URM1 Promoted Tumor Growth and Suppressed Apoptosis via the JNK Signaling Pathway in Hepatocellular Carcinoma

Proteomic Analysis Highlights the Impact of the Sphingolipid Metabolizing Enzyme β-Galactosylceramidase on Mitochondrial Plasticity in Human Melanoma

Mitochondrial plasticity, marked by a dynamism between glycolysis and oxidative phosphorylation due to adaptation to genetic and microenvironmental alterations, represents a characteristic feature of melanoma progression. Sphingolipids play a significant role in various aspects of cancer cell biology, including metabolic reprogramming. Previous observations have shown that the lysosomal sphingolipid-metabolizing enzyme β-galactosylceramidase (GALC) exerts pro-oncogenic functions in melanoma. Here, mining the cBioPortal for a Cancer Genomics data base identified the top 200 nuclear-encoded genes whose expression is negatively correlated with GALC expression in human melanoma. Their categorization indicated a significant enrichment in Gene Ontology terms and KEGG pathways related to mitochondrial proteins and function. In parallel, proteomic analysis by LC-MS/MS of two GALC overexpressing human melanoma cell lines identified 98 downregulated proteins when compared to control mock cells. Such downregulation was confirmed at a transcriptional level by a Gene Set Enrichment Analysis of the genome-wide expression profiling data obtained from the same cells. Among the GALC downregulated proteins, we identified a cluster of 42 proteins significantly associated with GO and KEGG categorizations related to mitochondrion and energetic metabolism. Overall, our data indicate that changes in GALC expression may exert a significant impact on mitochondrial plasticity in human melanoma cells.

Stress - Regulation of SUMO conjugation and of other Ubiquitin-Like Modifiers

Stress is unavoidable and essential to cellular and organismal evolution and failure to adapt or restore homeostasis can lead to severe diseases or even death. At the cellular level, stress drives a plethora of molecular changes, of which variations in the profile of protein post-translational modifications plays a key role in mediating the adaptative response of the genome and proteome to stress. In this context, post-translational modification of proteins by ubiquitin-like modifiers, (Ubl), notably SUMO, is an essential stress response mechanism. In this review, aiming to draw universal concepts of the Ubls stress response, we will decipher how stress alters the expression level, activity, specificity and/or localization of the proteins involved in the conjugation pathways of the various type-I Ubls, and how this result in the modification of particular Ubl targets that will translate an adaptive physiological stress response and allow cells to restore homeostasis.

Sphingomyelin Phodiesterase Acid-Like 3A Promotes Hepatocellular Carcinoma Growth Through the Enhancer of Rudimentary Homolog

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, with unclear pathogenesis. Sphingomyelin phodiesterase acid-like 3A (SMPDL3A) affects cell differentiation and participates in immune regulation. However, its molecular biological function in HCC has not yet been elucidated.

Methods

Data from 180 HCC patients were analyzed the relationship between the expression of SMPDL3A in liver cancer tissues and the prognosis of liver cancer patients. Crispr-Cas9 dual vector lentivirus was used to knock out SMPDL3A in HCC cell lines. The effects of SMPDL3A on cell viability were determined by CCK8 assay, clone formation experiment, cell cycle assay, cell scratch, TUNEL experiment and flow cytometry. Xenograft tumor assays in BALB/c nude mice confirmed that SMPDL3A promoted tumor growth and in vivo. Preliminary exploration of SMPDL3A interacting protein by mass spectrometry analysis and co-immunoprecipitation.

