p53-independent Noxa induction by cisplatin is regulated by ATF3/ATF4 in head and neck squamous cell carcinoma cells

ONC212 enhances YM155 cytotoxicity by triggering SLC35F2 expression and NOXA-dependent MCL1 degradation in acute myeloid leukemia cells

Although the anticancer activity of ONC212 has been reported, the precise mechanism underlying its apoptotic effects remains unclear. In this study, we investigated the apoptotic mechanism of ONC212 in acute myeloid leukemia (AML) cells. ONC212 induces apoptosis, MCL1 downregulation, and mitochondrial depolarization in AML U937 cells. Ectopic MCL1 expression alleviates mitochondria-mediated apoptosis in ONC212-treated U937 cells. ONC212 triggers AKT phosphorylation, inducing NOX4-dependent ROS production and promoting HuR transcription. HuR-mediated ATF4 mRNA stabilization stimulates NOXA and SLC35F2 expression; ONC212-induced upregulation of NOXA leads to MCL1 degradation. The synergistic effect of ONC212 on YM155 cytotoxicity was dependent on increased SLC35F2 expression. In addition, YM155 feedback facilitated the activation of the ONC212-induced signaling pathway. A similar mechanism explains ONC212- and ONC212/YM155-induced AML HL-60 cell death. The continuous treatment of U937 cells with the benzene metabolite hydroquinone (HQ) generated U937/HQ cells, exhibiting enhanced responsiveness to the cytotoxic effects of ONC212. In U937/HQ cells, ONC212 triggered apoptosis through NOXA-mediated MCL1 downregulation, enhancing YM155 cytotoxicity. Collectively, our data suggested that ONC212 upregulated SLC35F2 expression and triggered NOXA-mediated MCL1 degradation in U937, U937/HQ, and HL-60 cells by activating the AKT/NOX4/HuR/ATF4 pathway. The ONC212-induced signaling pathway showed anti-AML activity and enhanced YM155 cytotoxicity.

Discovery of a Novel Series of Homo sapiens Caseinolytic Protease P Agonists for Colorectal Adenocarcinoma Treatment via ATF3-Dependent Integrated Stress Response

Homo sapiens caseinolytic protease P (HsClpP) activation is a promising strategy for colon cancer treatment. In this study, CCG1423 was identified as a selective activator of HsClpP. After optimization, NCA029 emerged as the most potent compound, with an EC50 of 0.2 μM against HsClpP. Molecular dynamics revealed that the affinity of NCA029 for the YYW aromatic network is crucial for its selectivity toward HsClpP. Furthermore, NCA029 displayed favorable pharmacokinetics and safety profiles and significantly inhibited tumor growth in HCT116 xenografts, resulting in 83.6% tumor inhibition. Mechanistically, NCA029 targeted HsClpP, inducing mitochondrial dysfunction and activating the ATF3-dependent integrated stress response, ultimately causing cell death in colorectal adenocarcinoma. These findings highlight NCA029 as an effective HsClpP activator with potential for colon cancer therapy.

Clinical and therapeutical significances of the cluster and signature based on oxidative stress for osteosarcoma

BACKGROUND

It is of great clinical significance to find out the ideal tumor biomarkers and therapeutic targets to improve the prognosis of patients with osteosarcoma (OS). Oxidative stress (OXS) can directly target intracellular macromolecules and exhibit dual effects of tumor promotion and suppression.

METHODS

OXS-related genes (OXRGs) were extracted from public databases, including TARGET and GEO. Univariate Cox regression analysis, Random Survival Forest algorithm, and LASSO regression were performed to identify prognostic genes and establish the OXS-signature. The efficacy of the OXS-signature was further evaluated by Kaplan-Meier curves and timeROC package. Evaluation of immunological characteristics was achieved based on ESTIMATE algorithm and ssGSEA. Submap algorithm was used to explore the response to anti-PD1 and anti-CTLA4 therapy for OS. Drug response prediction was conducted by using pRRophetic package. The expression values of related genes in the OXS-signature were detected with PCR assays.

RESULTS

Two OXS-clusters were identified for OS, with remarkable differences of clusters presented in prognosis. Kyoto Encyclopedia of Genes Genomes (KEGG) analysis showed that differentially expressed genes (DEGs) between the OXS-clusters were significantly enriched in several immune-related pathways. Patients with lower OS-scores attained better clinical outcomes, and presented more sensitivity to ICB therapy. By contrast, OS patients with higher OS-scores revealed more sensitivity to certain drugs. Furthermore, critical genes, RHBDL2 and CGREF1 from the model, were significantly higher expressed in OS cell lines.

CONCLUSIONS

Our study identified the clusters and signature based on OXS, which would lay the foundation for molecular experimental research, disease prevention and treatment of OS.

Clarithromycin overcomes stromal cell-mediated drug resistance against proteasome inhibitors in myeloma cells via autophagy flux blockage leading to high NOXA expression

We previously reported that macrolide antibiotics, such as clarithromycin (CAM), blocked autophagy flux, and simultaneous proteasome and autophagy inhibition by bortezomib (BTZ) plus CAM resulted in enhanced apoptosis induction in multiple myeloma (MM) cells via increased endoplasmic reticulum (ER) stress loading. However, in actual therapeutic settings, cell adhesion-mediated drug resistance between bone marrow stromal cells (BMSC) and MM cells has been known to be a barrier to treatment. To investigate whether CAM could enhance BTZ-induced cytotoxicity in MM cells under direct cell adhesion with BMSC, we established a co-culture system of EGFP-labeled MM cells with BMSC. The cytotoxic effect of BTZ on MM cells was diminished by its interaction with BMSC; however, the attenuated cytotoxicity was recovered by the co-administration of CAM, which upregulates ER stress loading and NOXA expression. Knockout of NOXA in MM cells canceled the enhanced cell death by CAM, indicating that NOXA is a key molecule for cell death induction by the co-administration of CAM. Since NOXA is degraded by autophagy as well as proteasomes, blocking autophagy with CAM resulted in the sustained upregulation of NOXA in MM cells co-cultured with BMSC in the presence of BTZ. Our data suggest that BMSC-associated BTZ resistance is mediated by the attenuation of ER stress loading. However, the addition of CAM overcomes BMSC-associated resistance via upregulation of NOXA by concomitantly blocking autophagy-mediated NOXA degradation and transcriptional activation of NOXA by ER stress loading.

Competing endogenous RNAs in human astrocytes: crosstalk and interacting networks in response to lipotoxicity

Neurodegenerative diseases (NDs) are characterized by a progressive deterioration of neuronal function, leading to motor and cognitive damage in patients. Astrocytes are essential for maintaining brain homeostasis, and their functional impairment is increasingly recognized as central to the etiology of various NDs. Such impairment can be induced by toxic insults with palmitic acid (PA), a common fatty acid, that disrupts autophagy, increases reactive oxygen species, and triggers inflammation. Although the effects of PA on astrocytes have been addressed, most aspects of the dynamics of this fatty acid remain unknown. Additionally, there is still no model that satisfactorily explains how astroglia goes from being neuroprotective to neurotoxic. Current incomplete knowledge needs to be improved by the growing field of non-coding RNAs (ncRNAs), which is proven to be related to NDs, where the complexity of the interactions among these molecules and how they control other RNA expressions need to be addressed. In the present study, we present an extensive competing endogenous RNA (ceRNA) network using transcriptomic data from normal human astrocyte (NHA) cells exposed to PA lipotoxic conditions and experimentally validated data on ncRNA interaction. The obtained network contains 7 lncRNA transcripts, 38 miRNAs, and 239 mRNAs that showed enrichment in ND-related processes, such as fatty acid metabolism and biosynthesis, FoxO and TGF-β signaling pathways, prion diseases, apoptosis, and immune-related pathways. In addition, the transcriptomic profile was used to propose 22 potential key controllers lncRNA/miRNA/mRNA axes in ND mechanisms. The relevance of five of these axes was corroborated by the miRNA expression data obtained in other studies. MEG3 (ENST00000398461)/hsa-let-7d-5p/ATF6B axis showed importance in Parkinson's and late Alzheimer's diseases, while AC092687.3/hsa-let-7e-5p/[SREBF2, FNIP1, PMAIP1] and SDCBP2-AS1 (ENST00000446423)/hsa-miR-101-3p/MAPK6 axes are probably related to Alzheimer's disease development and pathology. The presented network and axes will help to understand the PA-induced mechanisms in astrocytes, leading to protection or injury in the CNS under lipotoxic conditions as part of the intricated cellular regulation influencing the pathology of different NDs. Furthermore, the five corroborated axes could be considered study targets for new pharmacologic treatments or as possible diagnostic molecules, contributing to improving the quality of life of millions worldwide.

