Interplay between c-Src and the APC/C co-activator Cdh1 regulates mammary tumorigenesis

Fetal Mammary Gland Development and Offspring's Breast Cancer Risk in Adulthood

While advancements in early detection and improved access to care have significantly enhanced breast cancer survival rates, the disease remains a significant global malignancy, constituting approximately 12.5% of all new cancer cases and claiming nearly 700,000 lives in 2020. As a result, there is widespread consensus that the most sustainable solution lies in prevention. Indeed, preventive strategies, including lifestyle modifications and research into risk-reducing interventions, offer the potential to address the root causes of noncommunicable diseases such as breast cancer. While conventional wisdom has long attributed established risk factors for breast cancer to age, lifestyle, familial history, and reproductive factors, evidence highlights the maternal environment as a pivotal stage for fetal programming of disease risk, as elucidated in the developmental origins of health and disease (DOHaD) framework. Consequently, a growing body of research has been focused on elucidating epigenomic signatures that influence fetal development while shaping health outcomes and susceptibility to diseases later in life. This review aims to identify fetal mammary developmental genes that have been implicated in breast cancer etiology and the potential interplay of maternal environment in epigenetic programming of breast cancer risk in adulthood.

Unraveling the relevance of SARS-Cov-2 infection and ferroptosis within the heart of COVID-19 patients

Background

The coronavirus disease 2019 (COVID-19) was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which led to a huge mortality rate and imposed significant costs on the health system, causing severe damage to the cells of different organs such as the heart. However, the exact details and mechanisms behind this damage are not clarified. Therefore, we aimed to identify the cell and molecular mechanism behind the heart damage caused by SARS-Cov-2 infection.

Methods

RNA-seq data for COVID-19 patients' hearts was analyzed to obtain differentially expressed genes (DEGs) and differentially expressed ferroptosis-related genes (DEFRGs). Then, DEFRGs were used for analyzing GO and KEGG enrichment, and perdition of metabolites and drugs. we also constructed a PPI network and identified hub genes and functional modules for the DEFRGs. Subsequently, the hub genes were validated using two independent RNA-seq datasets. Finally, the miRNA-gene interaction networks were predicted in addition to a miRNA-TF co-regulatory network, and important miRNAs and transcription factors (TFs) were highlighted.

Findings

We found ferroptosis transcriptomic alterations within the hearts of COVID-19 patients. The enrichment analyses suggested the involvement of DEFRGs in the citrate cycle pathway, ferroptosis, carbon metabolism, amino acid biosynthesis, and response to oxidative stress. IL6, CDH1, AR, EGR1, SIRT3, GPT2, VDR, PCK2, VDR, and MUC1 were identified as the ferroptosis-related hub genes. The important miRNAs and TFs were miR-124-3P, miR-26b-5p, miR-183-5p, miR-34a-5p and miR-155-5p; EGR1, AR, IL6, HNF4A, SRC, EZH2, PPARA, and VDR.

Conclusion

These results provide a useful context and a cellular snapshot of how ferroptosis affects cardiomyocytes (CMs) in COVID-19 patients' hearts. Besides, suppressing ferroptosis seems to be a beneficial therapeutic approach to mitigate heart damage in COVID-19.

Unveiling epithelial plasticity regulation in lung cancer: Exploring the cross-talk among Tks4 scaffold protein partners

The epithelial-to-mesenchymal transition (EMT) represents a hallmark event in the evolution of lung cancer. This work aims to study a recently described EMT-regulating protein, Tks4, and to explore its potential as a prognostic biomarker in non-small cell lung cancer. In this study, we used CRISPR/Cas9 method to knockout (KO) Tks4 to study its functional roles in invadopodia formation, migration, and regulation of EMT marker expressions and we identified Tks4-interacting proteins. Tks4-KO A549 cells exhibited an EMT-like phenotype characterized by elongated morphology and increased expression of EMT markers. Furthermore, analyses of a large-scale lung cancer database and a patient-derived tissue array data revealed that the Tks4 mRNA level was decreased in more aggressive lung cancer stages. To understand the regulatory role of Tks4 in lung cancer, we performed a Tks4-interactome analysis via Tks4 immunoprecipitation-mass spectrometry on five different cell lines and identified CAPZA1 as a novel Tks4 partner protein. Thus, we propose that the absence of Tks4 leads to disruption of a connectome of multiple proteins and that the resulting undocking and likely mislocalization of signaling molecules impairs actin cytoskeleton rearrangement and activates EMT-like cell fate switches, both of which likely influence disease severity.

