CSN6 promotes melanoma proliferation and metastasis by controlling the UBR5-mediated ubiquitination and degradation of CDK9

The role of UBR5 in tumor proliferation and oncotherapy

Ubiquitin (Ub) protein ligase E3 component n-recognin 5 (UBR5), as a crucial Ub ligase, plays a pivotal role in the field of cell biology, attracting significant attention for its functions in regulating protein degradation and signaling pathways. This review delves into the fundamental characteristics and structure of UBR5. UBR5, through ubiquitination, regulates various key proteins, directly or indirectly participating in cell cycle control, thereby exerting a direct impact on the proliferation of tumor cells. Meanwhile, we comprehensively review the expression levels of UBR5 in different types of tumors and its relationship with tumor development, providing key clues for the role of UBR5 in cancer. Furthermore, we summarize the current research status of UBR5 in cancer treatment. Through literature review, we find that UBR5 may play a crucial role in the sensitivity of tumor cells to radiotherapy chemotherapy, and other anti-tumor treatment, providing new insights for optimizing cancer treatment strategies. Finally, we discuss the challenges faced by UBR5 in cancer treatment, and looks forward to the future research directions. With the continuous breakthroughs in technology and in-depth research, we hope to further study the biological functions of UBR5 and lay the foundation for its anti-tumor treatment.

E3 ubiquitin ligase UBR5 modulates circadian rhythm by facilitating the ubiquitination and degradation of the key clock transcription factor BMAL1

The circadian clock is the inner rhythm of life activities and is controlled by a self-sustained and endogenous molecular clock, which maintains a ~ 24 h internal oscillation. As the core element of the circadian clock, BMAL1 is susceptible to degradation through the ubiquitin-proteasome system (UPS). Nevertheless, scant information is available regarding the UPS enzymes that intricately modulate both the stability and transcriptional activity of BMAL1, affecting the cellular circadian rhythm. In this work, we identify and validate UBR5 as a new E3 ubiquitin ligase that interacts with BMAL1 by using affinity purification, mass spectrometry, and biochemical experiments. UBR5 overexpression induced BMAL1 ubiquitination, leading to diminished stability and reduced protein level of BMAL1, thereby attenuating its transcriptional activity. Consistent with this, UBR5 knockdown increases the BMAL1 protein. Domain mapping discloses that the C-terminus of BMAL1 interacts with the N-terminal domains of UBR5. Similarly, cell-line-based experiments discover that HYD, the UBR5 homolog in Drosophila, could interact with and downregulate CYCLE, the BMAL1 homolog in Drosophila. PER2-luciferase bioluminescence real-time reporting assay in a mammalian cell line and behavioral experiments in Drosophila reveal that UBR5 or hyd knockdown significantly reduces the period of the circadian clock. Therefore, our work discovers a new ubiquitin ligase UBR5 that regulates BMAL1 stability and circadian rhythm and elucidates the underlying molecular mechanism. This work provides an additional layer of complexity to the regulatory network of the circadian clock at the post-translational modification level, offering potential insights into the modulation of the dysregulated circadian rhythm.

Mechanisms and potential applications of COPS6 in pan-cancer therapy

The COP9 signalosome subunit 6 (COPS6) is abnormally overexpressed in many malignancies, yet its precise role in carcinogenesis is unknown. To gain a better understanding of COPS6's role, the authors conducted a pan-cancer analysis using various bioinformatics techniques such as differential expression patterns, prognostic value, gene mutations, immune infiltration, correlation analysis, and functional enrichment assessment. Results showed that COPS6 was highly correlated with prognosis, immune cell infiltration level, tumor mutation burden, and microsatellite instability in patients with a range of tumor types. This suggests that COPS6 may be a potential target for cancer treatment. Overall, this research provides insight into COPS6's role in cancer development and its potential therapeutic applications.

Comprehensive pan-cancer analysis reveals SIRT5 is a predictive biomarker for prognosis and immunotherapy response

BACKGROUND

Sirtuin 5 (SIRT5) is a promising therapeutic target involved in regulating multiple metabolic pathways in cells and organisms. The role of SIRT5 in cancer is currently unclear, and a comprehensive systematic pan-cancer analysis is required to explore its value in diagnosis, prognosis, and immune function.