Results

This study showed that the expression of SMPDL3A in HCC tissue differed from that in tumor-adjacent tissues. Moreover, the overall survival rate and tumor-free survival rate of patients with high-SMPDL3A expression were significantly lower than those with low-SMPDL3A expression. SMPDL3A expression was closely related to the level of protein induced by PIVKA-II, liver cirrhosis, tumor diameter, microvascular invasion, and Barcelona clinic liver cancer staging. Thus, SMPDL3A is an independent risk factor that affects the tumor-free survival rate and overall survival rate of HCC patients. In vitro study using Crispr-Cas9 genome editing technology revealed the knockout effect of SMPDL3A on cell proliferation, apoptosis, and migration. Cell counting kit-8 assay and clone formation experiment showed that sgSMPDL3A inhibited tumor cell proliferation and migration. Flow cytometry and TUNEL assay showed that sgSMPDL3A promoted apoptosis in tumors. Moreover, sgSMPDL3A inhibited tumor growth during subcutaneous tumor formation in nude mice. Immunohistochemistry of Ki67 and PNCA also indicated that sgSMPDL3A inhibited subcutaneous tumor proliferation in tumor-bearing nude mice. Further experiments showed that SMPDL3A interacts with the enhancer of rudimentary homolog (ERH).

Conclusions

High-SMPDL3A expression was related to poor prognosis of patients with HCC. Knockout of SMPDL3A inhibited the proliferation and migration and accelerated the migration of HCC cells. SMPDL3A interacted with ERH to affect the tumorigenesis and progression of HCC.

The expression and prognostic value of REXO4 in hepatocellular carcinoma

Background

Globally, one of the dominant causes of cancer-related mortality is liver cancer. Identification of potent biomarkers for initial stage diagnosis and prognosis is a key factor to ensure efficient therapy and reduce the mortality rate in liver cancer patients. REXO4 has been reported in neuropathic pain and familial isolated pituitary adenoma (FIPA), however, its relationship with liver cancer is still elusive.

Methods

In an attempt to scrutinize the expression of REXO4 in liver cancer, the Oncomine, and TCGA databases were analyzed. Real-time PCR was employed to identify the REXO4 mRNA levels in 45 patient tissue samples and western blot was used to detect the REXO4 protein levels in hepatocellular carcinoma (HCC) cells. Evaluation of the prognostic value of REXO4 in liver cancer was made using Univariate and multivariate Cox proportional hazards regression models and Kaplan-Meier plots. Tumor-associated biological processes related to REXO4 were revealed by LinkedOmics. The correlation of REXO4 and immune infiltration was evaluated using the TIMER database.

Results

REXO4 is significantly up-regulated in liver cancer in comparison with the nontumor controls. Moreover, poor progression-free survival and overall survival is a frequent outcome related to high expression of REXO4, highlighting it as a risk factor in case of liver cancer. Additionally, the plausible role of REXO4 in tumor-immune interactions was also investigated and it was revealed that the immune infiltration and immune activation of liver cancer might have an association with REXO4.

Conclusions

REXO4 has a significant expression in liver cancer and could potentially become a predictor for the prognosis of liver cancers and a biomarker for targeted therapeutic regimens. Significant overexpression of REXO4 in HCC was revealed by the bioinformatics analysis, with REXO4 overexpression being related to a negative outcome in HCC patients, in addition, REXO4 might be associated with the immune infiltration in liver cancer. Such a vital understanding of the functioning of REXO4 may furnish a foundation for new targeted drug therapy as well as a new direction for additional investigation into the underlying mechanisms of REXO4 carcinogenesis in liver cancer.

The emerging roles of ubiquitin-like protein Urm1 in eukaryotes

The ubiquitin related modifier Urm1 protein was firstly identified in the yeast Saccharomyces cerevisiae, and was later found to play important roles in different eukaryotes. By the assistance of an E1-like activation enzyme Uba4, Urm1 can function as a modifier to target proteins, called urmylation. The thioredoxin peroxidase Ahp1 was the only identified Urm1 target in the early time. Recently, many other Urm1 targets were identified, which is important for us to fully understand functions of urmylation. Urm1 can also function as a sulfur carrier to play a key role in tRNAs thiolation. Mechanisms of the Urm1 in protein and RNA modifications were finely revealed in the past few years. Biological and physiological functions of Urm1 were also found in different organisms. In this review, we will summarize these emerging progresses.