Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2-dependent activation of muscle autophagy ameliorates sarcopenia and promotes healthy aging

Sarcopenia is a major contributor to disability in older adults, and thus, it is key to elucidate the mechanisms underlying its development. Increasing evidence suggests that impaired macroautophagy/autophagy contributes to the development of sarcopenia. However, the mechanisms leading to reduced autophagy during aging remain largely unexplored, and whether autophagy activation protects from sarcopenia has not been fully addressed. Here we show that the autophagy regulator TP53INP2/TRP53INP2 is decreased during aging in mouse and human skeletal muscle. Importantly, chronic activation of autophagy by muscle-specific overexpression of TRP53INP2 prevents sarcopenia and the decline of muscle function in mice. Acute re-expression of TRP53INP2 in aged mice also improves muscle atrophy, enhances mitophagy, and reduces ROS production. In humans, high levels of TP53INP2 in muscle are associated with increased muscle strength and healthy aging. Our findings highlight the relevance of an active muscle autophagy in the maintenance of muscle mass and prevention of sarcopenia.Abbreviation: ATG7: autophagy related 7; BMI: body mass index; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; ROS: reactive oxygen species; TP53INP2: tumor protein p53 inducible nuclear protein 2; WT: wild type.

Cytoplasmic TP53INP2 acts as an apoptosis partner in TRAIL treatment: the synergistic effect of TRAIL with venetoclax in TP53INP2-positive acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a hematopoietic malignancy with poor outcomes, especially in older AML patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered a promising anticancer drug because it selectively induces the extrinsic apoptosis of tumor cells without affecting normal cells. However, clinical trials have shown that the responses of patients to TRAIL are significantly heterogeneous. It is necessary to explore predictable biomarkers for the preselection of AML patients with better responsiveness to TRAIL. Here, we investigated the critical role of tumor protein p53 inducible nuclear protein 2 (TP53INP2) in the AML cell response to TRAIL treatment.

METHODS

First, the relationship between TP53INP2 and the sensitivity of AML cells to TRAIL was determined by bioinformatics analysis of Cancer Cell Line Encyclopedia datasets, Cell Counting Kit-8 assays, flow cytometry (FCM) and cell line-derived xenograft (CDX) mouse models. Second, the mechanisms by which TP53INP2 participates in the response to TRAIL were analyzed by Western blot, ubiquitination, coimmunoprecipitation and immunofluorescence assays. Finally, the effect of TRAIL alone or in combination with the BCL-2 inhibitor venetoclax (VEN) on cell survival was explored using colony formation and FCM assays, and the effect on leukemogenesis was further investigated in a patient-derived xenograft (PDX) mouse model.

RESULTS

AML cells with high TP53INP2 expression were more sensitive to TRAIL in vitro and in vivo. Gain- and loss-of-function studies demonstrated that TP53INP2 significantly enhanced TRAIL-induced apoptosis, especially in AML cells with nucleophosmin 1 (NPM1) mutations. Mechanistically, cytoplasmic TP53INP2 maintained by mutant NPM1 functions as a scaffold bridging the ubiquitin ligase TRAF6 to caspase-8 (CASP 8), thereby promoting the ubiquitination and activation of the CASP 8 pathway. More importantly, simultaneously stimulating extrinsic and intrinsic apoptosis signaling pathways with TRAIL and VEN showed strong synergistic antileukemic activity in AML cells with high levels of TP53INP2.

CONCLUSION

Our findings revealed that TP53INP2 is a predictor of responsiveness to TRAIL treatment and supported a potentially individualized therapeutic strategy for TP53INP2-positive AML patients.

Pachymic acid activates TP53INP2/TRAF6/caspase-8 pathway to promote apoptosis in renal cell carcinoma cells

While pachymic acid (PA), a key component of Poria cocos (Schw.), has demonstrated anti-tumor effects in lung, breast, and pancreatic cancers, its impact on renal cell carcinoma (RCC) is unclear. This study evaluated the effect of PA on proliferation, migration, and apoptosis in human renal cancer A498 and ACHN cells as well as in cancer xenograft mice using wound scratch test, Western blotting, and co-immunoprecipitation assays. In a dose- and time-dependent manner, PA exhibited significant inhibition of RCC cell proliferation, migration, and invasion, accompanied by the induction of apoptosis. Additionally, PA upregulated the expression of tumor protein p53-inducible nuclear protein 2 (TP53INP2) and tumor necrosis factor receptor-associated factor 6 (TRAF6), which were downregulated in renal papillary and chromophobe carcinoma, resulting in inhibited tumor growth in mice. PA treatment elevated cleaved-caspase 3 and 8, and PARP levels, and facilitated TP53INP2 and TRAF6 binding to caspase 8, promoting its ubiquitination. Molecular docking revealed interactions between PA and TP53INP2, TRAF6. In summary, PA inhibits RCC development by upregulating TP53INP2 and promoting TRAF6-induced caspase 8 ubiquitination, activating apoptotic pathways.

