Beclin 1 Promotes Endosome Recruitment of Hepatocyte Growth Factor Tyrosine Kinase Substrate to Suppress Tumor Proliferation

Roles of ubiquitin‑specific protease 13 in normal physiology and tumors (Review)

Ubiquitin-specific protease 13 (USP13) is one of the most important deubiquitinases involved in various diseases. As deubiquitinases are components of the deubiquitination process, a significant post-translational modification, they are potential treatment targets for different diseases. With recent technological developments, the structure of USP13 and its pathological and physiological functions have been investigated. However, USP13 expression and function differ in various diseases, especially in tumors, and the associated mechanisms are complex and remain to be fully investigated. The present review summarized the recent discoveries and the current understanding of the USP13 function in tumors.

Targeting autophagy and beyond: Deconvoluting the complexity of Beclin-1 from biological function to cancer therapy

Beclin-1 is the firstly-identified mammalian protein of the autophagy machinery, which functions as a molecular scaffold for the assembly of PI3KC3 (class III phosphatidylinositol 3 kinase) complex, thus controlling autophagy induction and other cellular trafficking events. Notably, there is mounting evidence establishing the implications of Beclin-1 in diverse tumorigenesis processes, including tumor suppression and progression as well as resistance to cancer therapeutics and CSC (cancer stem-like cell) maintenance. More importantly, Beclin-1 has been confirmed as a potential target for the treatment of multiple cancers. In this review, we provide a comprehensive survey of the structure, functions, and regulations of Beclin-1, and we discuss recent advances in understanding the controversial roles of Beclin-1 in oncology. Moreover, we focus on summarizing the targeted Beclin-1-regulating strategies in cancer therapy, providing novel insights into a promising strategy for regulating Beclin-1 to improve cancer therapeutics in the future.

COTE1 Facilitates Intrahepatic Cholangiocarcinoma Progression via Beclin1-Dependent Autophagy Inhibition

COTE1 was recently described as an oncogene in hepatocellular carcinoma and gastric cancer. However, the roles of COTE1 in intrahepatic cholangiocarcinoma (ICC) are little known. Our study is aimed at clarifying novel functions of COTE1 in ICC progression, including proliferation, invasion, and autophagy. By using quantitative real-time PCR, immunohistochemistry staining, and western blotting, we found that COTE1 expression was frequently upregulated in ICC tissues, compared to paracarcinoma tissues. High COTE1 expression was significantly correlated with aggressive clinical features and predicted poor prognosis of ICC patients. Functional experiments revealed that ectopic COTE1 expression promoted ICC cell proliferation, colony formation, cellular invasion, migration, and in vivo tumorigenicity; in contrast, COTE1 knockdown resulted in the opposite effects. At molecular mechanism in vitro and vivo, our study revealed that COTE1 overexpression suppressed autophagy via Beclin1 transcription inhibition; conversely, COTE1 silencing facilitated autophagy through promoting Beclin1 expression. Furthermore, the suppression of COTE1 knockdown on cellular growth and invasion was rescued/aggravated by Beclin1 inhibition/accumulation. Our data, for the first time, illustrate that COTE1 is an oncogene in ICC pathogenesis, and the ectopic COTE1 expression promotes ICC proliferation and invasion via Beclin1-dependent autophagy inhibition.

