Fatty Acid Synthase induced S6Kinase facilitates USP11-eIF4B complex formation for sustained oncogenic translation in DLBCL

Long noncoding RNA GMAN promotes hepatocellular carcinoma progression by interacting with eIF4B

Gastric cancer metastasis associated long noncoding RNA (GMAN), a long noncoding RNA, is associated with metastasis in gastric cancer. However, its underlying mechanisms in hepatocellular carcinoma (HCC) are unclear. We found that lncRNA-GMAN was significantly overexpressed in HCC tissues. GMAN expression is associated with vascular invasion, histological grade, tumor, node, metastasis (TNM) stage, short overall survival, and disease-free survival. Knockdown of GMAN induced apoptosis and suppressed invasive and migration potential in vitro and vivo, whereas ectopic GMAN expression produced the opposite effect. We also found that the inhibition of apoptosis, rather than promotion of proliferation, was responsible for GMAN-enhanced cellular viability. Mechanistic analyses indicated that GMAN directly combined with eukaryotic translation initiation factor 4B (eIF4B) and promoted its phosphorylation at serine-422 by preventing eIF4B binding and dephosphorization of the protein phosphatase 2A subunit B. The results demonstrated the stability of p-eIF4B and the elevation of mRNA translation and anti-apoptosis-related protein expression, which further induced proliferation and metastasis of HCC. The current study demonstrates that GMAN regulates the progression of HCC by inhibiting apoptosis and promoting the survival of cancer cells.

Identification of Circulating Serum Multi-MicroRNA Signatures in Human DLBCL Models

There remains a need to identify new sensitive diagnostic and predictive blood-based platforms in lymphoma. We previously discovered a novel circulating microRNA (miRNA) signature in a Smurf2-deficient mouse model that spontaneously develops diffuse large B-cell lymphoma (DLBCL). Herein, we investigated this 10-miRNA signature (miR-15a, let-7c, let-7b, miR-27a, miR-10b, miR-18a, miR-497, miR-130a, miR24, and miR-155) in human lymphoma cell lines, mice engrafted with patient-derived xenografts (PDXs), and DLBCL patient serum samples leveraging systems biology analyses and droplet digital PCR (ddPCR) technology. Overall, 90% of the miRNAs were enriched in PDX DLBCL models and human lymphoma cell lines. Circulating miRNAs from the serum of 86 DLBCL patients were significantly increased compared with healthy controls and had similar patterns to the murine models. Strikingly, miRNAs were identified up to 27-fold higher levels in the serum of PDX-bearing mice and human patients compared with lymphoma cell lysates, suggesting a concentration of these factors over time within sera. Using cut-points from recursive partitioning analysis, we derived a 5-miRNA signature (let-7b, let-7c, miR-18a, miR-24, and miR-15a) with a classification rate of 91% for serum from patients with DLBCL versus normal controls. In addition, higher levels of circulating let-7b miRNA were associated with more advanced stage disease (i.e., III-IV vs. I-II) in DLBCL patients and higher levels of miR-27a and miR-24 were associated with MYC rearrangement. Taken together, circulating multi-miRNAs were readily detectable in pre-clinical cell line and human lymphoma models as well as in DLBCL patients where they appeared to distinguish clinico-pathologic subtypes and disease features.

The role of deubiquitinating enzymes in gastric cancer

The epigenetic regulation of gene expression (via DNA methylation, histone modification and microRNA interference) contributes to a variety of diseases, particularly cancer. Protein deubiquitination serves a key role in the mechanism underlying histone modification, and consequently influences tumor development and progression. Improved characterization of the role of ubiquitinating enzymes has led to the identification of numerous deubiquitinating enzymes (DUBs) with various functions. Gastric cancer (GC) is a highly prevalent cancer type that exhibits a high mortality rate. Latest analysis about cancer patient revealed that GC is sixth deadliest cancer type, which frequently occur in male (7.2%) than female (4.1%). Complex associations between DUBs and GC progression have been revealed in multiple studies; however, the molecular mechanism underpinning the metastasis and recurrence of GC is yet to be elucidated. Generally, DUBs were upregulated in gastric cancer. The relation of DUBs and tumor size, classification and staging was observed in GC. Besides, 5-yar survival rate of patients with GC is effeccted by expression level of DUBs. Among the highly expressed DUBs, specifically six DUBs namely UCHs, USPs, OTUs, MJDs, JAMMs and MCPIPs effect on this survival rate. Consequently, the association between GC and DUBs has received increasing attention in recent years. Therefore, in the present review, literature investigating the association between DUBs and GC pathophysiology was analyzed and critically appraised.

