The PI3K/Akt signal hyperactivates Eya1 via the SUMOylation pathway

Distinctive tumorigenic significance and innovative oncology targets of SUMOylation

Protein SUMOylation, a post-translational modification, intricately regulates diverse biological processes including gene expression, cell cycle progression, signaling pathway transduction, DNA damage response, and RNA metabolism. This modification contributes to the acquisition of tumorigenicity and the maintenance of cancer hallmarks. In malignancies, protein SUMOylation is triggered by various cellular stresses, promoting tumor initiation and progression. This augmentation is orchestrated through its specific regulatory mechanisms and characteristic biological functions. This review focuses on elucidating the fundamental regulatory mechanisms and pathological functions of the SUMO pathway in tumor pathogenesis and malignant evolution, with particular emphasis on the tumorigenic potential of SUMOylation. Furthermore, we underscore the potential therapeutic benefits of targeting the SUMO pathway, paving the way for innovative anti-tumor strategies by perturbing this dynamic and reversible modifying process.

In Vitro Self-Assembly of a Modified Diphenylalanine Peptide to Nanofibers Induced by the Eye Absent Enzyme and Alkaline Phosphatase and Its Activity against Breast Cancer Cell Proliferation

Drug-resistant breast cancers such as Triple negative breast cancer (TNBC) do not respond successfully to chemotherapy treatments because they lack the expression of receptor targets. Drug-resistant anti-cancer treatments require innovative approaches to target these cells without relying on the receptors. Intracellular self-assembly of small molecules induced by enzymes is a nanotechnology approach for inhibiting cancer cell growth. In this approach, enzymes will induce the self-assembly of small molecules to nanofibers, which leads to cell death. Here, we investigate the self-assembly of a modified small peptide induced by two different phosphatases: alkaline phosphatase (ALP) and eye absent tyrosine phosphatase (EYA). ALPs are expressed in many adult human tissues and are critical for many cellular functions. EYAs are embryonic enzymes that are over-expressed in drug-resistant breast cancers. We synthesized a small diphenylalanine-based peptide with a tyrosine phosphate end group as the substrate of phosphatase enzymes. Peptides were synthesized with solid phase techniques and were characterized by HPLC and MALDI-TOF. To characterize the self-assembly of peptides exposed to enzymes, different techniques were used such as scattering light intensity, microscopes, and phosphate detection kit. We then determined the toxicity effect of the peptide against normal breast cancer cells, MCF-7, and drug-resistant breast cancer cells, MDA-MB-231. The results showed that the EYA enzyme is able to initiate self-assembly at lower peptide concentration with higher self-assembling intensity compared to ALP. A significant decrease in the TNBC cell number was observed even with a low peptide concentration of 60 μM. These results collectively support the exploration of enzyme self-assembly to treat TNBC.

Protein sumoylation in normal and cancer stem cells

Stem cells with the capacity of self-renewal and differentiation play pivotal roles in normal tissues and malignant tumors. Whereas stem cells are supposed to be genetically identical to their non-stem cell counterparts, cell stemness is deliberately regulated by a dynamic network of molecular mechanisms. Reversible post-translational protein modifications (PTMs) are rapid and reversible non-genetic processes that regulate essentially all physiological and pathological process. Numerous studies have reported the involvement of post-translational protein modifications in the acquirement and maintenance of cell stemness. Recent studies underscore the importance of protein sumoylation, i.e., the covalent attachment of the small ubiquitin-like modifiers (SUMO), as a critical post-translational protein modification in the stem cell populations in development and tumorigenesis. In this review, we summarize the functions of protein sumoylation in different kinds of normal and cancer stem cells. In addition, we describe the upstream regulators and the downstream effectors of protein sumoylation associated with cell stemness. We also introduce the translational studies aiming at sumoylation to target stem cells for disease treatment. Finally, we propose future directions for sumoylation studies in stem cells.

Effect of Tensile Frequency on the Osteogenic Differentiation of Periodontal Ligament Stem Cells

Purpose

The role of periodontal ligament stem cells (PDLSCs) in mediating osteogenesis involved in orthodontic tooth movement (OTM) is well established. However, various relevant in vitro studies vary in the frequency of tension. The effect of tensile frequency on the mechanotransduction of PDLSCs is not clear. The current study aimed to determine the effect of different tensile frequencies on the osteogenic differentiation of PDLSCs and to identify important mechano-sensitivity genes.