Macrophages originated IL-33/ST2 inhibits ferroptosis in endometriosis via the ATF3/SLC7A11 axis

Endometriosis is a gynecological inflammatory disease that is linked with immune cells, specifically macrophages. IL-33 secreted from macrophages is known to accelerate the progression of endometriosis. The periodic and repeated bleeding that occurs in women with endometriosis leads to excess iron in the microenvironment that is conducive to ferroptosis, a process related to intracellular ROS production, lipid peroxidation and mitochondrial damage. It is suggested that eESCs may specifically be able to inhibit ferroptosis. However, it is currently unclear whether IL-33 directly regulates ferroptosis to influence the disease course in endometriosis. In this study, eESCs co-cultured with macrophages or stimulated with IL-33/ST2 were observed to have increased cell viability and migration. Additionally, IL-33/ST2 decreased intracellular iron levels and lipid peroxidation in eESCs exposed to erastin treatment. Furthermore, IL-33/ST2 treatment resulted in a notable upregulation in SLC7A11 expression in eESCs due to the downregulation of negative transcription factor ATF3, thereby suppressing ferroptosis. The P38/JNK pathway activated by IL-33/ST2 was also found to inhibit the transcription factor ATF3. Therefore, we concluded that IL-33/ST2 inhibits the ATF3-mediated reduction in SLC7A11 transcript levels via the P38/JNK pathway. The findings reveal that macrophage-derived IL-33 upregulates SLC7A11 in eESCs through the p38/JNK/ATF3 pathway, ultimately resulting in protection against ferroptosis in eESCs. Moreover, we conducted an experiment using endometriosis model mice that showed that a combination of IL-33-Ab and erastin treatment alleviated the disease, showing the promise of combining immunotherapy and ferroptosis therapy.

Stress and Liver Fibrogenesis: Understanding the Role and Regulation of Stress Response Pathways in Hepatic Stellate Cells

Stress response pathways are crucial for cells to adapt to physiological and pathologic conditions. Increased transcription and translation in response to stimuli place a strain on the cell, necessitating increased amino acid supply, protein production and folding, and disposal of misfolded proteins. Stress response pathways, such as the unfolded protein response (UPR) and the integrated stress response (ISR), allow cells to adapt to stress and restore homeostasis; however, their role and regulation in pathologic conditions, such as hepatic fibrogenesis, are unclear. Liver injury promotes fibrogenesis through activation of hepatic stellate cells (HSCs), which produce and secrete fibrogenic proteins to promote tissue repair. This process is exacerbated in chronic liver disease, leading to fibrosis and, if unchecked, cirrhosis. Fibrogenic HSCs exhibit activation of both the UPR and ISR, due in part to increased transcriptional and translational demands, and these stress responses play important roles in fibrogenesis. Targeting these pathways to limit fibrogenesis or promote HSC apoptosis is a potential antifibrotic strategy, but it is limited by our lack of mechanistic understanding of how the UPR and ISR regulate HSC activation and fibrogenesis. This article explores the role of the UPR and ISR in the progression of fibrogenesis, and highlights areas that require further investigation to better understand how the UPR and ISR can be targeted to limit hepatic fibrosis progression.

Suppression of Ah Receptor (AhR) increases the aggressiveness of TNBC cells and 11-Cl-BBQ-activated AhR inhibits their growth

Triple-negative breast cancer (TNBC) represents around 15% of the 2.26 million breast cancers diagnosed worldwide annually and has the worst outcome. Despite recent therapeutic advances, there remains a lack of targeted therapies for this breast cancer subtype. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor with biological roles in regulating development, xenobiotic metabolism, cell cycle progression and cell death. AhR activation by select ligands can promote tumor suppression in multiple cancer types. AhR can negatively regulate the activity of different oncogenic signaling pathways and can directly upregulate tumor suppressor genes such as p27Kip1. To determine the role of AhR in TNBC, we generated AhR-deficient cancer cells and investigated the impact of AhR loss on TNBC cell growth phenotypes. We found that AhR-deficient MDA-MB-468 TNBC cells have increased proliferation and formed significantly more colonies compared to AhR expressing cells. These cells without AhR expression grew aggressively in vivo. To determine the molecular targets driving this phenotype, we performed transcriptomic profiling in AhR expressing and AhR knockout MDA-MB-468 cells and identified tyrosine receptor kinases, as well as other genes involved in proliferation, survival and clonogenicity that are repressed by AhR. In order to determine therapeutic targeting of AhR in TNBC, we investigated the anti-cancer effects of the novel AhR ligand 11-chloro-7H-benzimidazo[2,1-a]benzo[de]iso-quinolin-7-one (11-Cl-BBQ), which belongs to a class of high affinity, rapidly metabolized AhR ligands called benzimidazoisoquinolines (BBQs). 11-Cl-BBQ induced AhR-dependent cancer cell-selective growth inhibition and strongly inhibited colony formation in TNBC cells.

Induction of Aryl Hydrocarbon Receptor-Mediated Cancer Cell-Selective Apoptosis in Triple-Negative Breast Cancer Cells by a High-Affinity Benzimidazoisoquinoline

Triple-negative breast cancer (TNBC) remains a disease with a paucity of targeted treatment opportunities. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is involved in a wide range of physiological processes, including the sensing of xenobiotics, immune function, development, and differentiation. Different small-molecule AhR ligands drive strikingly varied cellular and organismal responses. In certain cancers, AhR activation by select small molecules induces cell cycle arrest or apoptosis via activation of tumor-suppressive transcriptional programs. AhR is expressed in triple-negative breast cancers, presenting a tractable therapeutic opportunity. Here, we identify a novel ligand of the aryl hydrocarbon receptor that potently and selectively induces cell death in triple-negative breast cancer cells and TNBC stem cells via the AhR. Importantly, we found that this compound, Analog 523, exhibits minimal cytotoxicity against multiple normal human primary cells. Analog 523 represents a high-affinity AhR ligand with potential for future clinical translation as an anticancer agent.

Tumor-Suppressive Functions of the Aryl Hydrocarbon Receptor (AhR) and AhR as a Therapeutic Target in Cancer

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in regulating a wide range of biological responses. A diverse array of xenobiotics and endogenous small molecules bind to the receptor and drive unique phenotypic responses. Due in part to its role in mediating toxic responses to environmental pollutants, AhR activation has not been traditionally viewed as a viable therapeutic approach. Nonetheless, the expression and activation of AhR can inhibit the proliferation, migration, and survival of cancer cells, and many clinically approved drugs transcriptionally activate AhR. Identification of novel select modulators of AhR-regulated transcription that promote tumor suppression is an active area of investigation. The development of AhR-targeted anticancer agents requires a thorough understanding of the molecular mechanisms driving tumor suppression. Here, we summarized the tumor-suppressive mechanisms regulated by AhR with an emphasis on the endogenous functions of the receptor in opposing carcinogenesis. In multiple different cancer models, the deletion of AhR promotes increased tumorigenesis, but a precise understanding of the molecular cues and the genetic targets of AhR involved in this process is lacking. The intent of this review was to synthesize the evidence supporting AhR-dependent tumor suppression and distill insights for development of AhR-targeted cancer therapeutics.

A Ubiquitination Cascade Regulating the Integrated Stress Response and Survival in Carcinomas

Systematic identification of signaling pathways required for the fitness of cancer cells will facilitate the development of new cancer therapies. We used gene essentiality measurements in 1,086 cancer cell lines to identify selective coessentiality modules and found that a ubiquitin ligase complex composed of UBA6, BIRC6, KCMF1, and UBR4 is required for the survival of a subset of epithelial tumors that exhibit a high degree of aneuploidy. Suppressing BIRC6 in cell lines that are dependent on this complex led to a substantial reduction in cell fitness in vitro and potent tumor regression in vivo. Mechanistically, BIRC6 suppression resulted in selective activation of the integrated stress response (ISR) by stabilization of the heme-regulated inhibitor, a direct ubiquitination target of the UBA6/BIRC6/KCMF1/UBR4 complex. These observations uncover a novel ubiquitination cascade that regulates ISR and highlight the potential of ISR activation as a new therapeutic strategy.

SIGNIFICANCE

We describe the identification of a heretofore unrecognized ubiquitin ligase complex that prevents the aberrant activation of the ISR in a subset of cancer cells. This provides a novel insight on the regulation of ISR and exposes a therapeutic opportunity to selectively eliminate these cancer cells. See related commentary Leli and Koumenis, p. 535. This article is highlighted in the In This Issue feature, p. 517.

Exploration of prognostic biomarkers in head and neck squamous cell carcinoma microenvironment from TCGA database

Background

Immune checkpoint blockade (ICB) therapies have redefined human cancer treatment, including for head and neck squamous cell carcinoma (HNSCC). However, clinical responses to various immune checkpoint inhibitors are often accompanied by immune-related adverse events (irAEs). Therefore, it is crucial to obtain a comprehensive understanding of the association between different immune tumor microenvironments (TMEs) and the immunotherapeutic response.

