Targeting the ubiquitin-proteasome pathway to overcome anti-cancer drug resistance

The role of proteasomes in tumorigenesis

Protein homeostasis is the basis of normal life activities, and the proteasome family plays an extremely important function in this process. The proteasome 20S is a concentric circle structure with two α rings and two β rings overlapped. The proteasome 20S can perform both ATP-dependent and non-ATP-dependent ubiquitination proteasome degradation by binding to various subunits (such as 19S, 11S, and 200 PA), which is performed by its active subunit β1, β2, and β5. The proteasome can degrade misfolded, excess proteins to maintain homeostasis. At the same time, it can be utilized by tumors to degrade over-proliferate and unwanted proteins to support their growth. Proteasomes can affect the development of tumors from several aspects including tumor signaling pathways such as NF-κB and p53, cell cycle, immune regulation, and drug resistance. Proteasome-encoding genes have been found to be overexpressed in a variety of tumors, providing a potential novel target for cancer therapy. In addition, proteasome inhibitors such as bortezomib, carfilzomib, and ixazomib have been put into clinical application as the first-line treatment of multiple myeloma. More and more studies have shown that it also has different therapeutic effects in other tumors such as hepatocellular carcinoma, non-small cell lung cancer, glioblastoma, and neuroblastoma. However, proteasome inhibitors are not much effective due to their tolerance and singleness in other tumors. Therefore, further studies on their mechanisms of action and drug interactions are needed to investigate their therapeutic potential.

USP3 promotes cisplatin resistance in non-small cell lung cancer cells by suppressing ACOT7-regulated ferroptosis

This study aims to investigate the role and mechanism of ubiquitin-specific protease 3 (USP3) in cisplatin (DDP) in non-small cell lung cancer (NSCLC). USP3 expression in NSCLC cells was detected using reverse transcription quantitative PCR and Western blot. DDP-resistant cells were constructed and cell counting kit-8 assay determined the IC 50 of cells to DDP. USP3 expression was silenced in DDP-resistant cells, followed by detection of cell proliferation by clone formation assay, iron ion contents, ROS, MDA, and GSH levels by kits, GPX4 and ACSL4 protein expressions by Western blot. The binding between USP3 and ACOT7 was analyzed using Co-IP, and the ubiquitination level of ACOT7 was measured. USP3 and ACOT7 were highly expressed in NSCLC cells and further increased in drug-resistant cells. USP3 silencing reduced the IC 50 of cells to DDP and diminished the number of cell clones. Moreover, USP3 silencing suppressed GSH and GPX4 levels, upregulated iron ion contents, ROS, MDA, and ACSL4 levels, and facilitated ferroptosis. Mechanistically, USP3 upregulated ACOT7 protein expression through deubiquitination. ACOT7 overexpression alleviated the promoting effect of USP7 silencing on ferroptosis in NSCLC cells and enhanced DDP resistance. To conclude, USP3 upregulated ACOT7 protein expression through deubiquitination, thereby repressing ferroptosis in NSCLC cells and enhancing DDP resistance.

Evaluation of drug resistance for EGFR-TKIs in lung cancer via multicellular lung-on-a-chip

Drug resistance to irreversible epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is a primary factor affecting their therapeutic efficacy in human non-small cell lung cancer (NSCLC). NSCLC cells can undergo epithelial-mesenchymal transition (EMT) induced by many factors in the tumour microenvironment (TME), which plays a crucial role in tumour drug resistance. In this study, a multicellular lung-on-a-chip that can realise the cell co-culture of the human non-small cell lung cancer cell line HCC827, human foetal lung fibroblasts (HFL-1), and human umbilical vein endothelial cells (HUVECs) is prepared. The TME was simulated on the chip combined with perfusion and other factors, and the drug evaluation of osimertinib was performed to explore the drug resistance mechanism of EGFR-TKIs. In the early stages, a two-dimensional static cell co-culture was achieved by microchip, and the results showed that HFL-1 cells could be transformed into cancer-associated fibroblasts (CAFs), and HCC827 cells could undergo EMT, both of which were mediated by Interleukin-6 (IL-6). Vimentin (VIM) and Alpha Skeletal Muscle Actin (a-SMA) expression of HFL-1 was upregulated, whereas E-cadherin (E-cad) expression of HCC827 was down-regulated. Further, N-cadherin (N-cad) expression of HCC827 was upregulated. In both the static cell co-culture and multicellular lung-on-a-chip, HCC827 cells with CAFs co-culture or IL-6 treatment developed resistance to osimertinib. Further use of the IL-6 antibody inhibitor tocilizumab could reverse EGFR-TKI resistance to a certain extent. Combination therapy with tocilizumab and EGFR-TKIs may provide a novel therapeutic strategy for overcoming EGFR-TKI resistance caused by EMT in NSCLC. Furthermore, the lung-on-a-chip can simulate complex TME and can be used for evaluating tumour resistance and exploring mechanisms, with the potential to become an important tool for personalised diagnosis, treatment, and biomedical research.

Evaluating the Role of Neddylation Modifications in Kidney Renal Clear Cell Carcinoma: An Integrated Approach Using Bioinformatics, MLN4924 Dosing Experiments, and RNA Sequencing

BACKGROUND

Neddylation, a post-translational modification process, plays a crucial role in various human neoplasms. However, its connection with kidney renal clear cell carcinoma (KIRC) remains under-researched.

METHODS

We validated the Gene Set Cancer Analysis Lite (GSCALite) platform against The Cancer Genome Atlas (TCGA) database, analyzing 33 cancer types and their link with 17 neddylation-related genes. This included examining copy number variations (CNVs), single nucleotide variations (SNVs), mRNA expression, cellular pathway involvement, and methylation. Using Gene Set Variation Analysis (GSVA), we categorized these genes into three clusters and examined their impact on KIRC patient prognosis, drug responses, immune infiltration, and oncogenic pathways. Afterward, our objective is to identify genes that exhibit overexpression in KIRC and are associated with an adverse prognosis. After pinpointing the specific target gene, we used the specific inhibitor MLN4924 to inhibit the neddylation pathway to conduct RNA sequencing and related in vitro experiments to verify and study the specificity and potential mechanisms related to the target. This approach is geared towards enhancing our understanding of the prognostic importance of neddylation modification in KIRC.

RESULTS

We identified significant CNV, SNV, and methylation events in neddylation-related genes across various cancers, with notably higher expression levels observed in KIRC. Cluster analysis revealed a potential trade-off in the interactions among neddylation-related genes, where both high and low levels of gene expression are linked to adverse prognoses. This association is particularly pronounced concerning lymph node involvement, T stage classification, and Fustat score. Simultaneously, our research discovered that PSMB10 exhibits overexpression in KIRC when compared to normal tissues, negatively impacting patient prognosis. Through RNA sequencing and in vitro assays, we confirmed that the inhibition of neddylation modification could play a role in the regulation of various signaling pathways, thereby influencing the prognosis of KIRC. Moreover, our results underscore PSMB10 as a viable target for therapeutic intervention in KIRC, opening up novel pathways for the development of targeted treatment strategies.

CONCLUSION

This study underscores the regulatory function and potential mechanism of neddylation modification on the phenotype of KIRC, identifying PSMB10 as a key regulatory target with a significant role in influencing the prognosis of KIRC.

PSMD9 promotes the malignant progression of hepatocellular carcinoma by interacting with c-Cbl to activate EGFR signaling and recycling

BACKGROUND

Mounting evidences shows that the ubiquitin‒proteasome pathway plays a pivotal role in tumor progression. The expression of 26S proteasome non-ATPase regulatory subunit 9 (PSMD9) is correlated with recurrence and radiotherapy resistance in several tumor types. However, the role and mechanism of PSMD9 in hepatocellular carcinoma (HCC) progression remain largely unclear.

METHODS

PSMD9 was identified as a prognosis-related biomarker for HCC based on analysis of clinical characteristics and RNA-seq data from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and the JP Project of the International Cancer Genome Consortium (ICGC-LIRI-JP). PSMD9 expression was analyzed in cancer tissues and adjacent noncancerous tissues via immunohistochemistry and Western blotting. Multiple in vivo and in vitro experimental techniques (such as CCK-8, colony formation, EdU, and Transwell assays; flow cytometry; Western blotting; quantitative RT-PCR; Coimmunoprecipitation assay and immunofluorescence confocal imaging) were used to assess the functions of PSMD9 in the pathogenesis of HCC.