Deletion of a core APC/C component reveals APC/C function in regulating neuronal USP1 levels and morphology

Introduction

The Anaphase Promoting Complex (APC/C), an E3 ubiquitin ligase, plays a key role in cell cycle control, but it is also thought to operate in postmitotic neurons. Most studies linking APC/C function to neuron biology employed perturbations of the APC/C activators, cell division cycle protein 20 (Cdc20) and Cdc20 homologue 1 (Cdh1). However, multiple lines of evidence indicate that Cdh1 and Cdc20 can function in APC/C-independent contexts, so that the effects of their perturbation cannot strictly be linked to APC/C function.

Methods

We therefore deleted the gene encoding Anaphase Promoting Complex 4 (APC4), a core APC/C component, in neurons cultured from conditional knockout (cKO) mice.

Results

Our data indicate that several previously published substrates are actually not APC/C substrates, whereas ubiquitin specific peptidase 1 (USP1) protein levels are altered in APC4 knockout (KO) neurons. We propose a model where the APC/C ubiquitylates USP1 early in development, but later ubiquitylates a substrate that directly or indirectly stabilizes USP1. We further discovered a novel role of the APC/C in regulating the number of neurites exiting somata, but we were unable to confirm prior data indicating that the APC/C regulates neurite length, neurite complexity, and synaptogenesis. Finally, we show that APC4 SUMOylation does not impact the ability of the APC/C to control the number of primary neurites or USP1 protein levels.

Discussion

Our data indicate that perturbation studies aimed at dissecting APC/C biology must focus on core APC/C components rather than the APC/C activators, Cdh20 and Cdh1.

LINC01234 promoted malignant behaviors of breast cancer cells via hsa-miR-30c-2-3p/CCT4/mTOR signaling pathway

OBJECTIVE

Despite continuous progress in treatment, recurrence and metastasis limit further improvement in the prognosis of breast cancer (BC) patients. Our aim was to search for a crucial prognostic biomarker of BC.

MATERIALS AND METHODS

Patient data were selected from The Cancer Genome Atlas (TCGA) and GTEx databases. Several online public databases, including Gene Expression Profiling Interactive Analysis (GEPIA), miRWalk, miRDB, and LncBase Predicted v.2, were used to identify potential upstream miRNAs and lncRNAs. These findings were validated through in vitro experiments.

RESULTS

A total of 1, 097 invasive BC samples and 572 normal breast tissues (including 113 samples from TCGA and 459 samples from GTEx) were collected for the study. CCT4 was not only significantly overexpressed in BC compared with normal breast tissues but also had important prognostic significance (P < 0.001). By intersecting miRWalk and miRDB and conducting correlation analysis, hsa-miR-30c-2-3p was identified as the most probable upstream miRNA of CCT4. Following an extensive assessment that included survival analysis, correlation analysis, and common binding-site prediction, LINC01234 was chosen as the most likely upstream lncRNA. In vitro experiments showed that LINC01234-siRNA inhibited the proliferation, invasion, and migration abilities of BC cells. Western blot analysis further confirmed that LINC01234 promoted malignant behaviors of BC cells via the CCT4/mTOR signaling pathway.

CONCLUSION

The LINC01234/hsa-miR-30c-2-3p/CCT4/mTOR axis was identified as a potential ceRNA regulatory mechanism in BC. These findings established the foundation for systematically unveiling the pathological mechanisms of BC and provided new insights for targeted therapy of BC patients.