Methods

The research data were obtained from The Cancer Genome Atlas (TCGA) database. We applied RNA-seq genomic data from tumor biopsies to assess the immune TME in HNSCC. As the TME is a heterogeneous system that is highly associated with HNSCC progression and clinical outcome, we relied on the Estimation of Stromal and Immune cells in Malignant Tumor tissues using Expression data (ESTIMATE) algorithm to calculate immune and stromal scores that were evaluated based on the immune or stromal components in the TME. Then, the Tumor Immune Dysfunction and Exclusion algorithm (TIDE) was used to predict the benefits of ICB to each patient. Finally, we identified specific prognostic tumor-infiltrating immune cells (TIICs) by quantifying the cellular composition of the immune response in HNSCC and its association to survival outcome, using the CIBERSORT algorithm.

Results

Utilizing the HNSCC cohort of the TCGA database and TIDE and ESTIMATE algorithm-derived immune scores, we obtained a list of microenvironment-associated lncRNAs that predicted different clinical outcomes in HNSCC patients. We validated these correlations in a different HNSCC cohort available from the TCGA database and provided insight into the prediction of response to ICB therapies in HNSCC.

Conclusions

This study confirmed that CD8⁺ T cells were significantly associated with better survival in HNSCC and verified that the top five significantly mutated genes (SMGs) in the TCGA HNSCC cohort were TP53, TTN, FAT1, CDKN2A, and MUC16. A high level of CD8⁺ T cells and high immune and stroma scores corresponded to a better survival probability in HNSCC.

The NAMPT Inhibitor FK866 Increases Metformin Sensitivity in Pancreatic Cancer Cells

Pancreatic cancer (pancreatic ductal adenocarcinoma: PDAC) is one of the most aggressive neoplastic diseases. Metformin use has been associated with reduced pancreatic cancer incidence and better survival in diabetics. Metformin has been shown to inhibit PDAC cells growth and survival, both in vitro and in vivo. However, clinical trials using metformin have failed to reduce pancreatic cancer progression in patients, raising important questions about molecular mechanisms that protect tumor cells from the antineoplastic activities of metformin. We confirmed that metformin acts through inhibition of mitochondrial complex I, decreasing the NAD⁺/NADH ratio, and that NAD⁺/NADH homeostasis determines metformin sensitivity in several cancer cell lines. Metabolites that can restore the NAD⁺/NADH ratio caused PDAC cells to be resistant to metformin. In addition, metformin treatment of PDAC cell lines induced a compensatory NAMPT expression, increasing the pool of cellular NAD⁺. The NAMPT inhibitor FK866 sensitized PDAC cells to the antiproliferative effects of metformin in vitro and decreased the cellular NAD⁺ pool. Intriguingly, FK866 combined with metformin increased survival in mice bearing KP4 cell line xenografts, but not in mice with PANC-1 cell line xenografts. Transcriptome analysis revealed that the drug combination reactivated genes in the p53 pathway and oxidative stress, providing new insights about the mechanisms leading to cancer cell death.

The Pt(S-pr-thiosal)2 and BCL1 Leukemia Lymphoma: Antitumor Activity In Vitro and In Vivo

B cell malignancies are, despite the development of targeted therapy in a certain percentage of the patients still a chronic disease with relapses, requiring multiple lines of therapy. Regimens that include platinum-based drugs provide high response rates in different B cell lymphomas, high-risk chronic lymphocytic leukemia (CLL), and devastating complication of CLL, Richter’s syndrome. The aim of this study was to explore the potential antitumor activity of previously synthetized platinum(IV) complex with alkyl derivatives of thyosalicilc acid, PtCl2(S-pr-thiosal)2, toward murine BCL1 cells and to delineate possible mechanisms of action. The PtCl2(S-pr-thiosal)2 reduced the viability of BCL1 cells in vitro but also reduced the growth of metastases in the leukemia lymphoma model in BALB/c mice. PtCl2(S-pr-thiosal)2 induced apoptosis, inhibited proliferation of BCL1 cells, and induced cell cycle disturbance. Treatment of BCL1 cells with PtCl2(S-pr-thiosal)2 inhibited expression of cyclin D3 and cyclin E and enhanced expression of cyclin-dependent kinase inhibitors p16, p21, and p27 resulting in cell cycle arrest in the G1 phase, reduced the percentage of BCL1 cells in the S phase, and decreased expression of Ki-67. PtCl2(S-pr-thiosal)2 treatment reduced expression of phosphorylated STAT3 and downstream-regulated molecules associated with cancer stemness and proliferation, NANOG, cyclin D3, and c-Myc, and expression of phosphorylated NFκB in vitro and in vivo. In conclusion, PtCl2(S-pr-thiosal)2 reduces STAT3 and NFκB phosphorylation resulting in inhibition of BCL1 cell proliferation and the triggering of apoptotic cell death.

Celastrol Inhibited Human Esophageal Cancer by Activating DR5-Dependent Extrinsic and Noxa/Bim-Dependent Intrinsic Apoptosis

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest digestive system cancers worldwide lacking effective therapeutic strategies. Recently, it has been found that the natural product celastrol plays an anti-cancer role in several human cancers by inducing cell cycle arrest and apoptosis. However, it remains elusive whether and how celastrol suppresses tumor growth of ESCC. In the present study, for the first time, we demonstrated that celastrol triggered both extrinsic and intrinsic apoptosis pathways to diminish the tumor growth of ESCC in vivo and in vitro. Mechanistic studies revealed that celastrol coordinatively induced DR5-dependent extrinsic apoptosis and Noxa-dependent intrinsic apoptosis through transcriptional activation of ATF4 in ESCC cells. Furthermore, we found that the FoxO3a-Bim pathway was involved in the intrinsic apoptosis of ESCC cells induced by celastrol. Our study elucidated the tumor-suppressive efficacy of celastrol on ESCC and revealed a previously unknown mechanism underlying celastrol-induced apoptosis, highlighting celastrol as a promising apoptosis-inducing therapeutic strategy for ESCC.

CCDC106 promotes the proliferation and invasion of ovarian cancer cells by suppressing p21 transcription through a p53-independent pathway

Ovarian cancers are the major cause of mortality for women worldwide. This study was aimed to elucidate the biological activities of CCDC106 in the proliferation and invasion of mutant p53 and of wild-type p53 ovarian cancer cells. CAOV3 (mutant p53) cells showed high expression levels of CCDC106, but it was expressed at low levels in SKOV3 (mutant p53) and in A2780 (wild-type p53) cells. The overexpression of CCDC106 promoted the expression of proliferation markers (cyclin family members), invasion and Epithelial-to-mesenchymal transition (EMT) markers (claudin-1, claudin-4, N-cadherin, snail, slug) while the knockdown of CCDC106 inhibited their expression in mutant p53 cells but not in wild-type p53 cells. Treatment with a CK2 inhibitor blocked the translocation of CCDC106 into the nuclei of mutant p53 cells. Immunoprecipitation assays confirmed that ATF4 is a potential binding partner of CCDC106. The overexpression of CCDC106 reduced p21 and p27 protein expression levels while treatment with an ATF4 siRNA rescued their expression. The overexpression of CCDC106 promoted colony formation and invasion of mutant p53 cells, which was suppressed by treatment with an ATF4 siRNA. Immunohistochemistry results showed that CCDC106 and ATF4 are expressed at high levels but p21 is expressed at low levels in FIGO III-IV stage and in mutant p53 ovarian cancer samples. A significant association between poor overall survival and high CCDC106 and ATF4 expression levels was observed in human ovarian cancer samples. In conclusion, CCDC106 promotes proliferation, invasion and EMT of mutant p53 ovarian cancer cells via the ATF4 mediated inhibition of p21.

The BCL-2 inhibitor ABT-199/venetoclax synergizes with proteasome inhibition via transactivation of the MCL-1 antagonist NOXA

Enhanced expression of anti-apoptotic B-cell lymphoma 2 (BCL-2) protein is frequent in cancer. Targeting of BCL-2 with the specific inhibitor ABT-199 (Venetoclax) has significant clinical activity in malignant diseases such as chronic lymphocytic leukemia and multiple myeloma. The small molecule drug ABT-199 mimics the pro-apoptotic BCL-2 homology domain 3 of BH3-only proteins and blocks the hydrophobic BC-groove in BCL-2. We have previously shown that ABT-199 synergizes with the proteasome inhibitor (PI) bortezomib in soft tissue sarcoma derived cells and cell lines to induce apoptosis. Synergistic apoptosis induction relies on the pore-forming effector BAX and expression of the pro-apoptotic BH3-only protein NOXA. Bortezomib augments expression of NOXA by blocking its proteasomal degradation. Interestingly, shown here for the first time, expression of NOXA is strongly enhanced by ABT-199 induced integrated stress response (ISR). ISR transcription factors ATF3 & ATF4 mediate transactivation of the BH3-only protein NOXA which specifically inhibits the anti-apoptotic MCL-1. Thus, NOXA potentiates the efficacy of the BCL-2 inhibitor ABT-199 by simultaneous inhibition of MCL-1. Hence, ABT-199 has a double impact by directly blocking anti-apoptotic BCL-2 and inhibiting MCL-1 via transactivated NOXA. By preventing degradation of NOXA PIs synergize with ABT-199. Synergism of ABT-199 and PIs therefore occurs on several, previously unexpected levels. This finding should prompt clinical evaluation of combinatorial regimens in further malignancies.

