Cancer Cells Employ Nuclear Caspase-8 to Overcome the p53-Dependent G2/M Checkpoint through Cleavage of USP28

Mitochondria-targeted catalase induced cell malignant transformation by the downregulation of p53 protein stability via USP28/miR-200b/PP2A-Cα axis

Antioxidants exert a paradoxical influence on cancer prevention. The latest explanation for this paradox is the different target sites of antioxidants. However, it remains unclear how mitochondria-targeted antioxidants trigger specific p53-dependent pathways in malignant transformation models. Our study revealed that overexpression of mitochondria-targeted catalase (mCAT) instigated such malignant transformation via mouse double minute 2 homolog (MDM2) -mediated p53 degradation. In mouse epithelial JB6 Cl41 cells, the stable expression of mCAT resulted in MDM2-mediated p53 degradation, unlike in catalase-overexpressed Cl41 cells. Further, we demonstrated that mCAT overexpression upregulated ubiquitin-specific protease 28 (USP28) expression, which in turn stabilized c-Jun protein levels. This alteration initiated the activation of the miR-200b promoter transcription activity and a subsequent increase in miR-200b expression. Furthermore, elevated miR-200b levels then promoted its binding to the 3'-untranslated region of protein phosphatase 2A catalytic subunit (PP2A-C) α-isoform mRNA, consequently resulting in PP2A-C protein downregulation. This cascade of events ultimately contributed to increased MDM2 phosphorylation and p53 protein degradation. Thus, the mCAT overexpression triggers MDM2/p53-dependent malignant transformation through USP28/miR-200b/PP2A-Cα pathway, which may provide a new information for understanding mitochondria-targeted antioxidants facilitate the progression to the tumorigenic state.

Structural basis for the bi-specificity of USP25 and USP28 inhibitors

The development of cancer therapeutics is often hindered by the fact that specific oncogenes cannot be directly pharmaceutically addressed. Targeting deubiquitylases that stabilize these oncogenes provides a promising alternative. USP28 and USP25 have been identified as such target deubiquitylases, and several small-molecule inhibitors indiscriminately inhibiting both enzymes have been developed. To obtain insights into their mode of inhibition, we structurally and functionally characterized USP28 in the presence of the three different inhibitors AZ1, Vismodegib and FT206. The compounds bind into a common pocket acting as a molecular sink. Our analysis provides an explanation why the two enzymes are inhibited with similar potency while other deubiquitylases are not affected. Furthermore, a key glutamate residue at position 366/373 in USP28/USP25 plays a central structural role for pocket stability and thereby for inhibition and activity. Obstructing the inhibitor-binding pocket by mutation of this glutamate may provide a tool to accelerate future drug development efforts for selective inhibitors of either USP28 or USP25 targeting distinct binding pockets.

Cell death shapes cancer immunity: spotlighting PANoptosis

PANoptosis represents a novel type of programmed cell death (PCD) with distinctive features that incorporate elements of pyroptosis, apoptosis, and necroptosis. PANoptosis is governed by a newly discovered cytoplasmic multimeric protein complex known as the PANoptosome. Unlike each of these PCD types individually, PANoptosis is still in the early stages of research and warrants further exploration of its specific regulatory mechanisms and primary targets. In this review, we provide a brief overview of the conceptual framework and molecular components of PANoptosis. In addition, we highlight recent advances in the understanding of the molecular mechanisms and therapeutic applications of PANoptosis. By elucidating the complex crosstalk between pyroptosis, apoptosis and necroptosis and summarizing the functional consequences of PANoptosis with a special focus on the tumor immune microenvironment, this review aims to provide a theoretical basis for the potential application of PANoptosis in cancer therapy.

Arginine methylation of caspase-8 controls life/death decisions in extrinsic apoptotic networks

Procaspase-8 is a key mediator of death receptor (DR)-mediated pathways. Recently, the role of post-translational modifications (PTMs) of procaspase-8 in controlling cell death has received increasing attention. Here, using mass spectrometry screening, pharmacological inhibition and biochemical assays, we show that procaspase-8 can be targeted by the PRMT5/RIOK1/WD45 methylosome complex. Furthermore, two potential methylation sites of PRMT5 on procaspase-8, R233 and R435, were identified in silico. R233 and R435 are highly conserved in mammals and their point mutations are among the most common mutations of caspase-8 in cancer. The introduction of mutations at these positions resulted in inhibitory effects on CD95L-induced caspase-8 activity, effector caspase activation and apoptosis. In addition, we show that procaspase-8 can undergo symmetric di-methylation. Finally, the pharmacological inhibition of PRMT5 resulted in the inhibitory effects on caspase activity and apoptotic cell death. Taken together, we have unraveled the additional control checkpoint in procaspase-8 activation and the arginine methylation network in the extrinsic apoptosis pathway.

Caspase 8 deletion causes infection/inflammation-induced bone marrow failure and MDS-like disease in mice

Myelodysplastic syndromes (MDS) are a heterogeneous group of pre-leukemic hematopoietic disorders characterized by cytopenia in peripheral blood due to ineffective hematopoiesis and normo- or hypercellularity and morphologic dysplasia in bone marrow (BM). An inflammatory BM microenvironment and programmed cell death of hematopoietic stem/progenitor cells (HSPCs) are thought to be the major causes of ineffective hematopoiesis in MDS. Pyroptosis, apoptosis and necroptosis (collectively, PANoptosis) are observed in BM tissues of MDS patients, suggesting an important role of PANoptosis in MDS pathogenesis. Caspase 8 (Casp8) is a master regulator of PANoptosis, which is downregulated in HSPCs from most MDS patients and abnormally spliced in HSPCs from MDS patients with SRSF2 mutation. To study the role of PANoptosis in hematopoiesis, we generated inducible Casp8 knockout mice (Casp8-/-). Mx1-Cre-Casp8-/- mice died of BM failure within 10 days of polyI:C injections due to depletion of HSPCs. Rosa-ERT2Cre-Casp8-/- mice are healthy without significant changes in BM hematopoiesis within the first 1.5 months after Casp8 deletion. Such mice developed BM failure upon infection or low dose polyI:C/LPS injections due to the hypersensitivity of Casp8-/- HSPCs to infection or inflammation-induced necroptosis which can be prevented by Ripk3 deletion. However, impaired self-renewal capacity of Casp8-/- HSPCs cannot be rescued by Ripk3 deletion due to activation of Ripk1-Tbk1 signaling. Most importantly, mice transplanted with Casp8-/- BM cells developed MDS-like disease within 4 months of transplantation as demonstrated by anemia, thrombocytopenia and myelodysplasia. Our study suggests an essential role for a balance in Casp8, Ripk3-Mlkl and Ripk1-Tbk1 activities in the regulation of survival and self-renewal of HSPCs, the disruption of which induces inflammation and BM failure, resulting in MDS-like disease.

12th Tuscany Retreat on Cancer Research and Apoptosis: Genetic profiling, resistance mechanisms and novel treatment concepts in cancer and neurodegeneration

The 12th Tuscany Retreat on Cancer Research and Apoptosis was held on August 19-26, 2023. The biennial retreat aims to bring together scientists who advance research in cancer, cell death, and neurodegenerative diseases. Topics covered ranged from drug resistance in cancer to insights into novel molecular cell signaling mechanisms and targets, all related to the pathways and molecules that regulate programmed cell death and the diseases that result from the dysregulation of programmed cell death. In this meeting review, we summarize the content of the most recent retreat.

