Autophagy mediates HIF2α degradation and suppresses renal tumorigenesis

Atractylenolide I inhibits angiogenesis and reverses sunitinib resistance in clear cell renal cell carcinoma through ATP6V0D2-mediated autophagic degradation of EPAS1/HIF2α

Clear cell renal cell carcinoma (ccRCC) is tightly associated with VHL (von Hippel-Lindau tumor suppressor) mutation and dysregulated angiogenesis. Accumulating evidence indicates that antiangiogenic treatment abolishing tumor angiogenesis can achieve longer disease-free survival in patients with ccRCC. Atractylenolide I (ATL-I) is one of the main active compounds in Atractylodes macrocephala root extract and exhibits various pharmacological effects, including anti-inflammatory and antitumor effects. In this study, we revealed the potent antitumor activity of ATL-I in ccRCC. ATL-I exhibited robust antiangiogenic capacity by inhibiting EPAS1/HIF2α-mediated VEGFA production in VHL-deficient ccRCC, and it promoted autophagic degradation of EPAS1 by upregulating the ATPase subunit ATP6V0D2 (ATPase H+ transporting V0 subunit d2) to increase lysosomal function and facilitated fusion between autophagosomes and lysosomes. Mechanistically, ATP6V0D2 directly bound to RAB7 and VPS41 and promoted the RAB7-HOPS interaction, facilitating SNARE complex assembly and autophagosome-lysosome fusion. Moreover, ATP6V0D2 promoted autolysosome degradation by increasing the acidification and activity of lysosomes during the later stages of macroautophagy/autophagy. Additionally, we found that ATL-I could decrease the level of EPAS1, which was upregulated in sunitinib-resistant cells, thus reversing sunitinib resistance. Collectively, our findings demonstrate that ATL-I is a robust antiangiogenic and antitumor lead compound with potential clinical application for ccRCC therapy.Abbreviations: ATL-I: atractylenolide I; ATP6V0D2: ATPase H+ transporting V0 subunit d2; CAM: chick chorioallantoic membrane; ccRCC: clear cell renal cell carcinoma; CTSB: cathepsin B; CTSD: cathepsin D; GO: Gene Ontology; HIF-1: HIF1A-ARNT heterodimer; HOPS: homotypic fusion and protein sorting; KDR/VEGFR: kinase insert domain receptor; KEGG: Kyoto Encyclopedia of Genes and Genomes; RCC: renal cell carcinoma; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; TCGA: The Cancer Genome Atlas; TEM: transmission electron microscopy; TKI: tyrosine kinase inhibitor; V-ATPase: vacuolar-type H±translocating ATPase; VEGF: vascular endothelial growth factor; VHL: von Hippel-Lindau tumor suppressor.

Targeting autophagy in urological system cancers: From underlying mechanisms to therapeutic implications

The urological system, including kidneys, ureters, bladder, urethra and prostate is known to be vital for blood filtration, waste elimination and electrolyte balance. Notably, urological system cancers represent a significant portion of global cancer diagnoses and mortalities. The current therapeutic strategies for early-stage cancer primarily involve resection surgery, which significantly affects the quality of life of patients, whereas advanced-stage cancer often relies on less effective chemo- or radiotherapy. Recently, accumulating evidence has revealed that autophagy, a crucial process in which excess organelles or inclusions within cells are removed to maintain cell homeostasis, has numerous links to urological system cancers. In this review, we focus on summarizing the underlying two-sided mechanisms of autophagy in urological system cancers. We also review the current clinical drugs targeting autophagy, which demonstrate significant potential in improving treatment outcomes for urological system cancers. In addition, we provide an overview of the research status of novel small molecule compounds targeting autophagy that are in the preclinical stages of investigation. Furthermore, drug combinations based on autophagy modulation strategies in urological system cancers are systematically summarized and discussed. These findings provide comprehensive new insight for the future discovery of more autophagy-related drug candidates.

USP7 depletion potentiates HIF2α degradation and inhibits clear cell renal cell carcinoma progression

Clear cell renal cell carcinoma (ccRCC) is characterized by Von Hippel Lindau (VHL) gene loss of function mutation, which leads to the accumulation of hypoxia-inducible factor 2α (HIF2α). HIF2α has been well-established as one of the major oncogenic drivers of ccRCC, however, its therapeutic targeting remains a challenge. Through an analysis of proteomic data from ccRCCs and adjacent non-tumor tissues, we herein revealed that Ubiquitin-Specific Peptidase 7 (USP7) was upregulated in tumor tissues, and its depletion by inhibitors or shRNAs caused significant suppression of tumor progression in vitro and in vivo. Mechanistically, USP7 expression is activated by the transcription factors FUBP1 and FUBP3, and it promotes tumor progression mainly by deubiquitinating and stabilizing HIF2α. Moreover, the combination of USP7 inhibitors and afatinib (an ERBB family inhibitor) coordinately induce cell death and tumor suppression. In mechanism, afatinib indirectly inhibits USP7 transcription and accelerates the degradation of HIF2α protein, and the combination of them caused a more profound suppression of HIF2α abundance. These findings reveal a FUBPs-USP7-HIF2α regulatory axis that underlies the progression of ccRCC and provides a rationale for therapeutic targeting of oncogenic HIF2α via combinational treatment of USP7 inhibitor and afatinib.

Selective Termination of Autophagy-Dependent Cancers

The goal of cancer research is to identify characteristics of cancer cells that allow them to be selectively eliminated without harming the host. One such characteristic is autophagy dependence. Cancer cells survive, proliferate, and metastasize under conditions where normal cells do not. Thus, the requirement in cancer cells for more energy and macromolecular biosynthesis can evolve into a dependence on autophagy for recycling cellular components. Recent studies have revealed that autophagy, as well as different forms of cellular trafficking, is regulated by five phosphoinositides associated with eukaryotic cellular membranes and that the enzymes that synthesize them are prime targets for cancer therapy. For example, PIKFYVE inhibitors rapidly disrupt lysosome homeostasis and suppress proliferation in all cells. However, these inhibitors selectively terminate PIKFYVE-dependent cancer cells and cancer stem cells with not having adverse effect on normal cells. Here, we describe the biochemical distinctions between PIKFYVE-sensitive and -insensitive cells, categorize PIKFYVE inhibitors into four groups that differ in chemical structure, target specificity and efficacy on cancer cells and normal cells, identify the mechanisms by which they selectively terminate autophagy-dependent cancer cells, note their paradoxical effects in cancer immunotherapy, and describe their therapeutic applications against cancers.

MFN2 suppresses the accumulation of lipid droplets and the progression of clear cell renal cell carcinoma

Dissolving the lipid droplets in tissue section with alcohol during a hematoxylin and eosin (H&E) stain causes the tumor cells to appear like clear soap bubbles under a microscope, which is a key pathological feature of clear cell renal cell carcinoma (ccRCC). Mitochondrial dynamics have been reported to be closely associated with lipid metabolism and tumor development. However, the relationship between mitochondrial dynamics and lipid metabolism reprogramming in ccRCC remains to be further explored. We conducted bioinformatics analysis to identify key genes regulating mitochondrial dynamics differentially expressed between tumor and normal tissues and immunohistochemistry and Western blot to confirm. After the target was identified, we created stable ccRCC cell lines to test the impact of the target gene on mitochondrial morphology, tumorigenesis in culture cells and xenograft models, and profiles of lipid metabolism. It was found that mitofusin 2 (MFN2) was downregulated in ccRCC tissues and associated with poor prognosis in patients with ccRCC. MFN2 suppressed mitochondrial fragmentation, proliferation, migration, and invasion of ccRCC cells and growth of xenograft tumors. Furthermore, MFN2 impacted lipid metabolism and reduced the accumulation of lipid droplets in ccRCC cells. MFN2 suppressed disease progression and improved prognosis for patients with ccRCC possibly by interrupting cellular lipid metabolism and reducing accumulation of lipid droplets.

TBC1D5 reverses the capability of HIF-2α in tumor progression and lipid metabolism in clear cell renal cell carcinoma by regulating the autophagy

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is known for abnormal lipid metabolism and widespread activation of HIF-2α. Recently, the importance of autophagy in ccRCC has been focused, and it has potential connections with HIF-2α and lipid metabolism. However, the specific regulatory mechanism between HIF-2α, autophagy, and lipid metabolism in ccRCC is still unclear.

