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Skeletal muscle serves fundamental roles in organismal health. Gene expression fluctuations are critical for muscle homeostasis and the response to environmental insults. Yet, little is known about post-transcriptional mechanisms regulating such fluctuations while impacting muscle proteome. Here we report genome-wide analysis of mRNA methyladenosine (m6A) dynamics of skeletal muscle hypertrophic growth following overload-induced stress. We show that increases in METTL3 (the m6A enzyme), and concomitantly m6A, control skeletal muscle size during hypertrophy; exogenous delivery of METTL3 induces skeletal muscle growth, even without external triggers. We also show that METTL3 represses activin type 2 A receptors (ACVR2A) synthesis, blunting activation of anti-hypertrophic signaling. Notably, myofiber-specific conditional genetic deletion of METTL3 caused spontaneous muscle wasting over time and abrogated overload-induced hypertrophy; a phenotype reverted by co-administration of a myostatin inhibitor. These studies identify a previously unrecognized post-transcriptional mechanism promoting the hypertrophic response of skeletal muscle via control of myostatin signaling., Muscle undergoes hypertrophy and atrophy in response to physiological stimuli or in pathological conditions, which is partially controlled through altered gene expression. Here the authors report that m6A methyltransferase METTL3 and mRNA m6A post-transcriptional modifications as a mechanism that regulates muscle hypertrophy and atrophy via myostatin signalling in mice.

N(6)-methyladenosine (m(6)A) is the most abundant mRNA modification, which is installed by the METTL3-METTL14-WTAP methyltransferase complex. Although the importance of m(6)A methylation in mRNA dynamics has been well-documented recently, the regulation of m(6)A machinery remains obscure. Through a genome-wide CRISPR screen, we identify the ERK pathway and USP5 as positive regulators of the m(6)A pathway. We find that ERK phosphorylates METTL3 at S43/S50/S525 and WTAP at S306/S341, followed by deubiquitination by USP5, resulting in stabilization of the m(6)A methyltransferase complex. Lack of METTL3/WTAP phosphorylation reduces decay of m(6)A-labeled pluripotent factors and traps mouse embryonic stem cells in the pluripotent state. The same phosphorylation can also be found in ERK-activated human cancer cells and contribute to tumorigenesis. Overall, our study reveals an unrecognized function of ERK in regulating m(6)A methylation.

HIF-1α, one of the most extensively studied oncogenes, is activated by a variety of microenvironmental factors. The resulting biological effects are thought to depend on its transcriptional activity. The RNAse enzyme Dicer is frequently downregulated in human cancers, which has been functionally linked to enhanced metastatic properties; however, current knowledge of the upstream mechanisms regulating Dicer is limited. In the present study, we identified Dicer as a HIF-1α-interacting protein in multiple types of cancer cell lines and different human tumors. HIF-1α downregulated Dicer expression by facilitating its ubiquitination by the E3 ligase Parkin, thereby enhancing autophagy-mediated degradation of Dicer, which further suppressed the maturation of known tumor suppressors, such as the microRNA let-7 and microRNA-200b. Consequently, expression of HIF-1α facilitated epithelial-mesenchymal transition (EMT) and metastasis in tumor-bearing mice. Thus, this study uncovered a connection between oncogenic HIF-1α and the tumor-suppressive Dicer. This function of HIF-1α is transcription independent and occurs through previously unrecognized protein interaction-mediated ubiquitination and autophagic proteolysis.

Targeted inhibition of oncogenic miRNA-21 has been proposed to treat glioblastoma by rescuing tumor suppressors, PTEN and PDCD4. However, systemic delivery of anti-miR-21 sequences requires a robust and efficient delivery platform to successfully inhibit this druggable target. Three-way-junction (3WJ)-based RNA nanoparticles (RNP), artificially derived from pRNA of bacteriophage phi29 DNA packaging motor, was recently shown to target glioblastoma. Here, we report that multi-valent folate (FA)-conjugated 3WJ RNP constructed to harbor anti-miR-21 LNA sequences (FA-3WJ-LNA-miR21) specifically targeted and delivered anti-miR-21 LNA and knocked down miR-21 expression in glioblastoma cells in vitro and in vivo with favorable biodistribution. Systemically injected FA-3WJ-LNA-miR21 RNP efficiently rescued PTEN and PDCD4, resulting in glioblastoma cell apoptosis and tumor growth regression. Overall survival rate was also significantly improved by FA-3WJ-LNA-miR21 RNP. These results are indicative of the clinical benefit of FA-3WJ RNP-based gene therapy for the successful targeted therapy of developing and even recurring glioblastoma.