Inhibition of CDC20 potentiates anti-tumor immunity through facilitating GSDME-mediated pyroptosis in prostate cancer

BACKGROUND

Increasing evidence suggests that immunotherapy, especially immune checkpoint inhibitors (ICIs), has the potential to facilitate long-term survival in various cancer besides prostate cancer. Emerging evidence indicated that pyroptosis, an immunogenic form of cell death, could trigger an anti-tumor immune microenvironment and enhance the effectiveness of immunotherapy. Nevertheless, the mechanism underlying the regulation of pyroptosis signaling in prostate cancer remains unclear.

METHODS

The differential expression of human E3 ligases in prostate cancer was integratedly analyzed from five independent public datasets. Moreover, the immunohistochemistry analysis of a tissue microarray derived from prostate cancer patients confirmed the results from the bioinformatic analysis. Furthermore, prostate cancer cell lines were evaluated via the next-generation RNA sequencing to assess transcriptomic profile upon CDC20 depletion. Next, qRT-PCR, Western blotting, cycloheximide assay, immunoprecipitation, and ubiquitination assay were employed to explore the correlation and interaction between CDC20 and GSDME. Both immune-deficient and immune-competent murine models were utilized to examine the anti-tumor efficacy of CDC20 inhibition with or without the anti-PD1 antibodies, respectively. To analyze the immune microenvironment of the xenografts, the tumor tissues were examined by immunohistochemistry and flow cytometry.

RESULTS

The analysis of multiple prostate cancer cohorts suggested that CDC20 was the most significantly over-expressed E3 ligase. In addition, CDC20 exerted a negative regulatory effect on the pyroptosis pathway by targeting GSDME for ubiquitination-mediated proteolysis in a degron-dependent manner. Knockdown of CDC20 leads to increased GSDME abundance and a transition from apoptosis to pyroptosis in response to death signals. Furthermore, in our syngeneic murine models, we found that depletion of CDC20 significantly enhances the anti-tumor immunity by promoting the infiltration of CD8⁺ T lymphocytes dependent on the existence of GSDME, as well as reducing myeloid immune cells. More importantly, Apcin, a small molecular inhibitor that targets CDC20, exhibited synergistic effects with anti-PD1-based immunotherapy in murine models of prostate cancer.

CONCLUSIONS

Overall, these findings provide new insights into the upstream regulation of GSDME-mediated pyroptosis by CDC20, which specifically interacts with GSDME and facilitates its ubiquitination in a degron-dependent manner. Importantly, our data highlight novel molecular pathways for targeting cellular pyroptosis and enhancing the effectiveness of anti-PD1-based immunotherapy.

Extensive review on breast cancer its etiology, progression, prognostic markers, and treatment

As the most frequent and vulnerable malignancy among women, breast cancer universally manifests a formidable healthcare challenge. From a biological and molecular perspective, it is a heterogenous disease and is stratified based on the etiological factors driving breast carcinogenesis. Notably, genetic predispositions and epigenetic impacts often constitute the heterogeneity of this disease. Typically, breast cancer is classified intrinsically into histological subtypes in clinical landscapes. These stratifications empower physicians to tailor precise treatments among the spectrum of breast cancer therapeutics. In this pursuit, numerous prognostic algorithms are extensively characterized, drastically changing how breast cancer is portrayed. Therefore, it is a basic requisite to comprehend the multidisciplinary rationales of breast cancer to assist the evolution of novel therapeutic strategies. This review aims at highlighting the molecular and genetic grounds of cancer additionally with therapeutic and phytotherapeutic context. Substantially, it also renders researchers with an insight into the breast cancer cell lines as a model paradigm for breast cancer research interventions.

The type II TGF-β receptor phosphorylates Tyr 182 in the type I receptor to activate downstream Src signaling

