Sentrin/small ubiquitin-like modifier-specific protease 5 protects oral cancer cells from oxidative stress-induced apoptosis

SUMO-specific proteases: SENPs in oxidative stress-related signaling and diseases

Oxidative stress is employed to depict a series of responses detrimental to normal cellular functions resulting from an imbalance between intracellular oxidants, mainly reactive oxygen species and antioxidant defenses. Oxidative stress often contributes to the development of various diseases, including cancer, cardiovascular diseases, and neurodegenerative diseases. In this process, the relationship between small ubiquitin-like modifier (SUMO) and oxidative stress has garnered significant attention, with its posttranslational modification (PTM) frequently serving as a marker of oxidative stress status. Sentrin/SUMO-specific proteases (SENPs), affected by alternative splicing, PTMs such as phosphorylation and ubiquitination, and various protein interactions, are crucial molecules in the SUMO process. The human SENP family has six members (SENP1-3, SENP5-7), which are classified into two categories based on sequence similarity, substrate specificity, and subcellular location. They have two core functions in the human body: first, by cleaving the precursor SUMO and exposing the C-terminal glycine, they initiate the SUMO process; second, they can specifically recognize and dissociate SUMO proteins bound to substrates, a process known as deSUMOylation. However, the connection between deSUMOylation and oxidative stress remains a relatively unexplored area despite their strong association with oxidative diseases such as cancer and cardiovascular disease. This article aims to illustrate the significant contribution of SENPs to the oxidative stress pathway through deSUMOylation by reviewing their structure and classification, their roles in oxidative stress, and the changes in their expression and activity in several typical oxidative stress-related diseases.

New insights into redox-related risk factors and therapeutic targets in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common cancer in the oral cavity accounting for 90 % of oral cancer with a global incidence of 350.000 new cases per year. Curative resection along with adjuvant radiation therapy or a combination of radiotherapy with chemotherapy remain as gold standard in treating OSCC. Still, local recurrence, lymph nodal recurrence, and complications of radiation remain the main cause of tumor-related mortality. Reactive oxygen species are not only correlated to the etiology of OSCC due to oxidative DNA damage, lipid peroxidation or effecting signal transduction cascades that effect cell proliferation and tumorigenesis, but are also of great interest in the therapy of OSCC patients. As induced oxidative stress can be used therapeutically for the induction of tumor cell death, redox targets might be a therapeutic addition to the conventional treatment options. In this review, we discuss markers of impaired redox homeostasis as well as potential redox-related treatment targets in OSCC.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

SENP Proteases as Potential Targets for Cancer Therapy

Simple Summary

Post-translational modification—the biochemical addition of functional groups or proteins—occurs following protein biosynthesis and contributes to an increase in the functional diversity of the proteome. Post-translational modifications include SUMOylation—the covalent attachment of small ubiquitin-related modifier (SUMO) proteins to substrate proteins. SUMOylation is a reversible modification, which is erased by SUMO-specific proteases (SENPs). Deregulation of SENPs leads to cellular dysfunction and is associated with various diseases, including cancer. The role of SENPs in cancer pathogenesis is expected, and thus these proteins are considered promising targets for drug design and development. In this review, we will discuss the role of SENPs, focusing on DNA repair and the cell cycle—cellular pathways malfunctioning in most cancer cells—and provide an update on advances in the development of SENP-oriented inhibitors.

Abstract

SUMOylation is a reversible post-translational modification (PTM) involving a covalent attachment of small ubiquitin-related modifier (SUMO) proteins to substrate proteins. SUMO-specific proteases (SENPs) are cysteine proteases with isopeptidase activity facilitating the de-conjugation of SUMO proteins and thus participating in maintaining the balance between the pools of SUMOylated and unSUMOylated proteins and in SUMO recycling. Several studies have reported that SENPs’ aberrant expression is associated with the development and progression of cancer. In this review, we will discuss the role of SENPs in the pathogenesis of cancer, focusing on DNA repair and the cell cycle—cellular pathways malfunctioning in most cancer cells. The plausible role of SENPs in carcinogenesis resulted in the design and development of their inhibitors, including synthetic protein-based, peptide-based, and small molecular weight inhibitors, as well as naturally occurring compounds. Computational methods including virtual screening have been implemented to identify a number of lead structures in recent years. Some inhibitors suppressed the proliferation of prostate cancer cells in vitro and in vivo, confirming that SENPs are suitable targets for anti-cancer treatment. Further advances in the development of SENP-oriented inhibitors are anticipated toward SENP isoform-specific molecules with therapeutic potential.