Advanced Strategies for Therapeutic Targeting of Wild-Type and Mutant p53 in Cancer

TP53 is a tumor suppressor gene that encodes a sequence-specific DNA-binding transcription factor activated by stressful stimuli; it upregulates target genes involved in growth suppression, cell death, DNA repair, metabolism, among others. TP53 is the most frequently mutated gene in tumors, with mutations not only leading to loss-of-function (LOF), but also gain-of-function (GOF) that promotes tumor progression, and metastasis. The tumor-specific status of mutant p53 protein has suggested it is a promising target for cancer therapy. We summarize the current progress of targeting wild-type and mutant p53 for cancer therapy through biotherapeutic and biopharmaceutical methods for (1) boosting p53 activity in cancer, (2) p53-dependent and p53-independent strategies for targeting p53 pathway functional restoration in p53-mutated cancer, (3) targeting p53 in immunotherapy, and (4) combination therapies targeting p53, p53 checkpoints, or mutant p53 for cancer therapy.

Epigenetic Priming with Decitabine Augments the Therapeutic Effect of Cisplatin on Triple-Negative Breast Cancer Cells through Induction of Proapoptotic Factor NOXA

Epigenetic alterations caused by aberrant DNA methylation have a crucial role in cancer development, and the DNA-demethylating agent decitabine, is used to treat hematopoietic malignancy. Triple-negative breast cancers (TNBCs) have shown sensitivity to decitabine; however, the underlying mechanism of its anticancer effect and its effectiveness in treating TNBCs are not fully understood. We analyzed the effects of decitabine on nine TNBC cell lines and examined genes associated with its cytotoxic effects. According to the effect of decitabine, we classified the cell lines into cell death (D)-type, growth inhibition (G)-type, and resistant (R)-type. In D-type cells, decitabine induced the expression of apoptotic regulators and, among them, NOXA was functionally involved in decitabine-induced apoptosis. In G-type cells, induction of the cyclin-dependent kinase inhibitor, p21, and cell cycle arrest were observed. Furthermore, decitabine enhanced the cytotoxic effect of cisplatin mediated by NOXA in D-type and G-type cells. In contrast, the sensitivity to cisplatin was high in R-type cells, and no enhancing effect by decitabine was observed. These results indicate that decitabine enhances the proapoptotic effect of cisplatin on TNBC cell lines that are less sensitive to cisplatin, indicating the potential for combination therapy in TNBC.

Co-existing TP53 and ARID1A mutations promote aggressive endometrial tumorigenesis

TP53 and ARID1A are frequently mutated across cancer but rarely in the same primary tumor. Endometrial cancer has the highest TP53-ARID1A mutual exclusivity rate. However, the functional relationship between TP53 and ARID1A mutations in the endometrium has not been elucidated. We used genetically engineered mice and in vivo genomic approaches to discern both unique and overlapping roles of TP53 and ARID1A in the endometrium. TP53 loss with oncogenic PIK3CA^H1047R in the endometrial epithelium results in features of endometrial hyperplasia, adenocarcinoma, and intraepithelial carcinoma. Mutant endometrial epithelial cells were transcriptome profiled and compared to control cells and ARID1A/PIK3CA mutant endometrium. In the context of either TP53 or ARID1A loss, PIK3CA mutant endometrium exhibited inflammatory pathway activation, but other gene expression programs differed based on TP53 or ARID1A status, such as epithelial-to-mesenchymal transition. Gene expression patterns observed in the genetic mouse models are reflective of human tumors with each respective genetic alteration. Consistent with TP53-ARID1A mutual exclusivity, the p53 pathway is activated following ARID1A loss in the endometrial epithelium, where ARID1A normally directly represses p53 pathway genes in vivo, including the stress-inducible transcription factor, ATF3. However, co-existing TP53-ARID1A mutations led to invasive adenocarcinoma associated with mutant ARID1A-driven ATF3 induction, reduced apoptosis, TP63+ squamous differentiation and invasion. These data suggest TP53 and ARID1A mutations drive shared and distinct tumorigenic programs in the endometrium and promote invasive endometrial cancer when existing simultaneously. Hence, TP53 and ARID1A mutations may co-occur in a subset of aggressive or metastatic endometrial cancers, with ARID1A loss promoting squamous differentiation and the acquisition of invasive properties.

Endometrial cancer is the most commonly diagnosed gynecologic malignancy in the United States, with annual incidence continuing to rise. Although the majority of endometrial cancer patients have an excellent overall prognosis if the disease is confined to the endometrium, myometrial invasion and metastasis to other sites correlate with poor survival. Here, we used genetically engineered mice, in vivo genomics, and public cancer patient data to understand the relationship between TP53 and ARID1A, two of the most commonly mutated genes in endometrial cancer, in the context of mutant PIK3CA. Mutations in TP53 and ARID1A change different aspects of endometrial cell health but also share some similarities. ARID1A mutations specifically promote cancer cells to invade nearby tissue, a hallmark of metastasis, associated with squamous differentiation. Mice with co-existing TP53 and ARID1A mutations developed more invasive disease. Our studies suggest that co-existing TP53 and ARID1A tumor mutations may promote invasion and metastasis.

The correlation between the expression of ATF4 and procalcitonin combined with the detection of RET mutation and the pathological stage and clinical prognosis of medullary thyroid carcinoma

To explore the correlation between the activating transcription factor 4 (ATF4) and procalcitonin (PCT) expressions combined with RET mutation and the pathological staging and clinical prognosis of sporadic medullary thyroid carcinoma (SMTC). Fifty cases (tumor tissue) of SMTC diagnosed by clinicopathology were collected and the patients with nodular goiter were selected as normal control. The RET mutation site was analyzed by detection kit and expressions of PCT and ATF4 in SMTC were analyzed by Western blot and immunohistochemistry. Multiple linear regression was used to analyze the correlation of risk factors (PCT or ATF4 expression, RET mutation, tumor differentiation, SMTC stage, lymphatic metastasis) for 5-year recurrence and survival of SMTC. The ATF4 and PCT expressions were significantly decreased and increased, respectively, with the increase of the SMTC stage. The most frequent mutation of RET gene in cancer tissue was M 22458A in exon 16. The ATF4 and PCT expressions, as well as RET mutation, were significantly associated with a 5-year recurrence, while the ATF4 expression was significantly related to better 5-year survival. ATF4 and PCT expressions combined with RET mutation are related to the clinical prognosis of SMTC and can predict SMTC staging.

Targeting the Integrated Stress Response in Cancer Therapy

The integrated stress response (ISR) is an evolutionarily conserved intra-cellular signaling network which is activated in response to intrinsic and extrinsic stresses. Various stresses are sensed by four specialized kinases, PKR-like ER kinase (PERK), general control non-derepressible 2 (GCN2), double-stranded RNA-dependent protein kinase (PKR) and heme-regulated eIF2α kinase (HRI) that converge on phosphorylation of serine 51 of eIF2α. eIF2α phosphorylation causes a global reduction of protein synthesis and triggers the translation of specific mRNAs, including activating transcription factor 4 (ATF4). Although the ISR promotes cell survival and homeostasis, when stress is severe or prolonged the ISR signaling will shift to regulate cellular apoptosis. We review the ISR signaling pathway, regulation and importance in cancer therapy.

APR-246 induces apoptosis and enhances chemo-sensitivity via activation of ROS and TAp73-Noxa signal in oesophageal squamous cell cancer with TP53 missense mutation

BACKGROUND

Mutations in p53, identified in 90% of oesophageal squamous cell carcinoma (ESCC), are associated with unfavourable prognosis and chemo-resistance. APR-246 induces apoptosis by restoring transcriptional ability of mutant p53, and may be a promising therapeutic agent to overcome chemo-resistance in ESCC.

METHODS

In ESCC cell lines differing in p53 status, we performed in vitro cell viability and apoptosis assays, evaluated reactive oxygen species (ROS) generation, and assessed signal changes by western blot after APR-246 administration with/without chemo-agent. Antitumour effects and signal changes were evaluated in in vivo experiments using xenograft and patient-derived xenograft (PDX) mouse models.

RESULTS

APR-246 administration induced significant apoptosis by upregulating p73 and Noxa via ROS induction in ESCC cell lines harbouring p53 missense mutations. Moreover, APR-246 plus chemotherapy exerted combined antitumour effects in ESCC with p53 missense mutations. This effect was also mediated through enhanced ROS activity, leading to massive apoptosis via upregulation of p73 and Noxa. These findings were confirmed by xenograft and PDX models with p53 mutant ESCC.

CONCLUSION

APR-246 strongly induced apoptosis by inducing ROS activity and p73-Noxa signalling, specifically in ESCC with p53 missense mutation. This antitumour effect was further enhanced by combination with 5-FU, which we first confirmed in ESCC preclinical model.

Platinum drugs and taxanes: can we overcome resistance?