RESULTS

We found that the expression of PSMD9 was upregulated and associated with a poor prognosis in HCC patients. PSMD9 promoted HCC cell proliferation, migration, invasion and metastasis. Knockdown of PSMD9 significantly inhibited HCC cell proliferation by inducing G1/S cell cycle arrest and apoptosis. Mechanistically, we demonstrated that PSMD9 promoted HCC cell proliferation and metastasis via direct interaction with the E3 ubiquitin ligase c-Cbl, suppresses EGFR ubiquitination, influenced EGFR endosomal trafficking and degradation and subsequently activated ERK1/2 and Akt signaling. In addition, we showed that PSMD9 knockdown sensitized HCC cells to the tyrosine kinase inhibitor erlotinib in vitro and in vivo.

CONCLUSIONS

Collectively, our results indicate that PSMD9 drives HCC progression and erlotinib resistance by suppressing c-Cbl mediated EGFR ubiquitination and therefore can be a potential therapeutic target for HCC.

Identification of crucial ubiquitin-associated genes for predicting the effects of immunotherapy and therapeutic agents in colorectal cancer

BACKGROUND

A growing body of research indicates that colorectal cancer (CRC) is significantly influenced by the ubiquitin-proteasome system. Nevertheless, reliable immune landscapes and ubiquitin-associated prognostic markers are still scarce.

METHODS

We systematically analyzed the RNA-seq data of 2,830 ubiquitin-related genes from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA). A CRC prognostic risk model was developed based on ubiquitin-associated gene signatures. In-depth multi-dimensional analyses were performed on ubiquitin-related subgroups with high and low risk. Drug response sensitivity for high-risk CRC patients was also predicted.

RESULTS

A total of 131 ubiquitin-related differentially expressed genes were retrieved, of which 9 prognostic genes for CRC were ultimately identified and further validated by our clinical CRC tumor and adjacent normal samples. The expression pattern of these 9 ubiquitin-associated genes was found to be strongly related to overall survival, immune cell fractions, and immune-related genes of CRC patients. CRC patients stratified by the ubiquitin prognostic model exhibited distinct clinicopathological characteristics and immune landscapes. A comprehensive framework for personalized medicine prediction identified regorafenib and sorafenib as the most promising therapeutic agents for high ubiquitin-related risk CRC patients, which was confirmed in cell viability assays.

CONCLUSIONS

Ubiquitin characteristics can reflect CRC prognosis and help develop innovative biomarkers for precision treatment.

Proteasome inhibitor bortezomib prevents proliferation and migration of pulmonary arterial smooth muscle cells

Pulmonary vascular remodeling is a key pathological process of pulmonary arterial hypertension (PAH), characterized by uncontrolled proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). Bortezomib (BTZ) is the first Food and Drug Administration (FDA)-approved proteasome inhibitor for multiple myeloma treatment. Recently, there is emerging evidence showing its effect on reversing PAH, although its mechanisms are not well understood. In this study, anti-proliferative and anti-migratory effects of BTZ on PASMCs were first examined by different inducers such as fetal bovine serum (FBS), angiotensin II (Ang II) and platelet-derived growth factor (PDGF)-BB, while potential mechanisms including cellular reactive oxygen species (ROS) and mitochondrial ROS were then investigated; finally, signal transduction of ERK and Akt was examined. Our results showed that BTZ attenuated FBS-, Ang II- and PDGF-BB-induced proliferation and migration, with associated decreased cellular ROS production and mitochondrial ROS production. In addition, the phosphorylation of ERK and Akt induced by Ang II and PDGF-BB was also inhibited by BTZ treatment. This study indicates that BTZ can prevent proliferation and migration of PASMCs, which are possibly mediated by decreased ROS production and down-regulation of ERK and Akt. Thus, proteasome inhibition can be a novel pharmacological target in the management of PAH.

USP3: Key deubiquitylation enzyme in human diseases

Ubiquitination and deubiquitylation are pivotal posttranslational modifications essential for regulating cellular protein homeostasis and are implicated in the development of human diseases. Ubiquitin-specific protease 3 (USP3), a member of the ubiquitin-specific protease family, serves as a key deubiquitylation enzyme, playing a critical role in diverse cellular processes including the DNA damage response, cell cycle regulation, carcinogenesis, tumor cell proliferation, migration, and invasion. Despite notable research efforts, our current understanding of the intricate and context-dependent regulatory networks governing USP3 remains incomplete. This review aims to comprehensively synthesize existing published works on USP3, elucidating its multifaceted roles, functions, and regulatory mechanisms, while offering insights for future investigations. By delving into the complexities of USP3, this review strives to provide a foundation for a more nuanced understanding of its specific roles in various cellular processes. Furthermore, the exploration of USP3's regulatory networks may uncover novel therapeutic strategies targeting this enzyme in diverse human diseases, thereby holding promising clinical implications. Overall, an in-depth comprehension of USP3's functions and regulatory pathways is crucial for advancing our knowledge and developing targeted therapeutic approaches for human diseases.

The mechanism by which SIRT1 regulates autophagy and EMT in drug-resistant oesophageal cancer cells

Cancer cell resistance presents a significant clinical challenge. The mechanisms underlying drug resistance in cancer cells are intricate and remain incompletely understood. Notably, tumor cell resistance often coincides with the epithelial-mesenchymal transition (EMT). In this study, we observed an elevation in autophagy levels following the development of drug resistance in oesophageal cancer cells. Inhibition of autophagy led to a reduction in drug-resistant cell migration and the inhibition of EMT. Furthermore, we identified an upregulation of SIRT1 expression in drug-resistant oesophageal cancer cells. Subsequent inhibition of SIRT1 expression in drug-resistant cells resulted in the suppression of autophagy levels, migration ability, and the EMT process. Our additional investigations revealed that a SIRT1 inhibitor effectively curbed tumor growth in human oesophageal cancer xenograft model mice (TE-1, TE-1/PTX) without evident toxic effects. This mechanism appears to be associated with the autophagy levels within the tumor tissue.

Mechanism study of ubiquitination in T cell development and autoimmune disease

T cells play critical role in multiple immune processes including antigen response, tumor immunity, inflammation, self-tolerance maintenance and autoimmune diseases et. Fetal liver or bone marrow-derived thymus-seeding progenitors (TSPs) settle in thymus and undergo T cell-lineage commitment, proliferation, T cell receptor (TCR) rearrangement, and thymic selections driven by microenvironment composed of thymic epithelial cells (TEC), dendritic cells (DC), macrophage and B cells, thus generating T cells with diverse TCR repertoire immunocompetent but not self-reactive. Additionally, some self-reactive thymocytes give rise to Treg with the help of TEC and DC, serving for immune tolerance. The sequential proliferation, cell fate decision, and selection during T cell development and self-tolerance establishment are tightly regulated to ensure the proper immune response without autoimmune reaction. There are remarkable progresses in understanding of the regulatory mechanisms regarding ubiquitination in T cell development and the establishment of self-tolerance in the past few years, which holds great potential for further therapeutic interventions in immune-related diseases.

Inhibition of NF-κB signaling unveils novel strategies to overcome drug resistance in cancers

Drug resistance in cancer remains a major challenge in oncology, impeding the effectiveness of various treatment modalities. The nuclear factor-kappa B (NF-κB) signaling pathway has emerged as a critical player in the development of drug resistance in cancer cells. This comprehensive review explores the intricate relationship between NF-κB and drug resistance in cancer. We delve into the molecular mechanisms through which NF-κB activation contributes to resistance against chemotherapeutic agents, targeted therapies, and immunotherapies. Additionally, we discuss potential strategies to overcome this resistance by targeting NF-κB signaling, such as small molecule inhibitors and combination therapies. Understanding the multifaceted interactions between NF-κB and drug resistance is crucial for the development of more effective cancer treatment strategies. By dissecting the complex signaling network of NF-κB, we hope to shed light on novel therapeutic approaches that can enhance treatment outcomes, ultimately improving the prognosis for cancer patients. This review aims to provide a comprehensive overview of the current state of knowledge on NF-κB and its role in drug resistance, offering insights that may guide future research and therapeutic interventions in the fight against cancer.

TRIM21/USP15 balances ACSL4 stability and the imatinib resistance of gastrointestinal stromal tumors

BACKGROUND

Imatinib has become an exceptionally effective targeted drug for treating gastrointestinal stromal tumors (GISTs). Despite its efficacy, the resistance to imatinib is common in GIST patients, posing a significant challenge to the effective treatment.

METHODS

The expression profiling of TRIM21, USP15, and ACSL4 in GIST patients was evaluated using Western blot and immunohistochemistry. To silence gene expression, shRNA was utilized. Biological function of TRIM21, USP15, and ACSL4 was examined through various methods, including resistance index calculation, colony formation, shRNA interference, and xenograft mouse model. The molecular mechanism of TRIM21 and USP15 in GIST was determined by conducting Western blot, co-immunoprecipitation, and quantitative real-time PCR (qPCR) analyses.

