In vitro and in vivo effects of easily administered, low-toxic retinoid and phenylacetate compounds on human neuroblastoma cells

Exploring Neuronal Differentiation Profiles in SH-SY5Y Cells through Magnetic Levitation Analysis

Magnetic levitation (MagLev) is a powerful and versatile technique that can sort objects based on their density differences. This paper reports the sorting of SH-SY5Y cells for neuronal differentiation by the MagLev technique. Herein, SH-SY5Y cells were differentiated with retinoic acid (RA) and brain-derived neurotrophic factor (BDNF). Neuronal differentiation was confirmed by neurite extension measurement and the immunostaining assay. Neurites reached the maximum length on day 9 after sequential treatment with RA-BDNF. Neuronal marker expression of un-/differentiated cells was investigated by β-III tubulin and neuronal nuclei (NeuN) and differentiated cells exhibited a higher fluorescence intensity compared to un-/differentiated cells. MagLev results revealed that the density of differentiated SH-SY5Y cells gradually increased from 1.04 to 1.06 g/mL, while it remained stable at 1.05 g/mL for un-/differentiated cells. These findings signified that cell density would be a potent indicator of neuronal differentiation. Overall, it was shown that MagLev methodology can provide rapid, label-free, and easy sorting to analyze the differentiation of cells at a single-cell level.

Metabolomics of cerebrospinal fluid reveals candidate diagnostic biomarkers to distinguish between spinal muscular atrophy type II and type III

AIMS

Classification of spinal muscular atrophy (SMA) is associated with the clinical prognosis; however, objective classification markers are scarce. This study aimed to identify metabolic markers in the cerebrospinal fluid (CSF) of children with SMA types II and III.

METHODS

CSF samples were collected from 40 patients with SMA (27 with type II and 13 with type III) and analyzed for metabolites.

RESULTS

We identified 135 metabolites associated with SMA types II and III. These were associated with lysine degradation and arginine, proline, and tyrosine metabolism. We identified seven metabolites associated with the Hammersmith Functional Motor Scale: 4-chlorophenylacetic acid, adb-chminaca,(+/-)-, dodecyl benzenesulfonic acid, norethindrone acetate, 4-(undecan-5-yl) benzene-1-sulfonic acid, dihydromaleimide beta-d-glucoside, and cinobufagin. Potential typing biomarkers, N-cyclohexylformamide, cinobufagin, cotinine glucuronide, N-myristoyl arginine, 4-chlorophenylacetic acid, geranic acid, 4-(undecan-5-yl) benzene, and 7,8-diamino pelargonate, showed good predictive performance. Among these, N-myristoyl arginine was unaffected by the gene phenotype.

CONCLUSION

This study identified metabolic markers are promising candidate prognostic factors for SMA. We also identified the metabolic pathways associated with the severity of SMA. These assessments can help predict the outcomes of screening SMA classification biomarkers.

Differentiating Neuroblastoma: A Systematic Review of the Retinoic Acid, Its Derivatives, and Synergistic Interactions

A neuroblastoma (NB) is a solid paediatric tumour arising from undifferentiated neuronal cells. Despite the recent advances in disease management and treatment, it remains one of the leading causes of childhood cancer deaths, thereby necessitating the development of new therapeutic agents and regimens. Retinoic acid (RA), a vitamin A derivative, is a promising agent that can induce differentiation in NB cells. Its isoform, 13-cis RA or isotretinoin, is used in NB therapy; however, its effectiveness is limited to treating a minimal residual disease as maintenance therapy. As such, research focuses on RA derivatives that might increase the anti-NB action or explores the potential synergy between RA and other classes of drugs, such as cellular processes mediators, epigenetic modifiers, and immune modulators. This review summarises the in vitro, in vivo, and clinical data of RA, its derivatives, and synergising compounds, thereby establishing the most promising RA derivatives and combinations of RA for further investigation.

Cell death-based treatment of neuroblastoma

Neuroblastoma (NB) is the most common solid childhood tumor outside the brain and causes 15% of childhood cancer-related mortality. The main drivers of NB formation are neural crest cell-derived sympathoadrenal cells that undergo abnormal genetic arrangements. Moreover, NB is a complex disease that has high heterogeneity and is therefore difficult to target for successful therapy. Thus, a better understanding of NB development helps to improve treatment and increase the survival rate. One of the major causes of sporadic NB is known to be MYCN amplification and mutations in ALK (anaplastic lymphoma kinase) are responsible for familial NB. Many other genetic abnormalities can be found; however, they are not considered as driver mutations, rather they support tumor aggressiveness. Tumor cell elimination via cell death is widely accepted as a successful technique. Therefore, in this review, we provide a thorough overview of how different modes of cell death and treatment strategies, such as immunotherapy or spontaneous regression, are or can be applied for NB elimination. In addition, several currently used and innovative approaches and their suitability for clinical testing and usage will be discussed. Moreover, significant attention will be given to combined therapies that show more effective results with fewer side effects than drugs targeting only one specific protein or pathway.