Background and aims Mouse models of colitis have been used to study the pathogenesis of inflammatory bowel disease (IBD) and for pre-clinical development of therapeutic agents. Various epigenetic pathways have been shown to play important regulatory roles in IBD. Reversible N6-methyladenosine (m6A) methylation represents a new layer of post-transcriptional gene regulation that affects a variety of biological processes. We aim to study how deletion of a critical component of m6A writer complex, METTL14, in T cells affects the development of colitis. Methods Conditional Mettl14 was lineage specifically deleted with CD4-regulated Cre in T cells. Colitis phenotype was determined by H&E staining, colon weight-to-length ratio and cytokine expression. We additionally utilized T cell transfer model of colitis and adoptive transfer of regulatory T cells. Mice were treated with antibiotics to determine if the colitis could be attenuated. Results METTL14 deficiency in T cells induced spontaneous colitis in mice. This was characterized by increased inflammatory cell infiltration, increased colonic weight-to-length ratio and increased Th1 and Th17 cytokines. The colitis development was due to dysfunctional regulatory T (Treg) cells, as adoptive transfer of WT Treg cells attenuated the colitis phenotype. The METTL14-deficient Treg cells have decreased RORγt expression compared with WT controls. METTL14 deficiency caused impaired induction of naïve T cells into induced Treg cells. Antibiotic treatment notably attenuated the colitis development. Conclusion Here we report a new mouse model of spontaneous colitis based on perturbation of RNA methylation in T cells. The colitis is T cell-mediated and dependent on the microbiome. This model represents a new tool for elucidating pathogenic pathways, studying the contribution of intestinal microbiome and preclinical testing of therapeutic agents for inflammatory bowel disease.

Epithelial-to-mesenchymal transition (EMT) is an essential physiologic process that promotes cancer cell migration, invasion, and metastasis. Several lines of evidence from both cellular and genetic studies suggest that AKT1/PKBα, but not AKT2 or AKT3, serves as a negative regulator of EMT and breast cancer metastasis. However, the underlying mechanism by which AKT1 suppresses EMT remains poorly defined. Here, we demonstrate that phosphorylation of Twist1 by AKT1 is required for β-TrCP–mediated Twist1 ubiquitination and degradation. The clinically used AKT inhibitor MK-2206, which possesses higher specificity toward AKT1, stabilized Twist1 and enhanced EMT in breast cancer cells. However, we discovered that resveratrol, a naturally occurring compound, induced β-TrCP–mediated Twist1 degradation to attenuate MK-2206–induced EMT in breast cancer cells. Taken together, our findings demonstrate that resveratrol counteracts the unexpected metastatic potential induced by anti-AKT therapy and therefore suggest that the addition of resveratrol to an anti-AKT therapeutic regimen may provide extra support for limiting EMT. Cancer Res; 76(6); 1451–62. ©2016 AACR.

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MicroRNA (miRNA) dysregulation is associated with the tumorigenesis and development of numerous human cancers. The defect in miRNA biogenesis is the main cause of miRNA dysregulation. We previously demonstrated that ERK-induced phosphorylation of XPO5 followed by peptidyl-prolyl cis/trans isomerase Pin1-mediated isomerization downregulates miRNA expression and contributes to hepatocellular carcinoma (HCC) development. However, how Pin1 precisely regulates miRNA biogenesis in HCC remains elusive. Here we reveal that Pin1 has a pivotal role in the miRNA maturation process by modulating phosphorylated Serine-Proline (pS-P) motif of XPO5 in a phosphorylation-dependent manner. By recognizing and binding to XPO5 via its WW domain, Pin1 catalyzes the conformation change of XPO5 and diminishes XPO5 ability to export pre-miRNAs from the nucleus to the cytoplasm, resulting in the reduced mature miRNA levels and promoted HCC development. Furthermore, downregulation of Pin1 by shRNA restores XPO5-dependent pre-miRNA export and effective biogenesis of mature miRNAs, leading to both in vitro and in vivo HCC inhibition. Therefore, our research discloses a new posttranscriptional regulatory mechanism of miRNA biosynthesis and provides the experimental basis for a novel HCC therapy by targeting Pin1.

