2,5-dimethylcelecoxib improves immune microenvironment of hepatocellular carcinoma by promoting ubiquitination of HBx-induced PD-L1

Ubiquitin modification in the regulation of tumor immunotherapy resistance mechanisms and potential therapeutic targets

Although immune checkpoint-based cancer immunotherapy has shown significant efficacy in various cancers, resistance still limits its therapeutic effects. Ubiquitination modification is a mechanism that adds different types of ubiquitin chains to proteins, mediating protein degradation or altering their function, thereby affecting cellular signal transduction. Increasing evidence suggests that ubiquitination modification plays a crucial role in regulating the mechanisms of resistance to cancer immunotherapy. Drugs targeting ubiquitination modification pathways have been shown to inhibit tumor progression or enhance the efficacy of cancer immunotherapy. This review elaborates on the mechanisms by which tumor cells, immune cells, and the tumor microenvironment mediate resistance to cancer immunotherapy and the details of how ubiquitination modification regulates these mechanisms, providing a foundation for enhancing the efficacy of cancer immunotherapy by intervening in ubiquitination modification.

Strategic advancement of E3 ubiquitin ligase in the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) presents a significant global health challenge due to its high incidence, poor prognosis, and limited treatment options. As a pivotal regulator of protein stability, E3 ubiquitin ligase plays a crucial role in tumorigenesis and development. This review provides an overview of the latest research on the involvement of E3 ubiquitin ligase in hepatocellular carcinoma and elucidates its significance in hepatocellular carcinoma cell proliferation, invasion, and evasion from immune surveillance. Special attention is given to the functions of RING, HECT, and RBR E3 ubiquitin ligases and their association with hepatocellular carcinoma progression. By dissecting the molecular mechanisms and regulatory networks governed by E3 ubiquitin ligase, several potential therapeutic strategies are proposed: including the development of specific inhibitors targeting E3 ligases; augmentation of their tumor suppressor activity through drug or gene therapy; utilization of E3 ubiquitin ligase to modulate immune checkpoint proteins for improved efficacy of immunotherapy; combination strategies integrating traditional therapies with E3 ubiquitin ligase inhibitors; as well as biomarker development based on E3 ubiquitin ligase activity. Furthermore, this review discusses the prospect of overcoming drug resistance in hepatocellular carcinoma treatment through these novel approaches. Overall, this review establishes a theoretical foundation and offers fresh insights into harnessing the potential of E3 ubiquitin ligase for treating hepatocellular carcinoma while highlighting future research directions that pave the way for clinical translation studies and new drug discoveries.

Pseudomonas aeruginosa two-component system LadS/PA0034 regulates macrophage phagocytosis via fimbrial protein cupA1

Pseudomonas aeruginosa is one of the most common nosocomial pathogens worldwide, known for its virulence, drug resistance, and elaborate sensor-response network. The primary challenge encountered by pathogens during the initial stages of infection is the immune clearance arising from the host. The resident macrophages of barrier organs serve as the frontline defense against these pathogens. Central to our understanding is the mechanism by which bacteria modify their behavior to circumvent macrophage-mediated clearance, ensuring their persistence and colonization. To successfully evade macrophage-mediated phagocytosis, bacteria must possess an adaptive response mechanism. Two-component systems provide bacteria the agility to navigate diverse environmental challenges, translating external stimuli into cellular adaptive responses. Here, we report that the well-documented histidine kinase, LadS, coupled to a cognate two-component response regulator, PA0034, governs the expression of a vital adhesin called chaperone-usher pathway pilus cupA. The LadS/PA0034 system is susceptible to interference from the reactive oxygen species likely to be produced by macrophages and further lead to a poor adhesive phenotype with scantily cupA pilus, impairing the phagocytosis efficiency of macrophages during acute infection. This dynamic underscores the intriguing interplay: as macrophages deploy reactive oxygen species to combat bacterial invasion, the bacteria recalibrate their exterior to elude these defenses.

IMPORTANCE

The notoriety of Pseudomonas aeruginosa is underscored by its virulence, drug resistance, and elaborate sensor-response network. Yet, the mechanisms by which P. aeruginosa maneuvers to escape phagocytosis during acute infections remain elusive. This study pinpoints a two-component response regulator, PA0034, coupled with the histidine kinase LadS, and responds to macrophage-derived reactive oxygen species. The macrophage-derived reactive oxygen species can impair the LadS/PA0034 system, resulting in reduced expression of cupA pilus in the exterior of P. aeruginosa. Since the cupA pilus is an important adhesin of P. aeruginosa, its deficiency reduces bacterial adhesion and changes their behavior to adopt a planktonic lifestyle, subsequently inhibiting the phagocytosis of macrophages by interfering with bacterial adhesion. Briefly, reactive oxygen species may act as environmental cues for the LadS/PA0034 system. Upon recognition, P. aeruginosa may transition to a poorly adhesive state, efficiently avoiding engulfment by macrophages.