A distinct class of pan-cancer susceptibility genes revealed by an alternative polyadenylation transcriptome-wide association study

Alternative polyadenylation plays an important role in cancer initiation and progression; however, current transcriptome-wide association studies mostly ignore alternative polyadenylation when identifying putative cancer susceptibility genes. Here, we perform a pan-cancer 3' untranslated region alternative polyadenylation transcriptome-wide association analysis by integrating 55 well-powered (n > 50,000) genome-wide association studies datasets across 22 major cancer types with alternative polyadenylation quantification from 23,955 RNA sequencing samples across 7,574 individuals. We find that genetic variants associated with alternative polyadenylation are co-localized with 28.57% of cancer loci and contribute a significant portion of cancer heritability. We further identify 642 significant cancer susceptibility genes predicted to modulate cancer risk via alternative polyadenylation, 62.46% of which have been overlooked by traditional expression- and splicing- studies. As proof of principle validation, we show that alternative alleles facilitate 3' untranslated region lengthening of CRLS1 gene leading to increased protein abundance and promoted proliferation of breast cancer cells. Together, our study highlights the significant role of alternative polyadenylation in discovering new cancer susceptibility genes and provides a strong foundational framework for enhancing our understanding of the etiology underlying human cancers.

PRKCSH contributes to TNFSF resistance by extending IGF1R half-life and activation in lung cancer

Tumor necrosis factor superfamily (TNFSF) resistance contributes to the development and progression of tumors and resistance to various cancer therapies. Tumor-intrinsic alterations involved in the adaptation to the TNFSF response remain largely unknown. Here, we demonstrate that protein kinase C substrate 80K-H (PRKCSH) abundance in lung cancers boosts oncogenic IGF1R activation, leading to TNFSF resistance. PRKCSH abundance is correlated with IGF1R upregulation in lung cancer tissues. Specifically, PRKCSH interacts with IGF1R and extends its half-life. The PRKCSH-IGF1R axis in tumor cells impairs caspase-8 activation, increases Mcl-1 expression, and inhibits caspase-9, leading to an imbalance between cell death and survival. PRKCSH deficiency augmented the antitumor effects of natural killer (NK) cells, representative TNFSF effector cells, in a tumor xenograft IL-2Rg-deficient NOD/SCID (NIG) mouse model. Our data suggest that PRKCSH plays a critical role in TNFSF resistance and may be a potential target to improve the efficacy of NK cell-based cancer therapy.

Exploring the apoptotic effects of sericin on HCT116 cells through comprehensive nanostring transcriptomics and proteomics analysis

Sericin, a silk protein from Bombyx mori (silkworms), has many applications, including cosmetics, anti-inflammation, and anti-cancer. Sericin complexes with nanoparticles have shown promise for breast cancer cell lines. Apoptosis, a programmed cell death mechanism, stops cancer cell growth. This study found that Sericin urea extract significantly affected HCT116 cell viability (IC50 = 42.00 ± 0.002 µg/mL) and caused apoptosis in over 80% of treated cells. S-FTIR analysis showed significant changes in Sericin-treated cells' macromolecule composition, particularly in the lipid and nucleic acid areas, indicating major cellular modifications. A transcriptomics study found upregulation of the apoptotic signaling genes FASLG, TNFSF10, CASP3, CASP7, CASP8, and CASP10. Early apoptotic proteins also showed that BAD, AKT, CASP9, p53, and CASP8 were significantly upregulated. A proteomics study illuminated Sericin-treated cells' altered protein patterns. Our results show that Sericin activated the extrinsic apoptosis pathway via the caspase cascade (CASP8/10 and CASP3/7) and the death receptor pathway, involving TNFSF10 or FASLG, in HCT116 cells. Upregulation of p53 increases CASP8, which activates CASP3 and causes HCT116 cell death. This multi-omics study illuminates the molecular mechanisms of Sericin-induced apoptosis, sheds light on its potential cancer treatment applications, and helps us understand the complex relationship between silk-derived proteins and cellular processes.

Exploring the tumor micro-environment in primary and metastatic tumors of different ovarian cancer histotypes

Ovarian cancer is a highly heterogeneous disease consisting of at least five different histological subtypes with varying clinical features, cells of origin, molecular composition, risk factors, and treatments. While most single-cell studies have focused on High grade serous ovarian cancer, a comprehensive landscape of the constituent cell types and their interactions within the tumor microenvironment are yet to be established in the different ovarian cancer histotypes. Further characterization of tumor progression, metastasis, and various histotypes are also needed to connect molecular signatures to pathological grading for personalized diagnosis and tailored treatment. In this study, we leveraged high-resolution single-cell RNA sequencing technology to elucidate the cellular compositions on 21 solid tumor samples collected from 12 patients with six ovarian cancer histotypes and both primary (ovaries) and metastatic (omentum, rectum) sites. The diverse collection allowed us to deconstruct the histotypes and tumor site-specific expression patterns of cells in the tumor, and identify key marker genes and ligand-receptor pairs that are active in the ovarian tumor microenvironment. Our findings can be used in improving precision disease stratification and optimizing treatment options.

DNAJC8: a prognostic marker and potential therapeutic target for hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the most common type of liver cancer, accounting for ~90% of the total cases. DnaJ heat shock protein family member C8 (DNAJC8), belonging to the heat shock protein 40 (HSP40) family, is known to regulate cancer biology function. However, the role of DNAJC8 on HCC development remains unknown.

Methods

The Cancer Genome Atlas, GTEx, cBioPortal, and Human Protein Atlas were used to analyze the expression and clinical significance of DNAJC8 in HCC. Two HCC cell lines, MHCC-97H and Huh-7, were utilized to determine the biological function of DNAJC8.

Results

DNAJC8 expression was upregulated in HCC tissues and correlated with poor clinical prognosis. It was closely related to spliceosome, nucleocytoplasmic transport, and cell cycle and might be involved in the formation of tumor immunosuppressive microenvironment. Knockdown of DNAJC8 severely inhibited HCC cell proliferation and induced apoptosis.

Conclusion

Our study demonstrate that DNAJC8 functions as an oncogene in HCC and hence may be used as a potential therapeutic target and prognostic marker for HCC.

