Dissection of N-, O- and glycosphingolipid glycosylation changes in PaTu-S pancreatic adenocarcinoma cells upon TGF-β challenge

Pancreatic ductal adenocarcinoma (PDAC) is characterized by poor prognosis and high mortality. Transforming growth factor-β (TGF-β) plays a key role in tumor progression, which is often associated with aberrant glycosylation. How PDAC cells respond to TGF-β and the role of glycosylation therein is, however, not well known. Here, we investigated the TGF-β-mediated response and glycosylation changes in SMAD4-deficient PaTu-8955S (PaTu-S) cell line. PaTu-S cells responded to TGF-β by upregulating SMAD2 phosphorylation and target gene expression. TGF-β induced expression of the mesenchymal marker N-cadherin, but did not significantly affect epithelial marker E-cadherin expression. The differences of N-glycans, O-glycans and glycosphingolipid (GSL) glycans in PaTu-S cells with TGF-β stimulation were examined. TGF-β treatment primarily induced N-glycome aberrations involving elevated levels of branching, core fucosylation, and sialylation in PaTu-S cells, in line with TGF-β-induced changes in the expression of glycosylation-related genes. In addition, we observed differences in O- and GSL-glycosylation profiles after TGF-β treatment, including lower levels of sialylated Tn antigen, and neoexpression of globosides. Furthermore, SOX4 expression was upregulated upon TGF-β stimulation, and its depletion blocked the TGF-β-induced N-glycomic changes. Thus, our study provides a mechanism by which TGF-β-induced N-glycosylation changes in SOX4 dependent and SMAD4 independent manner in pancreatic cancer cells. Our results open up avenues to study the relevance of glycosylation in TGF-β signaling in SMAD4 inactivated PDAC.

A tumor-promoting role for soluble TβRIII in glioblastoma

Purpose Members of the transforming growth factor (TGF)-β superfamily play a key role in the regulation of the malignant phenotype of glioblastoma by promoting invasiveness, angiogenesis, immunosuppression, and maintaining stem cell-like properties. Betaglycan, a TGF-β coreceptor also known as TGF-β receptor III (TβRIII), interacts with members of the TGF-β superfamily and acts as membrane-associated or shed molecule. Shed, soluble TβRIII (sTβRIII) is produced upon ectodomain cleavage of the membrane-bound form. Elucidating the role of TβRIII may improve our understanding of TGF-β pathway activity in glioblastoma Methods Protein levels of TβRIII were determined by immunohistochemical analyses and ex vivo single-cell gene expression profiling of glioblastoma tissue respectively. In vitro, TβRIII levels were assessed investigating long-term glioma cell lines (LTCs), cultured human brain-derived microvascular endothelial cells (hCMECs), glioblastoma-derived microvascular endothelial cells, and glioma-initiating cell lines (GICs). The impact of TβRIII on TGF-β signaling was investigated, and results were validated in a xenograft mouse glioma model Results Immunohistochemistry and ex vivo single-cell gene expression profiling of glioblastoma tissue showed that TβRIII was expressed in the tumor tissue, predominantly in the vascular compartment. We confirmed this pattern of TβRIII expression in vitro. Specifically, we detected sTβRIII in glioblastoma-derived microvascular endothelial cells. STβRIII facilitated TGF-β-induced Smad2 phosphorylation in vitro and overexpression of sTβRIII in a xenograft mouse glioma model led to increased levels of Smad2 phosphorylation, increased tumor volume, and decreased survival Conclusions These data shed light on the potential tumor-promoting role of extracellular shed TβRIII which may be released by glioblastoma endothelium with high sTβRIII levels.