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

MAP kinase ERK5 modulates cancer cell sensitivity to extrinsic apoptosis induced by death-receptor agonists

Death receptor ligand TRAIL is a promising cancer therapy due to its ability to selectively trigger extrinsic apoptosis in cancer cells. However, TRAIL-based therapies in humans have shown limitations, mainly due inherent or acquired resistance of tumor cells. To address this issue, current efforts are focussed on dissecting the intracellular signaling pathways involved in resistance to TRAIL, to identify strategies that sensitize cancer cells to TRAIL-induced cytotoxicity. In this work, we describe the oncogenic MEK5-ERK5 pathway as a critical regulator of cancer cell resistance to the apoptosis induced by death receptor ligands. Using 2D and 3D cell cultures and transcriptomic analyses, we show that ERK5 controls the proteostasis of TP53INP2, a protein necessary for full activation of caspase-8 in response to TNFα, FasL or TRAIL. Mechanistically, ERK5 phosphorylates and induces ubiquitylation and proteasomal degradation of TP53INP2, resulting in cancer cell resistance to TRAIL. Concordantly, ERK5 inhibition or genetic deletion, by stabilizing TP53INP2, sensitizes cancer cells to the apoptosis induced by recombinant TRAIL and TRAIL/FasL expressed by Natural Killer cells. The MEK5-ERK5 pathway regulates cancer cell proliferation and survival, and ERK5 inhibitors have shown anticancer activity in preclinical models of solid tumors. Using endometrial cancer patient-derived xenograft organoids, we propose ERK5 inhibition as an effective strategy to sensitize cancer cells to TRAIL-based therapies.

Natural compounds targeting mitochondrial dysfunction: emerging therapeutics for target organ damage in hypertension

Hypertension generally causes target organ damage (TOD) in the heart, brain, kidney, and blood vessels. This can result in atherosclerosis, plaque formation, cardiovascular and cerebrovascular events, and renal failure. Recent studies have indicated that mitochondrial dysfunction is crucial in hypertensive target organ damage. Consequently, mitochondria-targeted therapies attract increasing attention. Natural compounds are valuable resources for drug discovery and development. Many studies have demonstrated that natural compounds can ameliorate mitochondrial dysfunction in hypertensive target organ damage. This review examines the contribution of mitochondrial dysfunction to the development of target organ damage in hypertension. Moreover, it summarizes therapeutic strategies based on natural compounds that target mitochondrial dysfunction, which may be beneficial for preventing and treating hypertensive target organ damage.

Study on Sgc8 Aptamer-mediated Nucleic Acid Nanomaterial-doxorubicin Complex for Tumor Targeted Therapy

Chemotherapy is one of the most important treatments for malignant cancers, but most chemotherapeutic drugs are poorly targeted, highly toxic and expensive, resulting in unsatisfactory treatment results for cancer patients. Therefore, intelligent drug delivery platforms are needed to be explored urgently to enhance drug treatment and reduce toxicity on normal cells. Nucleic acid nanomaterials are a class of nanomaterials developed on the basis of the "base complementary pairing principle", which have the advantages of good programmability, high stability, good biocompatibility, and strong targeting. Herein, we present a simple Sgc8 aptamer-modified nucleic acid nanomaterial (Sgc8NM) for the targeted delivery of Doxorubicin (Dox), a widely used chemotherapy drug in clinic. Studies have shown the Sgc8NM-Dox performed a precise treatment effect on target cells and low toxicity on non-target cells, providing a new strategy for the potential application of nanocomposite drugs in targeted cancer delivery.

Inactivation of ZSCAN18 by promoter hypermethylation drives the proliferation via attenuating TP53INP2-mediated autophagy in gastric cancer cells

BACKGROUND

Zinc finger and scan domain containing 18 (ZSCAN18) belongs to the zinc finger transcription factor superfamily, which consists of hundreds of members that play critical roles in all steps of tumorigenesis.