Transforming growth factor–β (TGF-β) signaling has important roles during embryonic development and in tissue homeostasis. TGF-β ligands exert cellular effects by binding to type I (TβRI) and type II (TβRII) receptors and inducing both SMAD-dependent and SMAD-independent intracellular signaling pathways, the latter of which includes the activation of the tyrosine kinase Src. We investigated the mechanism by which TGF-β stimulation activates Src in human and mouse cells. Before TGF-β stimulation, inactive Src was complexed with TβRII. Upon TGF-β1 stimulation, TβRII associated with and phosphorylated TβRI at Tyr 182 . Binding of Src to TβRI involved the interaction of the Src SH2 domain with phosphorylated Tyr 182 and the interaction of the Src SH3 domain with a proline-rich region in TβRI and led to the activation of Src kinase activity and Src autophosphorylation. TGF-β1–induced Src activation required the kinase activities of TβRII and Src but not that of TβRI. Activated Src also phosphorylated TβRI on several tyrosine residues, which may stabilize the binding of Src to the receptor. Src activation was required for the ability of TGF-β to induce fibronectin production and migration in human breast carcinoma cells and to induce α–smooth muscle actin and actin reorganization in mouse fibroblasts. Thus, TGF-β induces Src activation by stimulating a direct interaction with TβRI that depends on tyrosine phosphorylation of TβRI by TβRII.

USP39 facilitates breast cancer cell proliferation through stabilization of FOXM1

Deubiquitinating enzyme dysregulation has been linked to the development of a variety of human malignancies, including breast cancer. However, the exact involvement of the deubiquitinating enzyme USP39 in the progression of breast cancer is yet unknown. Cell viability and colony formation analysis was used to assess the effects of USP39 knockdown on breast cancer cells in this study. The interaction between USP39 and FOXM1 was investigated using co-immunoprecipitation (co-IP) and in vitro deubiquitination analysis. The expression of USP39 and FOXM1 in breast cancer tissues was studied using the TCGA database. According to our findings, USP39 deubiquitinates and stabilizes FOXM1, promoting breast cancer cell proliferation, colony formation, and tumor growth in vivo. Furthermore, elevated USP39 expression lowers FOXM1 ubiquitination, resulting in increased transcriptional activity. In addition, the high expression of USP39 reduces the ubiquitination of FOXM1, thereby enhancing the transcriptional activity of FOXM1 and regulating the expression of downstream genes Cdc25b and Plk1. USP39 is positively correlated with the expression level of FOXM1 in breast cancer cells. In general, our research revealed the USP39-FOXM1 axis as a critical driver of breast cancer cell proliferation and provided a theoretical foundation for targeting the USP39-FOXM1 axis for pancreatic cancer treatment.

MiR-34a-5p negatively regulates oxidative stress on lens epithelial cells by silencing GPX3 - a novel target

Purpose MiR-34a-5p is reported to be related with age-related nuclear cataract. This study investigated the mechanism of miR-34a-5p in the regulation of oxidative stress on lens epithelial cells.Methods The three candidate miRNAs were screened by CCK-8 assays after transfection of mimics or inhibitor in H₂O₂-treated HLE-B3 cells. The apoptosis, ROS level and GPX activity of HLE-B3 cells transfected with miR-34a-5p mimics or inhibitor were analysed by flow cytometry, cellular ROS and GPX activity test. The target genes of miR-34a-5p were predicted by proteomic and bioinformatic analysis. The relationship between miR-34a-5p and GPX3 were internally validated by qRT-PCR and Western blot and externally verified by dual-luciferase reporter assay. The effect of miR-34a-5p-GPX3 axis on regulation of oxidative stress in HLE-B3 cells were conducted by overexpression of GPX3 and tested by flow cytometry analysis, cellular ROS and GPX detection.Results The viability of H₂O₂-treated HLE-B3 cells were weakened by up-regulated miR-34a-5p. Cell apoptosis and oxidative damage were also induced by overexpression of miR-34a-5p. GPX3 and SRC were identified as target genes of miR-34a-5p by combined analysis of proteomic and bioinformatics, while GPX3 was selected for further research for its connection with anti-oxidation. Western blot and qRT-PCR tests proved that GPX3 is negatively regulated by miR-34a-5p. Dual-luciferase reporter assay verified that GPX3 is the direct target of miR-34a-5p. The increased oxidative stress induced by transfection of miR-34a-5p mimics in H₂O₂-treated HLE-B3 cells was attenuated by overexpression of GPX3.Conclusions MiR-34a-5p is a negative regulator of oxidative stress on lens epithelial cells and the mechanism is by silencing the expression of GPX3. These data suggests that miR-34a-5p may be a potential novel therapeutic target for the prevention and treatment of age-related cataract.