A cytosolic mutp53(E285K) variant confers chemoresistance of malignant melanoma

Malignant melanoma (MM) is known to be intrinsically chemoresistant, even though only ~20% of MM carry mutations of the tumor suppressor p53. Despite improvement of systemic therapy the mortality rate of patients suffering from metastatic MM is still ~70%, highlighting the need for alternative treatment options or for the re-establishment of conventional therapeutic approaches, including chemotherapy. Screening the p53 mutation status in a cohort of 19 patient-derived melanoma samples, we identified one rarely described missense mutation of p53 leading to E285K amino acid exchange (mutp53(E285K)). Employing structural and computational analysis we revealed a major role of E285 residue in maintaining stable conformation of wild-type p53 (wtp53). E285K mutation was predicted to cause interruption of a salt-bridge network affecting the conformation of the C-terminal helix of the DNA-binding domain (DBD) thereby preventing DNA interaction. In this context, a cluster of frequently mutated amino acid residues in cancer was identified to putatively lead to similar structural effects as E285K substitution (E285 cluster). Functional analysis, including knockdown of endogenous p53 and reconstitution with diverse p53 missense mutants confirmed mutp53(E285K) to have lost transcriptional activity, to be localized in the cytosol of cancer cells, by both means conferring chemoresistance. Re-sensitization to cisplatin-induced cell death was achieved using clinically approved compounds aiming to restore p53 wild-type function (PRIMA1-Met), or inhibition of AKT-driven MAPK survival pathways (afuresertib), in both cases being partially due to ferroptosis induction. Consequently, active ferroptosis induction using the GPX4 inhibitor RSL3 proved superior in tumorselectively fighting MM cells. Due to high prevalence of the E285-cluster mutations in MM as well as in a variety of other tumor types, we conclude this cluster to serve an important function in tumor development and therapy and suggest new implications for ferroptosis induction in therapeutic applications fighting MM in particular and cancer in general.

Inhibition of Cysteine Proteases via Thiol-Michael Addition Explains the Anti-SARS-CoV-2 and Bioactive Properties of Arteannuin B

Artemisia annua is the plant that produces artemisinin, an endoperoxide-containing sesquiterpenoid used for the treatment of malaria. A. annua extracts, which contain other bioactive compounds, have been used to treat other diseases, including cancer and COVID-19, the disease caused by the virus SARS-CoV-2. In this study, a methyl ester derivative of arteannuin B was isolated when A. annua leaves were extracted with a 1:1 mixture of methanol and dichloromethane. This methyl ester was thought to be formed from the reaction between arteannuin B and the extracting solvent, which was supported by the fact that arteannuin B underwent 1,2-addition when it was dissolved in deuteromethanol. In contrast, in the presence of N-acetylcysteine methyl ester, a 1,4-addition (thiol-Michael reaction) occurred. Arteannuin B hindered the activity of the SARS CoV-2 main protease (nonstructural protein 5, NSP5), a cysteine protease, through time-dependent inhibition. The active site cysteine residue of NSP5 (cysteine-145) formed a covalent bond with arteannuin B as determined by mass spectrometry. In order to determine whether cysteine adduction by arteannuin B can inhibit the development of cancer cells, similar experiments were performed with caspase-8, the cysteine protease enzyme overexpressed in glioblastoma. Time-dependent inhibition and cysteine adduction assays suggested arteannuin B inhibits caspase-8 and adducts to the active site cysteine residue (cysteine-360), respectively. Overall, these results enhance our understanding of how A. annua possesses antiviral and cytotoxic activities.

Structure and function of the highly homologous deubiquitinases ubiquitin specific peptidase 25 and 28: Insights into their pathophysiological and therapeutic roles

Deubiquitination is the reverse process of ubiquitination, an important protein post-translational modification. Deubiquitination is assisted by deubiquitinating enzymes (DUBs), which catalyze the hydrolysis and removal of ubiquitin chains from targeted proteins and play an important role in regulating protein stability, cell signaling transduction, and programmed cell death. Ubiquitin-specific peptidases 25 and 28 (USP25 and USP28), important members of the USP subfamily of DUBs, are highly homologous, strictly regulated, and closely associated with various diseases, such as cancer and neurodegenerative diseases. Recently, the development of inhibitors targeting USP25 and USP28 for disease treatment has garnered extreme attention. Several non-selective and selective inhibitors have shown potential inhibitory effects. However, the specificity, potency, and action mechanism of these inhibitors remain to be further improved and clarified. Herein, we summarize the structure, regulation, emerging physiological roles, and target inhibition of USP25 and USP28 to provide a basis for the development of highly potent and specific inhibitors for the treatment of diseases, such as colorectal cancer, breast cancer and so on.

Caspase-8 and Tyrosine Kinases: A Dangerous Liaison in Cancer

Caspase-8 is a cysteine-aspartic acid protease that has been identified as an initiator caspase that plays an essential role in the extrinsic apoptotic pathway. Evasion of apoptosis is a hallmark of cancer and Caspase-8 expression is silenced in some tumors, consistent with its central role in apoptosis. However, in the past years, several studies reported an increased expression of Caspase-8 levels in many tumors and consistently identified novel "non-canonical" non-apoptotic functions of Caspase-8 that overall promote cancer progression and sustain therapy resistance. These reports point to the ability of cancer cells to rewire Caspase-8 function in cancer and raise the question of which are the signaling pathways aberrantly activated in cancer that may contribute to the hijack of Caspase-8 activity. In this regard, tyrosine kinases are among the first oncogenes ever identified and genomic, transcriptomic and proteomic studies indeed show that they represent a class of signaling molecules constitutively activated in most of the tumors. Here, we aim to review and discuss the role of Caspase-8 in cancer and its interplay with Src and other tyrosine kinases.

Mechanistic insights into the interactions between cancer drivers and the tumour immune microenvironment

BACKGROUND

The crosstalk between cancer and the tumour immune microenvironment (TIME) has attracted significant interest in the latest years because of its impact on cancer evolution and response to treatment. Despite this, cancer-specific tumour-TIME interactions and their mechanistic insights are still poorly understood.

METHODS

Here, we compute the significant interactions occurring between cancer-specific genetic drivers and five anti- and pro-tumour TIME features in 32 cancer types using Lasso regularised ordinal regression. Focusing on head and neck squamous cancer (HNSC), we rebuild the functional networks linking specific TIME driver alterations to the TIME state they associate with.

RESULTS

The 477 TIME drivers that we identify are multifunctional genes whose alterations are selected early in cancer evolution and recur across and within cancer types. Tumour suppressors and oncogenes have an opposite effect on the TIME and the overall anti-tumour TIME driver burden is predictive of response to immunotherapy. TIME driver alterations predict the immune profiles of HNSC molecular subtypes, and perturbations in keratinization, apoptosis and interferon signalling underpin specific driver-TIME interactions.

CONCLUSIONS

Overall, our study delivers a comprehensive resource of TIME drivers, gives mechanistic insights into their immune-regulatory role, and provides an additional framework for patient prioritisation to immunotherapy. The full list of TIME drivers and associated properties are available at http://www.network-cancer-genes.org .

USP28 controls SREBP2 and the mevalonate pathway to drive tumour growth in squamous cancer

SREBP2 is a master regulator of the mevalonate pathway (MVP), a biosynthetic process that drives the synthesis of dolichol, heme A, ubiquinone and cholesterol and also provides substrates for protein prenylation. Here, we identify SREBP2 as a novel substrate for USP28, a deubiquitinating enzyme that is frequently upregulated in squamous cancers. Our results show that silencing of USP28 reduces expression of MVP enzymes and lowers metabolic flux into this pathway. We also show that USP28 binds to mature SREBP2, leading to its deubiquitination and stabilisation. USP28 depletion rendered cancer cells highly sensitive to MVP inhibition by statins, which was rescued by the addition of geranyl-geranyl pyrophosphate. Analysis of human tissue microarrays revealed elevated expression of USP28, SREBP2 and MVP enzymes in lung squamous cell carcinoma (LSCC) compared to lung adenocarcinoma (LADC). Moreover, CRISPR/Cas-mediated deletion of SREBP2 selectively attenuated tumour growth in a KRas/p53/LKB1 mutant mouse model of lung cancer. Finally, we demonstrate that statins synergise with a dual USP28/25 inhibitor to reduce viability of SCC cells. Our findings suggest that combinatorial targeting of MVP and USP28 could be a therapeutic strategy for the treatment of squamous cell carcinomas.