The role of PD-1/PD-L1 signaling pathway in cancer pathogenesis and treatment: a systematic review

Aim: Cancer as a complex disease poses significant challenges for both diagnosis and treatment. Researchers have been exploring various avenues to find effective therapeutic strategies, with a particular emphasis on cellular signaling pathways and immunotherapy. One such pathway that has recently been suggested is the PD-1/PD-L1 pathway, which is an immune checkpoint signaling system that plays an important role in regulating the immune system and maintaining tissue homeostasis. Cancer cells exploit this pathway by producing PD-L1, which attaches to PD-1 on T cells, thus inhibiting immune responses and enabling the cancer cells to escape detection by the immune system. This study aimed to evaluate the role of the PD-1/PD-L1 pathway in cancer pathogenesis and treatment. Method: This study was performed based on the principles of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). All in vitro , in vivo , and clinical studies that were published in English have been considered during a thorough search of the Scopus, Web of Science, and PubMed databases without date restriction until March 2024. Results: According to the studies reviewed, the PD-1/PD-L1 signaling axis suggests promising therapeutic effects on various types of cancers such as non-small cell lung cancer, melanoma, breast cancer, hepatocellular carcinoma, squamous cell carcinoma, and colorectal cancer, among others. Additionally, research suggests that immune checkpoint inhibitors that block PD1/PD-L1, such as pembrolizumab, atezolizumab, nivolumab, durvalumab, cemiplimab, avelumab, etc. , can effectively prevent tumor cells from escaping the immune system. Moreover, there might be a possible interaction between microbiome, obesity, etc. on immune mechanisms and on the immune checkpoint inhibitors (ICIs). Conclusion: Although we have gained considerable knowledge about ICIs, we are still facing challenges in effectively prescribing the appropriate ICIs for individual patients. This is largely due to the complex interactions between different intracellular pathways, which need to be thoroughly studied. To resolve this issue, it is necessary to conduct more reliable clinical trials that can produce a scientific consensus.

Recent advances and mechanisms of action of PD-L1 degraders as potential therapeutic agents

PD-L1 is an important immune checkpoint protein that can bind to T cells' PD-1 receptor, thereby promoting immune escape from tumors. In recent years, many researchers have developed strategies to degrade PD-L1 to improve the effect of immunotherapy. The study of degrading PD-L1 provides new opportunities for immunotherapy. Here, we mainly summarize and review the current active molecules and mechanisms that mediate the degradation of immature and mature PD-L1 during the post-translational modification stages, involving PD-L1 phosphorylation, glycosylation, palmitoylation, ubiquitination, and the autophagy-lysosomal process. This review expects that by degrading PD-L1 protein, we will not only gain a better understanding of oncogenic mechanisms involving tumor PD-L1 protein but also provide a new way to improve immunotherapy.

Lnc-CCNH-8 promotes immune escape by up-regulating PD-L1 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common malignancy with poor prognosis. In recent years, immune checkpoint inhibitors (ICIs) have enabled breakthroughs in the clinical treatment of patients with HCC, but the overall response rate to ICIs in HCC patients is still low, and no validated biomarker is available to guide clinical decision making. Here, we demonstrated that the long non-coding RNA Lnc-CCNH-8 is highly expressed in HCC and correlates with poor prognosis. Functionally, elevated Lnc-CCNH-8 inactivated co-cultured T cells in vitro and compromised antitumor immunity in an immunocompetent mouse model. Mechanistically, up-regulated Lnc-CCNH-8 can sponge microRNA (miR)-217 to regulate the expression of PD-L1. In addition, Lnc-CCNH-8 can also stabilize PD-L1 through miR-3173/PKP3 axis. Furthermore, mice bearing tumors with high Lnc-CCNH-8 expression had significant therapeutic sensitivity to anti-PD-L1 monoclonal antibody treatment. More important, HCC patients with high levels of plasma exosomal Lnc-CCNH-8 had a better therapeutic response to ICIs. Taken together, our results reveal the function of Lnc-CCNH-8 in inducing immune escape from CD8+ T-cell-mediated killing by up-regulating PD-L1 in a miR-217/miR-3173-dependent manner, which also reveals a novel mechanism of PD-L1 regulation in HCC, and exosomal Lnc-CCNH-8 can serve as a predictive marker for immunotherapy response in HCC.