RESULTS

Here we demonstrated that downregulation of ACSL4 is associated with imatinib (IM) resistance in GIST. Moreover, clinical data showed that higher levels of ACSL4 expression are positively correlated with favorable clinical outcomes. Mechanistic investigations further indicated that the reduced expression of ACSL4 in GIST is attributed to excessive protein degradation mediated by the E3 ligase TRIM21 and the deubiquitinase USP15.

CONCLUSION

These findings demonstrate that the TRIM21 and USP15 control ACSL4 stability to maintain the IM sensitive/resistant status of GIST.

PSMD12 promotes non-small cell lung cancer progression through activating the Nrf2/TrxR1 pathway

BACKGROUND

Non-small cell lung cancer (NSCLC) contributes to the vast majority of cancer-related deaths. Proteasome 26S subunit, non-ATPase 12 (PSMD12), a subunit of 26S proteasome complex, is known to play the tumor-promoting role in several types of cancer but its function in NSCLC remains elusive.

OBJECTIVE

To explore the role and underlying mechanisms of PSMD12 in NSCLC.

METHODS

The PSMD12 expression in human normal lung epithelial cell line (BEAS-2B) and four NSCLC cell lines (A549, NCI-H1299, NCI-H1975, Calu-1) were determined by qRT-PCR and western blot. Malignant phenotypes of NSCLC cells were detected by CCK-8, EdU staining, immunofluorescence staining for E-cadherin, flow cytometry, and Transwell assays to assess cell viability, proliferation, epithelial-mesenchymal transition (EMT), apoptosis, migration and invasion. Dual luciferase assay was used to verify the regulatory role of transcription factor on the promoter.

RESULTS

We identified the upregulation of PSMD12 in NSCLC tissues based on the GEO datasets, which further verified in NSCLC and BEAS-2B cell lines. PSMD12 knockdown significantly suppressed malignant behaviors of NSCLC cells, including cell growth, invasion, and migration, while PSMD12 overexpression presented the opposite effects. Interestingly, we found that PSMD12 upregulated the tumor-promoting factor TrxR1 mRNA expression. For its potential mechanisms, we demonstrated that PSMD12 elevated transcription factor Nrf2 protein level and promoted Nrf2 nuclear translocation. And Nrf2 further increased TrxR1 promoter activity and enhanced TrxR1 transcription. Meanwhile, we proved that TrxR1 overexpression erased the inhibitory effect of PSMD12 knockdown.

CONCLUSION

PSMD12 promotes NSCLC progression by activating the Nrf2/TrxR1 pathway, providing a novel prognostic and therapeutic target for NSCLC treatment.

Proapoptotic effect of WS-299 induced by NOXA accumulation and NRF2-counterbalanced oxidative stress damage through targeting RBX1-UBE2M interaction in gastric cancers

The abnormal activation of Cullin RING E3 Ligases (CRLs) is closely associated with the occurrence and development of various cancers. Targeting the neddylation pathway represents an effective approach for cancer treatment. In this work, we reported that WS-299, structurally featuring a coumarin moiety attached to the triazolopyrimidine, exhibited excellent anti-proliferative activity in MGC-803 and HGC-27 cells. WS-299 exerted potent anticancer effects by inhibiting clone formation, EdU incorporation and inducing cell cycle arrest. WS-299 inhibited CUL3/5 neddylation and caused an obvious accumulation of Nrf2 and NOXA, substrates of CRL3 and CRL5, respectively. Biochemical studies showed that WS-299 inhibited CUL3 neddylation by inhibiting RBX1-UBE2M interaction. The anti-proliferative effect of WS-299 was mainly induced by NOXA-mediated apoptosis. Of note, Nrf2 attenuated WS-299-induced reactive oxygen species (ROS) levels. Furthermore, Nrf2 accumulation also had an antagonistic effect on NOXA-induced apoptosis. Therefore, WS-299 and siNrf2 synergistically increased ROS levels, apoptotic cells and suppressed tumor growth in vivo. Taken together, our research clarified the anti-cancer mechanisms of WS-299 through targeting the RBX1-UBE2M protein-protein interaction and inhibiting the neddylation modification of CUL3 and CUL5. More importantly, our studies also demonstrated that combination of WS-299 with shNrf2 could be an effective strategy for treating gastric cancers.

Interplay between proteasome inhibitors and NF-κB pathway in leukemia and lymphoma: a comprehensive review on challenges ahead of proteasome inhibitors

The current scientific literature has extensively explored the potential role of proteasome inhibitors (PIs) in the NF-κB pathway of leukemia and lymphoma. The ubiquitin-proteasome system (UPS) is a critical component in regulating protein degradation in eukaryotic cells. PIs, such as BTZ, are used to target the 26S proteasome in hematologic malignancies, resulting in the prevention of the degradation of tumor suppressor proteins, the activation of intrinsic mitochondrial-dependent cell death, and the inhibition of the NF-κB signaling pathway. NF-κB is a transcription factor that plays a critical role in the regulation of apoptosis, cell proliferation, differentiation, inflammation, angiogenesis, and tumor migration. Despite the successful use of PIs in various hematologic malignancies, there are limitations such as resistant to these inhibitors. Some reports suggest that PIs can induce NF-κB activation, which increases the survival of malignant cells. This article discusses the various aspects of PIs' effects on the NF-κB pathway and their limitations. Video Abstract.

CRIP1 involves the pathogenesis of multiple myeloma via dual-regulation of proteasome and autophagy

BACKGROUND

Multiple myeloma (MM) is an incurable hematological malignancy of the plasma cells. The maintenance of protein homeostasis is critical for MM cell survival. Elevated levels of paraproteins in MM cells are cleared by proteasomes or lysosomes, which are independent but inter-connected with each other. Proteasome inhibitors (PIs) work as a backbone agent and successfully improved the outcome of patients; however, the increasing activity of autophagy suppresses the sensitivity to PIs treatment.

METHODS

The transcription levels of CRIP1 were explored in plasma cells obtained from healthy donors, patients with newly diagnosed multiple myeloma (NDMM), and relapsed/refractory multiple myeloma (RRMM) using Gene expression omnibus datasets. Doxycycline-inducible CRIP1-shRNA and CRIP1 overexpressed MM cell lines were constructed to explore the role of CRIP1 in MM pathogenesis. Proliferation, invasion, migration, proteasome activity and autophagy were examined in MM cells with different CRIP1 levels. Co-immunoprecipitation (Co-IP) with Tandem affinity purification/Mass spectrum (TAP/MS) was performed to identify the binding proteins of CRIP1. The mouse xenograft model was used to determine the role of CRIP1 in the proliferation and drug-resistance of MM cells.

FINDINGS

High CRIP1 expression was associated with unfavorable clinical outcomes in patients with MM and served as a biomarker for RRMM with shorter overall survival. In vitro and in vivo studies showed that CRIP1 plays a critical role in protein homeostasis via the dual regulation of the activities of proteasome and autophagy in MM cells. A combined analysis of RNA-seq, Co-IP and TAP/MS demonstrated that CRIP1 promotes proteasome inhibitors resistance in MM cells by simultaneously binding to de-ubiquitinase USP7 and proteasome coactivator PA200. CRIP1 promoted proteasome activity and autophagosome maturation by facilitating the dequbiquitination and stabilization of PA200.

INTERPRETATION

Our findings clarified the pivotal roles of the CRIP1/USP7/PA200 complex in ubiquitin-dependent proteasome degradation and autophagy maturation involved in the pathogenesis of MM.

FUNDING

A full list of funding sources can be found in the acknowledgements section.

Molecular Modeling Studies to Probe the Binding Hypothesis of Novel Lead Compounds against Multidrug Resistance Protein ABCB1

The expression of drug efflux pump ABCB1/P-glycoprotein (P-gp), a transmembrane protein belonging to the ATP-binding cassette superfamily, is a leading cause of multidrug resistance (MDR). We previously curated a dataset of structurally diverse and selective inhibitors of ABCB1 to develop a pharmacophore model that was used to identify four novel compounds, which we showed to be potent and efficacious inhibitors of ABCB1. Here, we dock the inhibitors into a model structure of the human transporter and use molecular dynamics (MD) simulations to report the conformational dynamics of human ABCB1 induced by the binding of the inhibitors. The binding hypotheses are compared to the wider curated dataset and those previously reported in the literature. Protein-ligand interactions and MD simulations are in good agreement and, combined with LipE profiling, statistical and pharmacokinetic analyses, are indicative of potent and selective inhibition of ABCB1.