MicroRNAs (miRNAs) are small 19- to 24-nt noncoding RNAs that have the capacity to regulate fundamental biological processes essential for cancer initiation and progression. In cancer, miRNAs may function as oncogenes or tumor suppressors. Here, we conducted global profiling for miRNAs in a cohort of stage 1 nonsmall cell lung cancers ( n = 81) and determined that miR-486 was the most down-regulated miRNA in tumors compared with adjacent uninvolved lung tissues, suggesting that miR-486 loss may be important in lung cancer development. We report that miR-486 directly targets components of insulin growth factor (IGF) signaling including insulin-like growth factor 1 (IGF1), IGF1 receptor (IGF1R), and phosphoinositide-3-kinase, regulatory subunit 1 (alpha) (PIK3R1, or p85a) and functions as a potent tumor suppressor of lung cancer both in vitro and in vivo. Our findings support the role for miR-486 loss in lung cancer and suggest a potential biological link to p53.

While p21 is well known to inhibit cyclin-CDK activity in the nucleus and it has also been demonstrated to have oncogenic properties in different types of human cancers. In vitro studies showed that the oncogenic function of p21is closely related to its cytoplasmic localization. However, it is unclear whether cytoplasmic p21 contributes to tumorigenesis in vivo. To address this question, we generated transgenic mice expressing the Akt-phosphorylated form of p21 (p21T145D) in the mammary epithelium. The results showed that Akt-activated p21 was expressed in the cytoplasm of mammary epithelium. Overexpression of Akt-activated p21 accelerated tumor onset and promoted lung metastasis in MMTV/neu mice, providing evidence that p21, especially cytoplasmic phosphorylated p21, has an oncogenic role in promoting mammary tumorigenesis and metastasis.

Attacking angiogenesis is considered an effective strategy for controls the expansion and metastasis of tumors and other related-diseases. The aim of this study was to assess the effects of moscatilin, a bibenzyl derivative, on VEGF and bFGF-induced angiogenesis in cultured human umbilical vein endothelial cells (HUVECs) in vitro and in vivo. Moscatilin significantly inhibited growth of lung cancer cell line A549 (NSCLC) and suppressed growth factor-induced neovascularization. In addition, VEGF- and bFGF-induced cell proliferation, migration, and tube formation of HUVECs was markedly inhibited by moscatilin. Western blotting analysis of cell signaling molecules indicated that moscatilin inhibited ERK1/2, Akt, and eNOS signaling pathways in HUVECs. These results suggest that inhibition of angiogenesis by moscatilin may be a major mechanism in cancer therapy.

CHM-1 (2′-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone) has been identified as a potent antitumor agent in human hepatocellular carcinoma; however, its role in tumor angiogenesis is unclear. This study investigated the effects of CHM-1 and the mechanisms by which it exerts its antiangiogenic and vascular disrupting properties. Using a xenograft model antitumor assay, we found that CHM-1 significantly inhibits tumor growth and microvessel formation. Flow cytometry, immunofluorescence microscopy, and cell death enzyme-linked immunosorbent assay kit revealed that CHM-1 inhibits growth of human umbilical vein endothelial cells (HUVEC) by induction of apoptotic cell death in a concentration-dependent manner. CHM-1 also suppresses HUVEC migration and capillary-like tube formation. We were able to correlate CHM-1-induced apoptosis in HUVEC with the cleavage of procaspase-3, -7, and -8, as well as with the cleavage of poly(ADP-ribose) polymerase by Western blotting assay. Such sensitization was achieved through up-regulation of death receptor 5 (DR5) but not DR4 or Fas. CHM-1 was also capable of increasing the expression level of p53, and most importantly, the induction of DR5 by CHM-1 was abolished by p53 small interfering RNA. Taken together, the results of this study indicate that CHM-1 exhibits vascular targeting activity associated with the induction of DR5-mediated endothelial cell apoptosis through p53 up-regulation, which suggests its potential as an antivascular and antitumor therapeutic agent.