Retinoic acid is a cofactor for translational regulation of vascular endothelial growth factor in human endometrial stromal cells

Vascular endothelial growth factor (VEGF) and endometrial angiogenesis play a critical role in successful embryonic implantation. Despite many studies of the effects of estrogen and progesterone on VEGF expression, its focal regulation at the site of implantation is unknown. Retinoic acid (RA) has been reported to regulate VEGF in a variety of cell types. Because localized RA synthesis occurs within the periimplantation endometrium, we tested the possibility that RA regulates VEGF production in endometrial stromal cells. Using primary and telomerase-immortalized human endometrial stromal cells, we determined that RA alone did not alter constitutive levels of VEGF production, but markedly amplified secretion when the cells were cotreated with activators of VEGF gene transcription (12-O-tetradecanoyl phorbol-13-acetate, TPA; TGF-beta; and IL-1beta). Whereas TPA or TGF-beta alone stimulated VEGF promoter activity and up-regulated mRNA levels, significant protein secretion was detected only after RA was added to the culture systems. Analysis of retinoids in secretory phase endometrial biopsies indicated that endogenous RA accumulated at concentrations sufficient to induce VEGF secretion. Polyribosome profile analysis showed that the addition of RA to transcriptional activators of VEGF shifted the translational suppressed VEGF mRNA transcripts into larger polyribosome complexes engaged in active translation. Although the precise mechanism(s) of the RA effect remains to be defined, it appears to be mediated by reactive oxygen species; the antioxidant N-acetylcysteine inhibited RA+TPA-stimulated secretion of VEGF by more than 80%. Together, our results demonstrate that in human endometrial stromal cells, RA can combine with transcriptional activators of VEGF to augment VEGF secretion through a translational mechanism of action mediated by reactive oxygen species. These findings suggest a link between the spatiotemporal changes of retinoid synthesis in the periimplantation stroma and the capacity to quickly up-regulate focal VEGF secretion needed to induce early angiogenic events of pregnancy.

Carcinogenic effects in a phenylketonuria mouse model

Phenylketonuria (PKU) is a metabolic disorder caused by impaired phenylalanine hydroxylase (PAH). This condition results in hyperphenylalaninemia and elevated levels of abnormal phenylalanine metabolites, among which is phenylacetic acid/phenylacetate (PA). In recent years, PA and its analogs were found to have anticancer activity against a variety of malignancies suggesting the possibility that PKU may offer protection against cancer through chronically elevated levels of PA. We tested this hypothesis in a genetic mouse model of PKU (PAH(enu2)) which has a biochemical profile that closely resembles that of human PKU. Plasma levels of phenylalanine in homozygous (HMZ) PAH(enu2) mice were >12-fold those of heterozygous (HTZ) littermates while tyrosine levels were reduced. Phenylketones, including PA, were also markedly elevated to the range seen in the human disease. Mice were subjected to 7,12 dimethylbenz[a]anthracene (DMBA) carcinogenesis, a model which is sensitive to the anticancer effects of the PA derivative 4-chlorophenylacetate (4-CPA). Tumor induction by DMBA was not significantly different between the HTZ and HMZ mice, either in total tumor development or in the type of cancers that arose. HMZ mice were then treated with 4-CPA as positive controls for the anticancer effects of PA and to evaluate its possible effects on phenylalanine metabolism in PKU mice. 4-CPA had no effect on the plasma concentrations of phenylalanine, phenylketones, or tyrosine. Surprisingly, the HMZ mice treated with 4-CPA developed an unexplained neuromuscular syndrome which precluded its use in these animals as an anticancer agent. Together, these studies support the use of PAH(enu2) mice as a model for studying human PKU. Chronically elevated levels of PA in the PAH(enu2) mice were not protective against cancer.

Modulation by phenylacetate of early estrogen-mediated events in MCF-7 breast cancer cells

PURPOSE

Phenylacetate (PA) and its derivatives constitute a group of small aromatic fatty acids that have been of considerable interest due to their anticancer properties in a number of experimental systems. We previously showed that PA can inhibit the growth of estrogen receptor (ER)+ breast cancer cells and that this activity is, at least in part, mediated by the ability of the compound to inhibit transcriptional activation driven by estrogen response elements (EREs). We now shed additional light on the antiestrogenic action of PA by determining its effects on early events in the estrogen-signaling pathway.

METHODS

MCF-7 breast cancer cells were used in this study. ER-ERE binding activity, and subsequent effects on ER and progesterone receptors (PR), c-myc, and the cyclin-dependent kinase inhibitor p21ASF1/CP1/MDA-6 (p21) were evaluated using electrophoretic mobility shift assays, real-time RT-PCR, and western blotting methodologies. Effects of PA on p21 promoter activity were assessed in transient transfection experiments utilizing p21 promoter-reporter gene constructs.