Effects of the Natural Flavonoid Quercetin on Arenavirus Junín Infection

There is no specific chemotherapy approved for the treatment of pathogenic arenaviruses that cause severe hemorrhagic fever (HF) in the population of endemic regions in America and Africa. The present study reports the effects of the natural flavonoid quercetin (QUER) on the infection of A549 and Vero cells with Junín virus (JUNV), agent of the Argentine HF. By infectivity assays, a very effective dose-dependent reduction of JUNV multiplication was shown by cell pretreatment at 2-6 h prior to the infection at non-cytotoxic concentrations, with 50% effective concentration values in the range of 6.1-7.5 µg/mL. QUER was also active by post-infection treatment but with minor efficacy. Mechanistic studies indicated that QUER mainly affected the early steps of virus adsorption and internalization in the multiplication cycle of JUNV. Treatment with QUER blocked the phosphorylation of Akt without changes in the total protein expression, detected by Western blot, and the consequent perturbation of the PI3K/Akt pathway was also associated with the fluorescence redistribution from membrane to cytoplasm of TfR1, the cell receptor recognized by JUNV. Then, it appears that the cellular antiviral state, induced by QUER treatment, leads to the prevention of JUNV entry into the cell.

Mechanistic target of rapamycin (mTOR) regulates self-sustained quiescence, tumor indolence, and late clinical metastasis in a Beclin-1-dependent manner

Self-sustained quiescence (SSQ) has been characterized as a stable but reversible non-proliferative cellular state that limits the cloning of cultured cancer cells. By developing refined clonogenic assays, we showed here that cancer cells in SSQ can be selected with anticancer agents and that culture at low cell density induced SSQ in pancreas and prostate adenocarcinoma cells. Pre-culture of cells in 3D or their pretreatment with pharmacological inhibitors of mechanistic target of rapamycin (mTOR) synergize with low cell density for induction of SSQ in a Beclin-1-dependent manner. Dissociated pancreatic adenocarcinoma (PAAD) cells rendered defective for SSQ by down-regulating Beclin-1 expression exhibit higher tumor growth rate when injected subcutaneously into mice. Conversely, dissociated PAAD cells in SSQ promote the formation of small indolent tumors that eventually transitioned to a rapid growth phase. Ex vivo clonogenic assays showed that up to 40% of clonogenic cancer cells enzymatically dissociated from resected fast-growing tumors could enter SSQ, suggesting that SSQ could significantly impact the proliferation of cancer cells that are naturally dispersed from tumors. Remarkably, the kinetics of clinical metastatic recurrence in 124 patients with pancreatic adenocarcinoma included in the TGCA-PAAD project could be predicted from Beclin-1 and Cyclin-A2 mRNA levels in their primary tumor, Cyclin A2 mRNA being a marker of both cell proliferation and mTOR complex 1 activity. Overall, our data show that SSQ is likely to promote the late development of clinical metastases and suggest that identifying new agents targeting cancer cells in SSQ could help improve patient survival.

The role of BCL-2 family proteins in regulating apoptosis and cancer therapy

Apoptosis, as a very important biological process, is a response to developmental cues or cellular stress. Impaired apoptosis plays a central role in the development of cancer and also reduces the efficacy of traditional cytotoxic therapies. Members of the B-cell lymphoma 2 (BCL-2) protein family have pro- or anti-apoptotic activities and have been studied intensively over the past decade for their importance in regulating apoptosis, tumorigenesis, and cellular responses to anticancer therapy. Since the inflammatory response induced by apoptosis-induced cell death is very small, at present, the development of anticancer drugs targeting apoptosis has attracted more and more attention. Consequently, the focus of this review is to summarize the current research on the role of BCL-2 family proteins in regulating apoptosis and the development of drugs targeting BCL-2 anti-apoptotic proteins. Additionally, the mechanism of BCL-2 family proteins in regulating apoptosis was also explored. All the findings indicate the potential of BCL-2 family proteins in the therapy of cancer.

Beclin1-mediated interplay between autophagy and apoptosis: New understanding

The definition for autophagy holds a 'single' meaning as a conserved cellular process that constitutes a recycling pathway for damaged organelles and long-lived proteins to maintain nutrient homeostasis and mediate quality control within the cell. But this process of autophagy may behave ambiguously depending on the physiological stress as the stress progresses in the cellular microenvironment; the 'single' meaning of the autophagy changes from the 'cytoplasmic turnover process' to 'tumor suppressive' and a farther extent, 'tumor promoter' process. In a tumorigenic state, the chemotherapy-mediated resistance and intolerance due to upregulated autophagy in cancer cells have become a significant concern. This concern has provided insight to the scientific community to enter into the arena of cross-talk between autophagy and apoptosis. Recent findings and ongoing research have provided insights on some of the key regulators of this cross-talk; one of them is Beclin1 and their involvement in the physiological and the pathophysiological processes; however, reconciliation of these two forms of death remains an arena to be explored extensively. This review sheds light on the interplay between autophagy and apoptosis, emphasizing one of the key players, Beclin1, and its importance in health and diseases.