Purpose: Antiangiogenic therapy is considered as an effective strategy for controlling the growth and metastasis of tumors. Among a myriad of biological activities described for xanthone derivatives, the anticancer activity is quite remarkable, but the molecular mechanism is not clearly resolved. In the present study, we investigated the antiangiogenic mechanism of 3,6-di(2,3-epoxypropoxy)xanthone (EPOX), a novel Mcl-1 targeting drug. Experimental Design: To evaluate the antiangiogenic activity of EPOX, we did cell viability, cell cycle, tube formation assay in vitro, and Matrigel plug assay in vivo. To evaluate the effect of EPOX on the endothelial signaling pathway, we did immunoblotting, immunoprecipitation, and immunofluorescence analysis. Intracellular glutathione levels were determined with the use of monochlorobimane, a glutathione-specific probe. Results: EPOX induced endothelial cell apoptosis in association with proteasome-dependent Mcl-1 degradation. Down-regulation of Mcl-1 resulted in an increase in Mcl-1–free Bim, activation of Bax, and then signaling of mitochondria-mediated apoptosis. Additionally, glutathione depletion and extracellular signal-regulated kinase (ERK) inactivation was observed in EPOX-treated cells. Glutathione supplementation reversed the inhibitory effects of EPOX on ERK, which increases the phosphorylation of Mcl-1 at T163. Overexpression of mitogen-activated protein/ERK kinase (MEK) partially reversed the effect of EPOX on Mcl-1 dephosphorylation, ubiquitination, and degradation, further implicating ERK in the regulation of Mcl-1 stability. Conclusions: This study provides evidence that EPOX induces glutathione depletion, ERK inactivation, and Mcl-1 degradation on endothelial cells, which leads to inhibition of angiogenesis. Our results suggest that EPOX is a novel antiangiogenic agent, making it a promising lead compound for further development in the treatment of angiogenesis-related pathologies.

Quaking (QKI) is a tumor-suppressor gene encoding a conserved RNA-binding protein, whose expression is downregulated in several solid tumors. Here we report that QKI plays an important role in the immune response and suppression of leukemogenesis. We show that the expression of Qki is reduced in lipopolysaccharide (LPS)-challenged macrophages, suggesting that Qki is a key regulator of LPS signaling pathway. Furthermore, LPS-induced downregulation of Qki expression is miR-155-dependent. Qki overexpression impairs LPS-induced phosphorylation of JNK and particularly p38 MAPKs, in addition to increasing the production of anti-inflammatory cytokine IL-10. In contrast, Qki ablation decreases Fas expression and the rate of Caspase3/7 activity, while increasing the levels of IL-1α, IL-1β and IL-6, and p38 phosphorylation. Similarly, the p38 pathway is also a target of QKI activity in chronic lymphocytic leukemia (CLL)-derived MEC2 cells. Finally, B-CLL patients show lower levels of QKI expression compared with B cells from healthy donor, and Qki is similarily downregulated with the progression of leukemia in Eµ-miR-155 transgenic mice. Altogether, these data implicate QKI in the pathophysiology of inflammation and oncogenesis where miR-155 is involved.

Lung cancer is the leading cause of cancer-related deaths worldwide. Despite advancements and improvements in surgical and medical treatments, the survival rate of lung cancer patients remains frustratingly poor. Local control for early-stage nonsmall cell lung cancer (NSCLC) has dramatically improved over the last decades for both operable and inoperable patients. However, the molecular mechanisms of NSCLC invasion leading to regional and distant disease spread remain poorly understood. Here, we identify microRNA-224 (miR-224) to be significantly up-regulated in NSCLC tissues, particularly in resected NSCLC metastasis. Increased miR-224 expression promotes cell migration, invasion, and proliferation by directly targeting the tumor suppressors TNFα-induced protein 1 (TNFAIP1) and SMAD4. In concordance with in vitro studies, mouse xenograft studies validated that miR-224 functions as a potent oncogenic miRNA in NSCLC in vivo. Moreover, we found promoter hypomethylation and activated ERK signaling to be involved in the regulation of miR-224 expression in NSCLC. Up-regulated miR-224, thus, facilitates tumor progression by shifting the equilibrium of the partially antagonist functions of SMAD4 and TNFAIP1 toward enhanced invasion and growth in NSCLC. Our findings indicate that targeting miR-224 could be effective in the treatment of certain lung cancer patients.