Ubiquitination of Immune System and Cancer Therapy

Ubiquitination is a post-translational modification mechanism which regulates a variety of signaling pathways and crucial biological processes. It has long been known that ubiquitination regulates the fundamental cellular processes through the induction of proteasomal degradation of target proteins. Meanwhile, the nondegradative types of polyubiquitination modification have been appreciated as important regulatory machinery by modulating the activity or subcellular localization of key signaling proteins. The function of ubiquitination plays an important role in immune responses, which helps to maintain the stability of the internal environment and to control over protein stability and function and are thus critical for the regulation of both innate and adaptive immunity. Furthermore, ubiquitination also regulates both tumor-suppressing and tumor-promoting pathways in cancer. In this review, we will discuss recent progress regarding how ubiquitination regulates immune responses, focusing on Toll-like receptors signaling in innate immunity, T cell activation, TCR signaling, and tumor immunotherapy.

A modified immune cell infiltration score achieves ideal stratification for CD8+ T cell efficacy and immunotherapy benefit in hepatocellular carcinoma

Immunotherapy, which aims to enhance the function of T cells, has emerged as a novel therapeutic approach for hepatocellular carcinoma (HCC). Nevertheless, the clinical utility of using flow cytometry to assess immune cell infiltration (ICI) is hindered by its cumbersome procedures, prompting the need for more accessible methods. Here, we acquired gene expression profiles and survival data of HCC from TCGA and GSE10186 datasets. The patients were categorized into two clusters of ICI, and a set of 11 characteristic genes responsible for the differentiation performance of these ICI clusters were identified. Subsequently, we successfully developed a modified ICI score (mICIS) by utilizing the expression levels of these genes. The efficacy of our mICIS was confirmed via mass cytometry, flow cytometry, and immunohistochemistry. Our research indicated that the favorable overall survival (OS) rate could be attributed to the improved function of anti-tumor leukocytes rather than their infiltration. Furthermore, we observed that the low score group exhibited lower expression levels of T-cell exhaustion-associated genes, which was confirmed in both HCC tissues from patients and mice, which demonstrated that the benefits of the low scores were due to enhanced active/cytotoxic CD8+ T cells and reduced exhausted CD8+ T cells. Additionally, our mICIS stratified the benefits derived from immunotherapies. Lastly, we observed a misalignment between CD8+ T-cell infiltration and function in HCC. In summary, our mICIS demonstrated proficiency in assessing the OS rate of HCC and offering significant stratified data pertaining to distinct responses to immunotherapy.

Inhibition of mPGES-2 ameliorates NASH by activating NR1D1 via heme

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD), a complex metabolic syndrome, has limited therapeutic options. Microsomal prostaglandin E synthase-2 (mPGES-2) was originally discovered as a prostaglandin E 2 (PGE 2 ) synthase; however, it does not produce PGE 2 in the liver. Moreover, the role of mPGES-2 in NAFLD remains undefined. Herein, we aimed to determine the function and mechanism of mPGES-2 in liver steatosis and steatohepatitis.

APPROACH AND RESULTS

To evaluate the role of mPGES-2 in NAFLD, whole-body or hepatocyte-specific mPGES-2-deficient mice fed a high-fat or methionine-choline-deficient diet were used. Compared with control mice, mPGES-2-deficient mice showed reduced hepatic lipid accumulation, along with ameliorated liver injury, inflammation, and fibrosis. Furthermore, the protective effect of mPGES-2 deficiency against NAFLD was dependent on decreased cytochrome P450 4A14 and increased acyl-CoA thioesterase 4 levels regulated by the heme receptor nuclear receptor subfamily 1 group D member 1 (NR1D1), but not PGE 2 . Heme regulated the increased NR1D1 activity mediated by mPGES-2 deficiency. Further, we confirmed the protective role of the mPGES-2 inhibitor SZ0232 in NAFLD therapy.

CONCLUSION

Our study indicates the pathogenic role of mPGES-2 and outlines the mechanism in mediating NAFLD, thereby highlighting the therapeutic potential of mPGES-2 inhibition in liver steatosis and steatohepatitis.