The feedback loop of EFTUD2/c-MYC impedes chemotherapeutic efficacy by enhancing EFTUD2 transcription and stabilizing c-MYC protein in colorectal cancer

BACKGROUND

Chemoresistance presents a significant obstacle in the treatment of colorectal cancer (CRC), yet the molecular basis underlying CRC chemoresistance remains poorly understood, impeding the development of new therapeutic interventions. Elongation factor Tu GTP binding domain containing 2 (EFTUD2) has emerged as a potential oncogenic factor implicated in various cancer types, where it fosters tumor growth and survival. However, its specific role in modulating the sensitivity of CRC cells to chemotherapy is still unclear.

METHODS

Public dataset analysis and in-house sample validation were conducted to assess the expression of EFTUD2 in 5-fluorouracil (5-FU) chemotherapy-resistant CRC cells and the potential of EFTUD2 as a prognostic indicator for CRC. Experiments both in vitro, including MTT assay, EdU cell proliferation assay, TUNEL assay, and clone formation assay and in vivo, using cell-derived xenograft models, were performed to elucidate the function of EFTUD2 in sensitivity of CRC cells to 5-FU treatment. The molecular mechanism on the reciprocal regulation between EFTUD2 and the oncogenic transcription factor c-MYC was investigated through molecular docking, ubiquitination assay, chromatin immunoprecipitation (ChIP), dual luciferase reporter assay, and co-immunoprecipitation (Co-IP).

RESULTS

We found that EFTUD2 expression was positively correlated with 5-FU resistance, higher pathological grade, and poor prognosis in CRC patients. We also demonstrated both in vitro and in vivo that knockdown of EFTUD2 sensitized CRC cells to 5-FU treatment, whereas overexpression of EFTUD2 impaired such sensitivity. Mechanistically, we uncovered that EFTUD2 physically interacted with and stabilized c-MYC protein by preventing its ubiquitin-mediated proteasomal degradation. Intriguingly, we found that c-MYC directly bound to the promoter region of EFTUD2 gene, activating its transcription. Leveraging rescue experiments, we further confirmed that the effect of EFTUD2 on 5-FU resistance was dependent on c-MYC stabilization.

CONCLUSION

Our findings revealed a positive feedback loop involving an EFTUD2/c-MYC axis that hampers the efficacy of 5-FU chemotherapy in CRC cells by increasing EFTUD2 transcription and stabilizing c-MYC oncoprotein. This study highlights the potential of EFTUD2 as a promising therapeutic target to surmount chemotherapy resistance in CRC patients.

Regulation of Drp1 and enhancement of mitochondrial fission by the deubiquitinating enzyme PSMD14 facilitates the proliferation of bladder cancer cells

The protein Dynein‑related protein 1 (Drp1) plays a crucial role in regulating the process of mitochondrial fission, which is known to be associated with the onset and progression of various human diseases. However, the specific impact of Drp1 on bladder cancer has yet to be fully understood. In previous studies, evidence to support the theory that the deubiquitinating enzyme proteasome non‑ATPase regulatory subunit 14 (PSMD14) is responsible for stabilizing and promoting the activity of Drp1, ultimately resulting in increased mitochondrial fission, has been presented. The levels of PSMD14 in both bladder cancer tissues and cells were elevated, as confirmed through immunohistochemical and immunofluorescent staining. Co‑immunoprecipitation and reciprocal co‑IP tests demonstrated that PSMD14 and Drp1 interacted with each other. Upon knockdown of PSMD14, there was a corresponding decrease in Drp1 expression and subsequent inhibition of mitochondrial fission. However, when the Drp1 agonist Mdivi‑1 was applied to cells where PSMD14 expression had been knocked down, a significant increase in cell growth was observed, partially restoring the cancer‑promoting effects of PSMD14 on cell proliferation. In conclusion, these findings suggest that PSMD14 may stimulate bladder cancer cell proliferation by promoting mitochondrial fission through the stabilization of Drp1.

The Role of m6A-Mediated DNA Damage Repair in Tumor Development and Chemoradiotherapy Resistance

Among the post-transcriptional modifications, m6A RNA methylation has gained significant research interest due to its critical role in regulating transcriptional expression. This modification affects RNA metabolism in several ways, including processing, nuclear export, translation, and decay, making it one of the most abundant transcriptional modifications and a crucial regulator of gene expression. The dysregulation of m6A RNA methylation-related proteins in many tumors has been shown to lead to the upregulation of oncoprotein expression, tumor initiation, proliferation, cancer cell progression, and metastasis.Although the impact of m6A RNA methylation on cancer cell growth and proliferation has been extensively studied, its role in DNA repair processes, which are crucial to the pathogenesis of various diseases, including cancer, remains unclear. However, recent studies have shown accumulating evidence that m6A RNA methylation significantly affects DNA repair processes and may play a role in cancer drug resistance. Therefore, a comprehensive literature review is necessary to explore the potential biological role of m6A-modified DNA repair processes in human cancer and cancer drug resistance.In conclusion, m6A RNA methylation is a crucial regulator of gene expression and a potential player in cancer development and drug resistance. Its dysregulation in many tumors leads to the upregulation of oncoprotein expression and tumor progression. Furthermore, the impact of m6A RNA methylation on DNA repair processes, although unclear, may play a crucial role in cancer drug resistance. Therefore, further studies are warranted to better understand the potential biological role of m6A-modified DNA repair processes in human cancer and cancer drug resistance.

Targeting the Ubiquitin-Proteasome System and Recent Advances in Cancer Therapy

Ubiquitination is a reversible post-translational modification based on the chemical addition of ubiquitin to proteins with regulatory effects on various signaling pathways. Ubiquitination can alter the molecular functions of tagged substrates with respect to protein turnover, biological activity, subcellular localization or protein-protein interaction. As a result, a wide variety of cellular processes are under ubiquitination-mediated control, contributing to the maintenance of cellular homeostasis. It follows that the dysregulation of ubiquitination reactions plays a relevant role in the pathogenic states of human diseases such as neurodegenerative diseases, immune-related pathologies and cancer. In recent decades, the enzymes of the ubiquitin-proteasome system (UPS), including E3 ubiquitin ligases and deubiquitinases (DUBs), have attracted attention as novel druggable targets for the development of new anticancer therapeutic approaches. This perspective article summarizes the peculiarities shared by the enzymes involved in the ubiquitination reaction which, when deregulated, can lead to tumorigenesis. Accordingly, an overview of the main pharmacological interventions based on targeting the UPS that are in clinical use or still in clinical trials is provided, also highlighting the limitations of the therapeutic efficacy of these approaches. Therefore, various attempts to circumvent drug resistance and side effects as well as UPS-related emerging technologies in anticancer therapeutics are discussed.

UBE2O reduces the effectiveness of interferon-α via degradation of IFIT3 in hepatocellular carcinoma

Interferon (IFN) exerts its effects through interferon-stimulated genes (ISGs), but its efficacy is limited by interferon resistance, which can be caused by the ubiquitination of key proteins. UBE2O was initially identified as a promising therapeutic target based on data from the TCGA and iUUCD 2.0 databases. Through the inhibition of UBE2O, interferon α/β signaling and overall interferon signaling were activated. Integrating data from proteomic, mass spectrometry, and survival analyses led to the identification of IFIT3, a mediator of interferon signaling, as a ubiquitination substrate of UBE2O. The results of in vitro and in vivo experiments demonstrated that the knockdown of UBE2O can enhance the efficacy of interferon-α by upregulating IFIT3 expression. K236 was identified as a ubiquitination site in IFIT3, and the results of rescue experiments confirmed that the effect of UBE2O on interferon-α sensitivity is dependent on IFIT3 activity. ATO treatment inhibited UBE2O and increased IFIT3 expression, thereby increasing the effectiveness of interferon-α. In conclusion, these findings suggest that UBE2O worsens the therapeutic effect of interferon-α by targeting IFIT3 for ubiquitination and degradation.

Advances in research on potential inhibitors of multiple myeloma

Multiple myeloma (MM) is a common hematological malignancy. Although recent clinical applications of immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies have significantly improved the outcome of MM patient with increased survival, the incidence of drug resistance and severe treatment-related complications is gradually on the rise. This review article summarizes the characteristics and clinical investigations of several MM drugs in clinical trials, including their structures, mechanisms of action, structure-activity relationships, and clinical study progress. Furthermore, the application potentials of the drugs that have not yet entered clinical trials are also reviewed. The review also outlines the future directions of MM drug development.