Silibinin Inhibits TGF-β-induced MMP-2 and MMP-9 Through Smad Signaling Pathway in Colorectal Cancer HT-29 Cells

Background: Metastasis of cancer cells is the primary responsible for death in patients with colorectal cancer (CRC). Transforming growth factor-β (TGF-β)-induced matrix metalloproteinases (MMPs) are essential for the metastasis process. Silibinin is a natural compound extracted from the Silybum marianum that exhibits anti-neoplastic activity in cancer cell lines. In this study, we evaluated the effects of silibinin on MMP-2 and MMP-9 induced by TGF-β in human HT-29 CRC cell line and the potential mechanism underlying the effects. Methods: The present in vitro study was done on the HT-29 cell line. The HT-29 cell line was cultured in RPMI1640 and exposed to TGF- β (5 ng/ml) in the absence and presence of different concentrations of silibinin (10, 25, 50, and 100 μM). The effect of silibinin on HT-29 cell viability was measured with the MTT assay. A real-time polymerase chain reaction (Real-Time PCR) determined the relative mRNA expression of MMP-2 and MMP-9. Western blotting was employed to examine MMP-2 and MMP 9 protein expression and Smad2 phosphorylation. Results: Silibinin inhibits cell viability of HT-29 cell line at 24 hours in a dose-dependent manner. TGF-β increased the mRNA and protein expression of MMP-2, MMP-9, and phosphorylated Smad2 compared to controls. Pharmacological inhibition with silibinin markedly blocked TGF-β–induced MMP-2 and MMP-9 mRNA and protein expression and Smad2 phosphorylation. Conclusion: Silibinin decreased the cell viability of HT-29 cancer cells in a dose-dependent manner. Silibinin also inhibited TGF-β-stimulated MMP-2 and MMP-9 expression in HT-29 cells, possibly mediated with the Smad2 signaling pathway.

UV-Induced Reduction of ACVR1C Decreases SREBP1 and ACC Expression by the Suppression of SMAD2 Phosphorylation in Normal Human Epidermal Keratinocytes

Activin A receptor type 1C (ACVR1C), a type I transforming growth factor-β (TGF-β) receptor, has been implicated in sensitive skin and psoriasis and is involved in the regulation of metabolic homeostasis as well as cell proliferation and differentiation. In this study, we identified a novel role of ACVR1C in the ultraviolet (UV)-irradiation-induced reduction of epidermal lipogenesis in human skin. UV irradiation decreased ACVR1C expression and epidermal triglyceride (TG) synthesis in human skin in vivo and in primary normal human epidermal keratinocytes (NHEK) in vitro. Lipogenic genes, including genes encoding acetyl-CoA carboxylase (ACC) and sterol regulatory element binding protein-1 (SREBP1), were significantly downregulated in UV-irradiated NHEK. ACVR1C knockdown by shRNA resulted in greater decreases in SREBP1 and ACC in response to UV irradiation. Conversely, the overexpression of ACVR1C attenuated the UV-induced decreases in SREBP1 and ACC. Further mechanistic study revealed that SMAD2 phosphorylation mediated the ACVR1C-induced lipogenic gene modulation. Taken together, a decrease in ACVR1C may cause UV-induced reductions in SREBP1 and ACC as well as epidermal TG synthesis via the suppression of SMAD2 phosphorylation. ACVR1C may be a target for preventing or treating UV-induced disruptions in lipid metabolism and associated skin disorders.

An allosteric site on MKP5 reveals a strategy for small-molecule inhibition

The mitogen-activated protein kinase (MAPK) phosphatases (MKPs) have been considered “undruggable,” but their position as regulators of the MAPKs makes them promising therapeutic targets. MKP5 has been suggested as a potential target for the treatment of dystrophic muscle disease. Here, we identified an inhibitor of MKP5 using a p38α MAPK–derived, phosphopeptide-based small-molecule screen. We solved the structure of MKP5 in complex with this inhibitor, which revealed a previously undescribed allosteric binding pocket. Binding of the inhibitor to this pocket collapsed the MKP5 active site and was predicted to limit MAPK binding. Treatment with the inhibitor recapitulated the phenotype of MKP5 deficiency, resulting in activation of p38 MAPK and JNK. We demonstrated that MKP5 was required for TGF-β1 signaling in muscle and that the inhibitor blocked TGF-β1–mediated Smad2 phosphorylation. TGF-β1 pathway antagonism has been proposed for the treatment of dystrophic muscle disease. Thus, allosteric inhibition of MKP5 represents a therapeutic strategy against dystrophic muscle disease.