METHODS

In this study, Bioinformatics Analysis and Sequencing of the whole transcriptome were used to screen our target. The expression of TBC1D5 in renal clear cell carcinoma was confirmed by database analysis, immunohistochemistry, PCR and Western blot. The effects of TBC1D5 on tumor cell growth, migration, invasion and lipid metabolism were examined by CCK8, Transwell and oil red staining, and the mechanism of TBC1D5 on autophagy was investigated by Western blot, fluorescence microscopy and electron microscopy. Chloroquine and rapamycin were used to verified the key role of autophagy in effects of TBC1D5 on tumor cell. The regulatory mechanism of TBC1D5 in renal clear cell carcinoma (RCC) was investigated by shhif-2α, shTBC1D5, mimic, inhibitor, ChIP and Luciferase experiments. The animal model of ccRCC was used to evaluate the biological function of TBC1D5 in vivo.

RESULTS

In this study, TBC1D5 was found to be an important bridge between autophagy and HIF-2α. Specifically, TBC1D5 is significantly underexpressed in ccRCC, serving as a tumor suppressor which inhibits tumor progression and lipid accumulation, and is negatively regulated by HIF-2α. Further research has found that TBC1D5 regulates the autophagy pathway to reverse the biological function of HIF-2α in ccRCC. Mechanism studies have shown that HIF-2α regulates TBC1D5 through hsa-miR-7-5p in ccRCC, thereby affecting tumor progression and lipid metabolism through autophagy.

CONCLUSIONS

Our research reveals a completely new pathway, HIF-2α/hsa-miR-7-5p/TBC1D5 pathway affects ccRCC progression and lipid metabolism by regulating autophagy.

Chronic hypoxia stabilizes 3βHSD1 via autophagy suppression

Progression of prostate cancer depends on androgen receptor, which is usually activated by androgens. Therefore, a mainstay treatment is androgen deprivation therapy. Unfortunately, despite initial treatment response, resistance nearly always develops, and disease progresses to castration-resistant prostate cancer (CRPC), which remains driven by non-gonadal androgens synthesized in prostate cancer tissues. 3β-Hydroxysteroid dehydrogenase/Δ5-->4 isomerase 1 (3βHSD1) catalyzes the rate-limiting step in androgen synthesis. However, how 3βHSD1, especially the "adrenal-permissive" 3βHSD1(367T) that permits tumor synthesis of androgen from dehydroepiandrosterone (DHEA), is regulated at the protein level is not well understood. Here, we investigate how hypoxia regulates 3βHSD1(367T) protein levels. Our results show that, in vitro, hypoxia stabilizes 3βHSD1 protein by suppressing autophagy. Autophagy inhibition promotes 3βHSD1-dependent tumor progression. Hypoxia represses transcription of autophagy-related (ATG) genes by decreasing histone acetylation. Inhibiting deacetylase (HDAC) restores ATG gene transcription under hypoxia. Therefore, HDAC inhibition may be a therapeutic target for hypoxic tumor cells.

Targeting GABARAPL1/HIF-2a axis to induce tumor cell apoptosis in nasopharyngeal carcinoma

Objectives

The primary gene mutations associated with nasopharyngeal carcinoma (NPC) are located within the phosphoinositide 3-kinase-mammalian target of rapamycin signaling pathways, which have inhibitory effects on autophagy. Compounds that target autophagy could potentially be used to treat NPC. However, autophagy-related molecular targets in NPC remain to be elucidated. We aimed to examine levels of autophagy-related genes, including autophagy-related 4B cysteine peptidase (ATG4B) and gamma-aminobutyric acid (GABA) type A receptor-associated protein-like 1 (GABARAPL1), in NPC cells and explored their potential role as novel targets for the treatment of NPC.

Materials and Methods

The mRNA and protein expression of autophagy-related genes were detected in several NPC cells. Levels of GABARAPL1 were modified by either overexpression or knockdown, followed by examining downstream targets using RT-qPCR and western blotting. The role of GABARAPL1 in NPC proliferation and apoptosis was examined by flow cytometry. Furthermore, the role of GABARAPL1 was assessed in vivo using a nude mouse xenograft tumor model. The underlying mechanism by which GABARAPL1 regulated nasopharyngeal tumor growth was investigated.

Results

Autophagy-related 4B cysteine peptidase (ATG4B), GABARAPL1, and Unc-51-like kinase 1 (ULK1) were significantly down-regulated in multiple NPC cell lines. Overexpression of GABARAPL1 up-regulated the expression of autophagy-related proteins, decreased the level of hypoxia-inducible factor (HIF)-2α, and induced apoptosis in NPC cells. Importantly, overexpression of GABARAPL1 slowed tumor growth. Western blotting showed that autophagy was activated, and HIF-2α was down-regulated in tumor tissues.

Conclusion

HIF-2α, as a substrate for autophagic degradation, may play an interesting role during NPC progression.

Inhibiting stanniocalcin 2 reduces sunitinib resistance of Caki-1 renal cancer cells under hypoxia condition

Background

Our previous study has suggested that blocking stanniocalcin 2 (STC2) could reduce sunitinib resistance in clear cell renal cell carcinoma (ccRCC) under normoxia. The hypoxia is a particularly important environment for RCC occurrence and development, as well as sunitinib resistance. The authors proposed that STC2 also plays important roles in RCC sunitinib resistance under hypoxia conditions.

Methods

The ccRCC Caki-1 cells were treated within the hypoxia conditions. Real-time quantitative PCR and Western blotting were applied to detect the STC2 expression in ccRCC Caki-1 cells. STC2-neutralizing antibodies, STC2 siRNA, and the recombinant human STC2 (rhSTC2) were used to identify targeting regulation on STC2 in modulating sunitinib resistance, proliferation, epithelial-mesenchymal transition (EMT), migration, and invasion. In addition, autophagy flux and the lysosomal acidic environment were investigated by Western blotting and fluorescence staining, and the accumulation of sunitinib in cells was observed with the addition of STC2-neutralizing antibodies and autophagy modulators.

Results

Under hypoxia conditions, sunitinib disrupted the lysosomal acidic environment and accumulated in Caki-1 cells. Hypoxia-induced the STC2 mRNA and protein levels in Caki-1 cells. STC2-neutralizing antibodies and STC2 siRNA effectively aggravated sunitinib-reduced cell viability and proliferation, which were reversed by rhSTC2. In addition, sunitinib promoted EMT, migration, and invasion, which were reduced by STC2-neutralizing antibodies.

Conclusion

Inhibiting STC2 could reduce the sunitinib resistance of ccRCC cells under hypoxia conditions.

Global research trends and hot spots on autophagy and kidney diseases: a bibliometric analysis from 2000 to 2022

Background: Autophagy is an essential cellular process involving the self-degradation and recycling of organelles, proteins, and cellular debris. Recent research has shown that autophagy plays a significant role in the occurrence and development of kidney diseases. However, there is a lack of bibliometric analysis regarding the relationship between autophagy and kidney diseases. Methods: A bibliometric analysis was conducted by searching for literature related to autophagy and kidney diseases in the Web of Science Core Collection (WoSCC) database from 2000 to 2022. Data processing was carried out using R package "Bibliometrix", VOSviewers, and CiteSpace. Results: A total of 4,579 articles related to autophagy and kidney diseases were collected from various countries. China and the United States were the main countries contributing to the publications. The number of publications in this field showed a year-on-year increasing trend, with open-access journals playing a major role in driving the literature output. Nanjing Medical University in China, Osaka University in Japan, and the University of Pittsburgh in the United States were the main research institutions. The journal "International journal of molecular sciences" had the highest number of publications, while "Autophagy" was the most influential journal in the field. These articles were authored by 18,583 individuals, with Dong, Zheng; Koya, Daisuke; and Kume, Shinji being the most prolific authors, and Dong, Zheng being the most frequently co-cited author. Research on autophagy mainly focused on diabetic kidney diseases, acute kidney injury, and chronic kidney disease. "Autophagy", "apoptosis", and "oxidative stress" were the primary research hotspots. Topics such as "diabetic kidney diseases", "sepsis", "ferroptosis", "nrf2", "hypertension" and "pi3k" may represent potential future development trends. Research on autophagy has gradually focused on metabolic-related kidney diseases such as diabetic nephropathy and hypertension. Additionally, PI3K, NRF2, and ferroptosis have been recent research directions in the field of autophagy mechanisms. Conclusion: This is the first comprehensive bibliometric study summarizing the relationship between autophagy and kidney diseases. The findings aid in identifying recent research frontiers and hot topics, providing valuable references for scholars investigating the role of autophagy in kidney diseases.