USP11 promotes growth and metastasis of colorectal cancer via PPP1CA-mediated activation of ERK/MAPK signaling pathway

Background

USP11 is an ubiquitin-specific protease that plays an important role in tumor progression via different mechanisms. However, the expression and prognostic significance of USP11 in colorectal cancer (CRC) remain unknown.

Methods

Bioinformatics analyses, qRT-PCR, western blotting, and immunohistochemistry were applied for investigating USP11 expression in CRC tissues. Kaplan–Meier analysis with log-rank test was used for survival analyses. LC–MS/MS was performed for identifying potential protein interactions with USP11. In vitro and in vivo assays were used for exploring the function of USP11 during the progression of CRC.

Findings

USP11 was overexpressed in CRC tissues and functioned as an oncogene. Overexpression or knockdown of USP11 promoted or inhibited, respectively, the growth and metastasis of CRC cells in vitro and in vivo. Mechanically, USP11 stabilized PPP1CA by deubiquitinating and protecting it from proteasome-mediated degradation. Moreover, the USP11/PPP1CA complex promoted CRC progression by activating the ERK/MAPK signaling pathway.

Interpretation

USP11 promoted tumor growth and metastasis in CRC via the ERK/MAPK pathway by stabilizing PPP1CA, suggesting USP11 is a potential prognostic marker.

Fund

This work was supported by National Natural Science Foundation of China (NSFC81530044, NSFC81220108021, NSFC81802343), Technology Major Project of China Grants 2017ZX10203206, Shanghai Sailing Program (19YF1409600) and The project of Shanghai Jiaotong University (YG2017QN30).

MEF2A Regulates the MEG3-DIO3 miRNA Mega Cluster-Targeted PP2A Signaling in Bovine Skeletal Myoblast Differentiation

Understanding the molecular mechanisms of skeletal myoblast differentiation is essential for studying muscle developmental biology. In our previous study, we reported that knockdown of myocyte enhancer factor 2A (MEF2A) inhibited myoblast differentiation. Here in this study, we further identified that MEF2A controlled this process through regulating the maternally expressed 3 (MEG3)-iodothyronine deiodinase 3 (DIO3) miRNA mega cluster and protein phosphatase 2A (PP2A) signaling. MEF2A was sufficient to induce MEG3 expression in bovine skeletal myoblasts. A subset of miRNAs in the MEG3-DIO3 miRNA cluster was predicted to target PP2A subunit genes. Consistent with these observations, MEF2A regulated PP2A signaling through its subunit gene protein phosphatase 2 regulatory subunit B, gamma (PPP2R2C) during bovine myoblast differentiation. MiR-758 and miR-543 in the MEG3-DIO3 miRNA cluster were down-regulated in MEF2A-depleted myocytes. Expression of miR-758 and miR-543 promoted myoblast differentiation and repressed PPP2R2C expression. Luciferase activity assay showed that PPP2R2C was post-transcriptionally targeted by miR-758 and miR-543. Taken together, these results reveal that the MEG3-DIO3 miRNAs function at downstream of MEF2A to modulate PP2A signaling in bovine myoblast differentiation.