Sniping Cancer Stem Cells with Nanomaterials

Cancer stem cells (CSCs) drive tumor initiation, progression, and therapeutic resistance due to their self-renewal and differentiation capabilities. Despite encouraging progress in cancer treatment, conventional approaches often fail to eliminate CSCs, necessitating the development of precise targeted strategies. Recent advances in materials science and nanotechnology have enabled promising CSC-targeted approaches, harnessing the power of tailoring nanomaterials in diverse therapeutic applications. This review provides an update on the current landscape of nanobased precision targeting approaches against CSCs. We elucidate the nuanced application of organic, inorganic, and bioinspired nanomaterials across a spectrum of therapeutic paradigms, encompassing targeted therapy, immunotherapy, and multimodal synergistic therapies. By examining the accomplishments and challenges in this potential field, we aim to inform future efforts to advance nanomaterial-based therapies toward more effective "sniping" of CSCs and tumor clearance.

The Mechanism of Ubiquitination or Deubiquitination Modifications in Regulating Solid Tumor Radiosensitivity

Radiotherapy, a treatment method employing radiation to eradicate tumor cells and subsequently reduce or eliminate tumor masses, is widely applied in the management of numerous patients with tumors. However, its therapeutic effectiveness is somewhat constrained by various drug-resistant factors. Recent studies have highlighted the ubiquitination/deubiquitination system, a reversible molecular modification pathway, for its dual role in influencing tumor behaviors. It can either promote or inhibit tumor progression, impacting tumor proliferation, migration, invasion, and associated therapeutic resistance. Consequently, delving into the potential mechanisms through which ubiquitination and deubiquitination systems modulate the response to radiotherapy in malignant tumors holds paramount significance in augmenting its efficacy. In this paper, we comprehensively examine the strides made in research and the pertinent mechanisms of ubiquitination and deubiquitination systems in governing radiotherapy resistance in tumors. This underscores the potential for developing diverse radiosensitizers targeting distinct mechanisms, with the aim of enhancing the effectiveness of radiotherapy.

An impaired ubiquitin-proteasome system increases APOBEC3A abundance

Apolipoprotein B messenger RNA (mRNA) editing enzyme, catalytic polypeptide-like (APOBEC) cytidine deaminases cause genetic instability during cancer development. Elevated APOBEC3A (A3A) levels result in APOBEC signature mutations; however, mechanisms regulating A3A abundance in breast cancer are unknown. Here, we show that dysregulating the ubiquitin-proteasome system with proteasome inhibitors, including Food and Drug Administration-approved anticancer drugs, increased A3A abundance in breast cancer and multiple myeloma cell lines. Unexpectedly, elevated A3A occurs via an ∼100-fold increase in A3A mRNA levels, indicating that proteasome inhibition triggers a transcriptional response as opposed to or in addition to blocking A3A degradation. This transcriptional regulation is mediated in part through FBXO22, a protein that functions in SKP1-cullin-F-box ubiquitin ligase complexes and becomes dysregulated during carcinogenesis. Proteasome inhibitors increased cellular cytidine deaminase activity, decreased cellular proliferation and increased genomic DNA damage in an A3A-dependent manner. Our findings suggest that proteasome dysfunction, either acquired during cancer development or induced therapeutically, could increase A3A-induced genetic heterogeneity and thereby influence therapeutic responses in patients.

A ubiquitin-proteasome system-related signature to predict prognosis, immune infiltration, and therapy efficacy for breast cancer

The ubiquitin-proteasome system (UPS) is an essential regulatory system for maintaining homeostasis, and its dysfunction may cause various diseases. The activity of proteasome and ubiquitin-conjugating enzymes has been found to be greatly increased in breast cancer (BC), indicating that the heterogeneity of UPS may be related to the progression of BC. Gene data was obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases and performed in multiple algorithms to construct a UPS-related signature for BC. Patients in the UPS low-risk group had greater overall and recurrence-free survival probability than those in the UPS high-risk group. This signature was closely associated with functional enrichment. Some high metabolism-related pathways were more active in the UPS high-risk group. The UPS low-risk group had more abundant anti-tumor immune cells, while in the UPS high-risk group, immunosuppressive cells were dominant. More importantly, we found that the UPS low-risk group was more sensitive to immunotherapy, while the UPS high-risk group responded better to radiotherapy. Drug sensitivity analysis identified more effective chemotherapy drugs in different UPS-related risk groups. This UPS-related signature may serve as a novel biomarker and independent prognostic factor for BC. It can effectively predict prognosis, immune infiltration, and therapy efficacy, providing new strategies for individualized treatment.

Proteasome inhibition potentiates Kv1.3 potassium channel expression as therapeutic target in drug-sensitive and -resistant human melanoma cells

Primary and acquired therapy resistance is a major problem in patients with BRAF-mutant melanomas being treated with BRAF and MEK inhibitors (BRAFI, MEKi). Therefore, development of alternative therapy regimes is still required. In this regard, new drug combinations targeting different pathways to induce apoptosis could offer promising alternative approaches. Here, we investigated the combination of proteasome and Kv1.3 potassium channel inhibition on chemo-resistant, BRAF inhibitor-resistant as well as sensitive human melanoma cells. Our experiments demonstrated that all analyzed melanoma cell lines were sensitive to proteasome inhibitor treatment at concentrations that are not toxic to primary human fibroblasts. To further reduce proteasome inhibitor-associated side effects, and to foster apoptosis, potassium channels, which are other targets to induce pro-apoptotic effects in cancer cells, were blocked. In support, combined exposure of melanoma cells to proteasome and Kv1.3 channel inhibitor resulted in synergistic effects and significantly reduced cell viability. On the molecular level, enhanced apoptosis correlated with an increase of intracellular Kv1.3 channels and pro-apoptotic proteins such as Noxa and Bak and a reduction of anti-apoptotic proteins. Thus, use of combined therapeutic strategies triggering different apoptotic pathways may efficiently prevent the outgrowth of drug-resistant and -sensitive BRAF-mutant melanoma cells. In addition, this could be the basis for an alternative approach to treat other tumors expressing mutated BRAF such as non-small-cell lung cancer.

Methylcrotonyl-CoA carboxylase subunit 1 (MCCA) regulates multidrug resistance in multiple myeloma

AIMS

This study aimed to investigate the effect and mechanism of methylcrotonyl-CoA carboxylase subunit 1 (MCCA) on multidrug resistance in multiple myeloma (MM).

MATERIALS AND METHODS

The apoptosis kit and CCK-8 reagent were used to detect drug-induced cell apoptosis and viability. Immunoprecipitation, immunofluorescence staining, and protein structural simulation were used to detect the interaction between MCCA and Bad. Immunodeficient mice were injected with ARD cells and treated with bortezomib. Changes in tumor burden were recorded by bioluminescence imaging, and κ light chain content in the blood of mice was detected by enzyme-linked immunoassay.

KEY FINDINGS

Patients with high MCCA expression from a primary MM dataset had superior overall survival. After treatment with different anti-MM drugs, MCCA knockdown MM (MCCA-KD) cells had higher survival rates than control knockdown (CTR-KD) cells (p < 0.05). Mechanistic studies have revealed that MCCA-KD cells had dysfunctional mitochondria with decreased Bax and Bad levels and increased Bcl-xl and Mcl-1 levels. Furthermore, that MCCA and Bad demonstrated protein-protein interactions. The half-life of Bad in MCCA-KD cells is significantly shorter than that in CTR-KD cells (7.34 vs. 2.42 h, p < 0.05). In a human MM xenograft mouse model, we confirmed that MCCA-KD tumors had a poor response to anti-MM drugs in vivo. Finally, we showed that MCCA might contribute to multidrug resistance in different human cancers, particularly in solid tumors.

SIGNIFICANCE

Our findings demonstrated a novel function of MCCA in multidrug resistance. The lack of MCCA expression promoted antiapoptotic cell signaling in MM cells.

Cuproptosis: emerging biomarkers and potential therapeutics in cancers

The sustenance of human life activities depends on copper, which also serves as a crucial factor for vital enzymes. Under typical circumstances, active homeostatic mechanisms keep the intracellular copper ion concentration low. Excess copper ions cause excessive cellular respiration, which causes cytotoxicity and cell death as levels steadily rise above a threshold. It is a novel cell death that depends on mitochondrial respiration, copper ions, and regulation. Cuproptosis is now understood to play a role in several pathogenic processes, including inflammation, oxidative stress, and apoptosis. Copper death is a type of regulatory cell death(RCD).Numerous diseases are correlated with the development of copper homeostasis imbalances. One of the most popular areas of study in the field of cancer is cuproptosis. It has been discovered that cancer angiogenesis, proliferation, growth, and metastasis are all correlated with accumulation of copper ions. Copper ion concentrations can serve as a crucial marker for cancer development. In order to serve as a reference for clinical research on the product, diagnosis, and treatment of cancer, this paper covers the function of copper ion homeostasis imbalance in malignant cancers and related molecular pathways.