Dichloroacetophenone biphenylsulfone ethers as anticancer pyruvate dehydrogenase kinase inhibitors in non-small cell lung cancer models

Pyruvate dehydrogenase kinase 1 (PDK1) is an important metabolic enzyme which is often overexpressed in many types of cancers, including non-small-cell lung cancers (NSCLC). Targeting PDK1 appears to be an attractive anticancer strategy. Based on a previously reported moderate potent anticancer PDK1 inhibitor, 64, we developed three dichloroacetophenone biphenylsulfone ethers, 30, 31 and 32, which showed strong PDK1 inhibitions of 74%, 83% and 72% at 10 μM, respectively. Then we investigated the anticancer effects of 31 in two NSCLC cell lines, namely, NCI-H1299 and NCI-H1975. It was found that 31 exhibited sub-micromolar cancer cell IC50_s, suppressed colony formation, induced mitochondrial membrane potential depolarization, triggered apoptosis, altered cellular glucose metabolism, with concomitant reductions in extracellular lactate levels and enhanced the generation of reactive oxygen species in NSCLC cells. Moreover, 31 significantly suppressed the tumor growth in an NCI-H1975 mouse xenograft model, outperforming the anticancer effects of 64. Taken together our results suggested that inhibition of PDK1 via dichloroacetophenone biphenylsulfone ethers may provide a novel direction leading to an alternative treatment option in NSCLC therapy.

Characterizing the molecular heterogeneity of clear cell renal cell carcinoma subgroups classified by miRNA expression profile

Clear cell renal cell carcinoma (ccRCC) is a heterogeneous disease that is associated with poor prognosis. Recent works have revealed the significant roles of miRNA in ccRCC initiation and progression. Comprehensive characterization of ccRCC based on the prognostic miRNAs would contribute to clinicians’ early detection and targeted treatment. Here, we performed unsupervised clustering using TCGA-retrieved prognostic miRNAs expression profiles. Two ccRCC subtypes were identified after assessing principal component analysis (PCA), t-distributed stochastic neighbor embedding (t-SNE), and consensus heatmaps. We found that the two subtypes are associated with distinct clinical features, overall survivals, and molecular characteristics. C1 cluster enriched patients in relatively early stage and have better prognosis while patients in C2 cluster have poor prognosis with relatively advanced state. Mechanistically, we found the differentially expressed genes (DEGs) between the indicated subgroups dominantly enriched in biological processes related to transmembrane transport activity. In addition, we also revealed a miRNA-centered DEGs regulatory network, which severed as essential regulators in both transmembrane transport activity control and ccRCC progression. Together, our work described the molecular heterogeneity among ccRCC cancers, provided potential targets served as effective biomarkers for ccRCC diagnosis and prognosis, and paved avenues to better understand miRNA-directed regulatory network in ccRCC progression.

VHL-P138R and VHL-L163R Novel Variants: Mechanisms of VHL Pathogenicity Involving HIF-Dependent and HIF-Independent Actions

The von Hippel-Lindau (VHL) disease is an autosomal dominant cancer syndrome caused by mutations in the VHL tumor suppressor gene. VHL protein (pVHL) forms a complex (VBC) with Elongins B-C, Cullin2, and Rbx1. Although other functions have been discovered, the most described function of pVHL is to recognize and target hypoxia-inducible factor (HIF) for degradation. This work comprises the functional characterization of two novel variants of the VHL gene (P138R and L163R) that have been described in our center in patients with VHL disease by in vitro, in vivo, and in silico approaches. In vitro, we found that these variants have a significantly shorter half-life compared to wild-type VHL but still form a functional VBC complex. Altered fibronectin deposition was evidenced for both variants using immunofluorescence. In vivo studies revealed that both variants failed to suppress tumor growth. By means of molecular dynamics simulations, we inspected in silico the nature of the changes introduced by each variant in the VBC complex. We have demonstrated the pathogenicity of P138R and L163R novel variants, involving HIF-dependent and HIF-independent mechanisms. These results provide the basis for future studies regarding the impact of structural alterations on posttranslational modifications that drive pVHL's fate and functions.

Sequestosome 1/p62: A multitasker in the regulation of malignant tumor aggression (Review)

Sequestosome 1 (SQSTM1)/p62 is an adapter protein mainly involved in the transportation, degradation and destruction of various proteins that cooperates with components of autophagy and the ubiquitin‑proteasome degradation pathway. Numerous studies have shown that SQSTM1/p62 functions at multiple levels, including involvement in genetic stability or modification, post‑transcriptional regulation and protein function. As a result, SQSTM1/p62 is a versatile protein that is a critical core regulator of tumor cell genetic stability, autophagy, apoptosis and other forms of cell death, malignant growth, proliferation, migration, invasion, metastasis and chemoradiotherapeutic response, and an indicator of patient prognosis. SQSTM1/p62 regulates these processes via its distinct molecular structure, through which it participates in a variety of activating or inactivating tumor‑related and tumor microenvironment‑related signaling pathways, particularly positive feedback loops and epithelial‑mesenchymal transition‑related pathways. Therefore, functioning as a proto‑oncogene or tumor suppressor gene in various types of cancer and tumor‑associated microenvironments, SQSTM1/p62 is capable of promoting or retarding malignant tumor aggression, giving rise to immeasurable effects on tumor occurrence and development, and on patient treatment and prognosis.

Autophagy as a Vital Therapy Target for Renal Cell Carcinoma

Autophagy is a process that degrades and recycles superfluous organelles or damaged cellular contents. It has been found to have dual functions in renal cell carcinoma (RCC). Many autophagy-related proteins are regarded as prognostic markers of RCC. Researchers have attempted to explore synthetic and phytochemical drugs for RCC therapy that target autophagy. In this review, we highlight the importance of autophagy in RCC and potential treatments related to autophagy.

Multifaceted WNT Signaling at the Crossroads Between Epithelial-Mesenchymal Transition and Autophagy in Glioblastoma

Tumor cells can employ epithelial-mesenchymal transition (EMT) or autophagy in reaction to microenvironmental stress. Importantly, EMT and autophagy negatively regulate each other, are able to interconvert, and both have been shown to contribute to drug-resistance in glioblastoma (GBM). EMT has been considered one of the mechanisms that confer invasive properties to GBM cells. Autophagy, on the other hand, may show dual roles as either a GBM-promoter or GBM-suppressor, depending on microenvironmental cues. The Wingless (WNT) signaling pathway regulates a plethora of developmental and biological processes such as cellular proliferation, adhesion and motility. As such, GBM demonstrates deregulation of WNT signaling in favor of tumor initiation, proliferation and invasion. In EMT, WNT signaling promotes induction and stabilization of different EMT activators. WNT activity also represses autophagy, while nutrient deprivation induces β-catenin degradation via autophagic machinery. Due to the importance of the WNT pathway to GBM, and the role of WNT signaling in EMT and autophagy, in this review we highlight the effects of the WNT signaling in the regulation of both processes in GBM, and discuss how the crosstalk between EMT and autophagy may ultimately affect tumor biology.

Establishment and Validation of a Prognostic Risk Model for Autophagy-Related Genes in Clear Cell Renal Cell Carcinoma

Background

Autophagy plays an essential role in tumorigenesis. At present, due to the unclear role of autophagy in renal clear cell carcinoma, we studied the potential value of autophagy-related genes (ARGs) in renal clear cell carcinoma (ccRCC).