The transcription factor CBFB suppresses breast cancer through orchestrating translation and transcription

Translation and transcription are frequently dysregulated in cancer. These two processes are generally regulated by distinct sets of factors. The CBFB gene, which encodes a transcription factor, has recently emerged as a highly mutated driver in a variety of human cancers including breast cancer. Here we report a noncanonical role of CBFB in translation regulation. RNA immunoprecipitation followed by deep sequencing (RIP-seq) reveals that cytoplasmic CBFB binds to hundreds of transcripts and regulates their translation. CBFB binds to mRNAs via hnRNPK and enhances translation through eIF4B, a general translation initiation factor. Interestingly, the RUNX1 mRNA, which encodes the transcriptional partner of CBFB, is bound and translationally regulated by CBFB. Furthermore, nuclear CBFB/RUNX1 complex transcriptionally represses the oncogenic NOTCH signaling pathway in breast cancer. Thus, our data reveal an unexpected function of CBFB in translation regulation and propose that breast cancer cells evade translation and transcription surveillance simultaneously through downregulating CBFB.

CBFB is highly mutated in breast cancers and is known to interact with RUNX proteins to regulate transcription. Here, the authors describe a non-canonical role of CBFB in translation regulation in which it binds to mRNAs through hnRNPK, facilitating translation by eIF4B.

TGF-β signaling pathway mediated by deubiquitinating enzymes

Ubiquitination is a reversible cellular process mediated by ubiquitin-conjugating enzymes, whereas deubiquitinating enzymes (DUBs) detach the covalently conjugated ubiquitin from target substrates to counter ubiquitination. DUBs play a crucial role in regulating various signal transduction pathways and biological processes including apoptosis, cell proliferation, DNA damage repair, metastasis, differentiation, etc. Since the transforming growth factor-β (TGF-β) signaling pathway participates in various cellular functions such as inflammation, metastasis and embryogenesis, aberrant regulation of TGF-β signaling induces abnormal cellular functions resulting in numerous diseases. This review focuses on DUBs regulating the TGF-β signaling pathway. We discuss the molecular mechanisms of DUBs involved in TGF-β signaling pathway, and biological and therapeutic implications for various diseases.

Phosphorylation of TSC2 by PKC-δ reveals a novel signaling pathway that couples protein synthesis to mTORC1 activity

Downstream of insulin-like growth factor receptor, the TSC1/2/ TCB1D7 (tuberous sclerosis complex) and mTOR (mechanistic target of rapamycin) pathways are implicated in many human diseases, including cancer and diabetes. Targeting this pathway is currently an important approach for palliating or eradicating cancer. Downstream of mTOR, translational machinery targeting holds great promise for anticancer drug development. Therefore, we investigated whether the protein synthesis machinery that is regulated by mTORC1 (mTOR complex 1) signaling can in turn regulate mTORC1 activity. We found that inhibition of protein synthesis results in rapid activation of mTORC1 signaling, thereby uncovering a feedback loop between mTOR and the translation machinery. This mTORC1 activation requires tuberous sclerosis complex (TSC) but is independent of AKT. In addition, by using a PKC-δ (protein kinase c delta)-specific inhibitor and PKC-δ siRNA knockdown, we found that PKC-δ kinase activity is required for mTORC1 activation in response to translation inhibitors. Furthermore, translation inhibition activates PKC-δ. Subsequently, we investigated whether PKC-δ can phosphorylate and inactivate TSC1/2, leading to mTORC1 activation. In vitro kinase assays showed direct phosphorylation of TSC2 (S932 and S939) by PKC-δ, which was confirmed by mass spectrometry. In vivo kinase analysis further indicated that both S932 and S939 are phosphorylated in response to translation inhibitors. Finally, phosphorylation defective TSC2 mutants (S932A and S939A single mutants and a S932A/S939A double mutant) failed to upregulate mTORC1 activity in the presence of translation inhibitors, suggesting that activation of mTORC1 by translation inhibitors is mediated by PKC-δ phosphorylation of TSC2 at S932/S939, which inactivates TSC.