METHODS

We investigated the role of SIRT5 in tumorigenesis, diagnosis, prognosis, metabolic pathways, the immune microenvironment, and pan-cancer therapeutic response. Moreover, we explored chemicals affecting the expression of SIRT5 and computed the relationship between SIRT5 and drug sensitivity. Finally, the role of SIRT5 in melanoma was analyzed using a series of experiments in vitro and in vivo.

RESULTS

We found that SIRT5 is differentially expressed and shows early diagnostic value in various tumors and that somatic cell copy number alterations and DNA methylation contribute to its aberrant expression. SIRT5 expression correlates with clinical features. Besides, it is negatively (positively) correlated with several metabolic pathways and positively (negatively) correlated with several important metastasis-related and immune-related pathways. High SIRT5 expression predicts poor (or good) prognosis in various tumors and can affect drug sensitivity. We also demonstrated that SIRT5 expression significantly correlates with immunomodulator-associated molecules, lymphocyte subpopulation infiltration, and immunotherapeutic response biomarkers. In addition, we showed that SIRT5 is differentially expressed in immunotherapy cohorts. In addition, we explored various chemicals that may affect SIRT5 expression. In conclusion, we demonstrated that SIRT5 is a key pathogenic gene that promotes melanoma progression.

CONCLUSION

Our study provides a systematic analysis of SIRT5 and its regulatory genes. SIRT5 has excellent diagnostic and prognostic capabilities for many cancers. This may remodel the tumor microenvironment. The potential of SIRT5-based cancer therapies is emphasized and helps predict the response to immunotherapy.

COP9 signalosome complex is a prognostic biomarker and corresponds with immune infiltration in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is among the most common deadly tumors but still lacks specific biomarkers for diagnosis, prognosis, and treatment guidance. The COP9 signalosome (COPS) is an essential regulator of the ubiquitin conjugation pathway upregulated in various cancers. We evaluated the contributions of COPS subunits to HCC tumorigenesis and their utility for prognosis. We comprehensively evaluated the tumor expression pattern and tumorigenic functions of COPS subunits using The Cancer Genome Atlas (TCGA), The Human Protein Atlas and immunohistochemistry. Kaplan-Meier, Cox regression, ROC curve, and nomogram analyses were used to assess the predictive values of COPS subunits for clinical outcome. Expression levels of COPS subunits were significantly upregulated in HCC tissues, which predicted shorter overall survival (OS). Further, Cox regression analysis identified COPS5, COPS7B, and COPS9 as independent prognostic biomarkers for OS. High mutation rates were also found in COPS subunits. Functional network analysis indicated that COPS and neighboring genes regulate 'protein neddylation', 'protein deneddylation', and 'protein ubiquitination'. The COPS PPI included strong interactions with p53, CUL1/2/3/4, and JUN. Moreover, the correlations between COPS subunit expression levels and tumor immune cell infiltration rates were examined using TIMER, TISIDB, ssGSEA, and ESTIMATE packages. COPS subunits expression levels were positively correlated with specific tumor immune cell infiltration rates, immunoregulator expression levels, and microsatellite instability in HCC. Finally, knockout of COPS6 and COPS9 in HCC cells reduced while overexpression enhanced proliferation rate and metastasis capacity. Our study revealed that COPS potential biomarker for unfavorable HCC prognosis and indicators of immune infiltration, tumorigenicity, and metastasis.

Friend or foe? Reciprocal regulation between E3 ubiquitin ligases and deubiquitinases

Protein ubiquitination is a post-translational modification that entails the covalent attachment of the small protein ubiquitin (Ub), which acts as a signal to direct protein stability, localization, or interactions. The Ub code is written by a family of enzymes called E3 Ub ligases (∼600 members in humans), which can catalyze the transfer of either a single ubiquitin or the formation of a diverse array of polyubiquitin chains. This code can be edited or erased by a different set of enzymes termed deubiquitinases (DUBs; ∼100 members in humans). While enzymes from these distinct families have seemingly opposing activities, certain E3-DUB pairings can also synergize to regulate vital cellular processes like gene expression, autophagy, innate immunity, and cell proliferation. In this review, we highlight recent studies describing Ub ligase-DUB interactions and focus on their relationships.