Chemokines modulate angiogenesis and metastasis that dictate cancer development in tumor microenvironment. Osteosarcoma is the most frequent bone tumor and is characterized by a high metastatic potential. Chemokine CCL5 (previously called RANTES) has been reported to facilitate tumor progression and metastasis. However, the crosstalk between chemokine CCL5 and vascular endothelial growth factor (VEGF) as well as tumor angiogenesis in human osteosarcoma microenvironment has not been well explored. In this study, we found that CCL5 increased VEGF expression and production in human osteosarcoma cells. The conditioned medium (CM) from CCL5-treated osteosarcoma cells significantly induced tube formation and migration of human endothelial progenitor cells. Pretreatment of cells with CCR5 antibody or transfection with CCR5 specific siRNA blocked CCL5-induced VEGF expression and angiogenesis. CCL5/CCR5 axis demonstrably activated protein kinase Cδ (PKCδ), c-Src and hypoxia-inducible factor-1 alpha (HIF-1α) signaling cascades to induce VEGF-dependent angiogenesis. Furthermore, knockdown of CCL5 suppressed VEGF expression and attenuated osteosarcoma CM-induced angiogenesis in vitro and in vivo. CCL5 knockdown dramatically abolished tumor growth and angiogenesis in the osteosarcoma xenograft animal model. Importantly, we demonstrated that the expression of CCL5 and VEGF were correlated with tumor stage according the immunohistochemistry analysis of human osteosarcoma tissues. Taken together, our findings provide evidence that CCL5/CCR5 axis promotes VEGF-dependent tumor angiogenesis in human osteosarcoma microenvironment through PKCδ/c-Src/HIF-1α signaling pathway. CCL5 may represent a potential therapeutic target against human osteosarcoma.

T-cell leukemia/lymphoma 1 (TCL1) is an oncogene overexpressed in T-cell prolymphocytic leukemia and in B-cell malignancies including B-cell chronic lymphocytic leukemia and lymphomas. To date, only a limited number of Tcl1-interacting proteins that regulate its oncogenic function have been identified. Prior studies used a proteomic approach to identify a novel interaction between Tcl1 with Ataxia Telangiectasia Mutated. The association of Tcl1 and Ataxia Telangiectasia Mutated leads to activation of the NF-κB pathway. Here, we demonstrate that Tcl1 also interacts with heat shock protein (Hsp) 70. The Tcl1-Hsp70 complex was validated by coimmunoprecipitation experiments. In addition, we report that Hsp70, a protein that plays a critical role in the folding and maturation of several oncogenic proteins, associates with Tcl1 protein and stabilizes its expression. The inhibition of the ATPase activity of Hsp70 results in ubiquitination and proteasome-dependent degradation of Tcl1. The inhibition of Hsp70 significantly reduced the growth of lymphoma xenografts in vivo and down-regulated the expression of Tcl1 protein. Our findings reveal a functional interaction between Tcl1 and Hsp70 and identify Tcl1 as a novel Hsp70 client protein. These findings suggest that inhibition of Hsp70 may represent an alternative effective therapy for chronic lymphocytic leukemia and lymphomas via its ability to inhibit the oncogenic functions of Tcl1.

Aciculatin, a natural compound extracted from the medicinal herb Chrysopogon aciculatus, shows potent anti-cancer potency. This study is the first to prove that aciculatin induces cell death in human cancer cells and HCT116 mouse xenografts due to G1 arrest and subsequent apoptosis. The primary reason for cell cycle arrest and cell death was p53 accumulation followed by increased p21 level, dephosphorylation of Rb protein, PUMA expression, and induction of apoptotic signals such as cleavage of caspase-9, caspase-3, and PARP. We demonstrated that p53 allele-null (-/-) (p53-KO) HCT116 cells were more resistant to aciculatin than cells with wild-type p53 (+/+). The same result was achieved by knocking down p53 with siRNA in p53 wild-type cells, indicating that p53 plays a crucial role in aciculatin-induced apoptosis. Although DNA damage is the most common event leading to p53 activation, we found only weak evidence of DNA damage after aciculatin treatment. Interestingly, the aciculatin-induced downregulation of MDM2, an important negative regulator of p53, contributed to p53 accumulation. The anti-cancer activity and importance of p53 after aciculatin treatment were also confirmed in the HCT116 xenograft models. Collectively, these results indicate that aciculatin treatment induces cell cycle arrest and apoptosis via inhibition of MDM2 expression, thereby inducing p53 accumulation without significant DNA damage and genome toxicity.

