. In contrast, reduction of CXCR6 expression by shRNAs in these cells greatly reduce its invasion and metastasis ability. Mechanistic analyses show that CXCL16/CXCR6 chemokine axis is capable of modulating activation of RhoA through activating ERK1/2 signaling pathway, which then inhibits the activity of cofilin, thereby enhancing the stability of F-actin, responsible for invasiveness and metastasis of BC.

Taken together, our data shows for the first time that the CXCR6 / ERK1/2/ RhoA / cofilin /F-actin pathway plays a central role in the development of BC. Targeting the signaling pathway may prove beneficial to prevent metastasis and provide a more effective therapeutic strategy for BC.