METHODS

This study aims to investigate the roles of ZSCAN18 in gastric cancer (GC). The expression level in GC and the clinicopathologic features of ZSCAN18 were detected by immunohistochemistry staining. Methylation of ZSCAN18 promoter in GC tissues and cell lines was analyzed via MassARRAY; the same method was used to detect GC cell lines demethylated by 5-aza-2'-deoxycytidine treatment. The biological function of ZSCAN18 in GC cells was verified by in vitro and in vivo experiments. The downstream molecular mechanism of ZSCAN18 was explored using RNA next-generation sequencing, immunofluorescence and chromatin immunoprecipitation.

RESULTS

Our work revealed ZSCAN18 expression was markedly reduced in GC tissues compared with adjacent normal tissues as a result of hypermethylation in GC. Likewise, ZSCAN18 expression was significantly reduced in a panel of GC cell lines as a result of the densely methylated ZSCAN18 promoter. Functionally, ZSCAN18 overexpression inhibited the biological progression of GC cells, which was characterized by weaken proliferation, enhanced autophagy and suppressed tumor growth. ZSCAN18 acted as a transcription factor and played an important role in binding to the promoter of tumor protein 53-induced nuclear protein 2 (TP53INP2), and we also confirmed the anti-tumor effect of TP53INP2 in GC. Furthermore, the knockdown of TP53INP2 alleviated the inhibiting effects of ZSCAN18 in GC cells by in vitro and in vivo experiments.

CONCLUSIONS

Collectively, this study unveiled that ZSCAN18 played an anticancer role in GC by promoting autophagy and transcriptional regulation of TP53INP2 and provided a promising target for the diagnosis and treatment of GC.

Cytoplasmic Expression of TP53INP2 Modulated by Demethylase FTO and Mutant NPM1 Promotes Autophagy in Leukemia Cells

Acute myeloid leukemia (AML) with a nucleophosmin 1 (NPM1) mutation is a unique subtype of adult leukemia. Recent studies show that NPM1-mutated AML has high autophagy activity. However, the mechanism for upholding the high autophagic level is still not fully elucidated. In this study, we first identified that tumor protein p53 inducible nuclear protein 2 (TP53INP2) was highly expressed and cytoplasmically localized in NPM1-mutated AML cells. Subsequent data showed that the expression of TP53INP2 was upregulated by fat mass and obesity-associated protein (FTO)-mediated m⁶A modification. Meanwhile, TP53INP2 was delocalized to the cytoplasm by interacting with NPM1 mutants. Functionally, cytoplasmic TP53INP2 enhanced autophagy activity by promoting the interaction of microtubule-associated protein 1 light chain 3 (LC3) - autophagy-related 7 (ATG7) and further facilitated the survival of leukemia cells. Taken together, our study indicates that TP53INP2 plays an oncogenic role in maintaining the high autophagy activity of NPM1-mutated AML and provides further insight into autophagy-targeted therapy of this leukemia subtype.

TP53INP2 Contributes to TGF-β2-Induced Autophagy during the Epithelial–Mesenchymal Transition in Posterior Capsular Opacification Development

Background: Posterior capsule opacification (PCO) is the most common complication after cataract surgery, in which increased levels of transforming growth factor-beta 2 (TGF-β2) accelerate PCO formation; however, the pathological mechanisms are not fully understood. This study aims to explore the regulation mechanism of TGF-β2 in PCO formation via its autophagic functions. Methods: The autophagic effect of TGF-β2 was detected by transmission electron microscopy (TEM), Western blotting, and immunofluorescence analysis. The association between autophagy and the epithelial–mesenchymal transition (EMT) was evaluated by qPCR and Western blotting. The transcriptome analysis was used to uncover the molecular mechanism of TGF-β2-induced PCO formation. Results: TGF-β2 specifically promotes autophagy flux in human lens epithelial cells. The activation of autophagy by rapamycin can promote EMT marker synthesis and improve cell migration. However, the inhibition of autophagy by 3-MA attenuates EMT. To uncover the molecular mechanisms, we performed RNA sequencing and found that TGF-β2 elevated tumor protein p53-inducible nuclear protein2 (TP53INP2) expression, which was accompanied by a nuclear-to-cytoplasm translocation. Moreover, the knockdown of TP53INP2 blocked the TGF-β2-induced autophagy and EMT processes, revealing that TP53INP2 plays an important role in TGF-β2-induced autophagy during EMT. Conclusions: Taken together, the results of this study suggested that TP53INP2 was a novel regulator of PCO development by TGF-β2, and notably, TP53INP2, may be a potential target for the pharmacological treatment of PCO.