Cancer therapy is aimed at the elimination of tumor cells and acts via the cessation of cell proliferation and induction of cell death. Many research publications discussing the mechanisms of anticancer drugs use the terms "cell death" and "apoptosis" interchangeably, given that apoptotic pathways are the most common components of the action of targeted and cytotoxic compounds. However, there is sound evidence suggesting that other mechanisms of drug-induced cell death, such as necroptosis, ferroptosis, autophagy, etc. may significantly contribute to the fate of cancer cells. Molecular cross-talks between apoptotic and nonapoptotic death pathways underlie the successes and the failures of therapeutic interventions. Here we discuss the nuances of the antitumor action of two groups of the widely used anticancer drugs, i.e., platinum salts and taxane derivatives. The available data suggest that intelligent interference with the choice of cell death pathways may open novel opportunities for cancer treatment.

Fangchinoline Inhibits Human Esophageal Cancer by Transactivating ATF4 to Trigger Both Noxa-Dependent Intrinsic and DR5-Dependent Extrinsic Apoptosis

Esophageal squamous cell carcinoma (ESCC) is a recalcitrant cancer. The Chinese herbal monomer fangchinoline (FCL) has been reported to have anti-tumor activity in several human cancer cell types. However, the therapeutic efficacy and underlying mechanism on ESCC remain to be elucidated. In the present study, for the first time, we demonstrated that FCL significantly suppressed the growth of ESCC both in vitro and in vivo. Mechanistic studies revealed that FCL-induced G1 phase cell-cycle arrest in ESCC which is dependent on p21 and p27. Moreover, we found that FCL coordinatively triggered Noxa-dependent intrinsic apoptosis and DR5-dependent extrinsic apoptosis by transactivating ATF4, which is a novel mechanism. Our findings elucidated the tumor-suppressive efficacy and mechanisms of FCL and demonstrated FCL is a potential anti-ESCC agent.

Activation of the Integrated Stress Response and ER Stress Protect from Fluorizoline-Induced Apoptosis in HEK293T and U2OS Cell Lines

The prohibitin (PHB)-binding compound fluorizoline as well as PHB-downregulation activate the integrated stress response (ISR) in HEK293T and U2OS human cell lines. This activation is denoted by phosphorylation of eIF2α and increases in ATF4, ATF3, and CHOP protein levels. The blockage of the activation of the ISR by overexpression of GRP78, as well as an increase in IRE1 activity, indicate the presence of ER stress after fluorizoline treatment. The inhibition of the ER stress response in HEK293T and U2OS led to increased sensitivity to fluorizoline-induced apoptosis, indicating a pro-survival role of this pathway after fluorizoline treatment in these cell lines. Fluorizoline induced an increase in calcium concentration in the cytosol and the mitochondria. Finally, two different calcium chelators reduced fluorizoline-induced apoptosis in U2OS cells. Thus, we have found that fluorizoline causes increased ER stress and activation of the integrated stress response, which in HEK293T and U2OS cells are protective against fluorizoline-induced apoptosis.

Andrographolide Induces Noxa-Dependent Apoptosis by Transactivating ATF4 in Human Lung Adenocarcinoma Cells

Lung adenocarcinoma is the most common pathological type of lung cancer with poor patient outcomes; therefore, developing novel therapeutic agents is critically needed. Andrographolide (AD), a major active component derived from the traditional Chinese medicine (TCM) Andrographis paniculate, is a potential antitumor drug, but the role of AD in lung adenocarcinoma remains poorly understood. In the present study, we demonstrated that AD inhibited the proliferation of broad-spectrum lung cancer cell lines in a dose-dependent manner. Meanwhile, we found that a high dose of AD induced Noxa-dependent apoptosis in human lung adenocarcinoma cells (A549 and H1299). Further studies revealed that Noxa was transcriptionally activated by activating transcription factor 4 (ATF4) in AD-induced apoptosis. Knockdown of ATF4 by small interfering RNA (siRNA) significantly diminished the transactivation of Noxa as well as the apoptotic population induced by AD. These results of the present study indicated that AD induced apoptosis of human lung adenocarcinoma cells by activating the ATF4/Noxa axis and supporting the development of AD as a promising candidate for the new era of chemotherapy.

Krüppel-Like Factor 4 and Its Activator APTO-253 Induce NOXA-Mediated, p53-Independent Apoptosis in Triple-Negative Breast Cancer Cells

Inducing apoptosis is an effective treatment for cancer. Conventional cytotoxic anticancer agents induce apoptosis primarily through activation of tumor suppressor p53 by causing DNA damage and the resulting regulation of B-cell leukemia/lymphoma-2 (BCL-2) family proteins. Therefore, the effects of these agents are limited in cancers where p53 loss-of-function mutations are common, such as triple-negative breast cancer (TNBC). Here, we demonstrate that ultraviolet (UV) light-induced p53-independent transcriptional activation of NOXA, a proapoptotic factor in the BCL-2 family, results in apoptosis induction. This UV light-induced NOXA expression was triggered by extracellular signal-regulated kinase (ERK) activity. Moreover, we identified the specific UV light-inducible DNA element of the NOXA promoter and found that this sequence is responsible for transcription factor Krüppel-like factor 4 (KLF4)-mediated induction. In p53-mutated TNBC cells, inhibition of KLF4 by RNA interference reduced NOXA expression. Furthermore, treatment of TNBC cells with a KLF4-inducing small compound, APTO-253, resulted in the induction of NOXA expression and NOXA-mediated apoptosis. Therefore, our results help to clarify the molecular mechanism of DNA damage-induced apoptosis and provide support for a possible treatment method for p53-mutated cancers.

Transcriptional profiling of the response to the trichloroethylene metabolite S-(1,2-dichlorovinyl)-L-cysteine revealed activation of the eIF2α/ATF4 integrated stress response in two in vitro placental models

Trichloroethylene (TCE) is an industrial solvent and widespread environmental contaminant. Although TCE exposure is prevalent, epidemiological studies of TCE exposure associations with adverse birth outcomes are inconclusive. Prior studies show that the TCE metabolite S-(1,2-dichlorovinyl)-l-cysteine (DCVC) exhibits toxicity in a placental cell line. In the current study, genome-wide gene expression and gene set enrichment analyses were used to identify novel genes and pathway alterations in the HTR-8/SVneo human trophoblast cell line and human placental villous explants treated with DCVC at concentrations relevant to human exposures. In the cells, concentration- and time-dependent effects were observed, as evidenced by the magnitude of altered gene expression after treatment with 20 µM DCVC versus 10 µM, and 12-h versus 6-h of treatment. Comparing the two models for the transcriptional response to 12-h 20 µM DCVC treatment, no differentially expressed genes reached significance in villous explants, whereas 301 differentially expressed genes were detected in HTR-8/SVneo cells compared with non-treated controls (FDR < 0.05 + LogFC > 0.35 [FC > 1.3]). GSEA revealed five upregulated enriched pathways in common between explants and cells (FDR < 0.05). Moreover, all 12-h DCVC treatment groups from both models contained upregulated pathways enriched for genes regulated by the ATF4 transcription factor. The overrepresentation of ATF4 regulation of differentially expressed genes indicated activation of the integrated stress response (ISR), a condition triggered by multiple stress stimuli, including the unfolded protein response. DCVC-induced ISR activation was confirmed by elevated eIF2α phosphorylation, ATF4 protein concentrations, and decreased global protein synthesis in HTR-8/SVneo cells. This study identifies a mechanism of DCVC-induced cytotoxicity by revealing the involvement of a specific stress signaling pathway.

Establishment of a p53 Null Murine Oral Carcinoma Cell Line and the Identification of Genetic Alterations Associated with This Carcinoma

Head and neck squamous cell carcinoma (HNSCC), including oral squamous cell carcinoma (OSCC), ranks sixth in cancer incidence worldwide. To generate OSCC cells lines from human or murine tumors, greatly facilitates investigations into OSCC. This study describes the establishing of a mouse palatal carcinoma cell line (designated MPC-1) from a spontaneous tumor present in a heterozygous p53 gene loss C57BL/6 mouse. A MPC-1-GFP cell subclone was then generated by lentivirus infection resulting in stable expression of green fluorescent protein. Assays indicated that MPC-1 was a p53 null polygonal cell that was positive for keratinocyte markers; it also expressed vimentin and showed a loss of E-cadherin expression. Despite that MPC-1 having strong proliferation and colony formation capabilities, the potential for anchorage independent growth and tumorigenesis was almost absent. Like other murine MOC-L and MTCQ cell line series we have previously established, MPC-1 also expresses a range of stemness markers, various oncogenic proteins, and a number of immune checkpoint proteins at high levels. However, the synergistic effects of the CDK4/6 inhibitor palbociclib on other therapeutic drugs were not observed with MPC-1. Whole exon sequencing revealed that there were high rates of non-synonymous mutations in MPC-1 affecting various genes, including Akap9, Arap2, Cdh11, Hjurp, Mroh2a, Muc4, Muc6, Sp110, and Sp140, which are similar to that the mutations present in a panel of chemical carcinogenesis-related murine tongue carcinoma cell lines. Analysis has highlighted the dis-regulation of Akap9, Cdh11, Muc4, Sp110, and Sp140 in human HNSCC as indicated by the TCGA and GEO OSCC databases. Sp140 expression has also been associated with patient survival. This study describes the establishment and characterization of the MPC-1 cell line and this new cell model should help to advance genetic research into oral cancer.