Ubiquitin-specific protease 28: the decipherment of its dual roles in cancer development

As significant posttranslational modifications, ubiquitination and deubiquitination, whose balance is modulated by ubiquitin-conjugating enzymes and deubiquitinating enzymes (DUBs), can regulate many biological processes, such as controlling cell cycle progression, signal transduction and transcriptional regulation. Belonging to DUBs, ubiquitin-specific protease 28 (USP28) plays an essential role in turning over ubiquitination and then contributing to the stabilization of quantities of substrates, including several cancer-related proteins. In previous studies, USP28 has been demonstrated to participate in the progression of various cancers. Nevertheless, several reports have recently shown that in addition to promoting cancers, USP28 can also play an oncostatic role in some cancers. In this review, we summarize the correlation between USP28 and tumor behaviors. We initially give a brief introduction of the structure and related biological functions of USP28, and we then introduce some concrete substrates of USP28 and the underlying molecular mechanisms. In addition, the regulation of the actions and expression of USP28 is also discussed. Moreover, we concentrate on the impacts of USP28 on diverse hallmarks of cancer and discuss whether USP28 can accelerate or inhibit tumor progression. Furthermore, clinical relevance, including impacting clinical prognosis, influencing therapy resistance and being the therapy target in some cancers, is depicted systematically. Thus, assistance may be given to future experimental designs by the information provided here, and the potential of targeting USP28 for cancer therapy is emphasized.

Polo-like kinase 4 inhibitor CFI-400945 inhibits carotid arterial neointima formation but increases atherosclerosis

Neointima lesion and atherosclerosis are proliferative vascular diseases associated with deregulated proliferation of vascular smooth muscle cells (SMCs). CFI-400945 is a novel, highly effective anticancer drug that inhibits polo-like kinase 4 (PLK4) and targets mitosis. In this study, we aim to investigate how CFI-400945 affects the development of proliferative vascular diseases. In C57BL/6 mice, neointima formation was generated by complete carotid ligation. In apolipoprotein E knockout (ApoE^-/-) mice fed a high-fat diet, atherosclerosis was induced by partial carotid ligation. CFI-400945 was directly applied to carotid arteries via a perivascular collar. Our results showed that CFI-400945 drastically inhibited neointima formation but significantly accelerated atherosclerosis. In vitro studies showed that CFI-400945 treatment induced SMC polyploidization and arrested cells in the G2/M phase. CFI-400945 treatment upregulated p53 and p27 expression but decreased p21 and cyclin B1 expression. CFI-400945 also induced SMC apoptosis, which was inhibited by hydroxyurea, a DNA synthesis inhibitor that inhibits polyploidization. Furthermore, CFI-400945 caused supernumerary centrosomes, leading to mitotic failure, resulting in polyploidization. In conclusion, CFI-400945 prevents carotid arterial neointima formation in C57BL/6 mice but accelerates atherosclerosis in ApoE^-/- mice, likely through mitotic arrest and subsequent induction of polyploidization and apoptosis.

Caspase-8 as a novel mediator linking Src kinase signaling to enhanced glioblastoma malignancy

Caspase-8 is a cysteine protease that plays an essential role in apoptosis. Consistently with its canonical proapoptotic function, cancer cells may genetically or epigenetically downregulate its expression. Unexpectedly, Caspase-8 is often retained in cancer, suggesting the presence of alternative mechanisms that may be exploited by cancer cells to their own benefit. In this regard, we reported that Src tyrosine kinase, which is aberrantly activated in many tumors, promotes Caspase-8 phosphorylation on Tyrosine 380 (Y380) preventing its full activation. Here, we investigated the significance of Caspase-8 expression and of its phosphorylation on Y380 in glioblastoma, a brain tumor where both Caspase-8 expression and Src activity are often aberrantly upregulated. Transcriptomic analyses identified inflammatory response as a major target of Caspase-8, and in particular, NFκB signaling as one of the most affected pathways. More importantly, we could show that Src-dependent phosphorylation of Caspase-8 on Y380 drives the assembly of a multiprotein complex that triggers NFκB activation, thereby inducing the expression of inflammatory and pro-angiogenic factors. Remarkably, phosphorylation on Y380 sustains neoangiogenesis and resistance to radiotherapy. In summary, our work identifies a novel interplay between Src kinase and Caspase-8 that allows cancer cells to hijack Caspase-8 to sustain tumor growth.

When cell death goes wrong: inflammatory outcomes of failed apoptosis and mitotic cell death

Apoptosis is a regulated cellular pathway that ensures that a cell dies in a structured fashion to prevent negative consequences for the tissue or the organism. Dysfunctional apoptosis is a hallmark of numerous pathologies, and treatments for various diseases are successful based on the induction of apoptosis. Under homeostatic conditions, apoptosis is a non-inflammatory event, as the activation of caspases ensures that inflammatory pathways are disabled. However, there is an increasing understanding that under specific conditions, such as caspase inhibition, apoptosis and the apoptotic machinery can be re-wired into a process which is inflammatory. In this review we discuss how the death receptor and mitochondrial pathways of apoptosis can activate inflammation. Furthermore, we will highlight how cell death due to mitotic stress might be a special case when it comes to cell death and the induction of inflammation.

Protein degradation: expanding the toolbox to restrain cancer drug resistance

Despite significant progress in clinical management, drug resistance remains a major obstacle. Recent research based on protein degradation to restrain drug resistance has attracted wide attention, and several therapeutic strategies such as inhibition of proteasome with bortezomib and proteolysis-targeting chimeric have been developed. Compared with intervention at the transcriptional level, targeting the degradation process seems to be a more rapid and direct strategy. Proteasomal proteolysis and lysosomal proteolysis are the most critical quality control systems responsible for the degradation of proteins or organelles. Although proteasomal and lysosomal inhibitors (e.g., bortezomib and chloroquine) have achieved certain improvements in some clinical application scenarios, their routine application in practice is still a long way off, which is due to the lack of precise targeting capabilities and inevitable side effects. In-depth studies on the regulatory mechanism of critical protein degradation regulators, including E3 ubiquitin ligases, deubiquitylating enzymes (DUBs), and chaperones, are expected to provide precise clues for developing targeting strategies and reducing side effects. Here, we discuss the underlying mechanisms of protein degradation in regulating drug efflux, drug metabolism, DNA repair, drug target alteration, downstream bypass signaling, sustaining of stemness, and tumor microenvironment remodeling to delineate the functional roles of protein degradation in drug resistance. We also highlight specific E3 ligases, DUBs, and chaperones, discussing possible strategies modulating protein degradation to target cancer drug resistance. A systematic summary of the molecular basis by which protein degradation regulates tumor drug resistance will help facilitate the development of appropriate clinical strategies.