The Role of Non-Coding RNAs in Autophagy During Carcinogenesis

Macroautophagy (autophagy herein) is a cellular stress response and a survival pathway involved in self-renewal and quality control processes to maintain cellular homeostasis. The alteration of autophagy has been implicated in numerous diseases such as cancer where it plays a dual role. Autophagy serves as a tumor suppressor in the early phases of cancer formation with the restoration of homeostasis and eliminating cellular altered constituents, yet in later phases, autophagy may support and/or facilitate tumor growth, metastasis and may contribute to treatment resistance. Key components of autophagy interact with either pro- and anti-apoptotic factors regulating the proximity of tumor cells to apoptotic cliff promoting cell survival. Autophagy is regulated by key cell signaling pathways such as Akt (protein kinase B, PKB), mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) involved in cell survival and metabolism. The expression of critical members of upstream cell signaling, as well as those directly involved in the autophagic and apoptotic machineries are regulated by microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Consequently, non-coding RNAs play a relevant role in carcinogenesis and treatment response in cancer. The review is an update of the current knowledge in the regulation by miRNA and lncRNA of the autophagic components and their functional impact to provide an integrated and comprehensive regulatory network of autophagy in cancer.

Autophagy Regulation on Cancer Stem Cell Maintenance, Metastasis, and Therapy Resistance

Simple Summary

Certain types of cancer have higher relapse rates compared to others, and cancer stem cells (CSCs) have been shown as the main drivers of cancer relapse and cancer severity. This subpopulation of cells displays stem-like characteristics which bolster tumorigenesis along with metastasis and lead to poorer prognoses. Autophagy has been studied as a mechanism by which CSCs maintain stemness and acquire resistance to chemotherapy and radiation. The aim of this review is to condense and organize what has been recently published on the connection between cancer stem cells (CSCs) and autophagy. Multiple studies on autophagy have suggested that the pathway is a double-edged sword, which can either undermine or enhance CSC characteristics depending on interactions with different pathways. Thus, future research should investigate regulation of autophagy in combination with traditional cancer therapies as a possible method to effectively eliminate CSCs and minimize cancer relapse.

Abstract

Cancer stem cells (CSCs) are a subset of the tumor population that play critical roles in tumorigenicity, metastasis, and relapse. A key feature of CSCs is their resistance to numerous therapeutic strategies which include chemotherapy, radiation, and immune checkpoint inhibitors. In recent years, there is a growing body of literature that suggests a link between CSC maintenance and autophagy, a mechanism to recycle intracellular components during moments of environmental stress, especially since CSCs thrive in a tumor microenvironment that is plagued with hypoxia, acidosis, and lack of nutrients. Autophagy activation has been shown to aid in the upkeep of a stemness state along with bolstering resistance to cancer treatment. However, recent studies have also suggested that autophagy is a double-edged sword with anti-tumorigenic properties under certain circumstances. This review summarizes and integrates what has been published in the literature in terms of what role autophagy plays in stemness maintenance of CSCs and suggests that there is a more complex interplay between autophagy and apoptosis which involves multiple pathways of regulation. Future cancer therapy strategies are needed to eradicate this resistant subset of the cell population through autophagy regulation.

