OGA heterozygosity suppresses intestinal tumorigenesis in Apc min/+ mice

Emerging evidence suggests that aberrant O-GlcNAcylation is associated with tumorigenesis. Many oncogenic factors are O-GlcNAcylated, which modulates their functions. However, it remains unclear how O-GlcNAcylation and O-GlcNAc cycling enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), affect the development of cancer in animal models. In this study, we show that reduced level of OGA attenuates colorectal tumorigenesis induced by Adenomatous polyposis coli (Apc) mutation. The levels of O-GlcNAcylation and O-GlcNAc cycling enzymes were simultaneously upregulated in intestinal adenomas from mice, and in human patients. In two independent microarray data sets, the expression of OGA and OGT was significantly associated with poor cancer-specific survival of colorectal cancer (CRC) patients. In addition, OGA heterozygosity, which results in increased levels of O-GlcNAcylation, attenuated intestinal tumor formation in the Apc min/+ background. Apc min/+ OGA +/-mice exhibited a significantly increased survival rate compared with Apc min/+ mice. Consistent with this, Apc min/+ OGA +/-mice expressed lower levels of Wnt target genes than Apc min/+. However, the knockout of OGA did not affect Wnt/??-catenin signaling. Overall, these findings suggest that OGA is crucial for tumor growth in CRC independently of Wnt/??-catenin signaling.open2

Low free 25-hydroxyvitamin D and high vitamin D binding protein and parathyroid hormone in obese Caucasians. A complex association with bone?

Background Studies have shown altered vitamin D metabolism in obesity. We assessed differences between obese and normal-weight subjects in total, free, and bioavailable 25-hydroxyvitamin D (25(OH) D, 25(OH) D-Free, and 25(OH) D-Bio, respectively), vitamin D binding protein (DBP), parathyroid hormone (PTH) and bone traits. Methods 595 37-47-year-old healthy Finnish men and women stratified by BMI were examined in this cross-sectional study. Background characteristic and intakes of vitamin D and calcium were collected. The concentrations of 25(OH) D, PTH, DBP, albumin and bone turnover markers were determined from blood. 25(OH) D-Free and 25(OH) D-Bio were calculated. pQCT was performed at radius and tibia. Results Mean +/- SE (ANCOVA) 25(OH) D-Free (10.8 +/- 0.6 vs 12.9 +/- 0.4 nmol/L; P = 0.008) and 25(OH) DBio (4.1 +/- 0.3 vs 5.1 +/- 0.1 nmol/L; P = 0.003) were lower in obese than in normal-weight women. In men, 25(OH) D (48.0 +/- 2.4 vs 56.4 +/- 2.0 nmol/L, P = 0.003), 25(OH) D-Free (10.3 +/- 0.7 vs 12.5 +/- 0.6 pmol/L; P = 0.044) and 25(OH) D-Bio (4.2 +/- 0.3 vs 5.1 +/- 0.2 nmol/L; P = 0.032) were lower in obese. Similarly in all subjects, 25(OH) D, 25(OH) D-Free and 25(OH) D-Bio were lower in obese (P Conclusions The associations between BMI and 25(OH) D, 25(OH) D-Free, and 25(OH) D-Bio, DBP, and PTH suggest that obese subjects may differ from normal-weight subjects in vitamin D metabolism. BMI associated positively with trabecular bone traits and CSI in our study, and slightly negatively with cortical bone traits. Surprisingly, there was a negative association of free and bioavailable 25(OH) D and some of the bone traits in obese women.Peer reviewe

Gene and protein expression of O-GlcNAc-cycling enzymes in human laryngeal cancer

Aberrant protein O-GlcNAcylation may contribute to the development and malignant behavior of many cancers. This modification is controlled by O-linked β-N-acetylglucosamine transferase (OGT) and O-GlcNAcase (OGA). The aim of this study was to determine the expression of O-GlcNAc cycling enzymes mRNA/protein and to investigate their relationship with clinicopathological parameters in laryngeal cancer. The mRNA levels of OGT and MGEA5 genes were determined in 106 squamous cell laryngeal cancer (SCLC) cases and 73 non-cancerous adjacent laryngeal mucosa (NCLM) controls using quantitative real-time PCR. The level of OGT and OGA proteins was analyzed by Western blot. A positive expression of OGT and MGEA5 transcripts and OGT and OGA proteins was confirmed in 75.5 and 68.9 % and in 43.7 and 59.4 % samples of SCLC, respectively. Higher levels of mRNA/protein for both OGT and OGA as well as significant increases of 60 % in total protein O-GlcNAcylation levels were noted in SCLC compared with NCLM (p < 0.05). As a result, an increased level of OGT and MGEA5 mRNA was related to larger tumor size, nodal metastases, higher grade and tumor behavior according to TFG scale, as well as incidence of disease recurrence (p < 0.05). An inverse association between OGT and MGEA5 transcripts was determined with regard to prognosis (p < 0.05). In addition, the highest OGT and OGA protein levels were observed in poorly differentiated tumors (p < 0.05). No correlations with other parameters were noted, but the results showed a trend of more advanced tumors to be more frequently OGT and OGA positive. The results suggest that increased O-GlcNAcylation may have an effect on tumor aggressiveness and prognosis in laryngeal cancer.This work was supported, in part, by a grant from the National Science Council, Poland (N403 043 32/2326), by the statutory fund of the Department of Cytobiochemistry, University of Łódź, Poland (506/811