Prognostic Impact of Caspase-8, CDK9 and Phospho-CDK9 (Thr 186) Expression in Patients with Uterine Cervical Cancer Treated with Definitive Chemoradiation and Brachytherapy

Introduction: After primary platinum-based chemoradiation of locally advanced uterine cervical cancer, a substantial proportion of women present with persistent, recurrent or metastatic disease, indicating an unmet need for biomarker development. Methods: We evaluated the clinical records of 69 cervical cancer patients (Federation of Gynecology and Obstetrics, FIGO Stage > IB3) who were subjected to definitive CRT. Immunohistochemical scoring of caspase-8, cyclin dependent kinase 9 (CDK9) and phosphorylated (phospho-)CDK9 (threonine (Thr) 186) was performed on pretreatment samples and correlated with the histopathological and clinical endpoints, including relapse-free survival (RFS), distant metastasis-free survival (DMFS), cancer-specific survival (CSS) and overall survival (OS). Results: Lower levels of caspase-8 were more prevalent in patients with a higher T-stage (p = 0.002) and a higher FIGO stage (p = 0.003), and were significantly correlated with CDK9 expression (p = 0.018) and inversely with pCDK9 detection (p = 0.014). Increased caspase-8 levels corresponded to improved RFS (p = 0.005), DMFS (p = 0.038) and CSS (p = 0.017) in the univariate analyses. Low CDK9 expression was associated with worse RFS (p = 0.008), CSS (p = 0.015) and OS (p = 0.007), but not DMFS (p = 0.083), and remained a significant prognosticator for RFS (p = 0.003) and CSS (p = 0.009) in the multivariate analyses. Furthermore, low pCDK9 staining was significantly associated with superior RFS (p = 0.004) and DMFS (p = 0.001), and increased CSS (p = 0.022), and remained significant for these endpoints in the multivariate analyses. Conclusion: Increased caspase-8 and CDK9 levels correlate with improved disease-related outcomes in cervical cancer patients treated with CRT, whereas elevated pCDK9 levels predict worse survival in this patient population.

Cellular, Molecular and Proteomic Characteristics of Early Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) accounts for the majority of primary liver cancers. Early detection/diagnosis is vital for the prognosis of HCC, whereas diagnosis at late stages is associated with very low survival rate. Early diagnosis is based on 6-month surveillance of the patient and the use of at least two imaging modalities. The aim of this study was to investigate diagnostic markers for the detection of early HCC based on proteome analysis, microRNAs (miRNAs) and circulating tumor cells (CTCs) in the blood of patients with cirrhosis or early or advanced HCC. We studied 89 patients with HCC, of whom 33 had early HCC and 28 were cirrhotic. CTCs were detected by real-time quantitative reverse transcription PCR and immunofluorescence using the markers epithelial cell adhesion molecule (EPCAM), vimentin, alpha fetoprotein (aFP) and surface major vault protein (sMVP). Expression of the five most common HCC-involved miRNAs (miR-122, miR-200a, miR-200b, miR-221, miR-222) was examined in serum using quantitative real time PCR (qRT-PCR). Finally, patient serum was analyzed via whole proteome analysis (LC/MS). Of 53 patients with advanced HCC, 27 (51%) had detectable CTCs. Among these, 10/27 (37%) presented evidence of mesenchymal or intermediate stage cells (vimentin and/or sMVP positive). Moreover, 5/17 (29%) patients with early HCC and 2/28 (7%) cirrhotic patients had detectable CTCs. Patients with early or advanced HCC exhibited a significant increase in miR-200b when compared to cirrhotic patients. Our proteome analysis indicated that early HCC patients present a significant upregulation of APOA2, APOC3 proteins when compared to cirrhotic patients. When taken in combination, this covers the 100% of the patients with early HCC. miR-200b, APOA2 and APOC3 proteins are sensitive markers and can be potentially useful in combination for the early diagnosis of HCC.

Role of ubiquitin specific proteases in the immune microenvironment of prostate cancer: A new direction

Regulation of ubiquitination is associated with multiple processes of tumorigenesis and development, including regulation of the tumor immune microenvironment. Deubiquitinating enzymes (DUBs) can remove ubiquitin chains from substrates, thereby stabilizing target proteins and altering and remodeling biological processes. During tumorigenesis, deubiquitination-altered biological processes are closely related to tumor metabolism, stemness, and the immune microenvironment. Recently, tumor microenvironment (TME) modulation strategies have attracted considerable attention in cancer immunotherapy. Targeting immunosuppressive mechanisms in the TME has revolutionized cancer therapy. Prostate cancer (PC) is one of the most common cancers and the second most common cause of cancer-related death in men worldwide. While immune checkpoint inhibition has produced meaningful therapeutic effects in many cancer types, clinical trials of anti-CTLA4 or anti-PD1 have not shown a clear advantage in PC patients. TME affects PC progression and also enables tumor cell immune evasion by activating the PD-1/PD-L1 axis. Over the past few decades, an increasing number of studies have demonstrated that deubiquitination in PC immune microenvironment may modulate the host immune system’s response to the tumor. As the largest and most diverse group of DUBs, ubiquitin-specific proteases (USPs) play an important role in regulating T cell development and function. According to current studies, USPs exhibit a high expression signature in PC and may promote tumorigenesis. Elevated expression of USPs often indicates poor tumor prognosis, suggesting that USPs are expected to develop as the markers of tumor prognosis and even potential drug targets for anti-tumor therapy. Herein, we first summarized recent advances of USPs in PC and focused on the relationship between USPs and immunity. Additionally, we clarified the resistance mechanisms of USPs to targeted drugs in PC. Finally, we reviewed the major achievement of targeting USPs in cancers.

Deep Learning-Based Multi-Omics Integration Robustly Predicts Relapse in Prostate Cancer

Objective

Post-operative biochemical relapse (BCR) continues to occur in a significant percentage of patients with localized prostate cancer (PCa). Current stratification methods are not adequate to identify high-risk patients. The present study exploits the ability of deep learning (DL) algorithms using the H2O package to combine multi-omics data to resolve this problem.

Methods

Five-omics data from 417 PCa patients from The Cancer Genome Atlas (TCGA) were used to construct the DL-based, relapse-sensitive model. Among them, 265 (63.5%) individuals experienced BCR. Five additional independent validation sets were applied to assess its predictive robustness. Bioinformatics analyses of two relapse-associated subgroups were then performed for identification of differentially expressed genes (DEGs), enriched pathway analysis, copy number analysis and immune cell infiltration analysis.

Results

The DL-based model, with a significant difference (P = 6e-9) between two subgroups and good concordance index (C-index = 0.767), were proven to be robust by external validation. 1530 DEGs including 678 up- and 852 down-regulated genes were identified in the high-risk subgroup S2 compared with the low-risk subgroup S1. Enrichment analyses found five hallmark gene sets were up-regulated while 13 were down-regulated. Then, we found that DNA damage repair pathways were significantly enriched in the S2 subgroup. CNV analysis showed that 30.18% of genes were significantly up-regulated and gene amplification on chromosomes 7 and 8 was significantly elevated in the S2 subgroup. Moreover, enrichment analysis revealed that some DEGs and pathways were associated with immunity. Three tumor-infiltrating immune cell (TIIC) groups with a higher proportion in the S2 subgroup (p = 1e-05, p = 8.7e-06, p = 0.00014) and one TIIC group with a higher proportion in the S1 subgroup (P = 1.3e-06) were identified.