The Role of Iron in Cancer Progression

Iron is an essential trace element for the human body, and its deficiency or excess can induce a variety of biological processes. Plenty of evidences have shown that iron metabolism is closely related to the occurrence and development of tumors. In addition, iron plays an important role in cell death, which is very important for the development of potential strategies for tumor treatment. Here, we reviewed the latest research about iron metabolism disorders in various types of tumors, the functions and properties of iron in ferroptosis and ferritinophagy, and new opportunities for iron-based on treatment methods for tumors, providing more information regarding the prevention and treatment of tumors.

Endosomal trafficking and DNA damage checkpoint kinases dictate survival to replication stress by regulating amino acid uptake and protein synthesis

Atg6^{Beclin 1} mediates autophagy and endosomal trafficking. We investigated how Atg6 influences replication stress. Combining genetic, genomic, metabolomic, and proteomic approaches, we found that the Vps34-Vps15-Atg6^{Beclin 1}-Vps38^UVRAG-phosphatydilinositol-3 phosphate (PtdIns(3)P) axis sensitizes cells to replication stress by favoring the degradation of plasma membrane amino acid (AA) transporters via endosomal trafficking and ESCRT proteins, while the PtdIns(3)P phosphatases Ymr1 and Inp53 promote survival to replication stress by reversing this process. An impaired AA uptake triggers activation of Gcn2, which attenuates protein synthesis by phosphorylating eIF2α. Mec1^Atr-Rad53^Chk1/Chk2 activation during replication stress further hinders translation efficiency by counteracting eIF2α dephosphorylation through Glc7^PP1. AA shortage-induced hyperphosphorylation of eIF2α inhibits the synthesis of 65 stress response proteins, thus resulting in cell sensitization to replication stress, while TORC1 promotes cell survival. Our findings reveal an integrated network mediated by endosomal trafficking, translational control pathways, and checkpoint kinases linking AA availability to the response to replication stress.

CDK4, CDK6/cyclin-D1 Complex Inhibition and Radiotherapy for Cancer Control: A Role for Autophagy

The expanding clinical application of CDK4- and CDK6-inhibiting drugs in the managements of breast cancer has raised a great interest in testing these drugs in other neoplasms. The potential of combining these drugs with other therapeutic approaches seems to be an interesting work-ground to explore. Even though a potential integration of CDK4 and CDK6 inhibitors with radiotherapy (RT) has been hypothesized, this kind of approach has not been sufficiently pursued, neither in preclinical nor in clinical studies. Similarly, the most recent discoveries focusing on autophagy, as a possible target pathway able to enhance the antitumor efficacy of CDK4 and CDK6 inhibitors is promising but needs more investigations. The aim of this review is to discuss the recent literature on the field in order to infer a rational combination strategy including cyclin-D1/CDK4-CDK6 inhibitors, RT, and/or other anticancer agents targeting G1-S phase cell cycle transition.

Newcastle-disease-virus-induced ferroptosis through nutrient deprivation and ferritinophagy in tumor cells

A number of new cell death processes have been discovered in recent years, including ferroptosis, which is characterized by the accumulation of lipid peroxidation products derived from iron metabolism. The evidence suggests that ferroptosis has a tumor-suppressor function. However, the mechanism by which ferroptosis mediates the response of tumor cells to oncolytic viruses remains poorly understood. The Newcastle disease virus (NDV) can selectively replicate in tumor cells. We show that NDV-induced ferroptosis acts through p53-SLC7A11-GPX4 pathway. Meanwhile, the levels of intracellular reactive oxygen species and lipid peroxides increased in tumor cells. Ferritinophagy was induced by NDV promotion of ferroptosis through the release of ferrous iron and an enhanced Fenton reaction. Collectively, these observations demonstrated that the NDV can kill tumor cells through ferroptosis. Our study provides novel insights into the mechanisms of NDV-induced ferroptosis and highlights the critical role of viruses in treating therapy-resistant cancers.