Chemical hypoxia induces apoptosis of human pluripotent stem cells by a NOXA-mediated HIF-1α and HIF-2α independent mechanism

Human embryonic and induced pluripotent stem cells (hESCs and hiPSCs) are self-renewing human pluripotent stem cells (hPSCs) that can differentiate to a wide range of specialized cells. Notably, hPSCs enhance their undifferentiated state and self-renewal properties in hypoxia (5% O₂). Although thoroughly analyzed, hypoxia implication in hPSCs death is not fully determined. In order to evaluate the effect of chemically mimicked hypoxia on hPSCs cell survival, we analyzed changes in cell viability and several aspects of apoptosis triggered by CoCl₂ and dimethyloxalylglycine (DMOG). Mitochondrial function assays revealed a decrease in cell viability at 24 h post-treatments. Moreover, we detected chromatin condensation, DNA fragmentation and CASPASE-9 and 3 cleavages. In this context, we observed that P53, BNIP-3, and NOXA protein expression levels were significantly up-regulated at different time points upon chemical hypoxia induction. However, only siRNA-mediated downregulation of NOXA but not HIF-1α, HIF-2α, BNIP-3, and P53 did significantly affect the extent of cell death triggered by CoCl₂ and DMOG in hPSCs. In conclusion, chemically mimicked hypoxia induces hPSCs cell death by a NOXA-mediated HIF-1α and HIF-2α independent mechanism.

ATF4 Mediates Mitochondrial Unfolded Protein Response in Alveolar Epithelial Cells

Although endoplasmic reticulum (ER) unfolded protein response (UPR^ER) is well known, mitochondrial unfolded protein response (UPR^mt) has not been recognized in alveolar epithelial cells. Furthermore, ER stress and mitochondrial dysfunction are frequently encountered in alveolar epithelial cells from an array of lung disorders. However, these two scenarios have been often regarded as separate mechanisms contributing to the pathogeneses. It is unclear whether there is interplay between these two phenomena or an integrator that couples these two signaling cascades in the stressed alveolar epithelial cells from those pathologies. In this study, we defined UPR^mt in alveolar epithelial cells and identified ATF4 (activating transcription factor 4), but not ATF5, as the key regulator of UPR^mt. We found that UPR^ER led to UPR^mt and mitochondrial dysfunction in an ATF4-dependent manner. In contrast, mitochondrial stresses did not activate UPR^ER. We found that alveolar epithelial ATF4 and UPR^mt were induced in aged mice with experimental pulmonary fibrosis as well as in patients with idiopathic pulmonary fibrosis. Finally, we found that the inducible expression of ATF4 in mouse alveolar epithelial cells aggravated pulmonary UPR^mt, lung inflammation, body weight loss, and death upon bleomycin-induced lung injury. In conclusion, ER stress induces ATF4-dependent UPR^mt and mitochondrial dysfunction, indicating a novel mechanism by which ER stress contributes to the pathogeneses of a variety of pulmonary disorders.

Induction of NEDD8-conjugating enzyme E2 UBE2F by platinum protects lung cancer cells from apoptosis and confers to platinum-insensitivity

Platinum is a widely used first-line chemotherapy in treating non-small cell lung cancer of adenocarcinoma. Unfortunately, platinum resistance leads to relapse and therapeutic failure, enabling the development of platinum-sensitization strategies to be of great clinical significance. Here, we report that the upregulation of the NEDD8-conjugating enzyme UBE2F is an important way for lung cancer cells to escape platinum-induced cell apoptosis, which confers to insensitivity to platinum-based chemotherapy. Mechanistically, platinum treatment impairs the complex formation for proteasome-mediated UBE2F degradation, evidenced by the weaker association between UBE2F and Ring-box protein 1 (RBX1), an essential component of Cullin-Ring E3 ligases (CRLs), thus leading to the accumulation of UBE2F. The accumulated UBE2F promotes the neddylation levels and activity of Cullin5, in accord with the lower expression of pro-apoptotic protein NOXA, a well-known substrate of Cullin-Ring E3 ligase 5 (CRL5). Additionally, knockout of UBE2F significantly sensitizes lung cancer cells to platinum treatment by enhancing the protein levels of NOXA and subsequently promoting cell apoptosis. Our observations uncover a previously unknown regulatory mechanism of UBE2F stability upon platinum chemotherapy and suggest that UBE2F might be a novel therapy target for sensitizing lung cancer cells to platinum-based chemotherapy.

Proteotoxic Stress and Cell Death in Cancer Cells

To maintain proteostasis, cells must integrate information and activities that supervise protein synthesis, protein folding, conformational stability, and also protein degradation. Extrinsic and intrinsic conditions can both impact normal proteostasis, causing the appearance of proteotoxic stress. Initially, proteotoxic stress elicits adaptive responses aimed at restoring proteostasis, allowing cells to survive the stress condition. However, if the proteostasis restoration fails, a permanent and sustained proteotoxic stress can be deleterious, and cell death ensues. Many cancer cells convive with high levels of proteotoxic stress, and this condition could be exploited from a therapeutic perspective. Understanding the cell death pathways engaged by proteotoxic stress is instrumental to better hijack the proliferative fate of cancer cells.

NOXA upregulation by the prohibitin-binding compound fluorizoline is transcriptionally regulated by integrated stress response-induced ATF3 and ATF4

Fluorizoline is a new synthetic molecule that induces p53-independent apoptosis, in several tumor cell lines and in primary leukemia cells, by selectively targeting prohibitins (PHBs). In this study, we describe how fluorizoline induces BCL-2 homology 3-only protein NOXA, without modulating the protein levels of anti-apoptotic B-cell lymphoma-2 (BCL-2) family members prior to caspase activation, as well as how it synergizes with the BCL-2 and BCL-X_L inhibitor ABT-737 to induce apoptosis. Interestingly, fluorizolinetreatment triggers the activation of the integrated stress response (ISR) in HeLa and HAP1 cells, with increased eukaryotic translation initiation factor 2α phosphorylation, and induction of ATF3, ATF4, and CHOP. Moreover, PHB downregulation induces similar ISR activation and apoptosis as with fluorizoline treatment. In addition, we studied the essential role of the pro-apoptotic protein NOXA in fluorizoline-induced apoptosis and we describe its mechanism of induction in HeLa and HAP1 cells. Moreover, we identified ATF3 and ATF4 as the transcription factors that bind to NOXA promoter upon fluorizoline treatment. Furthermore, using ATF3 and ATF4 CRISPR HeLa and HAP1 cells, we confirmed that both factors mediate the induction of NOXA and apoptosis by fluorizoline. In conclusion, fluorizoline treatment triggers the activation of the ISR that results in the induction of ATF3 and ATF4, important regulators of NOXA transcription in fluorizoline-induced apoptosis.

Aspirin Induced Glioma Apoptosis through Noxa Upregulation

Clinically, high cyclooxygenase-2 expression in malignant glioma correlates well with poor prognosis and the use of aspirin is associated with a reduced risk of glioma. To extend the current understanding of the apoptotic potential of aspirin in most cell types, this study provides evidence showing that aspirin induced glioma cell apoptosis and inhibited tumor growth, in vitro and in vivo. We found that the human H4 glioma cell-killing effects of aspirin involved mitochondria-mediated apoptosis accompanied by endoplasmic reticulum (ER) stress, Noxa upregulation, Mcl-1 downregulation, Bax mitochondrial distribution and oligomerization, and caspase 3/caspase 8/caspase 9 activation. Genetic silencing of Noxa or Bax attenuated aspirin-induced viability loss and apoptosis, while silencing Mcl-1 augmented the effects of aspirin. Data from genetic and pharmacological studies revealed that the axis of ER stress comprised an apoptotic cascade leading to Noxa upregulation and apoptosis. The apoptotic programs and mediators triggered by aspirin in H4 cells were duplicated in human U87 glioma cell line as well as in tumor-bearing BALB/c nude mice. The involvement of ER stress in indomethacin-induced Mcl-1 downregulation was reported in our previous study on glioma cells. Therefore, the aforementioned phenomena indicate that ER stress may be a valuable target for intervention in glioma apoptosis.