Development and validation of a ubiquitin-proteasome system gene signature for prognostic prediction and immune microenvironment evaluation in hepatocellular carcinoma

BACKGROUND

The ubiquitin proteasome has a major role in the development of many tumors. However, the prognostic importance of ubiquitin proteasome-system genes (UPSGs) in hepatocellular carcinoma (HCC) is not fully defined.

METHODS

The TCGA and ICGC datasets were utilized to obtain transcriptional profiling data as well as clinicopathological information about HCC. The 3-UPSGs signature for the TCGA cohort was developed via univariate and LASSO Cox regression analyses. Differential expression of genes was demonstrated by qRT-PCR and immunohistochemistry (IHC). Biological pathways were studied using GSVA and GSEA. Six algorithms were used to compare immune infiltration between the two risk groups. Furthermore, drug sensitivity was measured using the "pRRophetic" R package. The predictive capacity of the 3-UPSGs signature for sensitivity to immunotherapy was also explored. Moreover, we performed a pan-cancer analysis of the 3-UPSGs signature.

RESULTS

A risk model containing 3 UPSGs (DCAF13, CDC20 and PSMB5) was developed. IHC and qRT-PCR results showed that signature genes were significantly overexpressed in HCC tissues. The high-risk group had a worse prognosis, with a higher clinicopathological grade, higher levels of tumor mutation burden (TMB), elevated levels of immune checkpoint (IC) expression, as well as increased sensitivity to immunotherapy. The two risk groups also differ in their sensitivity to chemotherapeutic drugs. Furthermore, the three UPSGs may play crucial roles in the progression of multiple types of cancers.

CONCLUSION

We created a 3-UPSGs signature to estimate the prognosis of HCC and to assist in individualized treatment.

Implications of ubiquitination and the maintenance of replication fork stability in cancer therapy

DNA replication forks are subject to intricate surveillance and strict regulation by sophisticated cellular machinery. Such close regulation is necessary to ensure the accurate duplication of genetic information and to tackle the diverse endogenous and exogenous stresses that impede this process. Stalled replication forks are vulnerable to collapse, which is a major cause of genomic instability and carcinogenesis. Replication stress responses, which are organized via a series of coordinated molecular events, stabilize stalled replication forks and carry out fork reversal and restoration. DNA damage tolerance and repair pathways such as homologous recombination and Fanconi anemia also contribute to replication fork stabilization. The signaling network that mediates the transduction and interplay of these pathways is regulated by a series of post-translational modifications, including ubiquitination, which affects the activity, stability, and interactome of substrates. In particular, the ubiquitination of replication protein A and proliferating cell nuclear antigen at stalled replication forks promotes the recruitment of downstream regulators. In this review, we describe the ubiquitination-mediated signaling cascades that regulate replication fork progression and stabilization. In addition, we discuss the targeting of replication fork stability and ubiquitination system components as a potential therapeutic approach for the treatment of cancer.

Analysis of Human microRNA Expression Profiling During Diquat-Induced Renal Proximal Tubular Epithelial Cell Injury

Background

We established a diquat-induced human kidney-2 cells (HK-2 cells) apoptosis model in this study to identify differentially expressed microRNAs (miRNAs) and signaling pathways involved in diquat poisoning via gene sequencing and bioinformatics analysis and explored the related therapeutic benefits.

Methods

The effects of diquat on the viability and apoptosis of HK-2 cells were explored using the CCK-8 and Annexin V-FITC/PI double staining methods. Total RNAs were extracted using the TRizol method and detected by Illumina HiSeq 2500. Bioinformatics analysis was performed to explore differentially expressed (DE) miRNAs, their enriched biological processes, pathways, and potential target genes. The RT-qPCR method was used to verify the reliability of the results.

Results

Diquat led to HK-2 cell injury and apoptosis played an important role, hence an HK-2 cell apoptosis model in diquat poisoning was established. Thirty-six DE miRNAs were screened in diquat-treated HK-2 cells. The enriched biological process terms were mainly cell growth, regulation of apoptotic signaling pathway, extrinsic apoptotic signaling pathway, and Ras protein signal transduction. The enriched cellular components were mainly cell-cell junction, cell-substrate junction, ubiquitin ligase complex, and protein kinase complex. The enriched molecular functions were mainly Ras GTPase binding, ubiquitin-like protein transferase activity, DNA-binding transcription factor binding, ubiquitin-protein transferase activity, nucleoside-triphosphatase regulator activity, transcription coactivator activity, and ubiquitin-like protein ligase binding. Signaling pathways such as MAPK, FoxO, Ras, PIK3-Akt, and Wnt were also enriched.

Conclusion

These findings aid in understanding the mechanisms of diquat poisoning and the related pathways, where DE miRNAs serve as targets for gene therapy.

AZGP1P2/UBA1/RBM15 Cascade Mediates the Fate Determinations of Prostate Cancer Stem Cells and Promotes Therapeutic Effect of Docetaxel in Castration-Resistant Prostate Cancer via TPM1 m6A Modification

Prostate cancer (PCa) is a common malignant tumor with high morbidity and mortality worldwide. The prostate cancer stem cell (PCSC) model provides novel insights into the pathogenesis of PCa and its therapeutic response. However, the roles and molecular mechanisms of specific genes in mediating fate decisions of PCSCs and carcinogenesis of PCa remain to be elusive. In this study, we have explored the expression, function, and mechanism of AZGP1P2, a pseudogene of AZGP1, in regulating the stemness and apoptosis of PCSCs and treatment resistance of docetaxel in castration-resistant prostate cancer (CRPC). We revealed that AZGP1P2 was downregulated in CRPC cell lines and PCSCs, while it was positively associated with progression-free interval. Upregulation of the AZGP1P2 enhanced the sensitivity of docetaxel treatment in CRPCs via inhibiting their stemness. RNA pull-down associated with mass spectrometry analysis, co-immunoprecipitation assay, and RNA immunoprecipitation assay demonstrated that AZGP1P2 could bind to UBA1 and RBM15 as a "writer" of methyltransferase to form a compound. UBA1, an E1 ubiquitin-activating enzyme, contributed to RBM15 protein degradation via ubiquitination modification. Methylated RNA immunoprecipitation assay displayed that RBM15 controlled the mRNA decay of TPM1 in m6A methylation. Furthermore, a xenograft mouse model and patient-derived organoids showed that the therapeutic effect of docetaxel in CRPC was increased by AZGP1P2 in vivo. Collectively, these results imply that AZGP1P2 mediates the stemness and apoptosis of PCSCs and promotes docetaxel therapeutic effect by suppressing tumor growth and metastasis via UBA1/RBM15-mediated TPM1 mRNA decay in CRPC.

An overview of the past decade of bufalin in the treatment of refractory and drug-resistant cancers: current status, challenges, and future perspectives

Profound progress has been made in cancer treatment in the past three decades. However, drug resistance remains prevalent and a critical challenge. Drug resistance can be attributed to oncogenes mutations, activated defensive mechanisms, ATP-bind cassette transporters overexpression, cancer stem cells, etc. Chinese traditional medicine toad venom has been used for centuries for different diseases, including resistant cancers. Bufalin is one of the bufadienolides in toad venom that has been extensively studied for its potential in refractory and drug-resistant cancer treatments in vitro and in vivo. In this work, we would like to critically review the progress made in the past decade (2013-2022) of bufalin in overcoming drug resistance in cancers. Generally, bufalin shows high potential in killing certain refractory and resistant cancer cells via multiple mechanisms. More importantly, bufalin can work as a chemo-sensitizer that enhances the sensitivity of certain conventional and targeted therapies at low concentrations. In addition, the development of bufalin derivatives was also briefly summarized and discussed. We also analyzed the obstacles and challenges and provided possible solutions for future perspectives. We hope that the collective information may help evoke more effort for more in-depth studies and evaluation of bufalin in both lab and possible clinical trials.

USP8 promotes gemcitabine resistance of pancreatic cancer via deubiquitinating and stabilizing Nrf2

Gemcitabine (Gem) is the first-line chemotherapy drug for pancreatic cancer, but the acquired chemoresistance also hinders its application. Therefore, research about Gem resistance plays a crucial role in enhancing the therapeutic effect of Gem. As a deubiquitinating enzyme, ubiquitin-specific protease 8 (USP8) was shown to play vital roles in the tumorigenesis processes of several cancers; however, the effect of USP8 on Gem resistance of pancreatic cancer still remains largely unknown. In the current study, we observed that the expression of USP8 was increased in pancreatic cancer patients, it is related to the recurrence of Gem chemotherapy, and USP8 expression could be induced by Gem application. Furthermore, USP8 was found to promote Gem resistance both in vivo and in vitro via regulating cell viability and apoptosis. Moreover, USP8 enhanced the activation of Nrf2 signaling which is dependent on its deubiquitinase ability. At last, we illustrated that USP8 interacted with Nrf2 directly and deubiquitinated K48-linked polyubiquitin chains from Nrf2, stabilizing the expression of Nrf2. In summary, the manuscript revealed the role of USP8 in Gem chemoresistance and suggested USP8 as a potential therapeutic target for pancreatic cancer.