Methods

We obtained all ccRCC data from The Cancer Genome Atlas (TCGA). We extracted the expression data of ARGs for difference analysis and carried out biological function analysis on the different results. The autophagy risk model was constructed. The 5-year survival rate was assessed using the model, and the predictive power of the model was evaluated from multiple perspectives. Cox regression analysis was use to assess whether the model could be an independent prognostic factor. Finally, the correlation between the model and clinical indicators is analyzed.

Results

The patients were divided into the high-risk group and low-risk group according to the median of autophagy risk score, and the results showed that the prognosis of the low-risk group was better than that of a high-risk group. The validation results of external data sets show that our model has good predictive value for ccRCC patients. The model can be an independent prognostic factor. Finally, the results show that our model has a stable predictive ability.

Conclusion

The autophagy gene model we constructed can be used as an excellent prognostic indicator for ccRCC. Our study provides the possibility of individualized and precise treatment for ccRCC patients.

Role of AMPK/mTOR-independent autophagy in clear cell renal cell carcinoma

We examined the status and role of autophagy, a process of lysosomal recycling of cellular material, in clear cell renal cell carcinoma (ccRCC). Paired samples of tumor and adjacent non-malignant tissue were collected from 20 patients with ccRCC after radical nephrectomy. The mRNA levels of apoptosis (BAD, BAX, BCL2, BCLXL, BIM) and autophagy (ATG4, BECN1, GABARAP, p62, UVRAG) regulators were measured by RT-qPCR. The protein levels of autophagosome-associated LC3-II, autophagy receptor p62, apoptotic marker PARP, as well as phosphorylation of autophagy initiator Unc 51-like kinase 1 (ULK1), its activator AMP-activated protein kinase (AMPK) and 4EBP1, the substrate of ULK1 inhibitor mechanistic target of rapamycin (mTOR), were analyzed by immunoblotting. The mRNA levels of pro-apoptotic BAX, anti-apoptotic BCLXL and pro-autophagic ATG4, p62 and UVRAG were higher in ccRCC tumors. Autophagy induction was confirmed by an increase in phospho-ULK1 and degradation of the autophagic target p62, while apoptotic PARP cleavage was unaltered. AMPK phosphorylation was reduced and 4EBP1 phosphorylation was increased in ccRCC tissue. The expression of apoptosis regulators did not correlate with clinicopathological features of ccRCC. Conversely, high mRNA levels of ATG4, GABARAP and p62 were associated with lower tumor stage, as well as with smaller tumor size and better disease-specific 5-year survival (ATG4 and p62). Accordingly, low p62 protein levels, corresponding to increased autophagic flux, were associated with lower tumor stage, reduced metastasis and improved 5-year survival. These data demonstrate that transcriptional induction of autophagy in ccRCC is accompanied by AMPK/mTOR-independent increase in ULK1 activation and autophagic flux, which might slow tumor progression and metastasis independently of apoptosis.

Beyond glycolysis: Hypoxia signaling as a master regulator of alternative metabolic pathways and the implications in clear cell renal cell carcinoma

The relationship between kidney cancer, specifically clear cell renal cell carcinoma (ccRCC), and the hypoxia signaling program has been extensively characterized. Its underlying role as the primary driver of the disease has led to the development of the most effective targeted therapies to date. Cellular responses to hypoxia or mutations affecting the von Hippel-Lindau (VHL) tumor suppressor gene stabilize the hypoxia inducible factor (HIF) transcription factors which then orchestrate elaborate downstream signaling events resulting in adaptations to key biological processes, such as reprogramming metabolism. The direct link of hypoxia signaling to glucose uptake and glycolysis has long been appreciated; however, the HIF family of proteins directly regulate many downstream targets, including other transcription factors with their own extensive networks. In this review, we will summarize our current understanding of how hypoxia signaling regulates other metabolic pathways and how this contributes to the development and progression of clear cell renal cell carcinomas.

Crosstalk Between Autophagy and Hypoxia-Inducible Factor-1α in Antifungal Immunity

Modern medicine is challenged by several potentially severe fungal pathogens such as Aspergillus fumigatus, Candida albicans, or Histoplasma capsulatum. Though not all fungal pathogens have evolved as primary pathogens, opportunistic pathogens can still cause fatal infections in immuno-compromised patients. After infection with these fungi, the ingestion and clearance by innate immune cells is an important part of the host immune response. Innate immune cells utilize two different autophagic pathways, the canonical pathway and the non-canonical pathway, also called microtubule-associated protein 1A/1B-light chain 3 (LC3) -associated pathway (LAP), to clear fungal pathogens from the intracellular environment. The outcome of autophagy-related host immune responses depends on the pathogen and cell type. Therefore, the understanding of underlying molecular mechanisms of autophagy is crucial for the development and improvement of antifungal therapies. One of those molecular mechanisms is the interaction of the transcription-factor hypoxia-inducible factor 1α (HIF-1α) with the autophagic immune response. During this review, we will focus on a comprehensive overview of the role of autophagy and HIF-1α on the outcome of fungal infections.

USP37 promotes deubiquitination of HIF2α in kidney cancer

Clear cell renal cell carcinoma (ccRCC) is characterized by loss of tumor suppressor Von Hippel Lindau (VHL) function, which leads to accumulation of hypoxia inducible factor α (including HIF1α and HIF2α). HIF2α was previously reported to be one of the major oncogenic drivers in ccRCC, however, its therapeutic targets remain challenging. Here we performed a deubiquitinase (DUB) complementary DNA (cDNA) library binding screen and discovered that ubiquitin-specific peptidase 37 (USP37) is a DUB that binds HIF2α and promotes HIF2α deubiquitination. As a result, USP37 promotes HIF2α protein stability in an enzymatically dependent manner, and depletion of USP37 leads to HIF2α down-regulation in ccRCC. Functionally, USP37 depletion causes decreased cell proliferation measured by MTS, two-dimensional (2D) colony formation as well as three-dimensional (3D) anchorage- independent growth. USP37 is also essential for maintaining kidney tumorigenesis in an orthotopic xenograft model and its depletion leads to both decreased primary kidney tumorigenesis and spontaneous lung metastasis. Our results suggest that USP37 is a potential therapeutic target in ccRCC.

PBRM1 loss defines a nonimmunogenic tumor phenotype associated with checkpoint inhibitor resistance in renal carcinoma

A non-immunogenic tumor microenvironment (TME) is a significant barrier to immune checkpoint blockade (ICB) response. The impact of Polybromo-1 (PBRM1) on TME and response to ICB in renal cell carcinoma (RCC) remains to be resolved. Here we show that PBRM1/Pbrm1 deficiency reduces the binding of brahma-related gene 1 (BRG1) to the IFNγ receptor 2 (Ifngr2) promoter, decreasing STAT1 phosphorylation and the subsequent expression of IFNγ target genes. An analysis of 3 independent patient cohorts and of murine pre-clinical models reveals that PBRM1 loss is associated with a less immunogenic TME and upregulated angiogenesis. Pbrm1 deficient Renca subcutaneous tumors in mice are more resistance to ICB, and a retrospective analysis of the IMmotion150 RCC study also suggests that PBRM1 mutation reduces benefit from ICB. Our study sheds light on the influence of PBRM1 mutations on IFNγ-STAT1 signaling and TME, and can inform additional preclinical and clinical studies in RCC.

How autophagy can restore proteostasis defects in multiple diseases?

Cellular evolution develops several conserved mechanisms by which cells can tolerate various difficult conditions and overall maintain homeostasis. Autophagy is a well-developed and evolutionarily conserved mechanism of catabolism, which endorses the degradation of foreign and endogenous materials via autolysosome. To decrease the burden of the ubiquitin-proteasome system (UPS), autophagy also promotes the selective degradation of proteins in a tightly regulated way to improve the physiological balance of cellular proteostasis that may get perturbed due to the accumulation of misfolded proteins. However, the diverse as well as selective clearance of unwanted materials and regulations of several cellular mechanisms via autophagy is still a critical mystery. Also, the failure of autophagy causes an increase in the accumulation of harmful protein aggregates that may lead to neurodegeneration. Therefore, it is necessary to address this multifactorial threat for in-depth research and develop more effective therapeutic strategies against lethal autophagy alterations. In this paper, we discuss the most relevant and recent reports on autophagy modulations and their impact on neurodegeneration and other complex disorders. We have summarized various pharmacological findings linked with the induction and suppression of autophagy mechanism and their promising preclinical and clinical applications to provide therapeutic solutions against neurodegeneration. The conclusion, key questions, and future prospectives sections summarize fundamental challenges and their possible feasible solutions linked with autophagy mechanism to potentially design an impactful therapeutic niche to treat neurodegenerative diseases and imperfect aging.

Autophagy-related gene P4HB: a novel diagnosis and prognosis marker for kidney renal clear cell carcinoma

Autophagy can protect cells and organisms from stressors such as nutrient deprivation, and is involved in many pathological processes including human cancer. Therefore, it is necessary to investigate the role of autophagy-related genes (ARGs) in cancer. In this study, we investigated the gene expression of 222 ARGs in 1048 Kidney Renal Clear Cell Carcinoma (KIRC) cases, from 5 independent cohorts. The gene expression of ARGs were first evaluated in the The Cancer Genome Atlas (TCGA) by Recevier Operating Characteristic (ROC) analysis to select potential biomarkers with extremely high ability in KIRC detection (AUC≥0.85 and p<0.0001). Then in silico procedure progressively leads to the selection of two genes in a three rounds of validation performed in four human KIRC-patients datasets including two independent Gene Expression Omnibus (GEO) datasets, Oncomine dataset and Human Protein Atlas dataset. Finally, only P4HB (Prolyl 4-hydroxylase, beta polypeptide) gene was experimentally validated by RT-PCR between control kidney cells and cancer cells. Following univariate and multivariate analyses of TCGA-KIRC clinical data showed that P4HB expression is an independent prognostic indicator of unfavorable overall survival (OS) for KIRC patients. Based on these findings, we proposed that P4HB might be one potential novel KIRC diagnostic and prognostic biomarker at both mRNA and protein levels.

Autophagy in Kidney Disease

Autophagy is a cellular homeostatic program for the turnover of cellular organelles and proteins, in which double-membraned vesicles (autophagosomes) sequester cytoplasmic cargos, which are subsequently delivered to the lysosome for degradation. Emerging evidence implicates autophagy as an important modulator of human disease. Macroautophagy and selective autophagy (e.g., mitophagy, aggrephagy) can influence cellular processes, including cell death, inflammation, and immune responses, and thereby exert both adaptive and maladaptive roles in disease pathogenesis. Autophagy has been implicated in acute kidney injury, which can arise in response to nephrotoxins, sepsis, and ischemia/reperfusion, and in chronic kidney diseases. The latter includes comorbidities of diabetes and recent evidence for chronic obstructive pulmonary disease-associated kidney injury. Roles of autophagy in polycystic kidney disease and kidney cancer have also been described. Targeting the autophagy pathway may have therapeutic benefit in the treatment of kidney disorders.

Mitochondrial E3 ubiquitin ligase 1 promotes autophagy flux to suppress the development of clear cell renal cell carcinomas

Clear cell renal cell carcinoma (ccRCC) is one of the most common malignant tumors in the urinary system. Surgical intervention is the preferred treatment for ccRCC, but targeted biological therapy is required for postoperative recurrent or metastatic ccRCC. Autophagy is an intracellular degradation system for misfolded/aggregated proteins and dysfunctional organelles. Defective autophagy is associated with many diseases. Mul1 is a mitochondrion-associated E3 ubiquitin ligase and involved in the regulation of divergent pathophysiological processes such as mitochondrial dynamics, and thus affects the development of various diseases including cancers. Whether Mul1 regulates ccRCC development and what is the mechanism remain unclear. Histochemical staining and immunoblotting were used to analyze the levels of Mul1 protein in human renal tissues. Statistical analysis of information associated with tissue microarray and The Cancer Genome Atlas (TCGA) database was conducted to show the relationship between Mul1 expression and clinical features and survival of ccRCC patients. Impact of Mul1 on rates of cell growth and migration and autophagy flux were tested in cultured cancer cells. Herein we show that Mul1 promoted autophagy flux to facilitate the degradation of P62-associated protein aggresomes and adipose differentiation-related protein (ADFP)-associated lipid droplets and suppressed the growth and migration of ccRCC cells. Levels of Mul1 protein and mRNA were significantly reduced so that autophagy flux was likely blocked in ccRCC tissues, which is potentially correlated with enhancement of malignancy of ccRCC and impairment of patient survival. Therefore, Mul1 may promote autophagy to suppress the development of ccRCC.

Identification of prognosis-related alternative splicing events in kidney renal clear cell carcinoma

Alternative splicing (AS) contributes to protein diversity by modifying most gene transcriptions. Cancer generation and progression are associated with specific splicing events. However, AS signature in kidney renal clear cell carcinoma (KIRC) remains unknown. In this study, genome‐wide AS profiles were generated in 537 patients with KIRC in the cancer genome atlas. With a total of 42 522 mRNA AS events in 10 600 genes acquired, 8164 AS events were significantly associated with the survival of patients with KIRC. Logistic regression analysis of the least absolute shrinkage and selection operator was conducted to identify an optimized multivariate prognostic predicting mode containing four predictors. In this model, the receptor‐operator characteristic curves of the training set were built, and the areas under the curves (AUCs) at different times were >0.88, thus indicating a stable and powerful ability in distinguishing patients' outcome. Similarly, the AUCs of the test set at different times were >0.73, verifying the results of the training set. Correlation and gene ontology analyses revealed some potential functions of prognostic AS events. This study provided an optimized survival‐predicting model and promising data resources for future in‐depth studies on AS mechanisms in KIRC.

Reactive Oxygen Species in the Tumor Microenvironment: An Overview

Reactive oxygen species (ROS) are important signaling molecules in cancer. The level of ROS will determine physiological effects. While high levels of ROS can cause damage to tissues and cell death, low levels of ROS can have a proliferative effect. ROS are produced by tumor cells but also cellular components that make up the tumor microenvironment (TME). In this review, we discuss the mechanisms by which ROS can affect the TME with particular emphasis on tumor-infiltrating leukocytes. Greater insight into ROS biology in this setting may allow for therapeutic manipulation of ROS levels in order to remodel the tumor microenvironment and increase anti-tumor activity.

Platelet HIF-2α promotes thrombogenicity through PAI-1 synthesis and extracellular vesicle release

Oxygen-compromised environments, such as high altitude, are associated with platelet hyperactivity. Platelets confined within the relatively impervious core of an aggregate/thrombus have restricted access to oxygen, yet they continue to perform energy-intensive procoagulant activities that sustain the thrombus. Studying platelet signaling under hypoxia is, therefore, critical to our understanding of the mechanistic basis of thrombus stability. We report here that hypoxia-inducible factor (HIF)-2α is translated from pre-existing mRNA and stabilized against proteolytic degradation in enucleate platelets exposed to hypoxia. Hypoxic stress, too, stimulates platelets to synthesize plasminogen-activator inhibitor-1 (PAI-1) and shed extracellular vesicles, both of which potentially contribute to the prothrombotic phenotype associated with hypoxia. Stabilization of HIF-α by administering hypoxia-mimetics to mice accelerates thrombus formation in mesenteric arterioles. In agreement, platelets from patients with chronic obstructive pulmonary disease and high altitude residents exhibiting thrombogenic attributes have abundant expression of HIF-2α and PAI- 1. Thus, targeting platelet hypoxia signaling could be an effective anti-thrombotic strategy.

ATG7 Promotes Bladder Cancer Invasion via Autophagy-Mediated Increased ARHGDIB mRNA Stability

Since invasive bladder cancer (BC) can progress to life threatening metastases, understanding the molecular mechanisms underlying BC invasion is crucial for potentially decreasing the mortality of this disease. Herein, it is discovered that autophagy-related gene 7 (ATG7) is remarkably overexpressed in human invasive BC tissues. The knockdown of ATG7 in human BC cells dramatically inhibits cancer cell invasion, revealing that ATG7 is a key player in regulating BC invasion. Mechanistic studies indicate that MIR190A is responsible for ATG7 mRNA stability and protein overexpression by directly binding to ATG7 mRNA 3'-UTR. Furthermore, ATG7-mediated autophagy promotes HNRNPD (ARE/poly(U)-binding/degradation factor 1) protein degradation, and in turn reduces HNRNPD interaction with ARHGDIB mRNA, resulting in the elevation of ARHGDIB mRNA stability, and subsequently leading to BC cell invasion. The identification of the MIR190A/ATG7 autophagic mechanism regulation of HNRNPD/ARHGDIB expression provides an important insight into understanding the nature of BC invasion and suggests that autophagy may represent a potential therapeutic strategy for the treatment of human BC patients.

A family of PIKFYVE inhibitors with therapeutic potential against autophagy-dependent cancer cells disrupt multiple events in lysosome homeostasis

High-throughput screening identified 5 chemical analogs (termed the WX8-family) that disrupted 3 events in lysosome homeostasis: (1) lysosome fission via tubulation without preventing homotypic lysosome fusion; (2) trafficking of molecules into lysosomes without altering lysosomal acidity, and (3) heterotypic fusion between lysosomes and autophagosomes. Remarkably, these compounds did not prevent homotypic fusion between lysosomes, despite the fact that homotypic fusion required some of the same machinery essential for heterotypic fusion. These effects varied 400-fold among WX8-family members, were time and concentration dependent, reversible, and resulted primarily from their ability to bind specifically to the PIKFYVE phosphoinositide kinase. The ability of the WX8-family to prevent lysosomes from participating in macroautophagy/autophagy suggested they have therapeutic potential in treating autophagy-dependent diseases. In fact, the most potent family member (WX8) was 100-times more lethal to 'autophagy-addicted' melanoma A375 cells than the lysosomal inhibitors hydroxychloroquine and chloroquine. In contrast, cells that were insensitive to hydroxychloroquine and chloroquine were also insensitive to WX8. Therefore, the WX8-family of PIKFYVE inhibitors provides a basis for developing drugs that could selectively kill autophagy-dependent cancer cells, as well as increasing the effectiveness of established anti-cancer therapies through combinatorial treatments. Abbreviations: ACTB: actin beta; Baf: bafilomycin A₁; BECN1: beclin 1; BODIPY: boron-dipyrromethene; BORC: BLOC-1 related complex; BRAF: B-Raf proto-oncogene, serine/threonine kinase; BSA: bovine serum albumin; CTSD: cathepsin D; CQ: chloroquine; DNA: deoxyribonucleic acid; EC₅₀: half maximal effective concentration; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HCQ: hydroxychloroquine; HOPS complex: homotypic fusion and protein sorting complex; Kd: equilibrium binding constant; IC50: half maximal inhibitory concentration; KO: knockout; LAMP1: lysosomal associated membrane protein 1; MAP1LC3A: microtubule associated protein 1 light chain 3 alpha; MES: 2-(N-morpholino)ethanesulphonic acid; MTOR: mechanistic target of rapamycin kinase; μM: micromolar; NDF: 3-methylbenzaldehyde (2,6-dimorpholin-4-ylpyrimidin-4-yl)hydrazine;NEM: N-ethylmaleimide; NSF: N-ethylmaleimide sensitive factor; PBS: phosphate-buffered saline; PIKFYVE: phosphoinositide kinase, FYVE-type zinc finger containing; PIP4K2C: phosphatidylinositol-5-phosphate 4-kinase type 2 gamma; PtdIns3P: phosphatidylinositol 3-phosphate; PtdIns(3,5)P₂: phosphatidylinositol 3,5-biphosphate; RFP: red fluorescent protein; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase B1; SQSTM1: sequestosome 1; TWEEN 20: polysorbate 20; V-ATPase: vacuolar-type H⁺-translocating ATPase; VPS39: VPS39 subunit of HOPS complex; VPS41: VPS41 subunit of HOPS complex; WWL: benzaldehyde [2,6-di(4-morpholinyl)-4-pyrimidinyl]hydrazone; WX8: 1H-indole-3-carbaldehyde [4-anilino-6-(4-morpholinyl)-1,3,5-triazin-2-yl]hydrazine; XBA: N-(3-chloro-4-fluorophenyl)-4,6-dimorpholino-1,3,5-triazin-2-amine hydrochloride; XB6: N-(4-ethylphenyl)-4,6-dimorpholino-1,3,5-triazin-2-amine hydrochloride.

Hypoxia-inducible factor (HIF)-prolyl hydroxylase 3 (PHD3) maintains high HIF2A mRNA levels in clear cell renal cell carcinoma

Most clear cell renal cell carcinomas (ccRCCs) have inactivation of the von Hippel-Lindau tumor suppressor protein (pVHL), resulting in the accumulation of hypoxia-inducible factor α-subunits (HIF-α) and their downstream targets. HIF-2α expression is particularly high in ccRCC and is associated with increased ccRCC growth and aggressiveness. In the canonical HIF signaling pathway, HIF-prolyl hydroxylase 3 (PHD3) suppresses HIF-2α protein by post-translational hydroxylation under sufficient oxygen availability. Here, using immunoblotting and immunofluorescence staining, qRT-PCR, and siRNA-mediated gene silencing, we show that unlike in the canonical pathway, PHD3 silencing in ccRCC cells leads to down-regulation of HIF-2α protein and mRNA. Depletion of other PHD family members had no effect on HIF-2α expression, and PHD3 knockdown in non-RCC cells resulted in the expected increase in HIF-2α protein expression. Accordingly, PHD3 knockdown decreased HIF-2α target gene expression in ccRCC cells and expression was restored upon forced HIF-2α expression. The effect of PHD3 depletion was pinpointed to HIF2A mRNA stability. In line with these in vitro results, a strong positive correlation of PHD3 and HIF2A mRNA expression in ccRCC tumors was detected. Our results suggest that in contrast to the known negative regulation of HIF-2α in most cell types, high PHD3 expression in ccRCC cells maintains elevated HIF-2α expression and that of its target genes, which may enhance kidney cancer aggressiveness.

Lactate inhibits ATP6V0d2 expression in tumor-associated macrophages to promote HIF-2α-mediated tumor progression

Macrophages perform key functions in tissue homeostasis that are influenced by the local tissue environment. Within the tumor microenvironment, tumor-associated macrophages can be altered to acquire properties that enhance tumor growth. Here, we found that lactate, a metabolite found in high concentration within the anaerobic tumor environment, activated mTORC1 that subsequently suppressed TFEB-mediated expression of the macrophage-specific vacuolar ATPase subunit ATP6V0d2. Atp6v0d2-/- mice were more susceptible to tumor growth, with enhanced HIF-2α-mediated VEGF production in macrophages that display a more protumoral phenotype. We found that ATP6V0d2 targeted HIF-2α but not HIF-1α for lysosome-mediated degradation. Blockade of HIF-2α transcriptional activity reversed the susceptibility of Atp6v0d2-/- mice to tumor development. Furthermore, in a cohort of patients with lung adenocarcinoma, expression of ATP6V0d2 and HIF-2α was positively and negatively correlated with survival, respectively, suggesting a critical role of the macrophage lactate/ATP6V0d2/HIF-2α axis in maintaining tumor growth in human patients. Together, our results highlight the ability of tumor cells to modify the function of tumor-infiltrating macrophages to optimize the microenvironment for tumor growth.

Chloramphenicol Induces Autophagy and Inhibits the Hypoxia Inducible Factor-1 Alpha Pathway in Non-Small Cell Lung Cancer Cells

Chloramphenicol is an inexpensive and excellent bactericidal antibiotic. It is used to combat anaerobic infections in the Third World countries, whereas its systemic application has been abandoned in developed countries. However, in recent years, clinicians have reintroduced chloramphenicol in clinical practice. In this study, chloramphenicol was found to repress the oxygen-labile transcription factor, hypoxia inducible factor-1 alpha (HIF-1α), in hypoxic A549 and H1299 cells. Furthermore, it suppressed the mRNA levels of vascular endothelial growth factor (VEGF) and glucose transporter 1, eventually decreasing VEGF release. Chloramphenicol initiated the autophagy pathway in treated cells, as observed by the increase in formation of Atg12-Atg5 conjugates, and in beclin-1 and LC3-II levels. The chloramphenicol-mediated HIF-1α degradation was completely reverted by autophagic flux blockage. In HIF-1α-overexpressing cells, the formation of HIF-1α/SENP-1 (Sentrin/SUMO-specific protease 1) protein complex seemed to facilitate the escape of HIF-1α from degradation. Chloramphenicol inhibited HIF-1α/SENP-1 protein interaction, thereby destabilizing HIF-1α protein. The enhancement in HIF-1α degradation due to chloramphenicol was evident during the incubation of the antibiotic before hypoxia and after HIF-1α accumulation. Since HIF-1α plays multiple roles in infections, inflammation, and cancer cell stemness, our findings suggest a potential clinical value of chloramphenicol in the treatment of these conditions.

Association of ATG7 Polymorphisms and Clear Cell Renal Cell Carcinoma Risk

BACKGROUND

Kidney cancer is one of the most common cancers worldwide. Recent studies have suggested that single nucleotide polymorphisms (SNPs) in autophagy-related gene are associated with the risk of kidney cancer.

OBJECTIVE

This study was undertaken to investigate the association of autophagyrelated gene 7 (ATG7) polymorphisms with the risk of clear cell renal cell carcinoma (ccRCC) in the Chinese Han population.

METHODS

Blood samples were collected from 293 ccRCC patients and 297 healthy controls. Three ATG7 polymorphisms (rs1375206, rs2606736 and rs6442260) were genotyped by Agena MassARRAY. The association was estimated by genetic models and stratification analyses.

RESULTS

A significant association was observed between allele A of rs6442260 and ccRCC risk (OR = 0.76, 95% CI: 0.58-0.99, p = 0.039). Genetic model analysis revealed that rs2606736 (OR = 0.57, 95% CI: 0.34-0.95, p = 0.031) and rs6442260 (OR = 0.44, 95% CI: 0.22-0.90, p = 0.021) were associated with decreased risk of ccRCC under recessive model. Age stratification analysis showed that rs2606736 (OR = 0.67, 95% CI: 0.46-0.98, p = 0.036) and rs6442260 (OR = 0.26, 95% CI: 0.07-0.89, p = 0.014) were significantly decreased risk of ccRCC under the log-additive model in age > 55 years old and ≤ 55 years old, respectively.

CONCLUSIONS

This study indicated that ATG7 polymorphisms (rs2606736 and rs6442260) have a protective role for ccRCC risk. Further large sample size and functional assays are needed to confirm our findings and reveal the role of ATG7 polymorphisms in ccRCC carcinogenesis.

Tumor Sidedness and Enriched Gene Groups for Efficacy of First-line Cetuximab Treatment in Metastatic Colorectal Cancer

Molecular differences in tumor locations may contribute to the sidedness-specific response to cetuximab in metastatic colorectal cancer (mCRC). We investigated genes associated with the response to cetuximab treatment depending on tumor sidedness. Our study included 77 patients with mCRC (13/63, right/left) with KRAS exon 2 wild-type tumors from phase II trials of first-line therapy with cetuximab. Expression levels of 2,551 genes were measured in tissue samples by HTG EdgeSeq Oncology Biomarker Panel. Univariate Cox regression analysis using log₂ values of counts per million (CPM) was conducted in each sidedness to assess associations with clinical outcomes, and to define the optimal cut-off point for clinically significant genes. In addition, a gene set enrichment analysis (GSEA) was performed to identify significant gene pathways in each sidedness. Sixty-nine patients were assessable for gene expression data. Overexpression of BECN1 [log₂(CPM) ≥ 6.8] was associated with favorable survival, regardless of tumor sidedness. High expression of NOTCH1 [log₂(CPM) ≥ 7.5] predicted significantly longer progression-free survival (PFS; median 14.7 vs. 11.1 months, HR 0.43, P = 0.01) and overall survival (OS; median 42.8 vs. 26.5 months, HR 0.35, P = 0.01) in left side but not in right side. The GSEA showed that regulation of DNA replication gene set correlated with favorable survival in the left, whereas the subcellular component and leukocyte migration gene sets were associated with good survival in the right. In conclusion, genes contributing to the efficacy of cetuximab treatment may differ according to the sidedness in mCRC. NOTCH1 may potentially discriminate favorable responders to cetuximab in patients with left-sided tumors.

VHL substrate transcription factor ZHX2 as an oncogenic driver in clear cell renal cell carcinoma

Inactivation of the von Hippel-Lindau (VHL) E3 ubiquitin ligase protein is a hallmark of clear cell renal cell carcinoma (ccRCC). Identifying how pathways affected by VHL loss contribute to ccRCC remains challenging. We used a genome-wide in vitro expression strategy to identify proteins that bind VHL when hydroxylated. Zinc fingers and homeoboxes 2 (ZHX2) was found as a VHL target, and its hydroxylation allowed VHL to regulate its protein stability. Tumor cells from ccRCC patients with VHL loss-of-function mutations usually had increased abundance and nuclear localization of ZHX2. Functionally, depletion of ZHX2 inhibited VHL-deficient ccRCC cell growth in vitro and in vivo. Mechanistically, integrated chromatin immunoprecipitation sequencing and microarray analysis showed that ZHX2 promoted nuclear factor κB activation. These studies reveal ZHX2 as a potential therapeutic target for ccRCC.

Reactive Oxygen Species-Mediated Autophagy Defines the Fate of Cancer Stem Cells

Significance: A fraction of tumorigenic cells, also known as tumor initiating or cancer stem cells (CSCs), is thought to drive tumor growth, metastasis, and chemoresistance. However, little is known regarding mechanisms that convey relevant pathways contributing to their self-renewal, proliferation, and differentiation abilities. Recent Advances: Recent works on CSCs provide evidence on the role of redox disruption and regulation of autophagic flux. This has been linked to increased DNA repair capacity and chemoresistance. Critical Issues: The current review summarizes the most recent studies assessing the role of redox homeostasis, autophagy, and chemoresistance in CSCs, including some novel findings on microRNAs and their role in horizontal transfer within cancer cell populations. Future Directions: Rational anticancer therapy and prevention should rely on the fact that cancer is a redox disease with the CSCs being the apex modulated by redox-mediated autophagy. Antioxid. Redox Signal. 28, 1066-1079.

d-limonene exhibits antitumor activity by inducing autophagy and apoptosis in lung cancer

Purpose

d-limonene is a plant extract with widespread application, and it has been recently reported to have antiproliferative and proapoptotic effects on cancer cells. However, the mechanisms by which d-limonene achieves these effects, especially in lung cancer, are not entirely clear. Therefore, the goal of this study was to examine the effects of d-limonene on lung cancer and explore its mechanisms of action.

Methods

We examined the therapeutic effects of d-limonene on lung cancer cells and in a xenograft animal model by characterizing its effects on the pathways of apoptosis and autophagy. Cell proliferation was measured using the Cell Counting Kit-8, and apoptosis was determined by flow cytometric analysis. Levels of LC3 puncta, an autophagy marker, were analyzed by laser scanning confocal microscopy. Autophagy and apoptosis-related gene expression were assessed by real-time quantitative polymerase chain reaction and Western blot.

Results

d-limonene inhibited the growth of lung cancer cells and suppressed the growth of transplanted tumors in nude mice. Expression of apoptosis and autophagy-related genes were increased in tumors after treatment with d-limonene. Furthermore, the use of chloroquine, an autophagy inhibitor, and knockdown of the atg5 gene, suppressed the apoptosis induced by d-limonene.

Conclusion

d-limonene may have a therapeutic effect on lung cancer as it can induce apoptosis of lung cancer cells by promoting autophagy.