Up-Regulation of Activating Transcription Factor 3 in Human Fibroblasts Inhibits Melanoma Cell Growth and Migration Through a Paracrine Pathway

The treatment of melanoma has remained a difficult challenge. Targeting the tumor stroma has recently attracted attention for developing novel strategies for melanoma therapy. Activating transcription factor 3 (ATF3) plays a crucial role in regulating tumorigenesis and development, but whether the expression of ATF3 in human dermal fibroblasts (HDFs) can affect melanoma development hasn't been studied. Our results show that ATF3 expression is downregulated in stromal cells of human melanoma. HDFs expressing high levels of ATF3 suppressed the growth and migration of melanoma cells in association with downregulation of different cytokines including IL-6 in vitro. In vivo, HDFs with high ATF3 expression reduced tumor formation. Adding recombinant IL-6 to melanoma cells reversed those in vitro and in vivo effects, suggesting that ATF3 expression by HDFs regulates melanoma progression through the IL-6/STAT3 pathway. More importantly, HDFs pretreated with cyclosporine A or phenformin to induce ATF3 expression inhibited melanoma cell growth in vitro and in vivo. In summary, our study reveals that ATF3 suppresses human melanoma growth and that inducing the expression of ATF3 in HDFs can inhibit melanoma growth, a new potential melanoma therapeutic approach.

Induction of p53-Dependent Apoptosis by Prostaglandin A2

Prostaglandin (PG) A2, one of cyclopentenone PGs, is known to induce activation of apoptosis in various cancer cells. Although PGA2 has been reported to cause activation of apoptosis by altering the expression of apoptosis-related genes, the role of p53, one of the most critical pro-apoptotic genes, on PGA2-induced apoptosis has not been clarified yet. To address this issue, we compared the apoptosis in HCT116 p53 null cells (HCT116 p53-/-) to that in HCT116 cells containing the wild type p53 gene. Cell death induced by PGA2 was associated with phosphorylation of histone H2A variant H2AX (H2AX), activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase 1 in HCT116 cells. Induction of apoptosis in PGA2-treated cells was almost completely prevented by pretreatment with a pan-caspase inhibitor, z-VAD-Fmk, or an inhibitor of protein synthesis, cycloheximide. While PGA2 induced apoptosis in HCT116 cells, phosphorylation of p53 and transcriptional induction of p53-target genes such as p21WAF1, PUMA, BAX, NOXA, and DR5 occurred. Besides, pretreatment of pifithrin-α (PFT-α), a chemical inhibitor of p53's transcriptional activity, interfered with the induction of apoptosis in PGA2-treated HCT116 cells. Pretreatment of NU7441, a small molecule inhibitor of DNA-activated protein kinase (DNA-PK) suppressed PGA2-induced phosphorylation of p53 and apoptosis as well. Moreover, among target genes of p53, knockdown of DR5 expression by RNA interference, suppressed PGA2-induced apoptosis. In the meanwhile, in HCT116 p53-/- cells, PGA2 induced apoptosis in delayed time points and with less potency. Delayed apoptosis by PGA2 in HCT116 p53-/- cells was also associated with phosphorylation of H2AX but was not inhibited by either PFT- or NU7441. Collectively, these results suggest the following. PGA2 may induce p53-dependent apoptosis in which DNA-PK activates p53, and DR5, a transcriptional target of p53, plays a pivotal role in HCT116 cells. In contrast to apoptosis in HCT116 cells, PGA2 may induce apoptosis in a fashion of less potency, which is independent of p53 and DNA-PK in HCT116 p53-/- cells.

Electron transport chain activity is a predictor and target for venetoclax sensitivity in multiple myeloma

The BCL-2 antagonist venetoclax is highly effective in multiple myeloma (MM) patients exhibiting the 11;14 translocation, the mechanistic basis of which is unknown. In evaluating cellular energetics and metabolism of t(11;14) and non-t(11;14) MM, we determine that venetoclax-sensitive myeloma has reduced mitochondrial respiration. Consistent with this, low electron transport chain (ETC) Complex I and Complex II activities correlate with venetoclax sensitivity. Inhibition of Complex I, using IACS-010759, an orally bioavailable Complex I inhibitor in clinical trials, as well as succinate ubiquinone reductase (SQR) activity of Complex II, using thenoyltrifluoroacetone (TTFA) or introduction of SDHC R72C mutant, independently sensitize resistant MM to venetoclax. We demonstrate that ETC inhibition increases BCL-2 dependence and the ‘primed’ state via the ATF4-BIM/NOXA axis. Further, SQR activity correlates with venetoclax sensitivity in patient samples irrespective of t(11;14) status. Use of SQR activity in a functional-biomarker informed manner may better select for MM patients responsive to venetoclax therapy.

Venetoclax monotherapy is effective in 40% of t(11:14) positive multiple myeloma (MM). Here, the authors show that electron transport chain complex I (CI) and complex II (CII) activity predict MM sensitivity to venetoclax, and inhibition of CI with IACS-010759 or CII with TTFA increase sensitivity.

Withaferin A triggers G2/M arrest and intrinsic apoptosis in glioblastoma cells via ATF4-ATF3-CHOP axis

OBJECTIVE

Withaferin A (WA) is a bioactive compound with a remarkable anti-cancer effect derived from Withania somnifera, commonly known as ashwagandha. However, the anti-cancer mechanisms of WA in glioblastoma multiforme (GBM) are still unclear.

MATERIALS AND METHODS

Cell viability assays and xenografted nude mice were used to evaluate the effects of WA, along with flow cytometry to detect apoptosis and cell cycle of GBM. RNA-seq analysis, Western blotting, immunofluorescence staining, qRT-PCR and siRNA gene silencing were carried out to determine the signalling pathways affected by WA.

RESULTS

Withaferin A significantly inhibited the growth of GBM in vitro and in vivo and triggered the intrinsic apoptosis of GBM cells by up-regulating expression of Bim and Bad. WA arrested GBM cells at the G2/M phase of the cell cycle through dephosphorylating Thr161 of CDK1 by activating p53-independent p21 up-regulation. Knockdown of p21 restored cell cycle progression and cell viability by down-regulating the expression of Bad rather than Bim. We demonstrated that endoplasmic reticulum (ER) stress induced by WA through the ATF4-ATF3-CHOP axis, initiated apoptosis and G2/M arrest in GBM cells.

CONCLUSION

We revealed a novel pathway that elucidated WA activation of apoptosis and G2/M arrest in GBM cells through the ATF4-ATF3-CHOP axis. This discovery is important for optimization of WA-based regimens for prevention and/or treatment of GBM.

Antitumor Potential and Phytochemical Profile of Plants from Sardinia (Italy), a Hotspot for Biodiversity in the Mediterranean Basin

Sardinia (Italy), with its wide range of habitats and high degree of endemism, is an important area for plant-based drug discovery studies. In this work, the antitumor activity of 35 samples from Sardinian plants was evaluated on human osteosarcoma cells U2OS. The results showed that five plants were strongly antiproliferative: Arbutus unedo (AuL), Cynara cardunculus (CyaA), Centaurea calcitrapa (CcA), Smilax aspera (SaA), and Tanacetum audibertii (TaA), the latter endemic to Sardinia and Corsica. Thus, their ability to induce cell cycle arrest and apoptosis was tested. All extracts determined cell cycle block in G2/M phase. Nevertheless, the p53 expression levels were increased only by TaA. The effector caspases were activated mainly by CycA, TaA, and CcA, while AuL and SaA did not induce apoptosis. The antiproliferative effects were also tested on human umbilical vein endothelial cells (HUVEC). Except for AuL, all the extracts were able to reduce significantly cell population, suggesting a potential antiangiogenic activity. The phytochemical composition was first explored by 1H NMR profiling, followed by further purifications to confirm the structure of the most abundant metabolites, such as phenolic compounds and sesquiterpene lactones, which might play a role in the measured bioactivity.

TFAP2C increases cell proliferation by downregulating GADD45B and PMAIP1 in non-small cell lung cancer cells

Background

Non-small cell lung cancer (NSCLC) is one of the leading causes of death in the world. NSCLC diagnosed at an early stage can be highly curable with a positive prognosis, but biomarker limitations make it difficult to diagnose lung cancer at an early stage. To identify biomarkers for lung cancer development, we previously focused on the oncogenic roles of transcription factor TFAP2C in lung cancers and revealed the molecular mechanism of several oncogenes in lung tumorigenesis based on TFAP2C-related microarray analysis.

Results

In this study, we analyzed microarray data to identify tumor suppressor genes and nine genes downregulated by TFAP2C were screened. Among the nine genes, we focused on growth arrest and DNA-damage-inducible beta (GADD45B) and phorbol-12-myristate-13-acetate-induced protein 1 (PMAIP1) as representative TFAP2C-regulated tumor suppressor genes. It was observed that overexpressed TFAP2C resulted in inhibition of GADD45B and PMAIP1 expressions at both the mRNA and protein levels in NSCLC cells. In addition, downregulation of GADD45B and PMAIP1 by TFAP2C promoted cell proliferation and cell motility, which are closely associated with NSCLC tumorigenesis.

Conclusion

This study indicates that GADD45B and PMAIP1 could be promising tumor suppressors for NSCLC and might be useful as prognostic markers for use in NSCLC therapy.

Electronic supplementary material

The online version of this article (10.1186/s40659-019-0244-5) contains supplementary material, which is available to authorized users.