Post-translational modifications and immune responses in liver cancer

Post-translational modification (PTM) refers to the covalent attachment of functional groups to protein substrates, resulting in structural and functional changes. PTMs not only regulate the development and progression of liver cancer, but also play a crucial role in the immune response against cancer. Cancer immunity encompasses the combined efforts of innate and adaptive immune surveillance against tumor antigens, tumor cells, and tumorigenic microenvironments. Increasing evidence suggests that immunotherapies, which harness the immune system's potential to combat cancer, can effectively improve cancer patient prognosis and prolong the survival. This review presents a comprehensive summary of the current understanding of key PTMs such as phosphorylation, ubiquitination, SUMOylation, and glycosylation in the context of immune cancer surveillance against liver cancer. Additionally, it highlights potential targets associated with these modifications to enhance the response to immunotherapies in the treatment of liver cancer.

2,5-dimethylcelecoxib alleviated NK and T-cell exhaustion in hepatocellular carcinoma via the gastrointestinal microbiota-AMPK-mTOR axis

BACKGROUND

2,5-dimethylcelecoxib (DMC), a derivative of celecoxib, is an inhibitor of microsomal prostaglandin E synthase-1 (mPGES-1). Our previous studies have demonstrated that DMC inhibits the expression of programmed death-ligand 1 on hepatocellular carcinoma (HCC) cells to prevent tumor progression. However, the effect and mechanism of DMC on HCC infiltrating immune cells remain unclear.

METHODS

In this study, single-cell-based high-dimensional mass cytometry was performed on the tumor microenvironment of HCC mice treated with DMC, celecoxib and MK-886 (a known mPGES-1 inhibitor). Moreover, 16S ribosomal RNA sequencing was employed to analyze how DMC improved the tumor microenvironment of HCC by remodeling the gastrointestinal microflora.

RESULTS

We found that (1) DMC significantly inhibited the growth of HCC and improved the prognosis of the mice, and this depended on the stronger antitumor activity of natural killer (NK) and T cells; (2) compared with celecoxib and MK-886, DMC significantly enhanced the cytotoxic and stem-like potential, and inhibited exhaustion of NK and T cells; (3) mechanistically, DMC inhibited the expression of programmed cell death protein-1 and upregulated interferon-γ expression of NK and T cells via the gastrointestinal microbiota (Bacteroides acidifaciens, Odoribacter laneus, and Odoribacter splanchnicus)-AMPK-mTOR axis.

CONCLUSIONS

Our study uncovers the role of DMC in improving the tumor microenvironment of HCC, which not only enriches the relationship between the mPGES-1/prostaglandin E2 pathway and the antitumor function of NK and T cells, but also provide an important strategic reference for multitarget or combined immunotherapy of HCC.Cite Now.

Mevalonate improves anti-PD-1/PD-L1 efficacy by stabilizing CD274 mRNA

Mevalonate metabolism plays an important role in regulating tumor growth and progression; however, its role in immune evasion and immune checkpoint modulation remains unclear. Here, we found that non-small cell lung cancer (NSCLC) patients with higher plasma mevalonate response better to anti-PD-(L)1 therapy, as indicated by prolonged progression-free survival and overall survival. Plasma mevalonate levels were positively correlated with programmed death ligand-1 (PD-L1) expression in tumor tissues. In NSCLC cell lines and patient-derived cells, supplementation of mevalonate significantly up-regulated the expression of PD-L1, whereas deprivation of mevalonate reduced PD-L1 expression. Mevalonate increased CD274 mRNA level but did not affect CD274 transcription. Further, we confirmed that mevalonate improved CD274 mRNA stability. Mevalonate promoted the affinity of the AU-rich element-binding protein HuR to the 3'-UTR regions of CD274 mRNA and thereby stabilized CD274 mRNA. By in vivo study, we further confirmed that mevalonate addition enhanced the anti-tumor effect of anti-PD-L1, increased the infiltration of CD8+ T cells, and improved cytotoxic function of T cells. Collectively, our findings discovered plasma mevalonate levels positively correlated with the therapeutic efficacy of anti-PD-(L)1 antibody, and provided the evidence that mevalonate supplementation could be an immunosensitizer in NSCLC.