miR-125a suppresses malignancy of multiple myeloma by reducing the deubiquitinase USP5

miR-125a is a microRNA that is frequently diminished in various human malignancies. However, the mechanism by which impaired miR-125a promotes cancer growth remains undefined. In this study, we investigated the role of miR-125a in the proliferation and apoptosis of multiple myeloma (MM). To do this, we used MM tissue samples (from 40 anonymous patients), normal matched control samples, and five MM-derived cell lines. We also established a mouse model of MM xenograft to explore the effect of overexpression of miR-125a on the MM growth in vivo. Quantitative real-time polymerase chain reaction revealed that the miR-125a expression was broadly reduced in MM tissues and cell lines. The impairment of miR-125a in MM tissues was functionally relevant because the overexpression of miR-125a remarkably decreased the cell viability and colony-forming activity, at least in part, by promoting apoptosis in two miR-125a-deficient MM cell lines: NCI-H929 and U266. Interestingly, we also discovered that the human gene encoding the ubiquitin-specific peptidase 5 (USP5), which is known to promote cellular deubiquitination and ubiquitin/proteasome-dependent proteolysis, was a direct transcriptional target for miR-125a to repress. More importantly, the heterologous expression of USP5 significantly reversed the growth-inhibitory effects of miR-125a on MM cells in vitro. In the mouse xenograft model, overexpressed miR-125a prominently inhibited the growth of MM tumors and concomitantly reduced the expression of USP5 in tumor tissues. These results suggest that miR-125a inhibits the expression of USP5, thereby mitigating the proliferation and survival of malignant MM cells. We propose that USP5 acts as an oncoprotein in miR-125a-missing cancers.

Momordin Ic, a new natural SENP1 inhibitor, inhibits prostate cancer cell proliferation

SUMO-specific protease 1 (SENP1), a member of the de-SUMOylation protease family, is elevated in prostate cancer (PCa) cells and is involved in PCa pathogenesis. Momordin Ιc (Mc), a natural pentacyclic triterpenoid, inhibited SENP1 in vitro, as reflected by reduced SENP1C-induced cleavage of SUMO2-ΔRanGAP1. Mc also altered the thermal stability of SENP1 in a newly developed cellular thermal shift assay, indicating that Mc directly interacts with SENP1 in PCa cells. Consistent with SENP1 inhibition, Mc increased SUMOylated protein levels, which was further confirmed by the accumulation of two known SUMOylated proteins, hypoxia inducible factor-1a and nucleus accumbens associated protein 1 in PC3 cells. Compared to LNCaP and normal prostate epithelial RWPE-1 cells, PC3 cells had higher levels of SENP1 mRNA and were more sensitive to Mc-induced growth inhibition. Mc also reduced SENP1 mRNA levels in PCa cells. Overexpression of SENP1 rescued PC3 cells from Mc-induced apoptosis. Finally, Mc suppressed cell proliferation and induced cell death in vivo in a xenograft PC3 tumor mouse model. These findings demonstrate that Mc is a novel SENP1 inhibitor with potential therapeutic value for PCa. Investigation of other pentacyclic triterpenoids may aid in the development of novel SENP1 inhibitor drugs.

SUMOylation-Mediated Regulation of Cell Cycle Progression and Cancer

Protein conjugation with Small ubiquitin-like modifier (SUMOylation) has critical roles during cell cycle progression. Many important cell cycle regulators, including many oncogenes and tumor suppressors, are functionally regulated via SUMOylation. The dynamic SUMOylation pattern observed throughout the cell cycle is ensured via distinct spatial and temporal regulation of the SUMO machinery. Additionally, SUMOylation cooperates with other post-translational modifications to mediate cell cycle progression. Deregulation of these SUMOylation and deSUMOylation enzymes causes severe defects in cell proliferation and genome stability. Different types of cancer were recently shown to be dependent on a functioning SUMOylation system, a finding that could be exploited in anticancer therapies.