Loss of PKCα increases arterial medial calcification in a uremic mouse model of chronic kidney disease

Arterial medial calcification is an independent risk factor for mortality in chronic kidney disease. We previously reported that knock-down of PKCα expression increases high phosphate-induced mineral deposition by vascular smooth muscle cells in vitro. This new study tests the hypothesis that PKCα regulates uremia-induced medial calcification in vivo. Female wild-type and PKCα−/− mice underwent a two-stage subtotal nephrectomy and were fed a high phosphate diet for 8 weeks. X-ray micro computed tomography demonstrated that uremia-induced medial calcification was increased in the abdominal aorta and aortic arch of PKCα−/− mice compared to wild-types. Blood urea nitrogen was also increased in PKCα−/− mice compared to wild-types; there was no correlation between blood urea nitrogen and calcification in PKCα−/− mice. Phosphorylated SMAD2 immunostaining was detected in calcified aortic arches from uremic PKCα−/− mice; the osteogenic marker Runx2 was also detected in these areas. No phosphorylated SMAD2 staining were detected in calcified arches from uremic wild-types. PKCα knock-down increased TGF-β1-induced SMAD2 phosphorylation in vascular smooth muscle cells in vitro, whereas the PKCα activator prostratin decreased SMAD2 phosphorylation. In conclusion, loss of PKCα increases uremia-induced medial calcification. The PKCα/TGF-β signaling axis could therefore represent a new therapeutic target for arterial medial calcification in chronic kidney disease.

SUN-552 Follistatin-Like 3 (FSTL3), a Transforming Growth Factor β (TGFβ) Ligand Inhibitor, Regulates Placental Development in Mice

Follistatin-like 3 (FSTL3), a glycoprotein that inhibits transforming growth factor-β (TGFβ) ligands such as activin, is expressed highly in the placenta and other vascular tissues. In addition, FSTL3 is strongly induced in pre-eclamptic placenta. To test the hypothesis that FSTL3 function is required for capillary bed structure and function we studied the placenta in FSTL3 gene deleted mice (FSTL3 KO). We have previously shown that FSTL3 deletion produces striking defects in the placenta when compared to WT. Placental size increases significantly in comparison to WT, at 16.5 and 18.5 dpc, with concurrent reduction in placental efficiency at 18.5 dpc. Histological analyses reveal structural differences in placental junctional zones in FSTL3 KO placenta compared to WT. Morphometric analyses show that the labyrinth area compared to the placenta area is significantly reduced in FSTL3 KO mice. We also found that activin-responsive FSTL3-synexpression genes are upregulated in FSTL3 KO placenta. Of these, EPHB4 protein is induced in the placenta along with its ligand EphrinB2. Here we show that FSTL3 deletion leads to endothelial cell expansion but reduction in blood vessel density along with increased extracellular matrix deposition. Further investigation of the placental phenotype revealed differential expression patterns of desmin and cytokeratin protein, reduced von Willebrand factor (VWF) and increased CD31 and VEGFR2 labelling within FSTL3 KO mice placental labyrinths. To identify mechanisms that might lead to the altered placental development in FSTL3 KO mice qPCR analyses were performed. Our results identified differences in the expression of crucial transcripts, such as Cdh5, Pgf, Fra1and Cited1, that are associated with the regulation of vascular biology. Additionally, we find increased Histone3 and SMAD2 phosphorylation in FSTL3 KO placenta indicating increased proliferation and activin signalling, respectively. These findings suggest that the balance between cellular proliferation and differentiation might be altered in the absence of FSTL3. Thus, we conclude that FSTL3 function, at least partly through the inhibition of activin action, is necessary for normal placental circulation and development.