Overexpression of TP53INP2 Promotes Apoptosis in Clear Cell Renal Cell Cancer via Caspase-8/TRAF6 Signaling Pathway

Clear cell renal cell cancer (ccRCC) is a tumor of high malignancy, which can escape apoptosis. The tumor protein p53-inducible nuclear protein 2 (TP53INP2), known as an autophagy protein, is the essential part for autophagosome formation and sensitizes cells to apoptosis. Our study is aimed at exploring the role of TP53INP2 in ccRCC. We have identified the autophagy-related genes (ARGs) of differential expression in ccRCC patients with the help of the TCGA database by bioinformatics analysis. Our assays of quantitative real-time polymerase chain reaction (qRT-PCR) and western blot were for the determination on the both levels of mRNA and protein. Overexpression of TP53INP2 on cellular proliferation, migration, and apoptosis of ccRCC was verified in the ways of performing CCK-8, wound scrape, transwell and flow cytometry assays in vitro, and a mice tumor model in vivo. Transmission electron microscopy was used to measure autophagy formation. The underlying mechanisms of TP53INP2 on ccRCC were determined via coimmunoprecipitation. TP53INP2 was found highly associated with an outcome of worse overall survival (OS) in Kaplan-Meier curves, and this parameter in ccRCC tissues was also lower than the normal tissues. Overexpression of TP53INP2 inhibited ccRCC cellular proliferation, migration, and invasion, as well as the tumor growth of mice. Those cells treated with autophagy inhibitor chloroquine (CQ) or TP53INP2 increased the apoptosis rate. TP53INP2 promoted autophagy formation and elevated the ratio of LC3 II/LC3 I. However, TP53INP2 did not significantly decrease the p-mTOR level. In addition, TP53INP2 activates the expressions of caspase-3, caspase-8, and PARP. Caspase-8 and TNF receptor associated factor 6 (TRAF6) were found to bind to each other in the presence of TP53INP2. TP53INP2 induces apoptosis in ccRCC cells through caspase-8/TRAF6 pathway, rather than the autophagy-dependent pathway.

Evolutionary Diversity and Function of Metacaspases in Plants: Similar to but Not Caspases

Caspase is a well-studied metazoan protease involved in programmed cell death and immunity in animals. Obviously, homologues of caspases with evolutionarily similar sequences and functions should exist in plants, and yet, they do not exist in plants. Plants contain structural homologues of caspases called metacaspases, which differ from animal caspases in a rather distinct way. Metacaspases, a family of cysteine proteases, play critical roles in programmed cell death during plant development and defense responses. Plant metacaspases are further subdivided into types I, II, and III. In the type I Arabidopsis MCs, AtMC1 and AtMC2 have similar structures, but antagonistically regulate hypersensitive response cell death upon immune receptor activation. This regulatory action is similar to caspase-1 inhibition by caspase-12 in animals. However, so far very little is known about the biological function of the other plant metacaspases. From the increased availability of genomic data, the number of metacaspases in the genomes of various plant species varies from 1 in green algae to 15 in Glycine max. It is implied that the functions of plant metacaspases will vary due to these diverse evolutions. This review is presented to comparatively analyze the evolution and function of plant metacaspases compared to caspases.

The complex interplay between autophagy and cell death pathways

Autophagy is a universal cellular homeostatic process, required for the clearance of dysfunctional macromolecules or organelles. This self-digestion mechanism modulates cell survival, either directly by targeting cell death players, or indirectly by maintaining cellular balance and bioenergetics. Nevertheless, under acute or accumulated stress, autophagy can also contribute to promote different modes of cell death, either through highly regulated signalling events, or in a more uncontrolled inflammatory manner. Conversely, apoptotic or necroptotic factors have also been implicated in the regulation of autophagy, while specific factors regulate both processes. Here, we survey both earlier and recent findings, highlighting the intricate interaction of autophagic and cell death pathways. We, Furthermore, discuss paradigms, where this cross-talk is disrupted, in the context of disease.

