Downregulation of Smurf2 ubiquitin ligase in pancreatic cancer cells reversed TGF-β-induced tumor formation

Expanding the ubiquitin code in pancreatic cancer

The ubiquitin-proteasome system (UPS) is a fundamental regulatory mechanism in cells, vital for maintaining cellular homeostasis, compiling signaling transduction, and determining cell fates. These biological processes require the coordinated signal cascades of UPS members, including ubiquitin ligases, ubiquitin-conjugating enzymes, deubiquitinases, and proteasomes, to ubiquitination and de-ubiquitination on substrates. Recent studies indicate that ubiquitination code rewriting is particularly prominent in pancreatic cancer. High frequency mutation or aberrant hyperexpression of UPS members dysregulates ferroptosis, tumor microenvironment, and metabolic rewiring processes and contribute to tumor growth, metastasis, immune evasion, and acquired drug resistance. We conduct an in-depth overview of ubiquitination process in pancreatic cancer, highlighting the role of ubiquitin code in tumor-promoting and tumor-suppressor pathways. Furthermore, we review current UPS modulators and analyze the potential of UPS modulators as cancer therapy.

Smurf2 suppresses the metastasis of hepatocellular carcinoma via ubiquitin degradation of Smad2

Purpose

Smurf2, one of C2-WW-HECT domain E3 ubiquitin ligases, is closely related to the development and progression in different cancer types, including hepatocellular carcinoma (HCC). This study aims to illustrate the expression and molecular mechanism of Smurf2 in regulating the progression of HCC.

Methods

The expression of Smurf2 in human HCC and adjacent non-tumor liver specimens was detected using tissue microarray studies from 220 HCC patients who underwent curative resection. The relationships of Smurf2 and HCC progression and survival were analyzed using the chi-square test, Kaplan–Meier analysis, and Cox proportional hazards model. For Smurf2 was low expression in HCC cell lines, Smurf2 overexpression cell lines were established. The effect of Smurf2 on cell proliferation and migration was detected by Cell Counting Kit-8 and colony formation assay, and the epithelial–mesenchymal transition (EMT) markers and its transcription factors were tested by immunoblotting. The interaction and ubiquitination of Smad2 by Smurf2 were detected by co-immunoprecipitation and immunoprecipitation assay. Finally, the effect of Smurf2 on HCC was verified using the mouse lung metastasis model.

Results

Smurf2 was downregulated in HCC tissues compared to that of corresponding non-tumor liver specimens. The low expression of Smurf2 in HCC was significantly associated with macrovascular or microvascular tumor thrombus and the impairment of overall survival and disease-free survival. In vitro and in vivo analysis showed that Smurf2 overexpression decreased the EMT potential of HCC cells by promoting the ubiquitination of Smad2 via the proteasome-dependent degradation pathway.

Conclusion

The expression of Smurf2 was downregulated in HCC specimens and affected the survival of patients. Smurf2 inhibited the EMT of HCC by enhancing Smad2 ubiquitin-dependent proteasome degradation.

E3 Ubiquitin Ligases: Key Regulators of TGFβ Signaling in Cancer Progression

Transforming growth factor β (TGFβ) is a secreted growth and differentiation factor that influences vital cellular processes like proliferation, adhesion, motility, and apoptosis. Regulation of the TGFβ signaling pathway is of key importance to maintain tissue homeostasis. Perturbation of this signaling pathway has been implicated in a plethora of diseases, including cancer. The effect of TGFβ is dependent on cellular context, and TGFβ can perform both anti- and pro-oncogenic roles. TGFβ acts by binding to specific cell surface TGFβ type I and type II transmembrane receptors that are endowed with serine/threonine kinase activity. Upon ligand-induced receptor phosphorylation, SMAD proteins and other intracellular effectors become activated and mediate biological responses. The levels, localization, and function of TGFβ signaling mediators, regulators, and effectors are highly dynamic and regulated by a myriad of post-translational modifications. One such crucial modification is ubiquitination. The ubiquitin modification is also a mechanism by which crosstalk with other signaling pathways is achieved. Crucial effector components of the ubiquitination cascade include the very diverse family of E3 ubiquitin ligases. This review summarizes the diverse roles of E3 ligases that act on TGFβ receptor and intracellular signaling components. E3 ligases regulate TGFβ signaling both positively and negatively by regulating degradation of receptors and various signaling intermediates. We also highlight the function of E3 ligases in connection with TGFβ's dual role during tumorigenesis. We conclude with a perspective on the emerging possibility of defining E3 ligases as drug targets and how they may be used to selectively target TGFβ-induced pro-oncogenic responses.

A novel metastatic promoter CEMIP and its downstream molecular targets and signaling pathway of cellular migration and invasion in SCLC cells based on proteome analysis

PURPOSE

Metastasis is an unavoidable event happened among almost all small cell lung cancer (SCLC) patients. However, the molecular driven factors have not been elucidated. Recently, a novel hydrolase called cell migration inducing hyaluronidase (CEMIP) triggered both migration and invasion in many tumors but not SCLC. Therefore, in this study, we verified that CEMIP promoted migration and invasion in SCLC and applied proteomics analysis to screen out potential target profiles and the signaling pathway related to CEMIP regulation.