Conclusion

We developed a novel, robust classification for understanding PCa relapse. This study validated the effectiveness of deep learning technique in prognosis prediction, and the method may benefit patients and prevent relapse by improving early detection and advancing early intervention.

Lethal and Non-Lethal Functions of Caspases in the DNA Damage Response

Members of the caspase family are well known for their roles in the initiation and execution of cell death. Due to their function in the removal of damaged cells that could otherwise become malignant, caspases are important players in the DNA damage response (DDR), a network of pathways that prevent genomic instability. However, emerging evidence of caspases positively or negatively impacting the accumulation of DNA damage in the absence of cell death demonstrates that caspases play a role in the DDR that is independent of their role in apoptosis. This review highlights the apoptotic and non-apoptotic roles of caspases in the DDR and how they can impact genomic stability and cancer treatment.

A pyroptosis-related gene signature predicts prognosis and immune microenvironment in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly malignant tumor with a very poor prognosis. Pyroptosis is an inflammatory form of cell death and plays an important role in cancer development. The prognostic value of pyroptosis-related genes (PRGs) in HCC has not been studied extensively.

METHODS

Unsupervised consensus clustering analysis was performed to identify two subtypes based on the expression profiles of prognostic PRGs in the The Cancer Genome Atlas (TCGA) database, and the differences between the two subtypes were compared. A prognostic model based on four PRGs was established by further least absolute shrinkage and selection operator (LASSO) Cox regression analysis and multivariate Cox regression analysis.

RESULTS

Two subtypes (clusters 1 and 2) were identified by consensus clustering based on prognostic PRGs in HCC. Survival outcomes, biological function, genomic alterations, immune cell infiltration, and immune checkpoint genes were compared between the subtypes. Cluster 2 had a worse survival outcome than cluster 1. Cluster 2 was enriched for hallmarks of cancer progression, TP53 mutation, tumor-promoting immune cells, and immune checkpoint genes, which may contribute to the poor prognosis. A prognostic risk signature that predicted the overall survival (OS) of patients was constructed and validated. Consequently, a risk score was calculated for each patient. Combined with the clinical characteristics, the risk score was found to be an independent prognostic factor for survival of HCC patients. Further analysis revealed that the risk score was closely associated with the levels of immune cell infiltration and the expression profiles of immune checkpoint genes.

CONCLUSIONS

Collectively, our study established a prognostic risk signature for HCC and revealed a significant correlation between pyroptosis and the HCC immune microenvironment.

USP28 enables oncogenic transformation of respiratory cells and its inhibition potentiates molecular therapy targeting mutant EGFR, BRAF and PI3K

Oncogenic transformation of lung epithelial cells is a multistep process, frequently starting with the inactivation of tumour suppressors and subsequent development of activating mutations in proto‐oncogenes, such as members of the PI3K or MAPK families. Cells undergoing transformation have to adjust to changes, including altered metabolic requirements. This is achieved, in part, by modulating the protein abundance of transcription factors. Here, we report that the ubiquitin carboxyl‐terminal hydrolase 28 (USP28) enables oncogenic reprogramming by regulating the protein abundance of proto‐oncogenes such as c‐JUN, c‐MYC, NOTCH and ∆NP63 at early stages of malignant transformation. USP28 levels are increased in cancer compared with in normal cells due to a feed‐forward loop, driven by increased amounts of oncogenic transcription factors such as c‐MYC and c‐JUN. Irrespective of oncogenic driver, interference with USP28 abundance or activity suppresses growth and survival of transformed lung cells. Furthermore, inhibition of USP28 via a small‐molecule inhibitor resets the proteome of transformed cells towards a ‘premalignant’ state, and its inhibition synergizes with clinically established compounds used to target EGFR^L858R‐, BRAF^V600E‐ or PI3K^H1047R‐driven tumour cells. Targeting USP28 protein abundance at an early stage via inhibition of its activity is therefore a feasible strategy for the treatment of early‐stage lung tumours, and the observed synergism with current standard‐of‐care inhibitors holds the potential for improved targeting of established tumours.

Focal adhesion kinase plays a dual role in TRAIL resistance and metastatic outgrowth of malignant melanoma

Despite remarkable advances in therapeutic interventions, malignant melanoma (MM) remains a life-threating disease. Following high initial response rates to targeted kinase-inhibition metastases quickly acquire resistance and present with enhanced tumor progression and invasion, demanding alternative treatment options. We show 2nd generation hexameric TRAIL-receptor-agonist IZI1551 (IZI) to effectively induce apoptosis in MM cells irrespective of the intrinsic BRAF/NRAS mutation status. Conditioning to the EC50 dose of IZI converted the phenotype of IZI-sensitive parental MM cells into a fast proliferating and invasive, IZI-resistant metastasis. Mechanistically, we identified focal adhesion kinase (FAK) to play a dual role in phenotype-switching. In the cytosol, activated FAK triggers survival pathways in a PI3K- and MAPK-dependent manner. In the nucleus, the FERM domain of FAK prevents activation of wtp53, as being expressed in the majority of MM, and consequently intrinsic apoptosis. Caspase-8-mediated cleavage of FAK as well as FAK knockdown, and pharmacological inhibition, respectively, reverted the metastatic phenotype-switch and restored IZI responsiveness. FAK inhibition also re-sensitized MM cells isolated from patient metastasis that had relapsed from targeted kinase inhibition to cell death, irrespective of the intrinsic BRAF/NRAS mutation status. Hence, FAK-inhibition alone or in combination with 2nd generation TRAIL-receptor agonists may be recommended for treatment of initially resistant and relapsed MM, respectively.

Cell cycle progression and transmitotic apoptosis resistance promote escape from extrinsic apoptosis

Extrinsic apoptosis relies on TNF-family receptor activation by immune cells or receptor-activating drugs. Here, we monitored cell cycle progression at a resolution of minutes to relate apoptosis kinetics and cell-to-cell heterogeneities in death decisions to cell cycle phases. Interestingly, we found that cells in S phase delay TRAIL receptor-induced death in favour of mitosis, thereby passing on an apoptosis-primed state to their offspring. This translates into two distinct fates, apoptosis execution post mitosis or cell survival from inefficient apoptosis. Transmitotic resistance is linked to Mcl-1 upregulation and its increased accumulation at mitochondria from mid-S phase onwards, which allows cells to pass through mitosis with activated caspase-8, and with cells escaping apoptosis after mitosis sustaining sublethal DNA damage. Antagonizing Mcl-1 suppresses cell cycle-dependent delays in apoptosis, prevents apoptosis-resistant progression through mitosis and averts unwanted survival after apoptosis induction. Cell cycle progression therefore modulates signal transduction during extrinsic apoptosis, with Mcl-1 governing decision making between death, proliferation and survival. Cell cycle progression thus is a crucial process from which cell-to-cell heterogeneities in fates and treatment outcomes emerge in isogenic cell populations during extrinsic apoptosis. This article has an associated First Person interview with the first author of the paper.