Immune escape and metastasis mechanisms in melanoma: breaking down the dichotomy

Melanoma is one of the most lethal neoplasms of the skin. Despite the revolutionary introduction of immune checkpoint inhibitors, metastatic spread, and recurrence remain critical problems in resistant cases. Melanoma employs a multitude of mechanisms to subvert the immune system and successfully metastasize to distant organs. Concerningly, recent research also shows that tumor cells can disseminate early during melanoma progression and enter dormant states, eventually leading to metastases at a future time. Immune escape and metastasis have previously been viewed as separate phenomena; however, accumulating evidence is breaking down this dichotomy. Recent research into the progressive mechanisms of melanoma provides evidence that dedifferentiation similar to classical epithelial to mesenchymal transition (EMT), genes involved in neural crest stem cell maintenance, and hypoxia/acidosis, are important factors simultaneously involved in immune escape and metastasis. The likeness between EMT and early dissemination, and differences, also become apparent in these contexts. Detailed knowledge of the mechanisms behind "dual drivers" simultaneously promoting metastatically inclined and immunosuppressive environments can yield novel strategies effective in disabling multiple facets of melanoma progression. Furthermore, understanding progression through these drivers may provide insight towards novel treatments capable of preventing recurrence arising from dormant dissemination or improving immunotherapy outcomes.

Computational exploration of the significance of COPS6 in cancer: Functional and clinical relevance across tumor types

BACKGROUND

The COP9 signalosome subunit 6 (COPS6) has been implicated in cancer progression, while its precise role in most types of cancer remains elusive.

AIM

To investigate the functional and clinical relevance of COPS6 across various tumor types using publicly available databases.

METHODS

We used R software and online analysis databases to analyze the differential expression, prognosis, mutation and related functions of COPS6 in pan-cancer.

RESULTS

Differential expression analysis and survival analysis demonstrated that COPS6 was highly expressed and associated with high-risk profiles in the majority of cancer types. Possible associations between COPS6 expression level and prognostic outcomes were found using data from public databases. Mutational analysis revealed that missense mutations were the predominant type of COPS6 mutation. Additionally, positive correlations were identified between COPS6 expression level and tumor mutational burden and microsatellite instability in most types of cancer. Immune infiltration analysis demonstrated a negative correlation between COPS6 expression level and CD8+ T cell infiltration in certain types of cancer. The correlation between COPS6 expression level and cancer-associated fibroblast infiltration exhibited heterogeneity, in which a positive correlation was found in head and neck squamous cell carcinoma and tenosynovial giant cell tumor, and a negative correlation was identified in diffuse large B-cell lymphoma and thymoma. The correlation between COPS6 expression level and macrophage infiltration was closely related to macrophage type. Gene co-expression and enrichment analysis highlighted transcription elongation factor B polypeptide 2 and G protein pathway suppressor 1 were significantly and positively associated with COPS6 expression level. These genes were predominantly involved in processes, such as ubiquitin-mediated proteolysis and human immunodeficiency virus 1 infection.

CONCLUSION

In conclusion, this study systematically explored the significance of COPS6 across different tumor types, providing a solid foundation for considering COPS6 as a novel biomarker in cancer research.

Evaluation of drug sensitivity, immunological characteristics, and prognosis in melanoma patients using an endoplasmic reticulum stress-associated signature based on bioinformatics and pan-cancer analysis

We aimed to develop endoplasmic reticulum (ER) stress-related risk signature to predict the prognosis of melanoma and elucidate the immune characteristics and benefit of immunotherapy in ER-related risk score-defined subgroups of melanoma based on a machine learning algorithm. Based on The Cancer Genome Atlas (TCGA) melanoma dataset (n = 471) and GTEx database (n = 813), 365 differentially expressed ER-associated genes were selected using the univariate Cox model and LASSO penalty Cox model. Ten genes impacting OS were identified to construct an ER-related signature by using the multivariate Cox regression method and validated with the Gene Expression Omnibus (GEO) dataset. Thereafter, the immune features, CNV, methylation, drug sensitivity, and the clinical benefit of anticancer immune checkpoint inhibitor (ICI) therapy in risk score subgroups, were analyzed. We further validated the gene signature using pan-cancer analysis by comparing it to other tumor types. The ER-related risk score was constructed based on the ARNTL, AGO1, TXN, SORL1, CHD7, EGFR, KIT, HLA-DRB1 KCNA2, and EDNRB genes. The high ER stress-related risk score group patients had a poorer overall survival (OS) than the low-risk score group patients, consistent with the results in the GEO cohort. The combined results suggested that a high ER stress-related risk score was associated with cell adhesion, gamma phagocytosis, cation transport, cell surface cell adhesion, KRAS signalling, CD4 T cells, M1 macrophages, naive B cells, natural killer (NK) cells, and eosinophils and less benefitted from ICI therapy. Based on the expression patterns of ER stress-related genes, we created an appropriate predictive model, which can also help distinguish the immune characteristics, CNV, methylation, and the clinical benefit of ICI therapy. KEY MESSAGES: Melanoma is the cutaneous tumor with a high degree of malignancy, the highest fatality rate, and extremely poor prognosis. Model usefulness should be considered when using models that contained more features. We constructed the Endoplasmic Reticulum stress-associated signature using TCGA and GEO database based on machine learning algorithm. ER stress-associated signature has excellent ability for predicting prognosis for melanoma.