METHOD

Immunofluorescence was conducted to exam the expression of CEMIP on SCLC and paired adjacent normal tissues among enrollment. RT-qPCR and Western blot (WB) assays were conducted to valuate cellular protein and mRNA expression of CEMIP and EMT markers. Lentivirus-CEMIP-shRNAs and CEMIP plasmid were used for expression manipulating. Changes of cellular migration and invasion were tested through transwell assays. Tandem Mass Tag (TMT) peptide labeling coupled with LC-MS/MS was used for quantifying proteins affected by reducing expression of CEMIP on H446 cells.

RESULTS

The expression of CEMIP showed 1.64 ± 0.16-fold higher in SCLC tissues than their normal counterpart. Decreasing the expression of CEMIP on SCLC cells H446 regressed both cellular migration and invasion ability, whereas the promoting cellular migration and invasion was investigated through over-expressing CEMIP on H1688. Proteomic and bioinformatics analysis revealed that total 215 differentially expressed proteins (DEPs) that either their increasing or decreasing relative expression met threshold of 1.2-fold changes with p value ≤ 0.05. The dramatic up-regulated DEPs included an unidentified peptide sequence (encoded by cDNA FLJ52096) SPICE1 and CRYAB, while the expression of S100A6 was largely down-regulated. DEPs mainly enriched on caveolae of cellular component, calcium ion binding of biological process and epithelial cell migration of molecular function. KEGG enrichment indicated that DEPs mainly exerted their function on TGF-β, GABAergic synapse and MAPK signaling pathway.

CONCLUSION

It is the first report illustrating that CEMIP might be one of the metastatic triggers in SCLC. And also, it provided possible molecular mechanism cue and potential downstream target on CEMIP-induced cellular migration and invasion on SCLC.

Proteostasis Dysregulation in Pancreatic Cancer

The most common form of pancreatic cancer, pancreatic ductal adenocarcinoma (PDAC), has a dismal 5-year survival rate of less than 5%. Radical surgical resection, in combination with adjuvant chemotherapy, provides the best option for long-term patient survival. However, only approximately 20% of patients are resectable at the time of diagnosis, due to locally advanced or metastatic disease. There is an urgent need for the identification of new, specific, and more sensitive biomarkers for diagnosis, prognosis, and prediction to improve the treatment options for pancreatic cancer patients. Dysregulation of proteostasis is linked to many pathophysiological conditions, including various types of cancer. In this review, we report on findings relating to the main cellular protein degradation systems, the ubiquitin-proteasome system (UPS) and autophagy, in pancreatic cancer. The expression of several components of the proteolytic network, including E3 ubiquitin-ligases and deubiquitinating enzymes, are dysregulated in PDAC, which accounts for approximately 90% of all pancreatic malignancies. In the future, a deeper understanding of the emerging role of proteostasis in pancreatic cancer has the potential to provide clinically relevant biomarkers and new strategies for combinatorial therapeutic options to better help treat the patients.

FOXO1: Another avenue for treating digestive malignancy?

Digestive malignancies are the leading cause of mortality among all neoplasms, contributing to estimated 3 million deaths in 2012 worldwide. The mortality rate hassurpassed lung cancer and prostate cancer in recent years. The transcription factor Forkhead Box O1 (FOXO1) is a key member of Forkhead Box family, regulating diverse cellular functions during tumor initiation, progression and metastasis. In this review, we focus on recent studies investigating the antineoplastic role of FOXO1 in digestive malignancy. This review aims to serve as a guide for further research and implicate FOXO1 as a potent therapeutic target in digestive malignancy.

Coordinated repression of BIM and PUMA by Epstein-Barr virus latent genes maintains the survival of Burkitt lymphoma cells

While the association of Epstein-Barr virus (EBV) with Burkitt lymphoma (BL) has long been recognised, the precise role of the virus in BL pathogenesis is not fully resolved. EBV can be lost spontaneously from some BL cell lines, and these EBV-loss lymphoma cells reportedly have a survival disadvantage. Here we have generated an extensive panel of EBV-loss clones from multiple BL backgrounds and examined their phenotype comparing them to their isogenic EBV-positive counterparts. We report that, while loss of EBV from BL cells is rare, it is consistently associated with an enhanced predisposition to undergo apoptosis and reduced tumorigenicity in vivo. Importantly, reinfection of EBV-loss clones with EBV, but surprisingly not transduction with individual BL-associated latent viral genes, restored protection from apoptosis. Expression profiling and functional analysis of apoptosis-related proteins and transcripts in BL cells revealed that EBV inhibits the upregulation of the proapoptotic BH3-only proteins, BIM and PUMA. We conclude that latent EBV genes cooperatively enhance the survival of BL cells by suppression of the intrinsic apoptosis pathway signalling via inhibition of the potent apoptosis initiators, BIM and PUMA.