Identification of Two Novel CIL-102 Upregulations of ERP29 and FUMH to Inhibit the Migration and Invasiveness of Colorectal Cancer Cells by Using the Proteomic Approach

CIL-102 (1-[4-(furo[2,3-b]quinolin-4-ylamino) phenyl]ethanone) is a major active agent of Camptotheca acuminata’s alkaloid derivative, and its anti-tumorigenic activity, a valuable biological property of the agent, has been reported in many types of cancer. In this study, we researched the novel CIL-102-induced protein for either the induction of cell apoptosis or the inhibition of cell migration/invasiveness in colorectal cancer cells (CRC) and their molecular mechanism. Firstly, our data showed that CIL-102 treatment not only increased the cytotoxicity of cells and the production of Reactive Oxygen Species (ROS), but it also decreased cell migration and invasiveness in DLD-1 cells. In addition, many cellular death-related proteins (cleavage caspase 9, cleavage caspase 3, Bcl-2, and TNFR1 and TRAIL) and JNK MAPK/p300 pathways were increased in a time-dependent manner. Using the proteomic approach with a MALDI-TOF-TOF analysis, CIL-102-regulated differentially expressed proteins were identified, including eight downregulated and 11 upregulated proteins. Among them, upregulated Endoplasmic Reticulum resident Protein 29 (ERP29) and Fumarate Hydratase (FUMH) by CIL-102 were blocked by the inhibition of ROS production, JNK activity, and p300/CBP (CREB binding protein) signaling pathways. Importantly, the knockdown of ERP29 and FUMH expression by shRNA abolished the inhibition of cell migration and invasion by CIL-102 in DLD-1 cells. Together, our findings demonstrate that ERP29 and FUMH were upregulated by CIL102 via ROS production, JNK activity, and p300/CBP pathways, and that they were involved in the inhibition of the aggressive status of colorectal cancer cells.

Impact of FasL Stimulation on Sclerostin Expression and Osteogenic Profile in IDG-SW3 Osteocytes

Simple Summary

FasL used to be considered as a classical ligand triggering cell death (apoptosis) via its receptor, Fas and thefollowing caspase cascade. As such, it is known to be involved in regulation within the bone. Recently, however, the knowledge has expanded about the non-apoptotic and caspase-independent engagement of the Fas/FasL pathway. The present investigation identified that stimulation of osteocytic IDG-SW3 cells by FasL leads to a dramatic decrease in expression of the major osteocytic marker, sclerostin. Additionally, other key components of the osteogenic pathways were impacted, notably in a caspase-independent manner. Such findings are of importance for basic biology as well as biomedical applications since osteocytes are the major population within adult bones and Fas signalling is one of therapeutical targets, e.g., in the anti-osteoporotic treatment.

Abstract

The Fas ligand (FasL) is known from programmed cell death, the immune system, and recently also from bone homeostasis. As such, Fas signalling is a potential target of anti-osteoporotic treatment based on the induction of osteoclastic cell death. Less attention has been paid to osteocytes, although they represent the majority of cells within the mature bone and are the key regulators. To determine the impact of FasL stimulation on osteocytes, differentiated IDG-SW3 cells were challenged by FasL, and their osteogenic expression profiles were evaluated by a pre-designed PCR array. Notably, the most downregulated gene was the one for sclerostin, which is the major marker of osteocytes and a negative regulator of bone formation. FasL stimulation also led to significant changes (over 10-fold) in the expression of other osteogenic markers: Gdf10, Gli1, Ihh, Mmp10, and Phex. To determine whether these alterations involved caspase-dependent or caspase-independent mechanisms, the IDG-SW3 cells were stimulated by FasL with and without a caspase inhibitor: Q-VD-OPh. The alterations were also detected in the samples treated by FasL along with Q-VD-OPh, pointing to the caspase-independent impact of FasL stimulation. These results contribute to an understanding of the recently emerging pleiotropic effects of Fas/FasL signalling and specify its functions in bone cells.