COPS6 promotes tumor progression and reduces CD8+ T cell infiltration by repressing IL-6 production to facilitate tumor immune evasion in breast cancer

Due to poor T cell infiltration, tumors evade immune surveillance. Increased CD8+ T cell infiltration in breast cancer suggests a satisfactory response to immunotherapy. COPS6 has been identified as an oncogene, but its role in regulating antitumor immune responses has not been defined. In this study, we investigated the impact of COPS6 on tumor immune evasion in vivo. Tumor transplantation models were established in C57BL/6 J mice and BALB/c nude mice. Flow cytometry was conducted to identify the role of COPS6 on tumor-infiltrating CD8+ T cells. By analyzing the TCGA and GTEx cohort, we found that COPS6 expression was significantly up-regulated in a variety of cancers. In human osteosarcoma cell line U2OS and non-small cell lung cancer cell line H1299, we showed that p53 negatively regulated COPS6 promoter activity. In human breast cancer MCF-7 cells, COPS6 overexpression stimulated p-AKT expression as well as the proliferation and malignant transformation of tumor cells, whereas knockdown of COPS6 caused opposite effects. Knockdown of COPS6 also significantly suppressed the growth of mouse mammary cancer EMT6 xenografts in BALB/c nude mice. Bioinformatics analysis suggested that COPS6 was a mediator of IL-6 production in the tumor microenvironment and a negative regulator of CD8+ T cell tumor infiltration in breast cancer. In C57BL6 mice bearing EMT6 xenografts, COPS6 knockdown in the EMT6 cells increased the number of tumor-infiltrating CD8+ T cells, while knockdown of IL-6 in COPS6KD EMT6 cells diminished tumor infiltrating CD8+ T cells. We conclude that COPS6 promotes breast cancer progression by reducing CD8+ T cell infiltration and function via the regulation of IL-6 secretion. This study clarifies the role of p53/COPS6/IL-6/CD8+ tumor infiltrating lymphocytes signaling in breast cancer progression and immune evasion, opening a new path for development of COPS6-targeting therapies to enhance tumor immunogenicity and treat immunologically "cold" breast cancer.

UBE2S interacting with TRIM21 mediates the K11-linked ubiquitination of LPP to promote the lymphatic metastasis of bladder cancer

Lymphatic metastasis is the most common pattern of bladder cancer (BCa) metastasis and has an extremely poor prognosis. Emerging evidence shows that ubiquitination plays crucial roles in various processes of tumors, including tumorigenesis and progression. However, the molecular mechanisms underlying the roles of ubiquitination in the lymphatic metastasis of BCa are largely unknown. In the present study, through bioinformatics analysis and validation in tissue samples, we found that the ubiquitin-conjugating E2 enzyme UBE2S was positively correlated with the lymphatic metastasis status, high tumor stage, histological grade, and poor prognosis of BCa patients. Functional assays showed that UBE2S promoted BCa cell migration and invasion in vitro, as well as lymphatic metastasis in vivo. Mechanistically, UBE2S interacted with tripartite motif containing 21 (TRIM21) and jointly induced the ubiquitination of lipoma preferred partner (LPP) via K11-linked polyubiquitination but not K48- or K63-linked polyubiquitination. Moreover, LPP silencing rescued the anti-metastatic phenotypes and inhibited the epithelial-mesenchymal transition of BCa cells after UBE2S knockdown. Finally, targeting UBE2S with cephalomannine distinctly inhibited the progression of BCa in cell lines and human BCa-derived organoids in vitro, as well as in a lymphatic metastasis model in vivo, without significant toxicity. In conclusion, our study reveals that UBE2S, by interacting with TRIM21, degrades LPP through K11-linked ubiquitination to promote the lymphatic metastasis of BCa, suggesting that UBE2S represents a potent and promising therapeutic target for metastatic BCa.