MiR-18a-5p acts as a novel serum biomarker for venous malformation and promotes angiogenesis by regulating the thrombospondin-1/P53 signaling axis

Venous malformation (VM) is a kind of congenital vascular anomaly with high recurrence, and screening for VM lacks an efficient, inexpensive and noninvasive approach now. Serum miRNAs with stable structures are expected to become new postoperative and postablative monitoring biomarkers. Thus, we identified a prognostic serum miR-18a-5p and validated its function in VM. Notably, higher expression level of miR-18a-5p was detected in VM patients than in healthy individuals. We found that miR-18a-5p plays a promotive role in human umbilical vein endothelial cells in vitro. In addition, immunohistochemistry (IHC) results showed a distinct increase of vessels in miR-18a-5p mimics group and a decrease of vessels in inhibitors group compared to the control group in a murine VM model. Furthermore, thrombospondin-1 (TSP1), a potential miR-18a-5p-binding protein, was identified via RNA-seq, luciferase reporter and RNA immunoprecipitation (RIP) assays. Moreover, miR-18a-5p regulated the activation of P53 signaling pathway constituents and consequently led to the regulation of proliferation, migration, invasion and angiogenesis. These results provide a strong theoretical basis for further investigations into pathological mechanism of VM and may provide novel and noninvasive biomarker for VM diagnosis and monitoring.

USP28: Oncogene or Tumor Suppressor? A Unifying Paradigm for Squamous Cell Carcinoma

Squamous cell carcinomas are therapeutically challenging tumor entities. Low response rates to radiotherapy and chemotherapy are commonly observed in squamous patients and, accordingly, the mortality rate is relatively high compared to other tumor entities. Recently, targeting USP28 has been emerged as a potential alternative to improve the therapeutic response and clinical outcomes of squamous patients. USP28 is a catalytically active deubiquitinase that governs a plethora of biological processes, including cellular proliferation, DNA damage repair, apoptosis and oncogenesis. In squamous cell carcinoma, USP28 is strongly expressed and stabilizes the essential squamous transcription factor ΔNp63, together with important oncogenic factors, such as NOTCH1, c-MYC and c-JUN. It is presumed that USP28 is an oncoprotein; however, recent data suggest that the deubiquitinase also has an antineoplastic effect regulating important tumor suppressor proteins, such as p53 and CHK2. In this review, we discuss: (1) The emerging role of USP28 in cancer. (2) The complexity and mutational landscape of squamous tumors. (3) The genetic alterations and cellular pathways that determine the function of USP28 in squamous cancer. (4) The development and current state of novel USP28 inhibitors.

Non-apoptotic function of caspase-8 confers prostate cancer enzalutamide resistance via NF-κB activation

Caspase-8 is a unique member of caspases with a dual role in cell death and survival. Caspase-8 expression is often lost in some tumors, but increased in others, indicating a potential pro-survival function in cancer. By analyzing transcriptome of enzalutamide-resistant prostate cancer cells, we found that resistance was conferred by a mild caspase-8 upregulation that in turn led to NF-κB activation and the subsequent upregulation of the downstream IL-8. Mechanistically, we found that the pro-survival and enzalutamide-resistance-promoting features of caspase-8 were independent of its proteolytic activity, using a catalytically-inactive caspase-8 mutant. We further demonstrated that caspase-8 pro-apoptotic function was inhibited via cFLIP binding. Moreover, high caspase-8 expression was correlated with a worse prognosis in prostate cancer patients. Collectively, our work demonstrates that enzalutamide-resistance is mediated by caspase-8 upregulation and the consequent increase in NF-κB/IL-8 mediated survival signaling, highlighting caspase-8 and NF-κB as potential therapeutic targets to overcome enzalutamide-resistance in CRPC.

Proteasome inhibition triggers the formation of TRAIL receptor 2 platforms for caspase-8 activation that accumulate in the cytosol

Cancer cells that are resistant to Bax/Bak-dependent intrinsic apoptosis can be eliminated by proteasome inhibition. Here, we show that proteasome inhibition induces the formation of high molecular weight platforms in the cytosol that serve to activate caspase-8. The activation complexes contain Fas-associated death domain (FADD) and receptor-interacting serine/threonine-protein kinase 1 (RIPK1). Furthermore, the complexes contain TRAIL-receptor 2 (TRAIL-R2) but not TRAIL-receptor 1 (TRAIL-R1). While RIPK1 inhibition or depletion did not affect proteasome inhibitor-induced cell death, TRAIL-R2 was found essential for efficient caspase-8 activation, since the loss of TRAIL-R2 expression abrogated caspase processing, significantly reduced cell death, and promoted cell re-growth after drug washout. Overall, our study provides novel insight into the mechanisms by which proteasome inhibition eliminates otherwise apoptosis-resistant cells, and highlights the crucial role of a ligand-independent but TRAIL-R2-dependent activation mechanism for caspase-8 in this scenario.

TRAIL-receptor 2-a novel negative regulator of p53

TNF-related apoptosis-inducing ligand (TRAIL) receptor 2 (TRAIL-R2) can induce apoptosis in cancer cells upon crosslinking by TRAIL. However, TRAIL-R2 is highly expressed by many cancers suggesting pro-tumor functions. Indeed, TRAIL/TRAIL-R2 also activate pro-inflammatory pathways enhancing tumor cell invasion, migration, and proliferation. In addition, nuclear TRAIL-R2 (nTRAIL-R2) promotes malignancy by inhibiting miRNA let-7-maturation. Here, we show that TRAIL-R2 interacts with the tumor suppressor protein p53 in the nucleus, assigning a novel pro-tumor function to TRAIL-R2. Knockdown of TRAIL-R2 in p53 wild-type cells increases the half-life of p53 and the expression of its target genes, whereas its re-expression decreases p53 protein levels. Interestingly, TRAIL-R2 also interacts with promyelocytic leukemia protein (PML), a major regulator of p53 stability. PML-nuclear bodies are also the main sites of TRAIL-R2/p53 co-localization. Notably, knockdown or destruction of PML abolishes the TRAIL-R2-mediated regulation of p53 levels. In summary, our finding that nTRAIL-R2 facilitates p53 degradation and thereby negatively regulates p53 target gene expression provides insight into an oncogenic role of TRAIL-R2 in tumorigenesis that particularly manifests in p53 wild-type tumors.

High tumour mutational burden and EGFR/MAPK pathway activation are therapeutic targets in metastatic porocarcinoma

BACKGROUND

Eccrine porocarcinoma (EPC) is a rare skin cancer arising from the eccrine sweat glands. Due to the lack of effective therapies, metastasis is associated with a high mortality rate.

OBJECTIVES

To investigate the drivers of EPC progression.

METHODS

We carried out genomic and transcriptomic profiling of metastatic EPC (mEPC), validation of the observed alterations in an EPC patient-derived cell line, confirmation of relevant observations in a large patient cohort of 30 tumour tissues, and successful treatment of a patient with mEPC under the identified treatment regimens.