Combination of fenretinide and ABT-263 induces apoptosis through NOXA for head and neck squamous cell carcinoma treatment

The overall survival for recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) remains low, with little progress made over decades. Cisplatin, most frequently used for HNSCC treatment, activates mitochondria-dependent apoptosis through the BCL-2 family proteins. We have previously demonstrated that the pro-apoptotic BH3-only protein, NOXA plays a critical role in this process. NOXA binds and inactivates anti-apoptotic MCL-1, while the BCL-2 inhibitor ABT-263 is capable of inactivating anti-apoptotic BCL-2 and BCL-XL. We hypothesized that combination of NOXA and ABT-263 treatment increases cell death by simultaneously inhibiting anti-apoptotic BCL-2 family proteins in HNSCC cells. Here, we demonstrated that combination of ectopic NOXA expression and ABT-263 enhanced apoptosis in p53-inactive, p53 wild-type, and human papillomavirus (HPV)-positive HNSCC cell lines. Furthermore, a retinoid derivative and an endoplasmic reticulum stress inducer, fenretinide, induced NOXA, and combination of fenretinide and ABT-263 strongly induced apoptosis in HNSCC cells regardless of the HPV or p53 statuses. We also found that MCL-1 and BCL-XL are the primary targets of apoptosis induced by the combinations. These results will develop novel and alternative therapeutic strategies to directly modify the cell death machinery in HNSCC.

Screening the expression of several miRNAs from TaqMan Low Density Array in traumatic brain injury: miR-219a-5p regulates neuronal apoptosis by modulating CCNA2 and CACUL1

Circulating microRNAs (miRNAs) have emerged as diagnostic and prognostic biomarkers for traumatic brain injury (TBI). However, a comprehensive characterization of the serum miRNA profile in patients with TBI and the roles of these potential markers in neuronal regulation have rarely been reported. In this study, the levels of 754 serum miRNAs were initially determined in two pooled samples of 15 severe traumatic brain injury (sTBI) patients and 15 healthy controls using a TaqMan Low Density Array. The markedly upregulated miRNAs in sTBI patients were subsequently validated individually by quantitative reverse-transcription PCR (RT-qPCR) in another larger cohort consisting of 81 sTBI patients, 81 mild traumatic brain injury (mTBI) patients and 82 age/sex-matched healthy controls. Seven miRNAs, including miR-103a-3p, miR-219a-5p, miR-302d-3p, miR-422a, miR-518f-3p, miR-520d-3p and miR-627, were significantly upregulated in both sTBI and mTBI patients compared with their expression in controls. Among these miRNAs, miR-219a-5p not only discriminated sTBI and mTBI patients from controls but also discriminated between sTBI and mTBI patients. We further show here that in the neuronal cell injury model, upregulated miR-219a-5p inhibits the expression of CCNA2 and CACUL1 and further regulates akt/Foxo3a and p53/Bcl-2 signaling pathways, causing a notable change in the expression of cleaved caspase-3, thereby inducing neuronal apoptosis. These results indicate that these seven selected miRNAs could serve as novel biomarkers for TBI. In particular, miR-219a-5p is a potentially valuable indicator of the diagnosis, prognosis of TBI and appears to regulate neuronal apoptosis and death.

mEAK-7 Forms an Alternative mTOR Complex with DNA-PKcs in Human Cancer

MTOR associated protein, eak-7 homolog (mEAK-7), activates mechanistic target of rapamycin (mTOR) signaling in human cells through an alternative mTOR complex to regulate S6K2 and 4E-BP1. However, the role of mEAK-7 in human cancer has not yet been identified. We demonstrate that mEAK-7 and mTOR signaling are strongly elevated in tumor and metastatic lymph nodes of patients with non-small-cell lung carcinoma compared with those of patients with normal lung or lymph tissue. Cancer stem cells, CD44+/CD90+ cells, yield elevated mEAK-7 and activated mTOR signaling. mEAK-7 is required for clonogenic potential and spheroid formation. mEAK-7 associates with DNA-dependent protein kinase catalytic subunit isoform 1 (DNA-PKcs), and this interaction is increased in response to X-ray irradiation to regulate S6K2 signaling. DNA-PKcs pharmacologic inhibition or genetic knockout reduced S6K2, mEAK-7, and mTOR binding with DNA-PKcs, resulting in loss of S6K2 activity and mTOR signaling. Therefore, mEAK-7 forms an alternative mTOR complex with DNA-PKcs to regulate S6K2 in human cancer cells.

Smyd2 conformational changes in response to p53 binding: role of the C-terminal domain

Smyd2 lysine methyltransferase regulates monomethylation of histone and nonhistone lysine residues using S‐adenosylmethionine cofactor as the methyl donor. The nonhistone interactors include several tumorigenic targets, including p53. Understanding this interaction would allow the structural principles that underpin Smyd2‐mediated p53 methylation to be elucidated. Here, we performed μ‐second molecular dynamics (MD) simulations on binary Smyd2‐cofactor and ternary Smyd2‐cofactor‐p53 peptide complexes. We considered both unmethylated and monomethylated p53 peptides (at Lys370 and Lys372). The results indicate that (a) the degree of conformational freedom of the C‐terminal domain of Smyd2 is restricted by the presence of the p53 peptide substrate, (b) the Smyd2 C‐terminal domain shows distinct dynamic properties when interacting with unmethylated and methylated p53 peptides, and (c) Lys372 methylation confines the p53 peptide conformation, with detectable influence on Lys370 accessibility to the cofactor. These MD results are therefore of relevance for studying the biology of p53 in cancer progression.

Planarians as models to investigate the bioactivity of gold(I) complexes in vivo

Gold(I)-containing complexes are used in drug discovery research for rheumatoid arthritis, cancer, and parasitic infections. In this study, we tested the bioactivity of gold(I) complexes in vivo using planarians. The planarian Schmidtea mediterranea possesses orthologues of tumor suppressor genes, such as p53, that, when silenced, cause deregulation of cell proliferation and apoptosis. In this context, we tested two triethylphosphine-gold(I) complexes (AdO and AdT) to determine if they can attenuate phenotypes that result from p53 inhibition. First, we identified the drug concentration that did not affect survival or regeneration and evaluated the drug's effect on cell division and apoptosis. We found that AdT treatment decreased the number of mitotic cells and that all drug treatments increased the number of apoptotic cells. We then performed p53(RNAi) and drug treatments concomitantly and observed the phenotype progression. Drug treatment increased survival three-fold and decreased apoptosis, which resulted in an attenuated phenotype. Our results indicate that planarians can be treated with gold(I) complexes, and that this treatment can diminish the p53(RNAi) phenotype and extend survival. In this work we show that planarians can be used as a model to study the in vivo effect of gold(I) complexes and to further investigate their mechanisms of action.

ABT-199-mediated inhibition of Bcl-2 as a potential therapeutic strategy for nasopharyngeal carcinoma

BACKGROUND

Aberrant overexpression of Bcl-2 protein has been detected in 80% of nasopharyngeal carcinoma (NPC), and Bcl-2 family proteins are implicated in both NPC oncogenesis and chemotherapy resistance. Previous studies have shown that while treatment of NPC cells with Bcl-2 family inhibitors alone is rarely effective, concomitant treatment with a cytotoxic reagent such as cisplatin can increase efficacy through a synergistic effect. The aim of the current work was to determine how we might increase the efficacy of Bcl-2 family inhibitors in the absence of cytotoxic reagents, which are associated with negative side effect profiles.

METHODS

We assessed cell proliferation in Bcl-2 high-expressing NPC cells by CCK-8 assay after treatment with the Bcl-2 inhibitor ABT-199 and/or the Mcl-1 inhibitor S63845. Apoptotic induction by ABT-199 was evaluated by Annexin V-FITC and PI double staining. We also evaluated Bcl-2 family protein expression (Bim, Mcl-1, Bcl-xL, Noxa) after treatment with ABT-199 by western blotting. Finally, xenografted Balb/c nude mice were used to test ABT-199 efficacy in vivo, H&E and immunohistochemistry assay were used to analyze tumor samples.

RESULTS

ABT-199 effectively induced NPC cell apoptosis in vitro and in the xenograft model. Following ABT-199 treatment in NPC cells, upregulation of Mcl-1 and Bcl-xL can lead to drug resistance, while concomitant Noxa overexpression partially neutralized the Mcl-1-caused resistance. Given that ABT-199 induces apoptosis in NPC cells through the Bcl-2/Noxa/Mcl-1 axis, treatment avenues further targeting this pathway should be promising. Indeed, the newly developed Mcl-1 inhibitor S63845 in combination with ABT-199 had a synergistic effect on NPC cell apoptosis.

CONCLUSION

Bcl-2 inhibition in NPC cells with ABT-199 triggers apoptosis through the Bcl-2/Noxa/Mcl-1 axis, and dual inhibition of the anti-apoptotic Bcl-2 family proteins Bcl-2 and Mcl-1 provided a strong synergistic effect without the need for adjunctive cytotoxic agent treatment with cisplatin.