Oxidative stress induces downregulation of TP53INP2 and suppresses osteogenic differentiation of BMSCs during osteoporosis through the autophagy degradation pathway

Oxidative stress plays an important role in the pathogenesis of osteoporosis and impaired bone formation. However, the mechanisms behind which oxidative stress represses bone formation remains unclear. TP53INP2, a target of the tumor suppressor p53, is ubiquitously expressed in various cell types including BMSCs and contributes to autophagosome formation by recruiting ubiquitinated substrates to autophagosomes for degradation. However, little is known about its function in BMSCs and its relation to osteoporosis. In this study, first, we verified that the expression of TP53INP2 was persistently decreased in BMSCs derived from osteoporosis patients and OVX mice, and that the antioxidant N-acetylcysteine could ameliorate this decreased TP53INP2 level in vitro. Second, we identified that the mRNA and protein levels of TP53INP2 decreased in BMSCs under H₂O₂ induced oxidative stress in a dose-dependent manner, with resultant co-location of LC3 and TP53INP2. Additionally, the autophagy-lysosome system was involved in the degradation process of TP53INP2 and applying autophagy inhibitors (Baf-A1) could significantly increase the TP53INP2 levels in murine and human BMSCs under oxidative stress. Third, gain- and loss-of-function assays revealed that knockdown of TP53INP2 inhibited osteogenic differentiation of BMSCs, while overexpression of TP53INP2 promoted osteogenic differentiation of BMSCs in vitro. Further analysis demonstrated that TP53INP2 promoted osteogenic differentiation of BMSCs by activating Wnt/β-cantenin signaling. DKK1, an inhibitor of Wnt signaling, resulted in osteogenic defects of BMSCs that had over-expressed TP53INP2. Lithium, a Wnt/β-catenin activator, improved the mineralization ability in TP53INP2-knockdown BMSCs. Moreover, restoring TP53INP2 levels recovered OVX-derived BMSCs osteogenic differentiation and attenuated bone loss in OVX mice. Taken together, our study indicated that oxidative stress-induced downregulation of TP53INP2 suppressed osteogenic differentiation of BMSCs during osteoporosis and was mediated by the autophagy degradation pathway. These findings may introduce a novel therapeutic target for osteoporosis.

Dysregulation of miR-638 in the progression of cancers

MicroRNA (miRNA) is a form of short, single-stranded and non-coding RNA that is important in regulating the post-transcriptional modification of multiple downstream targets. Many miRNAs have been reported to involve in controlling the progression of human diseases, and one of them is miR-638, which play essential roles in regulating the development of human cancer. By targeting the 3'-ends of its targets, miR-638 can regulate cellular processes including proliferation, invasion, metastases, angiogenesis, apoptosis and inflammation. This review was aimed to summarize current findings on the roles of miR-638 in different human cancers based on the results from various in vitro, in vivo and clinical studies. The biogenesis process and tissue expression, followed by the roles of miR-638 in regulating the development of various human cancers by targeting different downstream targets were covered in this review. The potential applications and challenges of employing miR-638 as cancer biomarker and therapeutic agent were also discussed.

Ursolic acid derivative UA232 evokes apoptosis of lung cancer cells induced by endoplasmic reticulum stress

CONTEXT

Ursolic acid (UA), a natural product, shows a broad spectrum of anticancer effects. However, the poor bioavailability and efficacy of UA limit its clinical application.

OBJECTIVE

We developed novel analogues of UA with enhanced antitumor activities by the extensive chemical modification of UA.

MATERIALS AND METHODS

We developed multiple compounds by structural modification of UA, and found that UA232 had stronger activity than UA. The effects of UA232 (0-50 μM) on inhibiting the proliferation of A549 and H460 cells were determined by CCK-8 for 24, 48, or 72 h. The proapoptotic effect of UA232 was analyzed by microscopy and flow cytometry, and the potential signal pathway affected by UA232 was further validated by Western blotting and flow cytometry.

RESULTS

Compared with UA, UA232 showed a stronger ability to inhibit the proliferation of lung cancer cells (IC50 = 5.4-6.1 μM for A549 and 3.9-5.7 μM for H460 cells). UA232 could induce not only cell cycle arrest in the G0/G1 phase but also apoptosis in both A549 and H460 cells. The treatment of UA232 could lead to an increase of CHOP expression rather than an increase in Bax or caspase-8, indicating that the apoptosis induced by UA232 was correlated with the endoplasmic reticulum stress (ER stress) pathway. Treatment with the ER stress-specific inhibitor, 4-PBA, decreased the ability of UA232 to induce apoptosis in A549 and H460 cells.

CONCLUSION

UA232 induced apoptosis through the ER stress pathway, and showed stronger growth-inhibitory effects in A549 and H460 cells compared to UA, which may be a potential anticancer drug to suppress the proliferation of lung cancer.