Methods

Human PDLSCs were isolated, identified, and subjected to cyclic equibiaxial tensile strain of 12% at different frequencies of 0.1 Hz, 0.5 Hz, 0.7 Hz, or static cultures. Osteogenic differentiation of PDLSCs was assessed by using Western blotting. High-throughput sequencing was used to identify differential mRNA expression. Short time-series expression miner (STEM) was utilized to describe the frequency patterns of the mRNAs. The functions and enriched pathways were identified, and the hub genes were identified and validated.

Results

We found that the osteoblastic differentiation capacity of PDLSCs increased with tensile frequency in the range of 0.1–0.7 Hz. Eight frequency-tendency gene expression profiles were identified to be statistically significant. Tensile frequency-specific expressed genes, such as SALL1 and EYA1, which decreased with the increase in tensile frequency, were found.

Conclusion

The osteoblastic differentiation of PDLSCs under mechanical tensile force is frequency dependent. EYA1 and SALL1 were identified as potential important tensile frequency-sensitive genes, which may contribute to the cyclic tension-induced osteogenic differentiation of PDLSCs in a frequency-dependent manner.

Targeting therapy-resistant lung cancer stem cells via disruption of the AKT/TSPYL5/PTEN positive-feedback loop

Cancer stem cells (CSCs) are regarded as essential targets to overcome tumor progression and therapeutic resistance; however, practical targeting approaches are limited. Here, we identify testis-specific Y-like protein 5 (TSPYL5) as an upstream regulator of CSC-associated genes in non-small cell lung cancer cells, and suggest as a therapeutic target for CSC elimination. TSPYL5 elevation is driven by AKT-dependent TSPYL5 phosphorylation at threonine-120 and stabilization via inhibiting its ubiquitination. TSPYL5-pT120 also induces nuclear translocation and functions as a transcriptional activator of CSC-associated genes, ALDH1 and CD44. Also, nuclear TSPYL5 suppresses the transcription of PTEN, a negative regulator of PI3K signaling. TSPYL5-pT120 maintains persistent CSC-like characteristics via transcriptional activation of CSC-associated genes and a positive feedback loop consisting of AKT/TSPYL5/PTEN signaling pathway. Accordingly, elimination of TSPYL5 by inhibiting TSPYL5-pT120 can block aberrant AKT/TSPYL5/PTEN cyclic signaling and TSPYL5-mediated cancer stemness regulation. Our study suggests TSPYL5 be an effective target for therapy-resistant cancer.

In order to assist the development of cancer stem cell (CSC) therapy, Kim et al identified testis-specific Y-like protein 5 (TSPYL5) as an upstream regulator of CSC-associated genes in non-small cell lung cancer cells. They demonstrated in cancer cell lines and in vivo that TSPYL5 activity is dependent on AKT signalling and that disruption of TSPYL5 signalling could serve as a potential strategy to tackle therapy-resistant cancers.

Co-transplantation with adipose-derived cells to improve parathyroid transplantation in a mice model

Background

Accidentally removed parathyroid glands are still challenging in neck surgery, leading to hypoparathyroidism characterized with abnormally low levels of parathyroid hormone. Parathyroid auto-transplantation is usually applied in compensation. To improve the efficiency of parathyroid transplantation, we introduced a method by co-transplanting with adipose-derived cells, including stromal vascular fractions (SVFs) and adipose-derived stem cells (ADSCs), and investigated the underlying molecular mechanisms involved in parathyroid transplantation survival.

Methods

Rat and human parathyroid tissues were transplanted into nude mice as parathyroid transplantation model to examine the effects of SVFs and ADSCs on grafts angiogenesis and survival rates, including blood vessel assembly and parathyroid hormone levels. Several angiogenic factors, such as vascular endothelial growth factor (VEGF)-A and fibroblast growth factor (FGF) 2, were assessed in parathyroid grafts. The effects of hypoxia were investigated on ADSCs. The modulatory roles of the eyes absent homolog 1 (EYA1), which is vital in parathyroid development, was also investigated on angiogenic factor production and secretion by ADSCs. All experimental data were statistically processed. Student’s t test was used to assess significant differences between 2 groups. For multiple comparisons with additional interventions, two-way ANOVA followed by Tukey’s post hoc test was performed. P < 0.05 was considered as significant.