Microsomal Prostaglandin E Synthase-1 and -2: Emerging Targets in Non-Alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) affects a substantial proportion of the general population and is even more prevalent in obese and diabetic patients. NAFLD, and particularly the more advanced manifestation of the disease, nonalcoholic steatohepatitis (NASH), increases the risk for both liver-related and cardiovascular morbidity. The pathogenesis of NAFLD is complex and multifactorial, with many molecular pathways implicated. Emerging data suggest that microsomal prostaglandin E synthase-1 and -2 might participate in the development and progression of NAFLD. It also appears that targeting these enzymes might represent a novel therapeutic approach for NAFLD. In the present review, we discuss the association between microsomal prostaglandin E synthase-1 and -2 and NAFLD.

The E3 ubiquitin ligases regulate PD-1/PD-L1 protein levels in tumor microenvironment to improve immunotherapy

The tumor microenvironment (TME) is the tumor surrounding environment, which is critical for tumor development and progression. TME is also involved in clinical intervention and treatment outcomes. Modulation of TME is useful for improving therapy strategies. PD-L1 protein on tumor cells interacts with PD-1 protein on T cells, contributing to T cell dysfunction and exhaustion, blockage of the immune response. Evidence has demonstrated that the expression of PD-1/PD-L1 is associated with clinical response to anti-PD-1/PD-L1 therapy in cancer patients. It is important to discuss the regulatory machinery how PD-1/PD-L1 protein is finely regulated in tumor cells. In recent years, studies have demonstrated that PD-1/PD-L1 expression was governed by various E3 ubiquitin ligases in TME, contributing to resistance of anti-PD-1/PD-L1 therapy in human cancers. In this review, we will discuss the role and molecular mechanisms of E3 ligases-mediated regulation of PD-1 and PD-L1 in TME. Moreover, we will describe how E3 ligases-involved PD-1/PD-L1 regulation alters anti-PD-1/PD-L1 efficacy. Altogether, targeting E3 ubiquitin ligases to control the PD-1/PD-L1 protein levels could be a potential strategy to potentiate immunotherapeutic effects in cancer patients.

An integrative pan-cancer analysis revealing the difference in small ring finger family of SCF E3 ubiquitin ligases

Background

The SCF (Skp1-cullin-F-box proteins) complex is the largest family of E3 ubiquitin ligases that mediate multiple specific substrate proteins degradation. Two ring-finger family members RBX1/ROC1 and RBX2/RNF7/SAG are small molecular proteins necessary for ubiquitin ligation activity of the multimeric SCF complex. Accumulating evidence indicated the involvement of RBX proteins in the pathogenesis and development of cancers, but no research using pan-cancer analysis for evaluating their difference has been directed previously.

Methods

We investigated RBX1/2 expression patterns and the association with clinicopathological features, and survivals of cancer patients obtained from the TCGA pan-cancer data. The binding energies of RBX1/2-CUL1 complexes were preliminarily calculated by using molecular dynamics simulations. Meanwhile, we assessed their immune infiltration level across numerous databases, including TISIDB and Timer database.

Results

High expression levels of RBX1/2 were observed in most cancer types and correlated with poor prognosis of patients analyzed. Nonetheless, exceptions were observed: RBX2 expression in KICH was higher than normal renal tissues and played a detrimental role in KICH. The expression of RBX1 was not associated with the prognostic risk of KICH. Moreover, the combination of RBX1 and CUL1 expression is more stable than that of RBX2 and CUL1. RBX1/2 expression showed their own specific characteristics in tumor pathological stages and grades, copy number variation and immune components.

Conclusions

These findings not only indicated that the difference of RBX1/2 might result in varying degrees of tumor progression, but also suggested that they might serve as biomarkers for immune infiltration in cancers, shedding new light on therapeutics of cancers.

Codelivery of HBx-siRNA and Plasmid Encoding IL-12 for Inhibition of Hepatitis B Virus and Reactivation of Antiviral Immunity