The dialogue between the ubiquitin-proteasome system and autophagy: Implications in ageing

Dysregulated proteostasis is one of the hallmarks of ageing. Damaged proteins may impair cellular function and their accumulation may lead to tissue dysfunction and disease. This is why protective mechanisms to safeguard the cell proteome have evolved. These mechanisms consist of cellular machineries involved in protein quality control, including regulators of protein translation, folding, trafficking and degradation. In eukaryotic cells, protein degradation occurs via two main pathways: the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway. Although distinct pathways, they are not isolated systems and have a complementary nature, as evidenced by recent studies. These findings raise the question of how autophagy and the proteasome crosstalk. In this review we address how the two degradation pathways impact each other, thereby adding a new layer of regulation to protein degradation. We also analyze the implications of the UPS and autophagy in ageing.

Novel regulator role of CIL-102 in the epigenetic modification of TNFR1/TRAIL to induce cell apoptosis in human gastric cancer

CIL-102 (1-[4-(furo [2,3-b]quinolin-4-ylamino)phenyl]ethanone) is a major active agent and an alkaloid derivative of Camptotheca acuminata, which has valuable biological properties, including anti-tumorigenic activity. However, the molecular mechanisms of CIL-102 related to inductive apoptosis in human gastric cancer remain unclear. By using diphenyltetrazolium bromide (MTT), annexin-V-fluorescein-isothiocyanate (FITC)/propidium iodide staining and a 2',7' -dichlorofluorescin diacetate (DCFDA), a Fluo-3 fluorescence staining assay, the cell death and cell viability in gastric cancer cells and an in vivo xenograft mouse model, with or without the addition of CIL-102, were measured, respectively. Furthermore, signaling pathways and apoptotic molecules were also detected by western blots and an immunohistochemical assay. Our results demonstrated that CIL-102 treatment significantly induced the cell apoptosis of gastric cancer cells, along with increased ROS production and increased intracellular Ca2+ levels. In addition, through the inactivation of CDK1/cyclin B1, CIL-102 treatment induced the cell cycle G2/M arrest of gastric cancer cells. Moreover, our data revealed that multiple signaling pathways were involved in the H3K4 trimethylation of TNFR1 and TRAIL proteins by CIL-102, including ROS-derived and JNK/mTOR/p300 pathways in gastric cancer AGS cells. The CIL-102 treatment also consistently inhibited tumor growth and increased tumor apoptosis, as measured by TUNEL assay in an in vivo xenograft mouse model. An immunohistochemical analysis revealed that the upregulation of the TNFR1 and TRAIL proteins and the downregulation of PCNA and CDK1 proteins were found in the CIL-102-treated gastric cancer xenograft mouse model, compared to that of the saline control. Together, this study sheds light on the novel mechanism associated with CIL-102 for inducing gastric cancer apoptosis.

Tumor protein p53-induced nuclear protein 2 modulates osteogenic differentiation of human adipose derived stem/stromal cells by activating Wnt/β-catenin signaling

Human adipose derived stem/stromal cells (hASCs) are frequently used as seed cells in bone tissue engineering. These cells have good osteogenic properties in various in vivo and in vitro models. Tumor protein p53-induced nuclear protein 2 (TP53INP2) regulates apoptosis, autophagy, and cell differentiation. However, whether TP53INP2 regulates osteogenic differentiation of hASCs has not been sufficiently studied. Herein, we explored this topic using siRNA experiments, osteogenic induction, quantitative real-time PCR (qRT-PCR) and western blot analysis. We found that siRNA decreased mRNA levels of osteoblast-specific genes in TP53INP2 cells. Western blots showed that RUNX2 protein expression decreased in siRNA-TP53INP2 cells at day 3, 7, and 21 after osteogenic induction. The level of β-catenin, LC3 and the LC3-II/LC3-I ratio in siRNA-TP53INP2 cells was decreased at day 3 and 7 after osteogenic induction. Further, treatment with lithium chloride (LiCl), an activator of Wnt signaling pathway, induced partial recovery of protein expression of β-catenin and RUNX2 (osteoblast-specific factor 2) in TP53INP2 knockdown cells. Collectively, these results show that TP53INP2 promotes osteogenic differentiation of hASCs by activating Wnt/β-catenin signaling.

