Forkhead Box Protein O1 Expression Research Articles

Forkhead Box Protein O3 Transcription Factor Negatively Regulates Autophagy in Human Cancer Cells by Inhibiting Forkhead Box Protein O1 Expression and Cytosolic Accumulation

FoxO proteins are important regulators in cellular metabolism and are recognized to be nodes in multiple signaling pathways, most notably those involving PI3K/AKT and mTOR. FoxO proteins primarily function as transcription factors, but recent study suggests that cytosolic FoxO1 participates in the regulation of autophagy. In the current study, we find that cytosolic FoxO1 indeed stimulates cellular autophagy in multiple cancer cell lines, and that it regulates not only basal autophagy but also that induced by rapamycin and that in response to nutrient deprivation. These findings illustrate the importance of FoxO1 in cell metabolism regulation independent of its transcription factor function. In contrast to FoxO1, we find the closely related FoxO3a is a negative regulator of autophagy in multiple cancer cell lines, a previously unrecognized function for this protein, different from its function in benign fibroblast and muscle cells. The induction of autophagy by the knockdown of FoxO3a was found not to be mediated through the suppression of mTORC1 signaling; rather, the regulatory role of FoxO3a on autophagy was determined to be through its ability to transcriptionally suppress FoxO1. This complicated interplay of FoxO1 and FoxO3a suggests a complex checks- and balances-relationship between FoxO3a and FoxO1 in regulating autophagy and cell metabolism.

FOXO1 expression in villous trophoblast of preeclampsia and fetal growth restriction placentas.

Oxidative stress and increased apoptosis are implicated in the pathogenesis of many disorders of pregnancy, including preeclampsia (PE) and fetal growth restriction (FGR). Since the transcription factor FOXO1 (forkhead box protein O1) is implicated in the regulation of a variety of cellular processes, including resistance to oxidative stress, apoptosis and morphogenesis of the placenta, we examined whether FOXO1 expression is abnormal in placentas from patients with PE or FGR. Paracentral sections from grossly unremarkable areas of 9 or 10 placentas each from early third trimester patients (31.7±5.0 weeks) with mild PE, severe PE, FGR and a gestational age-matched comparison group (GA controls) were double immunostained for FOXO1 and E-cadherin, the latter distinguishing villous cytotrophoblast cells (CTB) from syncytiotrophoblast (STB). The numbers of FOXO1-positive and FOXO1 negative STB and CTB nuclei were determined on ten 20x objective fields of each placenta section by three observers who were blinded to the clinical outcome. The results were evaluated by a generalized linear mixed model. In mild PE, FOXO1-positive STB nuclei were significantly decreased in number and FOXO1-negative STB nuclei were increased as compared to GA controls. However, the number of FOXO1-positive and FOXO1-negative CTB nuclei were not significantly changes as compared to GA controls. In severe PE and FGR, the numbers of FOXO-positive and FOXO1-negative STB and CTB were not statistically different from GA controls. Since FOXO1 is critical for placental cellular morphogenesis, abnormal FOXO1 expression may contribute in part to the abnormal trophoblast differentiation in mild PE. The differences in FOXO1 expression in mild and severe PE are consistent with other studies suggesting that the two forms of PE are different disease processes.

MiR-96 promotes cell proliferation and clonogenicity by down-regulating of FOXO1 in prostate cancer cells

The present study aimed to investigate the biological functions of miR-96 in the processes of proliferation and clonogenicity in the prostate cancer cells. miR-96 was identified to be markedly up-regulated in prostate cancer cell and cancer tissues compared with normal prostate cell and normal prostate tissues by microarray method and RT-PCR analysis. Down-regulation of miR-96 expression reduced the proliferation and colony formation ability of PC3 prostate cancer cells, while over-expression of miR-96 induced proliferation and colony formation ability of LNCaP prostate cancer cells. Forkhead box protein O1 (FOXO1) is key tumor suppressors and has been shown to play key roles in the regulation of diverse cellular processes, including cell proliferation, differentiation, cell cycle progression and apoptosis. The expression level of FOXO1 was strikingly up-regulated in PC3 cells after transfected with miR-96 inhibitor, and FOXO1 expression was down-regulated in LNCaP cells after transfected with miR-96 mimics. miR-96 may play a vital role in promoting cell proliferation in human prostate cancer cells. Inhibition of miR-96 caused expression increase of tumor suppressor gene FOXO1, thus manipulating miR-96 expression may be a promising approach in treatment of prostate cancer.

Gene expression of appetite regulatory factors and glucose transporters in hypothalamus, pectoralis major, abdominal fat and liver after insulin injection in chicken lines selected for high or low body weight

Chickens selected for high (HWS) and low (LWS) body weight for 55 generations differ by 12‐fold in body weight at 8 weeks old and display differences in appetite and body composition. We hypothesized that there are differences between the lines in appetite regulatory factor and glucose transporter (GLUT) mRNA that are accentuated by exogenous insulin. Female 87–92 d old HWS and LWS were injected with insulin or vehicle and at 60 min mRNA was measured in hypothalamus, pectoralis major skeletal muscle, abdominal fat and liver. In hypothalamus, neuropeptide Y (NPY) mRNA was lower (P < 0.05) in HWS than LWS, while Forkhead box protein O1 (FOXO1) was greater (P < 0.05) in HWS. Abundance of GLUT1 and GLUT9 mRNA were greater (P < 0.05) in HWS than LWS in all tissues. The GLUT1 mRNA was greater in liver (P < 0.05) than in hypothalamus or fat. Although GLUT3 mRNA was not detected in hypothalamus or muscle, expression was greater (P < 0.05) in fat than liver. For GLUT2, GLUT8 and GLUT9, mRNA was lowest in fat (P < 0.05). In liver, insulin was associated with reduced (P < 0.05) GLUT3 mRNA as compared with vehicle. These data show differential expression of NPY, FOXO1 and glucose transporters in HWS and LWS.