RESULTS

mEPC was characterized by a high tumour mutational burden (TMB) with an ultraviolet signature, widespread copy number alterations and gene expression changes that affected cancer-relevant cellular processes such as cell cycle regulation and proliferation, including a pathogenic TP53 (tumour protein 53) mutation, a copy number deletion in the CDKN2A (cyclin dependent kinase inhibitor 2A) region and a CTNND1/PAK1 [catenin delta 1/p21 (RAC1) activated kinase 1] gene fusion. The overexpression of EGFR (epidermal growth factor receptor), PAK1 and MAP2K1 (mitogen-activated protein kinase kinase 1; also known as MEK1) genes translated into strong protein expression and respective pathway activation in the tumour tissue. Furthermore, a patient-derived cell line was sensitive to EGFR and MEK inhibition, confirming the functional relevance of the pathway activation. Immunohistochemistry analyses in a large patient cohort showed the relevance of the observed changes to the pathogenesis of EPC. Our results indicate that mEPC should respond to immune or kinase inhibitor therapy. Indeed, the advanced disease of our index patient was controlled by EGFR-directed therapy and immune checkpoint inhibition for more than 2 years.

CONCLUSIONS

Molecular profiling demonstrated high TMB and EGFR/MAPK pathway activation to be novel therapeutic targets in mEPC.

CYLD Inhibits the Development of Skin Squamous Cell Tumors in Immunocompetent Mice

Cylindromatosis (CYLD) is a deubiquitinase (DUB) enzyme that was initially characterized as a tumor suppressor of adnexal skin tumors in patients with CYLD syndrome. Later, it was also shown that the expression of functionally inactive mutated forms of CYLD promoted tumor development and progression of non-melanoma skin cancer (NMSC). However, the ability of wild-type CYLD to inhibit skin tumorigenesis in vivo in immunocompetent mice has not been proved. Herein, we generated transgenic mice that express the wild type form of CYLD under the control of the keratin 5 (K5) promoter (K5-CYLDwt mice) and analyzed the skin properties of these transgenic mice by WB and immunohistochemistry, studied the survival and proliferating characteristics of primary keratinocytes, and performed chemical skin carcinogenesis experiments. As a result, we found a reduced activation of the nuclear factor kappa B (NF-κB) pathway in the skin of K5-CYLDwt mice in response to tumor necrosis factor-α (TNF-α); accordingly, when subjected to insults, K5-CYLDwt keratinocytes are prone to apoptosis and are protected from excessive hyperproliferation. Skin carcinogenesis assays showed inhibition of tumor development in K5-CYLDwt mice. As a mechanism of this tumor suppressor activity, we found that a moderate increase in CYLD expression levels reduced NF-κB activation, which favored the differentiation of tumor epidermal cells and inhibited its proliferation; moreover, it decreased tumor angiogenesis and inflammation. Altogether, our results suggest that increased levels of CYLD may be useful for anti-skin cancer therapy.

Intrinsic drug potential of oxazolo[5,4-d]pyrimidines and oxazolo[4,5-d]pyrimidines

The oxazole and pyrimidine rings are widely displayed in natural products and synthetic molecules. They are known as the prime skeletons for drug discovery. On the account of structural and chemical diversity, oxazole and pyrimidine-based molecules, as central scaffolds, not only provide different types of interactions with various receptors and enzymes, showing broad biological activities, but also occupy a core position in medicinal chemistry, showing their importance for development and discovery of newer potential therapeutic agents (Curr Top Med Chem, 16, 2016, 3133; Int J Pharm Pharm Sci, 8, 2016, 8; BMC Chem, 13, 2019, 44). For a long time, relatively little attention has been paid to their fused rings that are oxazolopyrimidines, whose chemical structure is similar to that of natural purines because probably none of these compounds were found in natural products or their biological activities turned out to be unexpressed (Bull Chem Soc Jpn, 43, 1970, 187). Recently, however, a significant number of studies have been published on the biological properties of oxazolo[5,4-d]pyrimidines, showing their significant activity as agonists and antagonists of signaling pathways involved in the regulation of the cell life cycle, whereas oxazolo[4,5-d]pyrimidines, on the contrary, represent a poorly studied class of compounds. Limited access to this scaffold has resulted in a corresponding lack of biological research (Eur J Organ Chem, 18, 2018, 2148). Actually, oxazolo[5,4-d]pyrimidine is a versatile scaffold used for the design of bioactive ligands against enzymes and receptors. This review focuses on biological targets and associated pathogenetic mechanisms, as well as pathological disorders that can be modified by well-known oxazolopyrimidines that have been proven to date. Many molecular details of these processes are omitted here, which the interested reader will find in the cited literature. This work also does not cover the methods for the synthesis of the oxazolopyrimidines, which are exhaustively described by De Coen et al. (Eur J Organ Chem, 18, 2018, 2148). The review as well does not discuss the structure-activity relationship, which is described in detail in the original works and deliberately, whenever possible, cites not primary sources, but mostly relevant review articles, so that the reader who wants to delve into a particular problem will immediately receive more complete information. It is expected that the information presented in this review will help readers better understand the purpose of the development of oxazolopyrimidines and the possibility of their development as drugs for the treatment of a wide range of diseases.

Modes of Regulated Cell Death in Cancer

Cell suicide pathways, termed regulated cell death (RCD), play a critical role in organismal development, homeostasis, and pathogenesis. Here, we provide an overview of key RCD modalities, namely apoptosis, entosis, necroptosis, pyroptosis, and ferroptosis. We explore how various RCD modules serve as a defense mechanism against the emergence of cancer as well as the manner in which they can be exploited to drive oncogenesis. Furthermore, we outline current therapeutic agents that activate RCD and consider novel RCD-based strategies for tumor elimination. SIGNIFICANCE: A variety of antitumor therapeutics eliminate cancer cells by harnessing the devastating potential of cellular suicide pathways, emphasizing the critical importance of RCD in battling cancer. This review supplies a mechanistic perspective of distinct RCD modalities and explores the important role they play in tumorigenesis. We discuss how RCD modules serve as a double-edged sword as well as novel approaches aimed at selectively manipulating RCD for tumor eradication.

The role of caspase-8 in the tumor microenvironment of ovarian cancer

Caspase-8 is an aspartate-specific cysteine protease, which is best known for its apoptotic functions. Caspase-8 is placed at central nodes of multiple signal pathways, regulating not only the cell cycle but also the invasive and metastatic cell behavior, the immune cell homeostasis and cytokine production, which are the two major components of the tumor microenvironment (TME). Ovarian cancer often has dysregulated caspase-8 expression, leading to imbalance between its apoptotic and non-apoptotic functions within the tumor and the surrounding milieu. The downregulation of caspase-8 in ovarian cancer seems to be linked to high aggressiveness with chronic inflammation, immunoediting, and immune resistance. Caspase-8 plays therefore an essential role not only in the primary tumor cells but also in the TME by regulating the immune response, B and T lymphocyte activation, and macrophage differentiation and polarization. The switch between M1 and M2 macrophages is possibly associated with changes in the caspase-8 expression. In this review, we are discussing the non-apoptotic functions of caspase-8, highlighting this protein as a modulator of the immune response and the cytokine composition in the TME. Considering the low survival rate among ovarian cancer patients, it is urgently necessary to develop new therapeutic strategies to optimize the response to the standard treatment. The TME is highly heterogenous and provides a variety of opportunities for new drug targets. Given the variety of roles of caspase-8 in the TME, we should focus on this protein in the development of new therapeutic strategies against the TME of ovarian cancer.