SRC kinase-mediated signaling pathways and targeted therapies in breast cancer

Breast cancer (BC) has been ranked the most common malignant tumor throughout the world and is also a leading cause of cancer-related deaths among women. SRC family kinases (SFKs) belong to the non-receptor tyrosine kinase (nRTK) family, which has eleven members sharing similar structure and function. Among them, SRC is the first identified proto-oncogene in mammalian cells. Oncogenic overexpression or activation of SRC has been revealed to play essential roles in multiple events of BC progression, including tumor initiation, growth, metastasis, drug resistance and stemness regulations. In this review, we will first give an overview of SRC kinase and SRC-relevant functions in various subtypes of BC and then systematically summarize SRC-mediated signaling transductions, with particular emphasis on SRC-mediated substrate phosphorylation in BC. Furthermore, we will discuss the progress of SRC-based targeted therapies in BC and the potential future direction.

NF2 Gene Participates in Regulation of the Cell Cycle of Meningiomas by Restoring Spindle Assembly Checkpoint Function and Inhibiting the Binding of Cdc20 Protein to Anaphase Promoting Complex/Cyclosome

BACKGROUND

The neurofibromatosis type 2 (NF2) gene mutation is the leading genetic event in meningiomas, usually accompanied by malignant features. Dysfunction of the spindle assembly checkpoint (SAC) induces tumorigenesis. However, the crosstalk between NF2 and SAC in meningiomas remains unclear.

METHODS

Cell proliferation, invasion, apoptosis, and cell cycle of meningiomas were determined by cell counting kit-8 assay, transwell assay, and flow cytometry, respectively. The expression of SAC in meningioma cells was detected by quantitative real-time polymerase chain reaction and Western blot. The interaction between anaphase promoting complex/cyclosome (APC/C) and cell division cycle 20 (Cdc20) protein in meningioma cells was further explored by co-immunoprecipitation.

RESULTS

We found that the expression of NF2/merlin was low or absent in malignant meningiomas. Overexpression of NF2 suppressed the proliferation and invasion of meningioma cells, prolonged the G₂/M phase, and elevated the expression of SAC proteins at posttranscription. Furthermore, the interaction between APC/C and Cdc20 was inhibited by NF2.

CONCLUSIONS

Our findings suggested that NF2 might restore SAC function by impairing the binding of APC/C and Cdc20, thereby limiting the mitotic rate and inhibiting proliferation of meningiomas.

Bioinformatics analysis for the identification of differentially expressed genes and related signaling pathways in H. pylori-CagA transfected gastric cancer cells

Aim

Helicobacter pylori cytotoxin-associated protein A (CagA) is an important virulence factor known to induce gastric cancer development. However, the cause and the underlying molecular events of CagA induction remain unclear. Here, we applied integrated bioinformatics to identify the key genes involved in the process of CagA-induced gastric epithelial cell inflammation and can ceration to comprehend the potential molecular mechanisms involved.

Materials and Methods

AGS cells were transected with pcDNA3.1 and pcDNA3.1::CagA for 24 h. The transfected cells were subjected to transcriptome sequencing to obtain the expressed genes. Differentially expressed genes (DEG) with adjusted P value < 0.05, — logFC —> 2 were screened, and the R package was applied for gene ontology (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The differential gene protein–protein interaction (PPI) network was constructed using the STRING Cytoscape application, which conducted visual analysis to create the key function networks and identify the key genes. Next, the Kaplan–Meier plotter survival analysis tool was employed to analyze the survival of the key genes derived from the PPI network. Further analysis of the key gene expressions in gastric cancer and normal tissues were performed based on The Cancer Genome Atlas (TCGA) database and RT-qPCR verification.