RESULTS

We demonstrate that PA treatment can block ER-ERE binding activity and that this effect is accompanied by downregulation of PR and c-myc, two genes which are transcriptionally regulated by estrogen through novel-ER-binding sites. Suppression of c-myc by PA is followed by increased mRNA levels of p21, an effect that is mediated by PA activation of the p21 promoter. Forced overexpression of c-myc through co-transfection of MCF-7 cells with a c-myc expression plasmid prevented PA upregulation of p21 promoter activity.

CONCLUSIONS

These findings confirm the potent antiestrogenic properties of PA, indicate that its effects are mediated by inhibiting ER-ERE interactions, and suggest that downregulation of c-myc is an early event leading to increased p21 expression and cell growth inhibition.

CSK controls retinoic acid receptor (RAR) signaling: a RAR-c-SRC signaling axis is required for neuritogenic differentiation

Herein, we report the first evidence that c-SRC is required for retinoic acid (RA) receptor (RAR) signaling, an observation that suggests a new paradigm for this family of nuclear hormone receptors. We observed that CSK negatively regulates RAR functions required for neuritogenic differentiation. CSK overexpression inhibited RA-mediated neurite outgrowth, a result which correlated with the inhibition of the SFK c-SRC. Consistent with an extranuclear effect of CSK on RAR signaling and neurite outgrowth, CSK overexpression blocked the downstream activation of RAC1. The conversion of GDP-RAC1 to GTP-RAC1 parallels the activation of c-SRC as early as 15 min following all-trans-retinoic acid treatment in LA-N-5 cells. The cytoplasmic colocalization of c-SRC and RARgamma was confirmed by immunofluorescence staining and confocal microscopy. A direct and ligand-dependent binding of RAR with SRC was observed by surface plasmon resonance, and coimmunoprecipitation studies confirmed the in vivo binding of RARgamma to c-SRC. Deletion of a proline-rich domain within RARgamma abrogated this interaction in vivo. CSK blocked the RAR-RA-dependent activation of SRC and neurite outgrowth in LA-N-5 cells. The results suggest that transcriptional signaling events mediated by RA-RAR are necessary but not sufficient to mediate complex differentiation in neuronal cells. We have elucidated a nongenomic extranuclear signal mediated by the RAR-SRC interaction that is negatively regulated by CSK and is required for RA-induced neuronal differentiation.

Inhibition of estrogen-induced mammary tumor formation in MMTV-aromatase transgenic mice by 4-chlorophenylacetate

Treatment of estrogen-sensitive breast cancer with selective estrogen selective modulators (SERMs) and, more recently, aromatase inhibitors has met with wide success. However, antagonism of estrogen receptor (ER) activity in breast carcinomas by SERMs such as tamoxifen has been associated with increased risk of cancer in other tissue such as the endometrium. Furthermore, current therapies using aromatase inhibitors have side effects on bone resulting in development of osteoporosis in some patients. We present in this paper the results of a study using 4-chlorophenylacetate (4-CPA), a compound which belongs to a family of small aromatic fatty acids that has been shown to possess anticancer properties, to treat DMBA exposed MMTV-aromatase mice. These animals exhibit elevated levels of estrogen in their mammary glands and develop estrogen-responsive tumors. Consistent with our earlier findings showing that 4-CPA inhibited the growth of ER positive breast cancer cells in vitro, we now demonstrate that this compound inhibits tumor formation in MMTV-aromatase mice. This effect was not associated with reduction of ER expression in their mammary tissue, or to alteration of aromatase levels or activity. The data suggest that 4-CPA is a novel therapeutic agent that could be used in the prevention or treatment of estrogen-sensitive breast cancer.

Intestinal absorption and metabolism of retinoyl beta-glucuronide in humans, and of 15-[14C]-retinoyl beta-glucuronide in rats of different vitamin A status

In order to prove the hypothesis that humans and animals with adequate vitamin A status do not absorb and metabolize orally administered all-trans retinoyl beta-glucuronide, unlabeled retinoyl glucuronide (0.1 mmol) was orally dosed to fasting well-nourished young men. Neither retinoyl glucuronide nor retinoic acid, a possible metabolite, appeared in the blood within 12 h after ingestion. Next, radiolabeled all-trans 15-[14C]-retinoyl beta-glucuronide was chemically synthesized by a new procedure, and fed orally to rats of different vitamin A status. Analysis of blood and other tissues 5 or 24 h after the dose, showed the presence of radioactivity ( approximately 0.5%) in the blood of vitamin A deficient rats, but not in sufficient rats. Livers of all rats contained small, but detectable amounts (0.3 to 1.1% of the dose) of radioactivity. The accumulation of radioactivity in the liver was highest in deficient rats. Analysis of the retinoids showed that the radioactivity in serum and liver was due to retinoic acid formed from retinoyl glucuronide. Within 24 h after the dose, 31 to 40% of the administered radioactivity was excreted in the feces, and 2 to 4.7% of the dose was excreted in the urine. Results of the present studies show that oral administration of retinoyl beta-glucuronide did not give rise to detectable changes in blood retinoyl glucuronide and/or retinoic acid concentrations in humans or rats with adequate vitamin A status.