Long non-coding RNA regulation of TRAIL in breast cancer: A tangle of non-coding threads

Breast cancer is a complex disease posing a serious threat to the female population worldwide. A complex molecular landscape and tumor heterogeneity render breast cancer cells resistant to drugs and able to promote metastasis and invasiveness. Despite the recent advancements in diagnostics and drug discovery, finding an effective cure for breast cancer is still a major challenge. Positive and negative regulation of apoptosis has been a subject of extensive study over the years. Numerous studies have shed light on the mechanisms that impede the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) signaling cascade. Long non-coding RNAs (lncRNAs) have been implicated in the orchestration, development, proliferation, differentiation and metastasis of breast cancer. However, the roles of lncRNAs in fine-tuning apoptosis regulating machinery in breast cancer remain to be elucidated. The present review illuminates the roles of these molecules in the regulation of breast cancer and the interplay between lncRNA and TRAIL in breast cancer. The present review also attempts to reveal their role in the regulation of apoptosis in breast cancer appears a promising approach for the development of new diagnostic and therapeutic regimens.

The bifunctional role of TP53INP2 in transcription and autophagy

Cells integrate intracellular and extracellular cues to precisely control the balance of anabolic and catabolic processes, which is essential for cells to maintain homeostasis. The nuclear protein TP53INP2 (tumor protein p53 inducible nuclear protein 2) has emerged as one of the key players participating in both anabolic and catabolic processes. In the nucleus including the nucleolus, TP53INP2 binds to multiple transcription-related factors to modulate transcription, such as the transcription of thyroid hormone-related genes and ribosomal DNA. Interestingly, upon nutrient deprivation, TP53INP2 rapidly moves from the nucleus to the cytoplasm and participates in the regulation of macroautophagy/autophagy. By acting as a nutrient status sensor, TP53INP2 switches its role between transcription and autophagy by changing its subcellular localization and helps the cell to cope with environmental changes.

ABBREVIATIONS

Atg: autophagy related; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; rDNA: ribosomal DNA; TP53INP2: tumor protein p53 inducible nuclear protein 2; UIM: ubiquitin-interacting motif.

LRP6 regulates Rab7-mediated autophagy through the Wnt/β-catenin pathway to modulate trophoblast cell migration and invasion

Pre-eclampsia is a common complication during pregnancy; however, the underlying mechanisms of the crosstalk between low-density lipoprotein receptor-related protein 6 (LRP6) and autophagy in trophoblast cells are still not fully explored. Messenger RNA (mRNA) and protein levels of LRP6, beclin 1, Unc-51-like autophagy activating kinase 1 (ULK1), p62, vimentin, matrix metallopeptidase-9 (MMP-9), β-catenin, c-Myc, and Rab7, as well as the ratio of LC3-II/LC3-I, were analysed by quantitative real-time polymerase chain reaction or Western blot analysis, respectively. An MTT assay was used to measure cell growth, and transwell and wound healing assays were carried out to evaluate the invasion and migration abilities of the trophoblasts used. An immunofluorescence assay was used to measure LC3. The mRFP-GFP-LC3 tandem fluorescence assay was applied to detect autophagic flow. LRP6 overexpression was achieved by constructing pcDNA3.1-LRP6 vectors. LRP6 was expressed at low levels in HTR-8/SVneo cells under hypoxia/reoxygenation (H/R) conditions. H/R inhibited the activation of autophagy. LRP6 overexpression promoted cell proliferation and activated autophagy, which led to the upregulation of beclin 1 and ULK1, as well as the ratio of LC3-II/LC3-I and the downregulation of p62. Furthermore, LRP6 overexpression elevated the migration and invasion abilities of the indicated cells and increased vimentin and MMP-9 expression levels. Furthermore, LRP6 upregulated Rab7 and activated autophagy through the Wnt/β-catenin pathway. The late autophagy inhibitor bafilomycin A1 (Baf-A1) and the Wnt/β-catenin pathway inhibitor PKF115-584 reversed the effects of LRP6 on trophoblast autophagy, migration and invasion. LRP6 promotes Rab7-mediated autophagy by activating the Wnt/β-catenin pathway, which leads to increasing migration and invasion of trophoblast cells. Our study paves a new avenue for clinical treatment, and LRP6 may serve as an essential target in pre-eclampsia.

TP53INP2 at the crossroad of apoptosis and autophagy in death receptor signaling

The binding of ligands to death receptors elicits distinct outcomes, such as apoptosis, inflammation and necroptosis, depending on the cellular context. We have recently described that the autophagic protein TP53INP2 favors apoptosis upon death receptor signaling and is a potential biomarker of responsiveness to TRAIL treatment.