Results

After transfection of AGS cells, the cell morphology changes in a hummingbird shape and causes the level of CagA phosphorylation to increase. Transcriptomics identified 6882 DEG, of which 4052 were upregulated and 2830 were downregulated, among which q-value < 0.05, FC > 2, and FC under the condition of ≤2. Accordingly, 1062 DEG were screened, of which 594 were upregulated and 468 were downregulated. The DEG participated in a total of 151 biological processes, 56 cell components, and 40 molecular functions. The KEGG pathway analysis revealed that the DEG were involved in 21 pathways. The PPI network analysis revealed three highly interconnected clusters. In addition, 30 DEG with the highest degree were analyzed in the TCGA database. As a result, 12 DEG were found to be highly expressed in gastric cancer, while seven DEG were related to the poor prognosis of gastric cancer. RT-qPCR verification results showed that Helicobacter pylori CagA caused up-regulation of BPTF, caspase3, CDH1, CTNNB1, and POLR2A expression.

Conclusion

The current comprehensive analysis provides new insights for exploring the effect of CagA in human gastric cancer, which could help us understand the molecular mechanism underlying the occurrence and development of gastric cancer caused by Helicobacter pylori.

Dysregulation of the Ubiquitin Proteasome System in Human Malignancies: A Window for Therapeutic Intervention

Simple Summary

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. Dysregulation of the UPS results in loss of ability to maintain protein quality through proteolysis, and is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss the mechanisms linking dysregulated UPS to human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

Abstract

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. This process is tightly regulated through the activation and transfer of polyubiquitin chains to target proteins which are then recognized and degraded by the 26S proteasome complex. The role of UPS is crucial in regulating protein levels through degradation to maintain fundamental cellular processes such as growth, division, signal transduction, and stress response. Dysregulation of the UPS, resulting in loss of ability to maintain protein quality through proteolysis, is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss functional links of dysregulated UPS in human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

E3 Ubiquitin Ligase APC/CCdh1 Regulation of Phenylalanine Hydroxylase Stability and Function

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by the dysfunction of the enzyme phenylalanine hydroxylase (PAH). Alterations in the level of PAH leads to the toxic accumulation of phenylalanine in the blood and brain. Protein degradation mediated by ubiquitination is a principal cellular process for maintaining protein homeostasis. Therefore, it is important to identify the E3 ligases responsible for PAH turnover and proteostasis. Here, we report that anaphase-promoting complex/cyclosome-Cdh1 (APC/C)Cdh1 is an E3 ubiquitin ligase complex that interacts and promotes the polyubiquitination of PAH through the 26S proteasomal pathway. Cdh1 destabilizes and declines the half-life of PAH. In contrast, the CRISPR/Cas9-mediated knockout of Cdh1 stabilizes PAH expression and enhances phenylalanine metabolism. Additionally, our current study demonstrates the clinical relevance of PAH and Cdh1 correlation in hepatocellular carcinoma (HCC). Overall, we show that PAH is a prognostic marker for HCC and Cdh1 could be a potential therapeutic target to regulate PAH-mediated physiological and metabolic disorders.

Ubiquitin-proteasome system (UPS) as a target for anticancer treatment

The ubiquitin-proteasome system (UPS) plays an important role in the cellular processes for protein quality control and homeostasis. Dysregulation of the UPS has been implicated in numerous diseases, including cancer. Indeed, components of UPS are frequently mutated or abnormally expressed in various cancers. Since Bortezomib, a proteasome inhibitor, received FDA approval for the treatment of multiple myeloma and mantle cell lymphoma, increasing numbers of researchers have been seeking drugs targeting the UPS as a cancer therapeutic strategy. Here, we introduce the essential component of UPS, including ubiquitinating enzymes, deubiquitinating enzymes and 26S proteasome, and we summarize their targets and mechanisms that are crucial for tumorigenesis. In addition, we briefly discuss some UPS inhibitors, which are currently in clinical trials as cancer therapeutics.