Distinct N7-methylguanosine profiles of circular RNAs in drug-resistant acute myeloid leukemia

Post-transcriptional methylation modifications, such as the N7-methylguanosine (m7G) modification, are increasingly acknowledged for their role in the development and resistance to chemotherapy in acute myeloid leukemia (AML). This study employed MeRIP-seq technology to investigate the m7G sites within circular RNAs (circRNAs) derived from human AML cells and drug-resistant AML cells, in order to identify these sites more comprehensively. In addition, a detailed analysis of the relationship between m7G and drug-resistant AML was conducted. The bioinformatics analysis was utilized to predict the functions of specific methylated transcripts. The findings revealed a significant difference in m7G level between AML cells and drug-resistant AML cells, suggesting a potentially critical role of m7G in circRNAs in drug-resistant AML development. The methylation of M7G could affect the circRNA-miRNA-mRNA co-expression during the development of AML resistance, which could further influence the regulation of resistance-associated target genes in AML. Furthermore, gene ontology analysis indicated that the distinct distribution pattern of circRNAs with m7G methylation in drug-resistant AML cells was correlated with metabolism-related pathways. These results suggested a potential association between drug-resistant AML and m7G methylation of circRNAs. Moreover, the results revealed a novel role of m7G RNA methylation in circRNAs in the progression of AML chemoresistance.

The multifaceted role of MUC1 in tumor therapy resistance

Tumor therapeutic resistances are frequently linked to the recurrence and poor prognosis of cancers and have been a key bottleneck in clinical tumor treatment. Mucin1 (MUC1), a heterodimeric transmembrane glycoprotein, exhibits abnormally overexpression in a variety of human tumors and has been confirmed to be related to the formation of therapeutic resistance. In this review, the multifaceted roles of MUC1 in tumor therapy resistance are summarized from aspects of pan-cancer principles shared among therapies and individual mechanisms dependent on different therapies. Concretely, the common mechanisms of therapy resistance across cancers include interfering with gene expression, promoting genome instability, modifying tumor microenvironment, enhancing cancer heterogeneity and stemness, and activating evasion and metastasis. Moreover, the individual mechanisms of therapy resistance in chemotherapy, radiotherapy, and biotherapy are introduced. Last but not least, MUC1-involved therapy resistance in different types of cancers and MUC1-related clinical trials are summarized.

Cell-in-cell: a potential biomarker of prognosis and a novel mechanism of drug resistance in cancer

The cell-in-cell (CIC) phenomenon has received increasing attention over recent years because of its wide existence in multiple cancer tissues. The mechanism of CIC formation is considerably complex as it involves interactions between two cells. Although the molecular mechanisms of CIC formation have been extensively investigated, the process of CIC formation remains ambiguous. Currently, CIC is classified into four subtypes based on different cell types and inducing factors, and the underlying mechanisms for each subtype are distinct. Here, we investigated the subtypes of CIC and their major mechanisms involved in cancer development. To determine the clinical significance of CIC, we reviewed several clinical studies on CIC and found that CIC could serve as a diagnostic and prognostic biomarker. The implications of CIC on the clinical management of cancers also remain largely unknown. To clarify this aspect, in the present review, we highlight the findings of recent investigations on the causal link between CIC and cancer treatment. We also indicate the existing issues that need to be resolved urgently to provide a potential direction for future research on CIC.

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.

Polyphyllin D punctures hypertrophic lysosomes to reverse drug resistance of hepatocellular carcinoma by targeting acid sphingomyelinase

Hypertrophic lysosomes are critical for tumor progression and drug resistance; however, effective and specific lysosome-targeting compounds for cancer therapy are lacking. Here we conducted a lysosomotropic pharmacophore-based in silico screen in a natural product library (2,212 compounds), and identified polyphyllin D (PD) as a novel lysosome-targeted compound. PD treatment was found to cause lysosomal damage, as evidenced by the blockade of autophagic flux, loss of lysophagy, and the release of lysosomal contents, thus exhibiting anticancer effects on hepatocellular carcinoma (HCC) cell both in vitro and in vivo. Closer mechanistic examination revealed that PD suppressed the activity of acid sphingomyelinase (SMPD1), a lysosomal phosphodieserase that catalyzes the hydrolysis of sphingomyelin to produce ceramide and phosphocholine, by directly occupying its surface groove, with Trp148 in SMPD1 acting as a major binding residue; this suppression of SMPD1 activity irreversibly triggers lysosomal injury and initiates lysosome-dependent cell death. Furthermore, PD-enhanced lysosomal membrane permeabilization to release sorafenib, augmenting the anticancer effect of sorafenib both in vivo and in vitro. Overall, our study suggests that PD can potentially be further developed as a novel autophagy inhibitor, and a combination of PD with classical chemotherapeutic anticancer drugs could represent a novel therapeutic strategy for HCC intervention.

Ubiquitin-proteasome system as a target for anticancer treatment-an update

As the ubiquitin-proteasome system (UPS) regulates almost every biological process, the dysregulation or aberrant expression of the UPS components causes many pathological disorders, including cancers. To find a novel target for anticancer therapy, the UPS has been an active area of research since the FDA's first approval of a proteasome inhibitor bortezomib in 2003 for treating multiple myeloma (MM). Here, we summarize newly described UPS components, including E3 ubiquitin ligases, deubiquitinases (DUBs), and immunoproteasome, whose malfunction leads to tumorigenesis and whose inhibitors have been investigated in clinical trials as anticancer therapy since 2020. We explain the mechanism and effects of several inhibitors in depth to better comprehend the advantages of targeting UPS components for cancer treatment. In addition, we describe attempts to overcome resistance and limited efficacy of some launched proteasome inhibitors, as well as an emerging PROTAC-based tool targeting UPS components for anticancer therapy.

Recent advances in access to overcome cancer drug resistance by nanocarrier drug delivery system

Cancer is currently one of the most intractable diseases causing human death. Although the prognosis of tumor patients has been improved to a certain extent through various modern treatment methods, multidrug resistance (MDR) of tumor cells is still a major problem leading to clinical treatment failure. Chemotherapy resistance refers to the resistance of tumor cells and/or tissues to a drug, usually inherent or developed during treatment. Therefore, an urgent need to research the ideal drug delivery system to overcome the shortcoming of traditional chemotherapy. The rapid development of nanotechnology has brought us new enlightenments to solve this problem. The novel nanocarrier provides a considerably effective treatment to overcome the limitations of chemotherapy or other drugs resulting from systemic side effects such as resistance, high toxicity, lack of targeting, and off-target. Herein, we introduce several tumor MDR mechanisms and discuss novel nanoparticle technology applied to surmount cancer drug resistance. Nanomaterials contain liposomes, polymer conjugates, micelles, dendrimers, carbon-based, metal nanoparticles, and nucleotides which can be used to deliver chemotherapeutic drugs, photosensitizers, and small interfering RNA (siRNA). This review aims to elucidate the advantages of nanomedicine in overcoming cancer drug resistance and discuss the latest developments.

Drug resistance related genes in lung adenocarcinoma predict patient prognosis and influence the tumor microenvironment

Lung adenocarcinoma (LUAD) is the predominant type of non-small lung cancer (NSCLC) with strong invasive ability and poor prognosis. The drug resistance related genes are potentially associated with prognosis of LUAD. Our research aimed to identify the drug resistance related genes and explore their potential prognostic value in LUAD patients. The data used in this study were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Firstly, we screened drug resistance related genes in LUAD by differential gene analysis, univariate Cox regression and drug sensitivity analyses. Subsequently, we constructed a risk score model using LASSO Cox regression analysis, and verified whether the risk score can predict the survival of LUAD patients independent of other factors. Moreover, we explored the immune infiltration of 22 immune cells between high-risk and low-risk patients. Totally 10 drug-resistance positively related genes (PLEK2, TFAP2A, KIF20A, S100P, GDF15, HSPB8, SASH1, WASF3, LAMA3 and TCN1) were identified in LUAD. The risk score model of LUAD constructed with these 10 genes could reliably predict the prognosis of LUAD patients. 18 pathways were significantly activated in high-risk group compared with low-risk group. In addition, the infiltration proportion of multiple immune cells was significantly different between high-risk and low-risk groups, and the proportion of M1 phagocytes was significantly higher in the high-risk group compared with the low-risk group. The drug resistance related genes (PLEK2, TFAP2A, KIF20A, S100P, GDF15, HSPB8, SASH1, WASF3, LAMA3 and TCN1) could predict the prognosis of LUAD patients. Clarifying the roles and mechanisms of these 10 genes in regulating drug resistance in LUAD will help to improve individualized clinical treatment protocols and predict patient sensitivity to treatment.