Chronic hepatitis B is a critical cause of many serious liver diseases such as hepatocellular carcinoma (HCC). The main challenges in hepatitis B treatment include the rebound of hepatitis B virus (HBV)-related antigen levels after drug withdrawal and the immunosuppression caused by the virus. Herein, we demonstrate that the HBV-related antigen can be effectively inhibited and antiviral immunity can be successfully reactivated through codelivery of the small interfering RNA (siRNA) targeting HBV X protein (HBx) and the plasmid encoding interleukin 12 (pIL-12) to hepatocytes and immune cells. After being treated by the siRNA/pIL-12 codelivery system, HBx mRNA and hepatitis B surface antigen (HBsAg) are dramatically reduced in HepG2.215 cells. More importantly, the downregulated CD47 and programmed death ligand 1 (PD-L1) and the upregulated interferon-β promoter stimulator-1 (IPS-1), retinoic acid-inducible gene-1 (RIG-1), CD80, and human leukocyte antigen-1 (HLA-1) in treated HepG2.215 cells indicate that the immunosuppression is reversed by the codelivery system. Furthermore, the codelivery system results in inhibition of extracellular regulated protein kinases (ERK) and phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) pathways, as well as downregulation of B-cell lymphoma-2 (Bcl-2) and upregulation of p53, implying its potential in preventing the progression of HBV-induced HCC. In addition, J774A.1 macrophages treated by the codelivery system were successfully differentiated into the M1 phenotype and expressed enhanced cytokines with anti-hepatitis B effects such as interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α). Therefore, we believe that codelivery of siRNA and pIL-12 can effectively inhibit hepatitis B virus, reverse virus-induced immunosuppression, reactivate antiviral immunity, and hinder the progression of HBV-induced hepatocellular carcinoma. This investigation provides a promising approach for the synergistic treatment of HBV infection.

E3 ubiquitin ligase RBX1 drives the metastasis of triple negative breast cancer through a FBXO45-TWIST1-dependent degradation mechanism

Triple-negative breast cancer (TNBC) patients are at high risk of recurrence and metastasis in the early stages, although receiving standard treatment. However, the underlying mechanism of TNBC remains unclear. Here, the critical effect of E3 ubiquitin ligase RBX1 in the metastasis of TNBC was reported for the first time. We discovered that RBX1 expression was evidently raised in the tissues of TNBC. Our clinical research displayed that high RBX1 expression was markedly related to poor distant invasion and survival. Functional analysis exhibited that RBX1 facilitated metastasis of TNBC cells through increasing EMT. Furthermore, we demonstrated that RBX1 knockdown increased the levels of the Twist family bHLH transcription factor 1 (TWIST1), is a significant regulator in the EMT process in some cancers. It can be observed an evident positive correlation between the TWIST1 and RBX1 levels, further confirming that EMT induced by RBX1 in TNBC cells is determined by TWIST1. Mechanistically, RBX1 modulates the expression of TWIST1 via modulating FBXO45, directly binding to FBXO45, and facilitating its degradation and ubiquitination. Briefly, our findings confirm that RBX1 is probably a new biomarker of TNBC carcinogenesis, thus suggesting that targeting the RBX1/FBXO45/TWIST1 axis may be an underlying strategy for TNBC treatment.

The roles of E3 ligases in Hepatocellular carcinoma

Hepatocarcinogenesis is a complex multistep biological process involving genetic and epigenetic alterations that are accompanied by activation of oncoproteins and inactivation of tumor suppressors, which in turn results in Hepatocellular carcinoma (HCC), one of the common tumors with high morbidity and mortality worldwide. The ubiquitin-proteasome system (UPS) is the key to protein degradation and regulation of physiological and pathological processes, and E3 ligases are key enzymes in the UPS that contain a variety of subfamily proteins involved in the regulation of some common signal pathways in HCC. There is growing evidence that many structural or functional dysfunctions of E3 are engaged in the development and progression of HCC. Herein, we review recent research advances in HCC-associated E3 ligases, describe their structure, classification, functional roles, and discuss some mechanisms of the abnormal activation or inactivation of the HCC-associated signal pathway due to the binding of E3 to known substrates. In addition, given the success of proteasome inhibitors in the treatment of malignant cancers, we characterize the current knowledge and future prospects for targeted therapies against aberrant E3 in HCC.

Increased effects of 2,5-dimethylcelecoxib on sensitivity of hepatocellular carcinoma cells to sorafenib via CYP3A5 expression and activation of AMPK

As the occurrence and development of HCC are often accompanied by inflammation, the combination of sorafenib with other therapeutic drugs, especially anti-inflammatory drugs, is one of the directions to be explored at present. Our previous research has been focused on the anti-inflammatory drug 2,5-dimethylcelecoxib (DMC), whether DMC combined with sorafenib could elevate the effect of inhibiting HCC deserves further exploration. In this study, we found that DMC induced CYP3A5 expression in HCC cells in a time-dependent and concentration dependent manner. We observed that sorafenib inhibited CYP3A5 expression in liver cancer cells, and activated the phosphorylation of Akt. Upregulated CYP3A5 and DMC treatment enhanced the ability of sorafenib to inhibit migration. The combination of DMC with sorafenib had a synergistic effect of enhancing drug sensitivity (CI < 1), meanwhile, inhibited the proliferation and promoted apoptosis of HCC. Activation of the AMPK pathway and inhibition of the PI3K/Akt pathway were observed in cells treated with DMC in combination with sorafenib and could be reverted by an AMPK pathway inhibitor. Our findings suggest that DMC induces CYP3A5 expression and enhances the anticancer effect of sorafenib by activating AMPK, which would be a novel strategy for drug combination to prevent drug resistance.