Several antiangiogenic drugs targeting VEGF/VEGF receptor (VEGFR) that were approved by the Food and Drug Administration for many cancer types, including colorectal and lung cancer, can effectively reduce tumor growth. However, targeting the VEGF signaling pathway will probably influence the normal function of endothelial cells in maintaining homeostasis and can cause unwanted adverse effects. Indeed, emerging experimental evidence suggests that VEGF-targeting therapy induced less tumor cell–specific cytotoxicity, allowing residual cells to become more resistant and eventually develop a more malignant phenotype. We report an antitumor therapeutic EndoCD fusion protein developed by linking endostatin (Endo) to cytosine deaminase and uracil phosphoribosyltransferase (CD). Specifically, Endo possesses tumor antiangiogenesis activity that targets tumor endothelial cells, followed by CD, which converts the nontoxic prodrug 5-fluorocytosine (5-FC) to the cytotoxic antitumor drug 5-fluorouracil (5-FU) in the local tumor area. Moreover, selective targeting of tumor sites allows an increasing local intratumoral concentration of 5-FU, thus providing high levels of cytotoxic activity. We showed that treatment with EndoCD plus 5-FC, compared with bevacizumab plus 5-FU treatment, significantly increased the 5-FU concentration around tumor sites and suppressed tumor growth and metastasis in human breast and colorectal orthotropic animal models. In addition, in contrast to treatment with bevacizumab/5-FU, EndoCD/5-FC did not induce cardiotoxicity leading to heart failure in mice after long-term treatment. Our results showed that, compared with currently used antiangiogenic drugs, EndoCD possesses potent anticancer activity with virtually no toxic effects and does not increase tumor invasion or metastasis. Together, these findings suggest that EndoCD/5-FC could become an alternative option for future antiangiogenesis therapy. Mol Cancer Ther; 10(8); 1327–36. ©2011 AACR.

Amplification or overexpression of murine double minute 2 (MDM2) promotes a variety of human tumors by degrading tumor suppressor proteins such as p53. Phosphorylation of MDM2 on Ser166 and Ser186 by the survival kinase Akt inhibits p53-mediated apoptosis. However, it is unclear whether this pathway contributes to normal or malignant pathophysiology in vivo. To address these questions, we generated transgenic mice expressing the Akt-phosphorylated form of MDM2 (MDM2DDS166D/S186D) in the mammary epithelium. Activation of MDM2 delayed mammary gland involution and accelerated tumor progression in mouse mammary tumor virus/neu transgenic mice by inhibiting apoptosis in a manner associated with decreased p53 expression. Our findings offer in vivo evidence that activation of MDM2 by Akt contributes to mammary development and tumorigenesis. Cancer Res; 70(19); 7684–9. ©2010 AACR.

TNFalpha has recently emerged as a regulator linking inflammation to cancer pathogenesis, but the detailed cellular and molecular mechanisms underlying this link remain to be elucidated. The tuberous sclerosis 1 (TSC1)/TSC2 tumor suppressor complex serves as a repressor of the mTOR pathway, and disruption of TSC1/TSC2 complex function may contribute to tumorigenesis. Here we show that IKKbeta, a major downstream kinase in the TNFalpha signaling pathway, physically interacts with and phosphorylates TSC1 at Ser487 and Ser511, resulting in suppression of TSC1. The IKKbeta-mediated TSC1 suppression activates the mTOR pathway, enhances angiogenesis, and results in tumor development. We further find that expression of activated IKKbeta is associated with TSC1 Ser511 phosphorylation and VEGF production in multiple tumor types and correlates with poor clinical outcome of breast cancer patients. Our findings identify a pathway that is critical for inflammation-mediated tumor angiogenesis and may provide a target for clinical intervention in human cancer.