A patent review of selective CDK9 inhibitors in treating cancer

INTRODUCTION

The dysregulation of CDK9 protein is greatly related to the proliferation and differentiation of various cancers due to its key role in the regulation of RNA transcription. Moreover, CDK9 inhibition can markedly downregulate the anti-apoptotic protein Mcl-1 which is essential for the survival of tumors. Thus, targeting CDK9 is considered to be a promising strategy for antitumor drug development, and the development of selective CDK9 inhibitors has gained increasing attention.

AREAS COVERED

This review focuses on the development of selective CDK9 inhibitors reported in patent publications during the period 2020-2022, which were searched from SciFinder and Cortellis Drug Discovery Intelligence.

EXPERT OPINION

Given that pan-CDK9 inhibitors may lead to serious side effects due to poor selectivity, the investigation of selective CDK9 inhibitors has attracted widespread attention. CDK9 inhibitors make some advance in treating solid tumors and possess the therapeutic potential in EGFR-mutant lung cancer. CDK9 inhibitors with short half-life and intravenous administration might result in transient target engagement and contribute to a better safety profile in vivo. However, more efforts are urgently needed to accelerate the development of CDK9 inhibitors, including the research on new binding modes between ligand and receptor or new protein binding sites.

CDK9 inhibitors downregulate DKK1 expression to suppress the metastatic potential of HCC cells

BACKGROUND

Elevated expression of Dickkopf-1 (DKK1) is frequently observed in hepatocellular carcinoma (HCC) patients with poor clinical outcomes. Several reports indicating the functional involvement of DKK1 in HCC progression have suggested DKK1 as a promising therapeutic target for HCC.

OBJECTIVE

In this study, to develop an efficient way to target DKK1, we assessed the effect of CDK9 inhibitors on DKK1 expression linked to metastatic movement of HCC.

METHODS

The expression of DKK1 in CDK9 inhibitor-treated HCC cells was measured by western blot, ELISA and quantitative real-time reverse transcription PCR. Wound healing assay, migration assay, invasion assay and western blot were examined to evaluate the functional role of DKK1 in CDK9 inhibitors-treated HCC.

RESULTS

Inactivation of CDK9 either by a catalytic inhibitor being clinically evaluated or by a specific CDK9 protein degrader largely downregulated DKK1 expression at the transcript and protein levels. In addition, CDK9 inhibitors suppressed the migration and invasion of HCC cells. We observed that ectopic high expression of DKK1 at least partially reversed the defects in metastatic movement of HCC cells mediated by CDK9 inhibitors. We further discovered that the DKK1-nuclear β-catenin axis associated with the metastatic potential of HCC cells was impaired by CDK9 inhibitors.

CONCLUSION

Taken together, our findings suggest that CDK9 inhibitors are potent tools to target DKK1, which can suppress the metastatic progression of HCC.

SH3BP1 Regulates Melanoma Progression Through Race1/Wace2 Signaling Pathway

Background

SH3-domain binding protein-1 (SH3BP1), which specifically inactivates Rac1 and its target protein Wave2, has been shown to be an important regulator of cancer metastasis. However, the effects of SH3BP1 in melanoma progression remain unclear. The current study aimed to explore the function of SH3BP1 in melanoma and its possible molecular mechanism.

Methods

TCGA database was used to analyze the expression of SH3BP1 in melanoma. Then, reverse transcription-quantitative polymerase chain reaction was performed to detect the expression of SH3BP1 in melanoma tissues and cells. Next, genes related to SH3BP1 were analyzed by LinkedOmics database, and protein interactions were analyzed by STRING database. These genes were further subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis. In addition, the signaling pathway of SH3BP1 action was screened by bioinformatics analysis. Finally, the function of SH3BP1 and its mediated signaling pathway in melanoma progression were investigated in vitro and in vivo.