The Evaluation of the FOXO1, KLF9 and YT521 Genes Expression in Human Endometrial Cancer

The current study was designed to explore the changes of the mRNA levels of the YT521, Forkhead box protein O1 (FOXO1), and Krüppel-like factor 9 (KLF9) proteins in human normal and cancerous endometrial tissue. The study was conducted in 30 premenopausal patients diagnosed with endometrial cancer and 20 premenopausal women with no clinically documented abnormalities of the endometrium undergoing hysterectomy. Gene expression levels were assayed using quantitative real-time PCR. The endometrial tissue FOXO1 mRNA level (0.82 +/- 0.27) of patients with endometrial cancer was significantly lower (p < 0.001) than controls (4.51 +/- 2.68). In subjects with endometrial cancer the KLF9 mRNA level (1.12 +/- 0.38) was lower (p < 0.001) when compared to controls (3.11 +/- 1.52). A remarkable (not significant, p = 0.069) increase was found in the YT521 mRNA level of patients' endometrial tissue (11.19 +/- 3.99) in comparison with the control subjects (8.82 +/- 5.01). No significant difference was detected for the FOXO1, KLF9 and YT521 mRNA levels of the endometrial tissue of patients with cancer at different stages. It is suggested that the alteration of the gene expression profiles of FOXO1, KLF9 and YT521, which occur in human endometrial cancers likely play a crucial role in initiation of cancer.

Upregulation of MircoRNA-370 Induces Proliferation in Human Prostate Cancer Cells by Downregulating the Transcription Factor FOXO1

Forkhead box protein O1 (FOXO1), a key member of the FOXO family of transcription factors, acts as a tumor suppressor and has been associated with various key cellular functions, including cell growth, differentiation, apoptosis and angiogenesis. Therefore, it is puzzling why FOXO protein expression is downregulated in cancer cells. MicroRNAs, non-coding 20∼22 nucleotide single-stranded RNAs, result in translational repression or degradation and gene silencing of their target genes, and significantly contribute to the regulation of gene expression. In the current study, we report that miR-370 expression was significantly upregulated in five prostate cancer cell lines, compared to normal prostatic epithelial (PrEC) cells. Ectopic expression of miR-370 induced proliferation and increased the anchorage-independent growth and colony formation ability of DU145 and LNCaP prostate cancer cells, while inhibition of miR-370 reduced proliferation, anchorage-independent growth and colony formation ability. Furthermore, upregulation of miR-370 promoted the entry of DU145 and LNCaP prostate cancer cells into the G1/S cell cycle transition, which was associated with downregulation of the cyclin-dependent kinase (CDK) inhibitors, p27Kip1 and p21Cip1, and upregulation of the cell-cycle regulator cyclin D1 mRNA. Additionally, we demonstrated that miR-370 can downregulate expression of FOXO1 by directly targeting the FOXO1 3′-untranslated region. Taken together, our results suggest that miR-370 plays an important role in the proliferation of human prostate cancer cells, by directly suppressing the tumor suppressor FOXO1.

Effects of long-term treatment with the dipeptidyl peptidase-4 inhibitor vildagliptin on islet endocrine cells in non-obese type 2 diabetic Goto-Kakizaki rats

Reduced β cell mass is a characteristic feature of type 2 diabetes and incretin therapy is expected to prevent this condition. However, it is unknown whether dipeptidyl peptidase-4 inhibitors influence β and α cell mass in animal models of diabetes that can be translated to humans. Therefore, we examined the long-term effects of treatment with the dipeptidyl peptidase-4 inhibitor vildagliptin on islet morphology in Goto-Kakizaki (GK) rats, a spontaneous, non-obese model of type 2 diabetes, and explored the underlying mechanisms. Four-week-old GK rats were orally administered with vildagliptin (15mg/kg) twice daily for 18 weeks. Glucose tolerance was monitored during the study. After 18 weeks, β and α cell morphology and the expression of molecules involved in cell proliferation and cell death were examined by immunohistochemistry and morphometric analysis. We found that vildagliptin improved glucose tolerance and insulin secretion, and suppressed hyperglucagonemia by increasing plasma active glucagon-like peptide-1 concentrations. β cell mass was reduced in GK rats to 40% of that in Wistar rats, but was restored to 80% by vildagliptin. Vildagliptin enhanced β and α cell proliferation, and increased the number of small neogenetic islets. Vildagliptin also reduced the number of 8-hydroxy-2′-deoxyguanosine-positive cells and forkhead box protein O1 expression, inhibited macrophage infiltration, and enhanced S6 ribosomal protein, molecule of target of rapamycin, and pancreatic duodenal homeobox 1 expression. These results indicate that starting vildagliptin treatment from an early age improved glucose tolerance and preserved islet β cell mass in GK rats by facilitating the proliferation of islet endocrine cells.