Cellular Mechanisms Triggered by the Cotreatment of Resveratrol and Doxorubicin in Breast Cancer: A Translational In Vitro-In Silico Model

Doxorubicin (Doxo) is the most effective chemotherapeutic agent for the treatment of breast cancer. However, resistance to Doxo is common. Adjuvant compounds capable of modulating mechanisms involved in Doxo resistance may potentiate the effectiveness of the drug. Resveratrol (Rsv) has been tested as an adjuvant in mammary malignancies. However, the cellular and molecular mechanisms underlying the effects of cotreatment with Doxo and Rsv in breast cancer are poorly understood. Here, we combined in vitro and in silico analysis to characterize these mechanisms. In vitro, we employed a clinically relevant experimental design consisting of acute (24 h) treatment followed by 15 days of analysis. Acute Rsv potentiated the long-lasting effect of Doxo through the induction of apoptosis and senescence. Cells that survived to the cotreatment triggered high levels of autophagy. Autophagy inhibition during its peak of activation but not concomitant with Doxo+Rsv increased the long-term toxicity of the cotreatment. To uncover key proteins potentially associated with in vitro effects, an in silico multistep strategy was implemented. Chemical-protein networks were predicted based on constitutive gene expression of MCF7 cells and interatomic data from breast cancer. Topological analysis, KM survival analysis, and a quantitative model based on the connectivity between apoptosis, senescence, and autophagy were performed. We found seven putative genes predicted to be modulated by Rsv in the context of Doxo treatment: CCND1, CDH1, ESR1, HSP90AA1, MAPK3, PTPN11, and RPS6KB1. Six out of these seven genes have been experimentally proven to be modulated by Rsv in cancer cells, with 4 of the 6 genes in MCF7 cells. In conclusion, acute Rsv potentiated the long-term toxicity of Doxo in breast cancer potentially through the modulation of genes and mechanisms involved in Doxo resistance. Rational autophagy inhibition potentiated the effects of Rsv+Doxo, a strategy that should be further tested in animal models.

The Effect of Dysfunctional Ubiquitin Enzymes in the Pathogenesis of Most Common Diseases

Ubiquitination is a multi-step enzymatic process that involves the marking of a substrate protein by bonding a ubiquitin and protein for proteolytic degradation mainly via the ubiquitin–proteasome system (UPS). The process is regulated by three main types of enzymes, namely ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin ligases (E3). Under physiological conditions, ubiquitination is highly reversible reaction, and deubiquitinases or deubiquitinating enzymes (DUBs) can reverse the effect of E3 ligases by the removal of ubiquitin from substrate proteins, thus maintaining the protein quality control and homeostasis in the cell. The dysfunction or dysregulation of these multi-step reactions is closely related to pathogenic conditions; therefore, understanding the role of ubiquitination in diseases is highly valuable for therapeutic approaches. In this review, we first provide an overview of the molecular mechanism of ubiquitination and UPS; then, we attempt to summarize the most common diseases affecting the dysfunction or dysregulation of these mechanisms.

APC/C ubiquitin ligase: Functions and mechanisms in tumorigenesis

The anaphase promoting complex/ cyclosome (APC/C), is an evolutionarily conserved protein complex essential for cellular division due to its role in regulating the mitotic transition from metaphase to anaphase. In this review, we highlight recent work that has shed light on our understanding of the role of APC/C coactivators, Cdh1 and Cdc20, in cancer initiation and development. We summarize the current state of knowledge regarding APC/C structure and function, as well as the distinct ways Cdh1 and Cdc20 are dysregulated in human cancer. We also discuss APC/C inhibitors, novel approaches for targeting the APC/C as a cancer therapy, and areas for future work.

Mechanisms for the temporal regulation of substrate ubiquitination by the anaphase-promoting complex/cyclosome

The anaphase-promoting complex/cyclosome (APC/C) is a multi-subunit, multifunctional ubiquitin ligase that controls the temporal degradation of numerous cell cycle regulatory proteins to direct the unidirectional cell cycle phases. Several different mechanisms contribute to ensure the correct order of substrate modification by the APC/C complex. Recent advances in biochemical, biophysical and structural studies of APC/C have provided a deep mechanistic insight into the working of this complex ubiquitin ligase. This complex displays remarkable conformational flexibility in response to various binding partners and post-translational modifications, which together regulate substrate selection and catalysis of APC/C. Apart from this, various features and modifications of the substrates also influence their recognition and affinity to APC/C complex. Ultimately, temporal degradation of substrates depends on the kind of ubiquitin modification received, the processivity of APC/C, and other extrinsic mechanisms. This review discusses our current understanding of various intrinsic and extrinsic mechanisms responsible for 'substrate ordering' by the APC/C complex.