O-GlcNAc transferase maintains metabolic homeostasis in response to CDK9 inhibition

Co-targeting of O-GlcNAc transferase (OGT) and the transcriptional kinase CDK9 is toxic to prostate cancer cells. As OGT is an essential glycosyltransferase, identifying an alternative target showing similar effects is of great interest. Here, we used a multiomics approach (transcriptomics, metabolomics and proteomics) to better understand the mechanistic basis of the combinatorial lethality between OGT and CDK9 inhibition. CDK9 inhibition preferentially affected transcription. In contrast, depletion of OGT activity predominantly remodeled the metabolome. Using an unbiased systems biology approach (weighted gene correlation network analysis), we discovered that CDK9 inhibition alters mitochondrial activity / flux, and high OGT activity is essential to maintain mitochondrial respiration when CDK9 activity is depleted. Our metabolite profiling data revealed that pantothenic acid (vitamin B5) is the metabolite that is most robustly induced by both OGT and OGT+CDK9 inhibitor treatments, but not by CDK9 inhibition alone. Finally, supplementing prostate cancer cell lines with vitamin B5 in the presence of CDK9 inhibitor mimics the effects of co-targeting OGT and CDK9

c-Myc antagonises the transcriptional activity of the androgen receptor in prostate cancer affecting key gene networks.

Prostate cancer (PCa) is the most common non-cutaneous cancer in men. The androgen receptor (AR), a ligand-activated transcription factor, constitutes the main drug target for advanced cases of the disease. However, a variety of other transcription factors and signaling networks have been shown to be altered in patients and to influence AR activity. Amongst these, the oncogenic transcription factor c-Myc has been studied extensively in multiple malignancies and elevated protein levels of c-Myc are commonly observed in PCa. Its impact on AR activity, however, remains elusive. In this study, we assessed the impact of c-Myc overexpression on AR activity and transcriptional output in a PCa cell line model and validated the antagonistic effect of c-MYC on AR-targets in patient samples. We found that c-Myc overexpression partially reprogrammed AR chromatin occupancy and was associated with altered histone marks distribution, most notably H3K4me1 and H3K27me3. We found c-Myc and the AR co-occupy a substantial number of binding sites and these exhibited enhancer-like characteristics. Interestingly, c-Myc overexpression antagonised clinically relevant AR target genes. Therefore, as an example, we validated the antagonistic relationship between c-Myc and two AR target genes, KLK3 (alias PSA, prostate specific antigen), and Glycine N-Methyltransferase (GNMT), in patient samples. Our findings provide unbiased evidence that MYC overexpression deregulates the AR transcriptional program, which is thought to be a driving force in PCa

Inhibition of O-GlcNAc transferase renders prostate cancer cells dependent on CDK9

O-GlcNAc transferase (OGT) is a nutrient-sensitive glycosyltransferase that is overexpressed in prostate cancer, the most common cancer in males. We recently developed a specific and potent inhibitor targeting this enzyme, and here, we report a synthetic lethality screen using this compound. Our screen identified pan-cyclin-dependent kinase (CDK) inhibitor AT7519 as lethal in combination with OGT inhibition. Follow-up chemical and genetic approaches identified CDK9 as the major target for synthetic lethality with OGT inhibition in prostate cancer cells. OGT expression is regulated through retention of the fourth intron in the gene and CDK9 inhibition blunted this regulatory mechanism. CDK9 phosphorylates carboxy-terminal domain (CTD) of RNA Polymerase II to promote transcription elongation. We show that OGT inhibition augments effects of CDK9 inhibitors on CTD phosphorylation and general transcription. Finally, the combined inhibition of both OGT and CDK9 blocked growth of organoids derived from patients with metastatic prostate cancer, but had minimal effects on normal prostate spheroids. We report a novel synthetic lethal interaction between inhibitors of OGT and CDK9 that specifically kills prostate cancer cells, but not normal cells. Our study highlights the potential of combining OGT inhibitors with other treatments to exploit cancer-specific vulnerabilities

Lipid degradation promotes prostate cancer cell survival.

Prostate cancer is the most common male cancer and androgen receptor (AR) is the major driver of the disease. Here we show that Enoyl-CoA delta isomerase 2 (ECI2) is a novel AR-target that promotes prostate cancer cell survival. Increased ECI2 expression predicts mortality in prostate cancer patients (p = 0.0086). ECI2 encodes for an enzyme involved in lipid metabolism, and we use multiple metabolite profiling platforms and RNA-seq to show that inhibition of ECI2 expression leads to decreased glucose utilization, accumulation of fatty acids and down-regulation of cell cycle related genes. In normal cells, decrease in fatty acid degradation is compensated by increased consumption of glucose, and here we demonstrate that prostate cancer cells are not able to respond to decreased fatty acid degradation. Instead, prostate cancer cells activate incomplete autophagy, which is followed by activation of the cell death response. Finally, we identified a clinically approved compound, perhexiline, which inhibits fatty acid degradation, and replicates the major findings for ECI2 knockdown. This work shows that prostate cancer cells require lipid degradation for survival and identifies a small molecule inhibitor with therapeutic potential