Results

SH3BP1 was significantly upregulated in melanoma tissues and cells. The pathways regulated by SH3BP1 are closely related to the occurrence and development of tumors. And we found that overexpression of SH3BP1 promoted the proliferation, migration, and invasion of melanoma cells by increasing Rac1 activity and Wave2 protein levels in vitro. Similarly, overexpression of SH3BP1 facilitated melanoma progression by upregulating Wave2 protein expression in vivo.

Conclusion

In summary, this study revealed for the first time that SH3BP1 promoted melanoma progression through Rac1/Wave2 signaling pathway, providing a new therapeutic target for melanoma.

The COP9 signalosome: A versatile regulatory hub of Cullin-RING ligases

The COP9 signalosome (CSN) is a universal regulator of Cullin-RING ubiquitin ligases (CRLs) - a family of modular enzymes that control various cellular processes via timely degradation of key signaling proteins. The CSN, with its eight-subunit architecture, employs multisite binding of CRLs and inactivates CRLs by removing a small ubiquitin-like modifier named neural precursor cell-expressed, developmentally downregulated 8 (Nedd8). Besides the active site of the catalytic subunit CSN5, two allosteric sites are present in the CSN, one of which recognizes the substrate recognition module and the presence of CRL substrates, and the other of which can 'glue' the CSN-CRL complex by recruitment of inositol hexakisphosphate. In this review, we present recent findings on the versatile regulation of CSN-CRL complexes.

Discovery of Small-Molecule Degraders of the CDK9-Cyclin T1 Complex for Targeting Transcriptional Addiction in Prostate Cancer

Aberrant hyperactivation of cyclins results in carcinogenesis and therapy resistance in cancers. Direct degradation of the specific cyclin or cyclin-dependent kinase (CDK)-cyclin complex by small-molecule degraders remains a great challenge. Here, we applied the first application of hydrophobic tagging to induce degradation of CDK9-cyclin T1 heterodimer, which is required to keep productive transcription of oncogenes in cancers. LL-K9-3 was identified as a potent small-molecule degrader of CDK9-cyclin T1. Quantitative and time-resolved proteome profiling exhibited LL-K9-3 induced selective and synchronous degradation of CDK9 and cyclin T1. The expressions of androgen receptor (AR) and cMyc were reduced by LL-K9-3 in 22RV1 cells. LL-K9-3 exhibited enhanced anti-proliferative and pro-apoptotic effects compared with its parental CDK9 inhibitor SNS032 and suppressed downstream signaling of CDK9 and AR more effectively than SNS032. Moreover, LL-K9-3 inhibited AR and Myc-driven oncogenic transcriptional programs and exerted stronger inhibitory effects on several intrinsic target genes of AR than the monomeric CDK9 PROTAC (Thal-SNS032).

UBR5 targets tumor suppressor CDC73 proteolytically to promote aggressive breast cancer

UBR5, a HECT-domain E3 ubiquitin ligase, is an attractive therapeutic target for aggressive breast cancers. Defining the substrates of UBR5 is crucial for scientific understanding and clinical intervention. Here, we demonstrate that CDC73, a component of the RNA polymerase II-associated factor 1 complex, is a key substrate that impedes UBR5's profound tumorigenic and metastatic activities in triple-negative breast cancer (TNBC) via mechanisms of regulating the expression of β-catenin and E-cadherin, tumor cell apoptosis and CD8+ T cell infiltration. Expression of CDC73 is also negatively associated with the progression of breast cancer patients. Moreover, we show that UBR5 destabilizes CDC73 by polyubiquitination at Lys243, Lys247, and Lys257 in a non-canonical manner that is dependent on the non-phosphorylation state of CDC73 at Ser465. CDC73 could serve as a molecular switch to modulate UBR5's pro-tumor activities and may provide a potential approach to developing breast cancer therapeutic interventions.

Targeting the COP9 signalosome for cancer therapy

The COP9 signalosome (CSN) is a highly conserved protein complex composed of 8 subunits (CSN1 to CSN8). The individual subunits of the CSN play essential roles in cell proliferation, tumorigenesis, cell cycle regulation, DNA damage repair, angiogenesis, and microenvironmental homeostasis. The CSN complex has an intrinsic metalloprotease that removes the ubiquitin-like activator NEDD8 from cullin-RING ligases (CRLs). Binding of neddylated CRLs to CSN is sensed by CSN4 and communicated to CSN5 with the assistance of CSN6, thus leading to the activation of deneddylase. Therefore, CSN is a crucial regulator at the intersection between neddylation and ubiquitination in cancer progression. Here, we summarize current understanding of the roles of individual CSN subunits in cancer progression. Furthermore, we explain how the CSN affects tumorigenesis through regulating transcription factors and the cell cycle. Finally, we discuss individual CSN subunits as potential therapeutic targets to provide new directions and strategies for cancer therapy.