Results

SVFs improve rat parathyroid transplantation survival and blood vessel assembly, as well as FGF2 and VEGF-A expression levels in parathyroid transplantation mice. Functional human parathyroid grafts have higher microvessel density and increased VEGF-A expression. The supernatant of ADSCs induced tubule formation and migration of human endothelial cells in vitro. Hypoxia had no effect on proliferation and apoptosis of human ADSCs but induced higher angiogenic factor levels of VEGF-A and FGF2, modulated by EYA1, which was confirmed by parathyroid glands transplantation in mice.

Conclusions

Adipose-derived cells, including ADSCs and SVFs, improve parathyroid transplantation survival via promoting angiogenesis through EYA1-regulating angiogenetic factors in vitro and in vivo. Our studies proved an effective method to improve the parathyroid autotransplantation, which is promising for clinical patients with hypoparathyroidism when parathyroid glands were accidentally injured, removed, or devascularized.

EYA1 promotes cell migration and tumor metastasis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) patients are at high risk for both local recurrence and distant metastasis and tightly associated with poor prognosis. Exploring the molecular mechanism will provide a new opportunity in developing personal treatment for advanced HCC patients. As a critical member of the Retinal Determination Gene Network (RDGN), EYA1 has been identified as a tumor promoter in various cancers; however, its role in HCC has never been investigated. The present study was aimed to explore the role of EYA1 in HCC development. By analyzing public microarray datasets, we found that the EYA1 mRNA level was enhanced in HCC, which was significantly correlated with an aggressive phenotype and poor prognosis. Besides, EYA1 was coordinated with the fibronectin type III domain containing 3B (FNDC3B) to promote the migration and invasion of HCC cells. Western blot assays indicated that EYA1 not only increased the abundance of FNDC3B but also contributed to Epithelial-Mesenchymal Transition (EMT)-like phenotype change, like increased N-cadherin and decreased E-cadherin expression. Collectively, this study suggested that EYA1 activated FNDC3B to promote the migration and invasion in HCC. The aberrant expressions of EYA1 and FNDC3B may become the poor predictors for HCC patients.

Regulation of cancer stem cell properties by SIX1, a member of the PAX-SIX-EYA-DACH network

The PAX-SIX-EYA-DACH network (PSEDN) is a central developmental transcriptional regulatory network from Drosophila to humans. The PSEDN is comprised of four conserved protein families; including paired box (PAX), sine oculis (SIX), eyes absent (EYA), and dachshund (DACH). Aberrant expression of PSEDN members, particularly SIX1, has been observed in multiple human cancers, where SIX1 expression correlates with increased aggressiveness and poor prognosis. In conjunction with its transcriptional activator EYA, the SIX1 transcription factor increases cancer stem cell (CSC) numbers and induces epithelial-mesenchymal transition (EMT). SIX1 promotes multiple hallmarks and enabling characteristics of cancer via regulation of cell proliferation, senescence, apoptosis, genome stability, and energy metabolism. SIX1 also influences the tumor microenvironment, enhancing recruitment of tumor-associated macrophages and stimulating angiogenesis, to promote tumor development and progression. EYA proteins are multifunctional, possessing a transcriptional activation domain and tyrosine phosphatase activity, that each contributes to cancer stem cell properties. DACH proteins function as tumor suppressors in solid cancers, opposing the actions of SIX-EYA and reducing CSC prevalence. Multiple mechanisms can lead to increased SIX1 expression, including loss of SIX1-targeting tumor suppressor microRNAs (miRs), whose expression correlates inversely with SIX1 expression in cancer patient samples. In this review, we discuss the major mechanisms by which SIX1 confers CSC and EMT features and other important cancer cell characteristics. The roles of EYA and DACH in CSCs and cancer progression are briefly highlighted. Finally, we summarize the clinical significance of SIX1 in cancer to emphasize the potential therapeutic benefits of effective strategies to disrupt PSEDN protein interactions and functions.