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Oncolytic viruses NDV caused tumor cells death through ferroptosis

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NDV-induced ferroptosis acts through nutrient deprivation by suppression of System Xc⁻

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P53 activation is required for NDV-induced ferroptosis initiation

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Ferritinophagy induced by NDV promotes ferroptosis through release of ferrous iron

Ubiquitin proteasome system and autophagy associated proteins in human testicular tumors

Ubiquitin proteasome sytem (UPS) and autophagy govern protein quality control by degradation and clearance of damaged proteins. Many proteins working in these pathways such as p97/VCP, Ubiquitin (Ub), Jab1/CSN5, p62, LC3B and Beclin 1 are known to be essential for different pathological conditions, especially in cancer, but their expression in human testicular tumors has not been characterized yet. In the present study, we aimed to investigate the expression of UPS (p97/VCP, Ubiquitin, Jab1/CSN5) and autophagic (p62, LC3B, Beclin 1) proteins in human testicular tumors and cancer adjacent normal testicular tissues. We used an immunohistochemical staining technique. 120 cases of testicular germ and non-germ cell tumors, which are 42 seminomas, 31 embryonal carcinomas, 11 yolk sac tumors, 25 intratubular germ cell neoplasms, 6 Leydig cell tumors, 5 Sertoli cell tumors, were collected and evaluated on tissue microarray. For the first time, the expression of p97/VCP, Ub, Jab1/CSN5, p62, LC3B and Beclin 1 in different type of human testicular tumors has been confirmed. We found that p97/VCP, Ub and Jab1/CSN5 were frequently expressed at higher levels in testicular tumours. In contrast to UPS markers, p62, LC3B and Beclin 1 showed significantly diminished expressions in testicular tumors. Accordingly, a negative correlation between p97/VCP and autophagic markers (p62 and LC3B) was found, suggesting a relationship between UPS and autophagy in different type of testicular tumors. The current results displayed elevated level of p97/VCP, Ub and Jab1/CSN5 expressions in contrast to the diminished expression of p62, LC3B and Beclin 1 in human testicular tumors, thereby supporting a correlation between p97/VCP and autophagic markers in testicular tumors.

An overview of autophagy: Mechanism, regulation and research progress

Autophagy refers to the formation of autophagosomes by membrane wrapping part of the cytoplasm and the organelles and proteins that need to be degraded in the cells. Autophagosomes are fused with lysosomes to form autophagolysosome, which degrade the contents of the inclusions, to achieve cell homeostasis and organelle renewal. The regulatory mechanism of autophagy is complex, and its upstream signaling pathway mainly involves mTOR dependent pathway and mTOR independent pathway (AMPK, PI3K, Ras-MAPK, p53, PTEN, endoplasmic reticulum stress). Autophagy is a phenomenon of "self-eating" in cells. Apoptosis is a phenomenon of "self-killing". Both of them share the same stimulating factors and regulatory proteins, but the threshold of induction is different. How to transform and coordinate is not clear at present. This paper summarizes the history of autophagy discovery, the structure and function of related molecules, the biological function of autophagy, the regulatory mechanism and the research results of the relationship between autophagy and apoptosis.

The beclin 1 interactome: Modification and roles in the pathology of autophagy-related disorders

Beclin 1 a yeast Atg6/VPS30 orthologue has a significant role in autophagy process (Macroautophagy) and protein sorting. The function of beclin 1 depends on the interaction with several autophagy-related genes (Atgs) and other proteins during the autophagy process. The role mediated by beclin 1 is controlled by various conditions and factors. Beclin 1 is regulated at the gene and protein levels by different factors. These regulations could subsequently alter the beclin 1 induced autophagy process. Therefore, it is important to study the components of beclin 1 interactome and factors affecting its expression. Expression of this gene is differentially regulated under different conditions in different cells or tissues. So, the regulation part is important to study as beclin 1 is one of the candidate genes involved in diseases related to autophagy dysfunction. This review focuses on the functions of beclin 1, its interacting partners, regulations at gene and protein level, and the role of beclin 1 interactome in relation to various diseases along with the recent developments in the field.