Role of tumor necrosis factor-α in epithelial-to-mesenchymal transition in transplanted kidney cells in recipients with chronic allograft dysfunction

BACKGROUND

Chronic allograft dysfunction (CAD) is characterized by allograft kidney interstitial fibrosis, the underlying mechanism of which is unclear. Our aim was to elucidate the role and mechanism of TNF-α-induced epithelial-to-mesenchymal transition (EMT) in transplant kidney tubular interstitial fibrosis.

METHODS

Human kidney tissues from normal volunteers and CAD patients were assessed using periodic acid-Schiff, Masson trichrome and immunohistochemical staining. mRNA and protein expression of E-cadherin, α-smooth muscle actin (SMA) and fibronectin(FN) in renal proximal tubule epithelial (HK-2) cells after treatment with TNF-α under different conditions were assessed using western blot and qRT-PCR analysis. Cell motility and migration were assessed using wound healing and transwell assays. Expression of Smurf2 and TNF-α-signaling pathway-related proteins in HK-2 cells treated with TNF-α was detected by western blotting. E-cadherin and α-SMA expression was also assessed in Smurf2 plasmid-transfected or Smurf2 siRNA-treated HK-2 cells.

RESULTS

The expression of TNF-α, Smurf2, α-SMA, and fibronectin was significantly upregulated, while the expression of E-cad was downregulated in the CAD group compared with the normal group. The in vitro results showed that TNF-α remarkably upregulated the expression of Smurf2, α-SMA and fibronectin and downregulated the expression of E-cadherin in HK-2 cells and enhanced motility and migration in HK-2 cells. Overexpression of Smurf2 could promote the expression of α-SMA and inhibit the expression of E-cad, whereas knockdown of Smurf2 expression reversed TNF-α-induced upregulation of α-SMA and prohibited the reduction of E-cad expression. Furthermore, TNF-α-induced Smurf2 expression promoted EMT through the Akt signaling pathway.

CONCLUSIONS

TNF-α induced EMT via the TNF-α/Akt/Smurf2 signaling pathways, and it may play a role in aggravating allograft kidney interstitial fibrosis in CAD patients.

EBV and Apoptosis: The Viral Master Regulator of Cell Fate?

Epstein-Barr virus (EBV) was first discovered in cells from a patient with Burkitt lymphoma (BL), and is now known to be a contributory factor in 1-2% of all cancers, for which there are as yet, no EBV-targeted therapies available. Like other herpesviruses, EBV adopts a persistent latent infection in vivo and only rarely reactivates into replicative lytic cycle. Although latency is associated with restricted patterns of gene expression, genes are never expressed in isolation; always in groups. Here, we discuss (1) the ways in which the latent genes of EBV are known to modulate cell death, (2) how these mechanisms relate to growth transformation and lymphomagenesis, and (3) how EBV genes cooperate to coordinately regulate key cell death pathways in BL and lymphoblastoid cell lines (LCLs). Since manipulation of the cell death machinery is critical in EBV pathogenesis, understanding the mechanisms that underpin EBV regulation of apoptosis therefore provides opportunities for novel therapeutic interventions.

MiR-9 is involved in TGF-β1-induced lung cancer cell invasion and adhesion by targeting SOX7

MicroRNA (miR)‐9 plays different roles in different cancer types. Here, we investigated the role of miR‐9 in non‐small‐cell lung cancer (NSCLC) cell invasion and adhesion in vitro and explored whether miR‐9 was involved in transforming growth factor‐beta 1 (TGF‐β1)‐induced NSCLC cell invasion and adhesion by targeting SOX7. The expression of miR‐9 and SOX7 in human NSCLC tissues and cell lines was examined by reverse transcription‐quantitative polymerase chain reaction. Gain‐of‐function and loss‐of‐function experiments were performed on A549 and HCC827 cells to investigate the effect of miR‐9 and SOX7 on NSCLC cell invasion and adhesion in the presence or absence of TGF‐β1. Transwell–Matrigel assay and cell adhesion assay were used to examine cell invasion and adhesion abilities. Luciferase reporter assay was performed to determine whether SOX7 was a direct target of miR‐9. We found miR‐9 was up‐regulated and SOX7 was down‐regulated in human NSCLC tissues and cell lines. Moreover, SOX7 expression was negatively correlated with miR‐9 expression. miR‐9 knockdown or SOX7 overexpression could suppress TGF‐β1‐induced NSCLC cell invasion and adhesion. miR‐9 directly targets the 3′ untranslated region of SOX7, and SOX7 protein expression was down‐regulated by miR‐9. TGF‐β1 induced miR‐9 expression in NSCLC cells. miR‐9 up‐regulation led to enhanced NSCLC cell invasion and adhesion; however, these effects could be attenuated by SOX7 overexpression. We concluded that miR‐9 expression was negatively correlated with SOX7 expression in human NSCLC. miR‐9 was up‐regulated by TGF‐β1 and contributed to TGF‐β1‐induced NSCLC cell invasion and adhesion by directly targeting SOX7.