EYA1 promotes tumor angiogenesis by activating the PI3K pathway in colorectal cancer

Blood vessels are one of the major routes for the dissemination of cancer cells. Malignant tumors release growth factors such as vascular endothelial growth factor(VEGF) to induce angiogenesis, thereby promoting metastasis. Here, we report that The Drosophila Eyes Absent Homologue 1 (EYA1), which is overexpressed in colorectal tumor cells, can promote colorectal tumor angiogenesis by coordinating with the hypoxia-inducible factor 1 (HIF-1α) to increase the expression of VEGF-A. Moreover, data indicated that the enhancement of HIF-1α expression by Eya1 depended on its ability to activate the phosphatidylinositol 3-kinase (PI3K) signaling pathways to increase the phosphorylation of AKT subunits. Overexpression of Eya1 increased tumor angiogenesis in vivo and in vitro. Our study suggested that Eya1 is essential in regulating cancer cell-mediated angiogenesis and contributes to tumor growth, and that Eya1 provides a potential and specific target for new anti-angiogenesis drug development.

The retinal determination gene network: from developmental regulator to cancer therapeutic target

Although originally identified for its function in Drosophila melanogaster eye specification, the Retinal Determination Gene Network (RDGN) is essential for the development of multiple organs in mammals. The RDGN regulates proliferation, differentiation and autocrine signaling, and interacts with other key signaling pathways. Aberrant expression of RDGN members such as DACH, EYA and SIX contributes to tumor initiation and progression; indeed, the levels of RDGN members are clinically prognostic factors in various cancer types. Stimulation or suppression of the activities of these crucial components can block cancer cell proliferation, prevent cancer stem cell expansion and even reverse the EMT process, thereby attenuating malignant phenotypes. Thus, cancer therapeutic interventions targeting RDGN members should be pursued in future studies.

Methylation of the phosphatase-transcription activator EYA1 by protein arginine methyltransferase 1: mechanistic, functional, and structural studies

The eyes absent (EYA) family proteins are conserved transcriptional coactivators with intrinsic protein phosphatase activity. They play an essential role in the development of various organs in metazoans. These functions are associated with a unique combination of phosphatase and transactivation activities. However, it remains poorly understood how these activities and the consequent biologic functions of EYA are regulated. Here, we demonstrate that 2 conserved arginine residues, R304 and R306, of EYA1 are essential for its in vitro phosphatase activity and in vivo function during Drosophila eye development. EYA1 physically interacts with protein arginine methyltransferase 1, which methylates EYA1 at these residues both in vitro and in cultured mammalian and insect cells. Moreover, we show that wild-type, but not methylation-defective, EYA1 associates with γ-H2A.X in response to ionizing radiation. Taken together, our results identify the conserved arginine residues of EYA1 that play an important role for its activity, thus implicating arginine methylation as a novel regulatory mechanism of EYA function.-Li, X., Eberhardt, A., Hansen, J. N., Bohmann, D., Li, H., Schor, N. F. Methylation of the phosphatase-transcription activator EYA1 by protein arginine methyltransferase 1: mechanistic, functional, and structural studies.

EYA1 expression and subcellular localization in neuroblastoma and its association with prognostic markers

Neuroblastoma, the most frequently occurring extracranial solid tumor of childhood, arises from neural crest-derived cells that are arrested at an early stage of differentiation in the developing sympathetic nervous system. There is an urgent need to identify clinically relevant biomarkers for better prognosis and treatment of this aggressive malignancy. Eyes Absent 1 (EYA1) is an essential transcriptional coactivator for neuronal developmental programs during organogenesis. Whether or not EYA1 is implicated in neuroblastoma and subcellular localization of EYA1 is relevant to clinical behaviour of neuroblastoma is not known. We studied EYA1 expression and subcellular localization by immunohistochemistry in tissue microarrays containing tumor specimens from 98 patients, 66 of which were characterized by known clinical prognostic markers of neuroblastoma. Immunostaining results were evaluated and statistically correlated with the degree of histologic differentiation and with neuroblastoma risk stratification group characteristics, including stage of disease, patient age, tumor histology and mitosis-karyorrhexis index (MKI), respectively. We found that EYA1 levels were significantly higher in neuroblastomas than in ganglioneuromas and ganglioneuroblastomas. EYA1 was more highly expressed in stage 1,2,3 or 4S tumors as compared to stage 4 tumors (P<0.01). Tumors with high levels of nuclear EYA1 were more frequently associated with high nuclear MYCN levels. These results suggest that modulation of expression and intracellular localization of EYA1 in neural crest cells may provide a novel direction for therapeutic strategies.

MicroRNA-101 inhibits cell proliferation and induces apoptosis by targeting EYA1 in breast cancer

MicroRNAs (miRNAs or miRs) regulate gene expression by negatively modulating the stability or translational efficiency of their target genes by targeting the 3'-untranslated region (3'-UTR). Aberrant miRNA expression has been reported in various types of cancer; miRNAs can function as either oncogenes or tumor suppressor genes in cancer. In this study, we examined the expression level of miR‑101 in breast cancer tissues and cell lines by RT-qPCR, and found that miR‑101 expression was downregulated in breast cancer tissues and cell lines; indeed, in 6 of the 28 tissue samples, miR‑101 could not be detected. Furthermore, miR‑101, when transfected into SKBR3 cells, inhibited cell proliferation and promoted apoptosis, while miR‑101 inhibitor had the opposite effect. A dual-luciferase reporter assay revealed that miR‑101 targeted the 3'-UTR of eyes absent homolog 1 (Drosophila) (EYA1). Western blot analysis demonstrated a significantly decreased protein level of EYA1 in the SKBR3 cells transfected with miR‑101 mimic, whereas transfection with miR‑101 inhibitor led to an increased level of EYA1. Moreover, an increased expression of EYA1 was also found in breast cancer tissues and cell lines. The silencing of EYA1 using siRNA targeting EYA1 (EYA1‑siRNA) significantly inhibited SKBR3 cell proliferation and promoted apoptosis, and also suppressed the increased proliferation induced by transfection with miR‑101 inhibitor. The protein expression levels of Notch signaling components (jagged1, Hes1 and Hey1) were significantly decreased by transfection with miR‑101 mimic and EYA1-siRNA, and were increased by transfection with miR‑101 inhibitor. Furthermore, the elevated protein expression levels of jagged1, Hes1 and Hey1 induced by transfection with miR‑101 inhibitor in the SKBR3 cells were significantly decreased by transfection with EYA1-siRNA. Taken together, these results suggest that miR‑101 is down-regulated in breast cancer, and can inhibit cell proliferation and promote apoptosis by targeting EYA1 through the Notch signaling pathway.

Roles of ubiquitination and SUMOylation on prostate cancer: mechanisms and clinical implications

The initiation and progression of human prostate cancer are highly associated with aberrant dysregulations of tumor suppressors and proto-oncogenes. Despite that deletions and mutations of tumor suppressors and aberrant elevations of oncogenes at the genetic level are reported to cause cancers, emerging evidence has revealed that cancer progression is largely regulated by posttranslational modifications (PTMs) and epigenetic alterations. PTMs play critical roles in gene regulation, cellular functions, tissue development, diseases, malignant progression and drug resistance. Recent discoveries demonstrate that ubiquitination and SUMOylation are complicated but highly-regulated PTMs, and make essential contributions to diseases and cancers by regulation of key factors and signaling pathways. Ubiquitination and SUMOylation pathways can be differentially modulated under various stimuli or stresses in order to produce the sustained oncogenic potentials. In this review, we discuss some new insights about molecular mechanisms on ubiquitination and SUMOylation, their associations with diseases, oncogenic impact on prostate cancer (PCa) and clinical implications for PCa treatment.

Mass spectrometry-based detection and assignment of protein posttranslational modifications

Recent advances in mass spectrometry (MS)-based proteomics allow the identification and quantitation of thousands of posttranslational modification (PTM) sites in a single experiment. This follows from the development of more effective class enrichment strategies, new high performance instrumentation and bioinformatic algorithms with rigorous scoring strategies. More widespread use of these combined capabilities have led to a vast expansion in our knowledge of the complexity of biological processes mediated by PTMs. The classes most actively pursued include phosphorylation, ubiquitination, O-GlcNAcylation, methylation, and acetylation. Very recently succinylation, SUMOylation, and citrullination have emerged. Among the some 260 000 PTM sites that have been identified in the human proteome thus far, only a few have been assigned to key regulatory and/or other biological roles. Here, we provide an update of MS-based PTM analyses, with a focus on current enrichment strategies coupled with revolutionary advances in high performance MS. Furthermore, we discuss examples of the discovery of recently described biological roles of PTMs and address the challenges of defining site-specific functions.