Bortezomib-loaded mixed micelles realize a "three-in-one" effect for enhanced breast cancer treatment

Comprehensively regulating the TME is now regarded as a promising approach for cancer treatment. Herein, a novel "three-in-one" effect is presented for simultaneously killing tumor cells, inhibiting the EMT of CAFs, and improving immune responses. In this study, bortezomib (BTZ) is selected for the treatment of breast cancer; it has multiple pharmacological mechanisms for killing tumor cells through the NF-κB signaling pathway, inhibiting the activity of CAFs by activating caspase-3, and enhancing the function of CD8+ T cells by regulating the expression of immune-stimulating factors. To improve the druggability of BTZ in solid tumors, BTZ-loaded lipid/glycocholic acid mixed micelles (BTZ-LGs) were prepared to verify the "three-in-one" effect in killing tumor cells, inhibiting CAFs, and improving immune responses. In the present work, BTZ-LGs were verified to show enhanced in vitro cytotoxicity in both 4T1 cells and 4T1/NIH3T3 co-cultured cells, as well as a superior in vivo treatment effect in different tumor-bearing mouse models. Additionally, BTZ-LGs could regulate the expression of α-SMA, caspase-3, E-cadherin, and N-cadherin, indicating their good inhibiting ability on both tumor cells and CAFs. More importantly, immunological analysis revealed that BTZ-LGs promoted the expression of the immunostimulatory factor IL-2 in tumor tissues, activated anti-tumor T cells, and overcame tumor-induced CD8+ T cell dysfunction. All these findings suggest that BTZ-LGs can achieve a "three-in-one" effect in terms of killing tumor cells, suppressing CAFs, and improving immune responses. This simple and multi-effective therapeutic strategy offers a promising approach for cancer therapy.

Role of Molecular Targeted Therapeutic Drugs in Treatment of Glioblastoma: A Review Article

Glioblastoma is remarkably periodic primary brain tumor, characterizing an eminently heterogeneous pattern of neoplasms that are utmost destructive and threatening cancers. An enhanced and upgraded knowledge of the various molecular pathways that cause malignant changes in glioblastoma has resulted in advancement of numerous biomarkers and the interpretation of various agents that pointedly target tumor cells and microenvironment. In this review, literature or information on various targeted therapy for glioblastoma is discussed. English language articles were scrutinized in plentiful directory or databases like PubMed, ScienceDirect, Web of Sciences, Google Scholar, and Scopus. The important keywords used for searching databases are "Glioblastoma," "Targeted therapy in glioblastoma," "Therapeutic drugs in glioblastoma," and "Molecular targets in glioblastoma."

NF-κB in Cell Deaths, Therapeutic Resistance and Nanotherapy of Tumors: Recent Advances

The transcription factor nuclear factor-κB (NF-κB) plays a complicated role in multiple tumors. Mounting evidence demonstrates that NF-κB activation supports tumorigenesis and development by enhancing cell proliferation, invasion, and metastasis, preventing cell death, facilitating angiogenesis, regulating tumor immune microenvironment and metabolism, and inducing therapeutic resistance. Notably, NF-κB functions as a double-edged sword exerting positive or negative influences on cancers. In this review, we summarize and discuss recent research on the regulation of NF-κB in cancer cell deaths, therapy resistance, and NF-κB-based nano delivery systems.

G6PD drives glioma invasion by regulating SQSTM1 protein stability

Glioma is an incurable brain tumor with high recurrence due to the frequent invasion of neoplastic cells. Glucose-6-phosphate dehydrogenase (G6PD) is a critical enzyme in the pentose phosphate pathway (PPP) whose aberrant expression drives the pathogenesis of various cancers. Recent research has identified other moonlight modes of enzymes besides the well-known regulation of metabolic reprogramming. Here, we identified previously unexplored roles of G6PD in glioma via gene set variation analysis (GSVA) based on the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) database. Furthermore, survival analyses revealed that glioma patients with high G6PD expression had a worse outcome than patients with low G6PD expression (Hazard Ratio (95%CI): 2.96 (2.41, 3.64), p = 3.5E-22). Combined with functional assays, G6PD was shown to be related with the migration and invasion in glioma. G6PD knockdown could inhibit the migration in LN229 cells. And G6PD overexpression enhanced LN229 cell migration and invasion. Mechanically, the knockdown of G6PD reduced sequestosome 1 (SQSTM1) protein stability under cycloheximide (CHX) treatment. Moreover, the overexpression of SQSTM1 rescued the impaired migrated and invasive phenotypes in G6PD-silenced cells. Clinically, we validated the role of G6PD-SQSTM1 axis in glioma prognosis by constructing the multivariate cox proportional hazards regression model. These results define a pivotal function of G6PD in modulating SQSTM1 to promote glioma aggressiveness. And G6PD may be a prognostic biomarker and potential therapeutic target in glioma. G6PD-SQSTM1 axis may be a potential prognostic biomarker in glioma.

An update on Alectinib: a first line treatment for ALK-positive advanced lung cancer

INTRODUCTION

Alectinib is a second-generation, anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor (TKI) for the treatment of ALK+ non-small cell lung cancer (NSCLC) and is able to induce significant and durable CNS responses. However, long-term use of alectinib has been clinically reported to cause some serious and even life-threatening adverse events. There are currently no effective interventions for its adverse events, and this undoubtedly leads to delays in patient treatment and limits its long-term clinical use.

AREAS COVERED

Based on the clinical trials conducted so far, we summarize the efficacy and adverse events that occurred, especially those related to cardiovascular disorders, gastrointestinal disorders, hepatobiliary disorders, musculoskeletal and connective tissue disorders, skin and subcutaneous tissue disorders, and respiratory disorders. The factors that may influence alectinib selection are also described. Findings are based on a PubMed literature search of clinical and basic science research papers spanning 1998-2023.

EXPERT OPINION

The significant prolongation of patient survival compared with first-generation ALK inhibitor suggests its potential as a first-line treatment for the NSCLC, but the severe adverse events of alectinib limit its long-term clinical use. Future research should focus on the exact mechanisms of these toxicities, how to alleviate the adverse events caused by alectinib clinically, and the development of next-generation drugs with reduced toxicities.

Proteasome inhibitor MG132 enhances the sensitivity of human OSCC cells to cisplatin via a ROS/DNA damage/p53 axis

Cis-diamine-dichloroplatinum II (cisplatin, CDDP) is a key chemotherapeutic regimen in the treatment of oral squamous cell carcinoma (OSCC). However, the therapeutic efficacy of cisplatin in OSCC may be hampered by chemoresistance. Therefore, the development of novel combination therapy strategies to overcome the limitations of CDDP is of great importance. The proteasome inhibitor MG132 exhibits anti-cancer properties against various types of cancer. However, our knowledge of its anti-cancer effects in combination with CDDP in OSCC cells remains limited. In the current study, the synergetic effects of MG132 and CDDP were evaluated in the human CAL27 OSCC cell line. CAL27 cells were treated with CDDP alone or in combination with MG132. The results showed that MG132 significantly reduced cell viability in a dose-dependent manner. Additionally, cell viability was significantly reduced in CAL27 cells treated with 0.2 µM MG132 and 2 µM CDDP compared with cells treated with MG132 or CDDP alone. In addition, MG132 significantly enhanced the CDDP-induced generation of intracellular reactive oxygen species and DNA damage in OSCC cells. Furthermore, treatment with CDDP or MG132 alone notably inhibited colony formation and proliferation of OSCC cells. However, co-treatment of OSCC cells with MG132 and CDDP further hampered colony formation and proliferation compared with cells treated with either MG132 or CDDP alone. Finally, in cells co-treated with MG132 and CDDP, the expression of p53 was markedly elevated and the p53-mediated apoptotic pathway was further activated compared with cells treated with MG132 or CDDP alone, as shown by the enhanced cell apoptosis, Bax upregulation, and Bcl-2 downregulation. Overall, the results of the current study support the synergistic anti-cancer effects of a combination of MG132 and CDDP against OSCC, thus suggesting that the combination of MG132 and CDDP may be a promising therapeutic strategy for the management of OSCC.