Targeted Nanotherapeutics Using LACTB Gene Therapy Against Melanoma

Introduction

β-lactamase (LACTB) is a tumor suppressor gene in various tumors including melanoma. However, it remains challenging to efficiently deliver the LACTB gene into melanoma. Recently, we designed a nonviral nanocarrier iRGD/DOTAP/MPEG-PDLLA (iDPP) that could deliver gene targetedly to melanoma efficiently without obvious adverse effects.

Methods

In this study, the tumor-targeted nanoparticle iDPP was prepared to deliver LACTB gene to treat melanoma in vitro and in vivo. First, the expression level of LACTB in 6 clinical specimens of melanoma patients was evaluated. Subsequently, the characteristics of iDPP/LACTB nanocomplexes were studied. Afterwards, the in vitro and in vivo anti-tumor efficacy of the iDPP/LACTB nanocomplexes were explored utilizing the B16-F10 mouse melanoma cell line and the B16-F10 subcutaneous melanoma model.

Results

Compared with the normal epithelium, the expression level of LACTB in melanoma tissues was significantly downregulated. In vitro B16-F10 cell tests showed iDPP/LACTB nanocomplexes could increase the mRNA levels of P21, Bid, Bax, Pidd1, and Sival genes and up-regulate the p53 signaling pathway of melanoma cells, thus promoting cell apoptosis and blocking the cell cycle. Injected intravenously, iDPP nanoparticles could deliver DNA to the subcutaneous melanoma targetedly. Based on in vivo mouse xenograft model, iDPP/LACTB nanocomplexes could effectively inhibit tumor proliferation and induce tumor apoptosis, thus significantly inhibiting melanoma growth (tumor inhibition rate is about 68%) in the subcutaneous B16-F10 melanoma model.

Conclusion

The downregulated LACTB might be a potential target for melanoma therapy. The iDPP/LACTB nanocomplexes could inhibit the growth of the mouse melanoma without obvious side effects, which provide a new option for melanoma gene therapy research.

Targeting CDK9 for Anti-Cancer Therapeutics

Cyclin Dependent Kinase 9 (CDK9) is one of the most important transcription regulatory members of the CDK family. In conjunction with its main cyclin partner-Cyclin T1, it forms the Positive Transcription Elongation Factor b (P-TEFb) whose primary function in eukaryotic cells is to mediate the positive transcription elongation of nascent mRNA strands, by phosphorylating the S2 residues of the YSPTSPS tandem repeats at the C-terminus domain (CTD) of RNA Polymerase II (RNAP II). To aid in this process, P-TEFb also simultaneously phosphorylates and inactivates a number of negative transcription regulators like 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) Sensitivity-Inducing Factor (DSIF) and Negative Elongation Factor (NELF). Significantly enhanced activity of CDK9 is observed in multiple cancer types, which is universally associated with significantly shortened Overall Survival (OS) of the patients. In these cancer types, CDK9 regulates a plethora of cellular functions including proliferation, survival, cell cycle regulation, DNA damage repair and metastasis. Due to the extremely critical role of CDK9 in cancer cells, inhibiting its functions has been the subject of intense research, resulting the development of multiple, increasingly specific small-molecule inhibitors, some of which are presently in clinical trials. The search for newer generation CDK9 inhibitors with higher specificity and lower potential toxicities and suitable combination therapies continues. In fact, the Phase I clinical trials of the latest, highly specific CDK9 inhibitor BAY1251152, against different solid tumors have shown good anti-tumor and on-target activities and pharmacokinetics, combined with manageable safety profile while the phase I and II clinical trials of another inhibitor AT-7519 have been undertaken or are undergoing. To enhance the effectiveness and target diversity and reduce potential drug-resistance, the future of CDK9 inhibition would likely involve combining CDK9 inhibitors with inhibitors like those against BRD4, SEC, MYC, MCL-1 and HSP90.