Putting phage to work in deubiquitinase ligand discovery

Inhibiting deubiquitinase (DUB) function is a promising strategy for the treatment of cancers and other human diseases. Of the hundreds of human DUBs, USP11 has emerged as an ideal therapeutic target, as it regulates DNA double-strand break repair by homologous recombination (HR) and other functions central to eukaryotic cell survival. A new study by Spiliotopoulos et al. cleverly uses next-generation phage display (NGPD) to identify peptide ligands that bind USP11 in a unique pocket that impacts HR. The study provides an important step toward novel DUB inhibitors that may reduce the resistance of some cancers to current treatment options.

Inhibition of de novo lipogenesis targets androgen receptor signaling in castration-resistant prostate cancer

Standard of care for metastatic castration-resistant prostate cancer (mCRPC) mainly relies on suppression of androgen receptor (AR) signaling. This approach has no lasting benefit due to the emergence of resistance mechanisms, such as ligand-independent splicing variant AR-V7. A metabolic feature of mCRPC is the upregulation of de novo lipogenesis to provide substrates and fuel for metastatic spread. Whether increased levels of fats affect AR signaling to promote an aggressive disease remains to be determined. Using a selective and potent inhibitor of fatty acid synthase we demonstrate that suppression of this key enzyme inhibits AR, most importantly AR-V7, and reduces mCRPC growth. Our findings offer a therapeutic opportunity for mCRPC and a potential mechanism to overcome resistance to AR inhibitors.

A hallmark of prostate cancer progression is dysregulation of lipid metabolism via overexpression of fatty acid synthase (FASN), a key enzyme in de novo fatty acid synthesis. Metastatic castration-resistant prostate cancer (mCRPC) develops resistance to inhibitors of androgen receptor (AR) signaling through a variety of mechanisms, including the emergence of the constitutively active AR variant V7 (AR-V7). Here, we developed an FASN inhibitor (IPI-9119) and demonstrated that selective FASN inhibition antagonizes CRPC growth through metabolic reprogramming and results in reduced protein expression and transcriptional activity of both full-length AR (AR-FL) and AR-V7. Activation of the reticulum endoplasmic stress response resulting in reduced protein synthesis was involved in IPI-9119–mediated inhibition of the AR pathway. In vivo, IPI-9119 reduced growth of AR-V7–driven CRPC xenografts and human mCRPC-derived organoids and enhanced the efficacy of enzalutamide in CRPC cells. In human mCRPC, both FASN and AR-FL were detected in 87% of metastases. AR-V7 was found in 39% of bone metastases and consistently coexpressed with FASN. In patients treated with enzalutamide and/or abiraterone FASN/AR-V7 double-positive metastases were found in 77% of cases. These findings provide a compelling rationale for the use of FASN inhibitors in mCRPCs, including those overexpressing AR-V7.

Ovarian Cancer-Intrinsic Fatty Acid Synthase Prevents Anti-tumor Immunity by Disrupting Tumor-Infiltrating Dendritic Cells

Fatty acid synthase (FASN), the key metabolic enzyme of de novo lipogenesis, provides proliferative and metastatic capacity directly to cancer cells have been described. However, the impact of aberrant activation of this lipogenic enzyme on host anti-tumor immune milieu remains unknown. In this study, we depicted that elevated FASN expression presented in ovarian cancer with more advanced clinical phenotype and correlated with the immunosuppressive status, which characterized by the lower number and dysfunction of infiltrating T cells. Notably, in a mouse model, we showed that tumor cell-intrinsic FASN drove ovarian cancer (OvCa) progression by blunting anti-tumor immunity. Dendritic cells (DCs) are required to initiate and sustain T cell-dependent anti-tumor immunity. Here, our data showed that constitutive activation of FASN in ovarian cancer cell lead to abnormal lipid accumulation and subsequent inhibition of tumor-infiltrating DCs (TIDCs) capacity to support anti-tumor T cells. Mechanistically, FASN activation in ovarian cancer cell-induced the resulting increase of lipids present at high concentrations in the tumor microenvironment. Dendritic cells educated by FASN^high OvCa ascites are defective in their ability to present antigens and prime T cells. Accordingly, inhibiting FASN by FASN inhibitor can partly restore the immunostimulatory activity of TIDCs and extended tumor control by evoking protective anti-tumor immune responses. