Identification of the central role of RNA polymerase mitochondrial for angiogenesis.

Mitochondria are central to endothelial cell activation and angiogenesis, with the RNA polymerase mitochondrial (POLRMT) serving as a key protein in regulating mitochondrial transcription and oxidative phosphorylation. In our study, we examined the impact of POLRMT on angiogenesis and found that its silencing or knockout (KO) in human umbilical vein endothelial cells (HUVECs) and other endothelial cells resulted in robust anti-angiogenic effects, impeding cell proliferation, migration, and capillary tube formation. Depletion of POLRMT led to impaired mitochondrial function, characterized by mitochondrial depolarization, oxidative stress, lipid oxidation, DNA damage, and reduced ATP production, along with significant apoptosis activation. Conversely, overexpressing POLRMT promoted angiogenic activity in the endothelial cells. In vivo experiments demonstrated that endothelial knockdown of POLRMT, by intravitreous injection of endothelial specific POLRMT shRNA adeno-associated virus, inhibited retinal angiogenesis. In addition, inhibiting POLRMT with a first-in-class inhibitor IMT1 exerted significant anti-angiogenic impact in vitro and in vivo. Significantly elevated expression of POLRMT was observed in the retinal tissues of streptozotocin-induced diabetic retinopathy (DR) mice. POLRMT endothelial knockdown inhibited pathological retinal angiogenesis and mitigated retinal ganglion cell (RGC) degeneration in DR mice. At last, POLRMT expression exhibited a substantial increase in the retinal proliferative membrane tissues of human DR patients. These findings collectively establish the indispensable role of POLRMT in angiogenesis, both in vitro and in vivo.

The requirement of the mitochondrial protein NDUFS8 for angiogenesis.

Mitochondria are important for the activation of endothelial cells and the process of angiogenesis. NDUFS8 (NADH:ubiquinone oxidoreductase core subunit S8) is a protein that plays a critical role in the function of mitochondrial Complex I. We aimed to investigate the potential involvement of NDUFS8 in angiogenesis. In human umbilical vein endothelial cells (HUVECs) and other endothelial cell types, we employed viral shRNA to silence NDUFS8 or employed the CRISPR/Cas9 method to knockout (KO) it, resulting in impaired mitochondrial functions in the endothelial cells, causing reduction in mitochondrial oxygen consumption and Complex I activity, decreased ATP production, mitochondrial depolarization, increased oxidative stress and reactive oxygen species (ROS) production, and enhanced lipid oxidation. Significantly, NDUFS8 silencing or KO hindered cell proliferation, migration, and capillary tube formation in cultured endothelial cells. In addition, there was a moderate increase in apoptosis within NDUFS8-depleted endothelial cells. Conversely, ectopic overexpression of NDUFS8 demonstrated a pro-angiogenic impact, enhancing cell proliferation, migration, and capillary tube formation in HUVECs and other endothelial cells. NDUFS8 is pivotal for Akt-mTOR cascade activation in endothelial cells. Depleting NDUFS8 inhibited Akt-mTOR activation, reversible with exogenous ATP in HUVECs. Conversely, NDUFS8 overexpression boosted Akt-mTOR activation. Furthermore, the inhibitory effects of NDUFS8 knockdown on cell proliferation, migration, and capillary tube formation were rescued by Akt re-activation via a constitutively-active Akt1. In vivo experiments using an endothelial-specific NDUFS8 shRNA adeno-associated virus (AAV), administered via intravitreous injection, revealed that endothelial knockdown of NDUFS8 inhibited retinal angiogenesis. ATP reduction, oxidative stress, and enhanced lipid oxidation were detected in mouse retinal tissues with endothelial knockdown of NDUFS8. Lastly, we observed an increase in NDUFS8 expression in retinal proliferative membrane tissues obtained from human patients with proliferative diabetic retinopathy. Our findings underscore the essential role of the mitochondrial protein NDUFS8 in regulating endothelial cell activation and angiogenesis.

USP18 enhances the resistance of BRAF-mutated melanoma cells to vemurafenib by stabilizing cGAS expression to induce cell autophagy.

This study aims to discern the possible molecular mechanism of the effect of ubiquitin-specific peptidase 18 (USP18) on the resistance to BRAF inhibitor vemurafenib in BRAF V600E mutant melanoma by regulating cyclic GMP-AMP synthase (cGAS). The cancer tissues of BRAF V600E mutant melanoma patients before and after vemurafenib treatment were collected, in which the protein expression of USP18 and cGAS was determined. A BRAF V600E mutant human melanoma cell line (A2058R) resistant to vemurafenib was constructed with its viability, apoptosis, and autophagy detected following overexpression and depletion assays of USP18 and cGAS. Xenografted tumors were transplanted into nude mice for in vivo validation. Bioinformatics analysis showed that the expression of cGAS was positively correlated with USP18 in melanoma, and USP18 was highly expressed in melanoma. The expression of cGAS and USP18 was up-regulated in cancer tissues of vemurafenib-resistant patients with BRAF V600E mutant melanoma. Knockdown of cGAS inhibited the resistance to vemurafenib in A2058R cells and the protective autophagy induced by vemurafenib in vitro. USP18 could deubiquitinate cGAS to promote its protein stability. In vivo experimentations confirmed that USP18 promoted vemurafenib-induced protective autophagy by stabilizing cGAS protein, which promoted resistance to vemurafenib in BRAF V600E mutant melanoma cells. Collectively, USP18 stabilizes cGAS protein expression through deubiquitination and induces autophagy of melanoma cells, thereby promoting the resistance to vemurafenib in BRAF V600E mutant melanoma.

The mitochondrial protein TIMM44 is required for angiogenesis in vitro and in vivo.

The mitochondrial integrity and function in endothelial cells are essential for angiogenesis. TIMM44 (translocase of inner mitochondrial membrane 44) is essential for integrity and function of mitochondria. Here we explored the potential function and the possible mechanisms of TIMM44 in angiogenesis. In HUVECs, human retinal microvascular endothelial cells and hCMEC/D3 brain endothelial cells, silence of TIMM44 by targeted shRNA largely inhibited cell proliferation, migration and in vitro capillary tube formation. TIMM44 silencing disrupted mitochondrial functions in endothelial cells, causing mitochondrial protein input arrest, ATP reduction, ROS production, and mitochondrial depolarization, and leading to apoptosis activation. TIMM44 knockout, by Cas9-sgRNA strategy, also disrupted mitochondrial functions and inhibited endothelial cell proliferation, migration and in vitro capillary tube formation. Moreover, treatment with MB-10 ("MitoBloCK-10"), a TIMM44 blocker, similarly induced mitochondrial dysfunction and suppressed angiogenic activity in endothelial cells. Contrarily, ectopic overexpression of TIMM44 increased ATP contents and augmented endothelial cell proliferation, migration and in vitro capillary tube formation. In adult mouse retinas, endothelial knockdown of TIMM44, by intravitreous injection of endothelial specific TIMM44 shRNA adenovirus, inhibited retinal angiogenesis, causing vascular leakage, acellular capillary growth, and retinal ganglion cells degeneration. Significant oxidative stress was detected in TIMM44-silenced retinal tissues. Moreover, intravitreous injection of MB-10 similarly induced oxidative injury and inhibited retinal angiogenesis in vivo. Together, the mitochondrial protein TIMM44 is important for angiogenesis in vitro and in vivo, representing as a novel and promising therapeutic target of diseases with abnormal angiogenesis.

PIK3R2 predicts poor outcomes for patients with melanoma and contributes to the malignant progression via PI3K/AKT/NF-κB axis.

BACKGROUND: Melanoma is an aggressive form of skin cancer worldwide. Phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) exerts carcinogenic roles in various tumors. So far, the function and mechanism of PIK3R2 in melanoma are not been fully clarified. OBJECTIVE: We aimed to clarify the role of PIK3R2 in melanoma. METHODS: PIK3R2 expressions in melanoma clinical tissues and melanoma cells were measured using quantitative real-time PCR and Western blot. In addition, PIK3R2 expressions in different tumor stages of melanoma were determined by immunohistochemistry assay. Meanwhile, PIK3R2 function was evaluated using loss or gain-of-function assays, Cell Counting Kit-8 assay, flow cytometry, and Transwell analysis. Furthermore, PIK3R2 mechanism in melanoma was assessed by a series of rescue experiments. RESULTS: PIK3R2 was highly expressed in melanoma tissues and cells, and PIK3R2 expressions were the highest in Stage IV. Functionally, PIK3R2 knockdown repressed melanoma cell proliferation, invasion, epithelial-mesenchymal transition, and facilitated cell apoptosis. Also, PIK3R2 overexpression produced an opposite trend. Mechanistically, PIK3R2 facilitated melanoma progression by activating PI3K/AKT/NF-κB pathway. Furthermore, PIK3R2 knockdown restrained the melanoma tumor growth in vivo. CONCLUSIONS: PIK3R2 aggravated melanoma by activating PI3K/AKT/NF-κB pathway, prompting that PIK3R2 might be a therapeutic target for melanoma.

Discovery of novel analogs of KHS101 as transforming acidic coiled coil containing protein 3 (TACC3) inhibitors for the treatment of glioblastoma.

Transforming acidic coiled coil containing protein 3 (TACC3) is emerging as an attractive anticancer target in recent years, however, few TACC3 small-molecular inhibitors have been reported up to now. In this study, fifteen compounds were designed and synthesized based on the lead compound KHS101 to find more potent TACC3 inhibitors. Among them, the most potent compound 7g exhibited about 10-folds more potent antiproliferative activities than KHS101 in various cancer cell lines. Two different protein-drug binding assays including DARTS, and CETSA revealed TACC3 as a biologically relevant target of compound 7g. In addition, compound 7g induced cell cycle arrest at the G2/M phase and induced cell apoptosis. Furthermore, compound 7g depolarized the MMP and induced ROS generation in a dose-dependent manner in U87 cells. More importantly, 7g reduced tumor weight by 72.7% in U87 xenograft model at a dose of 20 mg/kg/day without obvious toxicity. Altogether, compound 7g deserved further investigations as a novel, safe and efficacious TACC3 inhibitor for the treatment of GBM.

WNT signaling modulates chemoresistance to temozolomide in p53-mutant glioblastoma multiforme.

Glioblastoma multiforme (GBM) has been characterized by the high incidence, therapy tolerance and relapse. The molecular events controlling GBM resistant to chemotherapy temozolomide (TMZ) remain to be elusive. Here, we identified WNT signaling was amplified by TMZ and mediated drug response in GBM. We found O6-methylguanine DNA methyltransferase (MGMT) was redundant to WNT-mediated chemoresistance, which was highly associated with p53 mutation status. In GBM with p53 mutation, loss of function of p53 downregulated miR-34a expression, which represses transcription of WNT ligand 6 (WNT6) by directly binding to 3' UTR of WNT6 mRNA, leading to activation of WNT signaling, and the eventual WNT-mediated chemoresistance to TMZ. Combined treatment of TMZ with WNT inhibitor or miR34a mimic induced drug sensitivity of p53-mutant GBM cells and extended survival in xenograft mice in vivo. Our findings provide insight into understanding the molecular mechanism of GBM chemoresistance to TMZ and facilitating to develop novel treatment strategy to combat p53-mutant GBM by targeting miR-34a/WNT6 axis.

Carboplatin activates the cGAS-STING pathway by upregulating the TREX-1 (three prime repair exonuclease 1) expression in human melanoma.

Human melanoma is a highly aggressive type of cancer, causing significant mortalities despite the advances in treatment. Carboplatin is a cisplatin analog necessary for the treatment of various cancers and can also be used to treat human melanoma. We assessed the effects and mechanisms leading to inhibited proliferation and induced apoptosis of human melanoma after carboplatin therapy in vitro and in vivo. TREX1, cGAS/STING, and apoptotic protein expressions were determined through RT-qPCR and western blot assays. Cell proliferation was validated through MTT assays. The study used SK-MEL-1 and SK-HEP-1 tumor cell line inoculations along with carboplatin in nude mice to validate the results. The TREX1 levels were down-regulated in human melanoma cell lines. TREX1 overexpression-induced apoptosis and decreased proliferation in the human melanoma cell lines. TREX1 overexpression also activated the cGAS/STING pathway to induce apoptosis and decrease cell growth. Carboplatin activated TREX1, induced apoptosis, and decreased proliferation in the human melanoma cancerous cell lines. Finally, carboplatin reduced the in-vivo tumor size and weight. In conclusion, the study revealed that carboplatin activated TREX1 and cGAS/STING pathways to upregulate apoptosis. The work also provides in vitro and in vivo evidence to understand the effects of TREX overexpression on tumor suppression. Targeting of TREX1/cGAS/STING pathway could be an effective therapeutic alternative to human melanoma.

ß-Elemene Triggers ROS-dependent Apoptosis in Glioblastoma Cells Through Suppressing STAT3 Signaling Pathway.

Glioblastoma is one of the most aggressive primary brain tumors with few treatment strategies. ß-Elemene is a sesquiterpene known to have broad spectrum antitumor activity against various cancers. However, the signaling pathways involved in ß-elemene induced apoptosis of glioblastoma cells remains poorly understood. In this study, we reported that ß-elemene exhibited antiproliferative activity on U87 and SHG-44 cells, and induced cell death through induction of apoptosis. Incubation of these cells with ß-elemene led to the activation of caspase-3 and generation of reactive oxygen species (ROS). Western blot assay showed that ß-elemene suppressed phosphorylation of STAT3, and subsequently down-regulated the activation of p-JAK2 and p-Src. Moreover, pre-incubation of cells with ROS inhibitor N-acetyl-L-cysteine (NAC) significantly reversed ß-elemene-mediated apoptosis effect and down-regulation of JAK2/Src-STAT3 signaling pathway. Overall, our findings implied that generation of ROS and suppression of STAT3 signaling pathway is critical for the apoptotic activity of ß-elemene in glioblastoma cells.

A novel selective mitochondrial-targeted curcumin analog with remarkable cytotoxicity in glioma cells.

Naturally occurring polyphenol curcumin (4) or demethoxycurcumin (5) and their synthetic derivatives display promising anticancer activities. However, their further development is limited by low bioavailability and poor selectivity. Thus, a mitochondria-targeted compound 14 (DMC-TPP) was prepared in the present study by conjugating a triphenylphosphine moiety to the phenolic hydroxyl group of demethoxycurcumin to enhance its bioavailability and treatment efficacy. The in vitro biological experiments of DMC-TPP showed that it not only displayed higher cytotoxicity as compared with its parent compound 5, but also exhibited superior mitochondria accumulation ability. Glioma cells were more sensitive to DMC-TPP, which inhibited the proliferation of U251 cells with an IC50 of 0.42 µM. The mechanism studies showed that DMC-TPP triggers mitochondria-dependent apoptosis, caused by caspase activation, production of reactive oxygen species (ROS) and decrease of mitochondrial membrane potential (MMP). In addition, DMC-TPP efficiently inhibited cellular thioredoxin reductase, which contributed to its cytotoxicity. Significantly, DMC-TPP delayed tumor progression in a mouse xenograft model of human glioma cancer. Taken together, the potent in vitro and in vivo antitumor activity of DMC-TPP warrant further comprehensive evaluation as a novel anti-glioma agent.

Primary cilia-dependent signaling is involved in regulating mesenchymal stem cell proliferation and pluripotency maintenance.

Using a large-scale quantitative mesenchymal stem cells (MSCs) membrane proteomics analysis, we identified a large group of ciliary proteins in the MSCs membrane fraction, which prompted us to examine the cilia, intricate organelles that were originally discovered approximately 100 years ago. Here we characterize their primary structure and function in MSCs. We first characterized the primary cilia on undifferentiated human MSCs by immunostaining and verified these observation with scanning and 3D electronic microscopy. To investigate the function of the primary cilia of the MSCs we induced loss of function by means of siRNA knockdown (targeted to two known ciliary proteins: IFT172 and KIF3A). After either of these two proteins was knocked down by the respective siRNA, the MSCs showed fewer and shortened primary cilia. The MSCs proliferation assays showed increased cell proliferative activity under confluent conditions after the siRNA knockdown of IFT172 or KIF3A; among these MSCs, the proportion in S phase was increased in the IFT172 siRNA knockdown group. The expression of stem cell markers on the MSCs, namely, Oct4, Nanog and Sox2, were downregulated after the siRNA-induced knockdown of IFT172 or KIF3A, and the gene expression upregulation of ectoderm lineage markers was notable. Furthermore, manipulation of the primary cilia-dependent Shh pathway, using the Shh activator SAG (smoothened agonist), upregulated the gene expression of pluripotency markers, including Nanog and Oct4, and transcriptional target genes in the Shh pathway. This study confirms that MSCs have primary cilia and provides evidence that primary cilia-dependent signaling pathways play functional roles in MSCs proliferation and stemness maintenance.

Allicin alleviates lead-induced hematopoietic stem cell aging by up-regulating PKM2.

Hematopoietic stem cells (HSCs) aging is associated with hematopoietic dysfunction and diseases. Our previous study showed that lead exposure induced a functional decline in HSCs. Allicin, a chemical extracted from the garlic (Allium sativum L.), has been reported to have antioxidative and anti-inflammatory effects. However, the biological activities of allicin on lead-induced toxicity, especially in the hematopoietic system, remain unclear. Here, we found that lead exposure elicited aging phenotypes in HSCs, including perturbed cell quiescence, disabled self-renewal function and colony-forming ability, and myeloid-biased differentiation, all of which contributed to significant hematopoietic disorders in mice. Intragastric administration of allicin substantially ameliorated lead-induced HSCs aging phenotypes in vivo Lead exposure induced a peroxide condition in HSCs leading to DNA damage, which reduced expression of the glycolytic enzyme pyruvate kinase M2 isoform (PKM2), a phenotype which was significantly ameliorated by allicin treatment. These findings suggested that allicin alleviated lead-induced HSCs aging by up-regulating PKM2 expression; thus, it could be a natural herb for preventing lead toxicity.