RNF216 contributes to proliferation and migration of colorectal cancer via suppressing BECN1-dependent autophagy

Originally identified as an E3 ligase regulating toll-like receptor (TLR) signaling, ring finger protein 216 (RNF216) also plays an essential role in autophagy, which is fundamental to cellular homeostasis. Autophagy dysfunction leads to an array of pathological events, including tumor formation. In this study, we found that RNF216 was upregulated in human colorectal cancer (CRC) tissues and cell lines, and was associated with progression of CRC. RNF216 promoted CRC cell proliferation and migration in vitro and in vivo, largely by enhancing proteasomal degradation of BECN1, a key autophagy regulator and tumor suppressor. RNF216 restricted CRC cell autophagy through BECN1 inhibition under nutritional starvation conditions. RNF216 knockdown increased the autophagy, limiting CRC cell proliferation and migration. Moreover, BECN1 knockdown or autophagy inhibition restored proliferation and migration of RNF216-knockdown CRC cells. Collectively, our results suggested that RNF216 promoted CRC cell proliferation and migration by negatively regulating BECN1-dependent autophagy. This makes RNF216 as a potential biomarker and novel therapeutic target for inhibiting CRC development and progression.

Autophagy protects ovarian cancer-associated fibroblasts against oxidative stress

RNA-Seq and gene set enrichment anylysis revealed that ovarian cancer associated fibroblasts (CAFs) are mitotically active compared with normal fibroblasts (NFs). Cellular senescence is observed in CAFs treated with H₂O₂ as shown by elevated SA-β-gal activity and p21 (WAF1/Cip1) protein levels. Reactive oxygen species (ROS) production and p21 (WAF1/Cip1) elevation may account for H₂O₂-induced CAFs cell cycle arrest in S phase. Blockage of autophagy can increase ROS production in CAFs, leading to cell cycle arrest in S phase, cell proliferation inhibition and enhanced sensitivity to H₂O₂-induced cell death. ROS scavenger NAC can reduce ROS production and thus restore cell viability. Lactate dehydrogenase A (LDHA), monocarboxylic acid transporter 4 (MCT4) and superoxide dismutase 2 (SOD2) were up-regulated in CAFs compared with NFs. There was relatively high lactate content in CAFs than in NFs. Blockage of autophagy decreased LDHA, MCT4 and SOD2 protein levels in CAFs that might enhance ROS production. Blockage of autophagy can sensitize CAFs to chemotherapeutic drug cisplatin, implicating that autophagy might possess clinical utility as an attractive target for ovarian cancer treatment in the future.

Low neighbor of Brca1 gene expression predicts poor clinical outcome and resistance of sunitinib in clear cell renal cell carcinoma

Objective

To study the expression of Neighbor of Brca1 gene (NBR1) in clear cell renal cell carcinoma (ccRCC), renal cancer cells and the chemoresistance cells and to elucidate its clinical prognostic and chemoresistance value.

Materials and Methods

We screened the NBR1 mRNA in ccRCC from The Cancer Genome Atlas (TCGA) database and examined expression levels of NBR1 mRNA in 48 cases of ccRCC tissues, renal cancer cell lines and chemoresistance cells by qRT-PCR. Then, we extended two additional data sets in oncomine datebase (https://www.oncomine.org) to further confirm the results of the TCGA database. Immunohistochemistry (IHC) assay data performed in ccRCC tissues and normal tissues were downloaded from The Human Protein Atlas.

Results

The mRNA levels of NBR1 were downregulated in TCGA-KIRC database (n = 533) and ccRCC patient samples (n=48) as well as in RCC cell lines and their chemoresistance cells. Similarly, the protein levels of NBR1 were lower in ccRCC patient samples. NBR1 level was associated with the clinical pathological stage and could discriminate metastasis, recurrence and prognosis in ccRCC patients. Low level of NBR1 mRNA showed a significance poor prognostic of overall survival (OS), disease–free survival (DFS) with univariate and multivariate analyses in ccRCC patients and sunitinib resistance.

Conclusions

Taken together, our results suggest that low level of NBR1 can predict poor clinical outcome and resistance of sunitinib in patients with ccRCC.

Autophagy as a potential therapeutic target during epithelial to mesenchymal transition in renal cell carcinoma: An in vitro study

Cancer progression toward invasive and metastatic disease is aided by reactivation of epithelial-mesenchymal transition (EMT), involving transdifferentiation of epithelial cells into mesenchymal phenotype. This leads to increased migratory and stem cell-like features in the cells. These EMT cells are more resistant to chemotherapy and it is hypothesized that the phenomenon of autophagy induces resistance, providing a survival strategy for cells. In the present study, we induced EMT-like phenotype in renal carcinoma cells and identified corresponding higher autophagy flux in these cells. The EMT transformed cells may be a representative of the resistant cancer stem cell(CSC)-like phenotype. Autophagy was identified as a potential mechanism of cell survival in these cells thus implying that autophagy inhibition can lead to enhanced cell death. We also observed that tumor cells especially EMT transformed cells, have been 'primed' to undergo autophagy by mTOR inhibition. We observed that combined use of autophagy inhibitor and temsirolimus (TEM) improved antitumor activity against RCC in EMT transformed metastatic cells. One of the approaches for inhibiting autophagy was the use of lysosomotropic anti-malarial drug, chloroquine (CQ) and we explored the therapeutic potential of combination of CQ and the mTOR inhibitor, TEM. EMT transformed cells showed increased cell cytotoxicity when autophagy was impaired by addition CQ with TEM. This led us to conclude that inhibition of autophagy with the current therapeutic regimen could be useful in targeting the EMT transformed cells along with the bulk tumor cells in RCC.

Cross-talk of Brassinosteroid signaling in controlling growth and stress responses

Plants are faced with a barrage of stresses in their environment and must constantly balance their growth and survival. As such, plants have evolved complex control systems that perceive and respond to external and internal stimuli in order to optimize these responses, many of which are mediated by signaling molecules such as phytohormones. One such class of molecules called Brassinosteroids (BRs) are an important group of plant steroid hormones involved in numerous aspects of plant life including growth, development and response to various stresses. The molecular determinants of the BR signaling pathway have been extensively defined, starting with the membrane-localized receptor BRI1 and co-receptor BAK1 and ultimately culminating in the activation of BES1/BZR1 family transcription factors, which direct a transcriptional network controlling the expression of thousands of genes enabling BRs to influence growth and stress programs. Here, we highlight recent progress in understanding the relationship between the BR pathway and plant stress responses and provide an integrated view of the mechanisms mediating cross-talk between BR and stress signaling.

Selective Autophagy of BES1 Mediated by DSK2 Balances Plant Growth and Survival

Plants encounter a variety of stresses and must fine-tune their growth and stress-response programs to best suit their environment. BES1 functions as a master regulator in the brassinosteroid (BR) pathway that promotes plant growth. Here, we show that BES1 interacts with the ubiquitin receptor protein DSK2 and is targeted to the autophagy pathway during stress via the interaction of DSK2 with ATG8, a ubiquitin-like protein directing autophagosome formation and cargo recruitment. Additionally, DSK2 is phosphorylated by the GSK3-like kinase BIN2, a negative regulator in the BR pathway. BIN2 phosphorylation of DSK2 flanking its ATG8 interacting motifs (AIMs) promotes DSK2-ATG8 interaction, thereby targeting BES1 for degradation. Accordingly, loss-of-function dsk2 mutants accumulate BES1, have altered global gene expression profiles, and have compromised stress responses. Our results thus reveal that plants coordinate growth and stress responses by integrating BR and autophagy pathways and identify the molecular basis of this crosstalk.

Autophagy regulates Endothelial-Mesenchymal transition by decreasing the phosphorylation level of Smad3

Transforming growth factor-beta2 (TGF-β2) induces Endothelial-Mesenchymal transition (EndoMT) and autophagy in a variety of cells. Previous studies have indicated that activation of autophagy might decrease TGF-β2 induced EndoMT. However, the precise role remains unclear. In the present study, we found that TGF-β2 could induce EndoMT and autophagy in human retinal microvascular endothelial cells (hRMECs). Activation of autophagy by Rapamycin or Trehalose could reduce the expression of Snail, demonstrating a role of autophagy in regulating Snail production both by transcriptional and post-transcriptional mechanism. Co-immunoprecipitation (CoIP) demonstrated that LC3 co-immunoprecipitated with Smad3 and western blot showed that autophagy inducers, Rapamycin and Trehalose, could decrease the phosphorylation level of Smad3. Therefore, our results demonstrate that autophagy counteracts the EndoMT process triggered by TGF-β2 by decreasing the phosphorylation level of Smad3.