LncRNA KCNQ1OT1 Secreted by Tumor Cell-Derived Exosomes Mediates Immune Escape in Colorectal Cancer by Regulating PD-L1 Ubiquitination via MiR-30a-5p/USP22

Background: This study tried to explore the mechanism of long non-coding RNA (lncRNA) KCNQ1OT1 in tumor immune escape. Methods: Gene Expression Omnibus (GEO) and microarray analysis were used to screen the differentially expressed lncRNA and microRNA (miRNA) in normal tissues and tumor tissues. Quantitative reverse transcription PCR (RT-qPCR) was used to quantify KCNQ1OT1, miR-30a-5p, ubiquitin-specific peptidase 22 (USP22), and programmed death-ligand 1 (PD-L1). The interactive relationship between KCNQ1OT1 and miR-30a-5p was verified using dual-luciferase reporter gene assay and ribonucleoprotein immunoprecipitation (RIP) assay. Cell Counting Kit (CCK)-8, clone formation, wound healing, and apoptosis are used to detect the occurrence of tumor cells after different treatments. Protein half-life and ubiquitination detection are used to study the influence of USP22 on PD-L1 ubiquitination. BALB/c mice and BALB/c nude mice are used to detect the effects of different treatments on tumor growth and immune escape in vivo. Results: The expression of lncRNA KCNQ1OT1 in tumor tissues and tumor cell-derived exosomes was significantly increased. The tumor-promoting effect of lncRNA KCNQ1OT1 was through the autocrine effect of tumor cell-derived exosomes, which mediates the miR-30a-5p/USP22 pathway to regulate the ubiquitination of PD-L1 and inhibits CD8+ T-cell response, thereby promoting colorectal cancer development. Conclusion: Tumor cell-derived exosomes' KCNQ1OT1 could regulate PD-L1 ubiquitination through miR-30a-5p/USP22 to promote colorectal cancer immune escape.

Celecoxib Analogues for Cancer Treatment: An Update on OSU-03012 and 2,5-Dimethyl-Celecoxib

Cyclooxygenase-2 (COX-2) is an important enzyme involved in prostaglandins biosynthesis from arachidonic acid. COX-2 is frequently overexpressed in human cancers and plays a major tumor promoting function. Accordingly, many efforts have been devoted to efficiently target the catalytic site of this enzyme in cancer cells, by using COX-2 specific inhibitors such as celecoxib. However, despite their potent anti-tumor properties, the myriad of detrimental effects associated to the chronic inhibition of COX-2 in healthy tissues, has considerably limited their use in clinic. In addition, increasing evidence indicate that these anti-cancerous properties are not strictly dependent on the inhibition of the catalytic site. These findings have led to the development of non-active COX-2 inhibitors analogues aiming at preserving the antitumor effects of COX-2 inhibitors without their side effects. Among them, two celecoxib derivatives, 2,5-Dimethyl-Celecoxib and OSU-03012, have been developed and suggested for the treatment of viral (e.g., recently SARS-CoV-2), inflammatory, metabolic diseases and cancers. These molecules display stronger anti-tumor properties than celecoxib and thus may represent promising anti-cancer molecules. In this review, we discuss the impact of these two analogues on cancerous processes but also their potential for cancer treatment alone or in combination with existing approaches.

The Role of Prostaglandins in Different Types of Cancer

The prostaglandins constitute a family of lipids of 20 carbon atoms that derive from polyunsaturated fatty acids such as arachidonic acid. Traditionally, prostaglandins have been linked to inflammation, female reproductive cycle, vasodilation, or bronchodilator/bronchoconstriction. Recent studies have highlighted the involvement of these lipids in cancer. In this review, existing information on the prostaglandins associated with different types of cancer and the advances related to the potential use of them in neoplasm therapies have been analyzed. We can conclude that the effect of prostaglandins depends on multiple factors, such as the target tissue, their plasma concentration, and the prostaglandin subtype, among others. Prostaglandin D2 (PGD₂) seems to hinder tumor progression, while prostaglandin E2 (PGE₂) and prostaglandin F2 alpha (PGF_2α) seem to provide greater tumor progression and aggressiveness. However, more studies are needed to determine the role of prostaglandin I2 (PGI₂) and prostaglandin J2 (PGJ₂) in cancer due to the conflicting data obtained. On the other hand, the use of different NSAIDs (non-steroidal anti-inflammatory drugs), especially those selective of COX-2 (cyclooxygenase 2), could have a crucial role in the fight against different neoplasms, either as prophylaxis or as an adjuvant treatment. In addition, multiple targets, related to the action of prostaglandins on the intracellular signaling pathways that are involved in cancer, have been discovered. Thus, in depth research about the prostaglandins involved in different cancer and the different targets modulated by them, as well as their role in the tumor microenvironment and the immune response, is necessary to obtain better therapeutic tools to fight cancer.

Nanomedicine Approach to Immunotherapy of Hepatocellular Carcinoma

In recent years, the growing studies focused on the immunotherapy of hepatocellular carcinoma and proved the preclinical and clinical promises of host antitumor immune response. However, there were still various obstacles in meeting satisfactory clinic need, such as low response rate, primary resistance and secondary resistance to immunotherapy. Tackling these barriers required a deeper understanding of immune underpinnings and a broader understanding of advanced technology. This review described immune microenvironment of liver and HCC which naturally decided the complexity of immunotherapy, and summarized recent immunotherapy focusing on different points. The ever-growing clues indicated that the instant killing of tumor cell and the subsequent relive of immunosuppressive microenvironment were both indis- pensables. The nanotechnology applied in immunotherapy and the combination with intervention technology was also discussed.

Transcriptome Analysis Reveals Possible Immunomodulatory Activity Mechanism of Chlorella sp. Exopolysaccharides on RAW264.7 Macrophages

In this study, the exopolysaccharides of Chlorella sp. (CEP) were isolated to obtain the purified fraction CEP4. Characterization results showed that CEP4 was a sulfated heteropolysaccharide. The main monosaccharide components of CEP4 are glucosamine hydrochloride (40.8%) and glucuronic acid (21.0%). The impact of CEP4 on the immune activity of RAW264.7 macrophage cytokines was detected, and the results showed that CEP4 induced the production of nitric oxide (NO), TNF-α, and IL-6 in a dose-dependent pattern within a range of 6 μg/mL. A total of 4824 differentially expressed genes (DEGs) were obtained from the results of RNA-seq. Gene enrichment analysis showed that immune-related genes such as NFKB1, IL-6, and IL-1β were significantly upregulated, while the genes RIPK1 and TLR4 were significantly downregulated. KEGG pathway enrichment analysis showed that DEGs were significantly enriched in immune-related biological processes, including toll-like receptor (TLR) signaling pathway, cytosolic DNA-sensing pathway, and C-type lectin receptor signaling pathway. Protein–protein interaction (PPI) network analysis showed that HSP90AB1, Rbx1, ISG15, Psmb6, Psmb3, Psmb8, PSMA7, Polr2f, Rpsa, and NEDD8 were the hub genes with an essential role in the immune activity of CEP4. The preliminary results of the present study revealed the potential mechanism of CEP4 in the immune regulation of RAW264.7 macrophages, suggesting that CEP4 is a promising immunoregulatory agent.

Emerging Role of Ubiquitination in the Regulation of PD-1/PD-L1 in Cancer Immunotherapy

A growing amount of evidence suggests that ubiquitination and deubiquitination of programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) play crucial roles in the regulation of PD-1 and PD-L1 protein stabilization and dynamics. PD-1/PD-L1 is a major coinhibitory checkpoint pathway that modulates immune escape in cancer patients, and its engagement and inhibition has significantly reshaped the landscape of tumor clearance. The abnormal ubiquitination and deubiquitination of PD-1/PD-L1 influence PD-1/PD-L1-mediated immunosuppression. In this review, we describe the ubiquitination- and deubiquitination-mediated modulation of PD-1/PD-L1 signaling through a variety of E3 ligases and deubiquitinating enzymes (DUBs). Moreover, we briefly expound on the anticancer potential of some agents that target related E3 ligases, which further modulate the ubiquitination of PD-1/PD-L1 in cancers. Therefore, this review reveals the development of a highly promising therapeutic approach for cancer immunotherapy by targeting PD-1/PD-L1 ubiquitination.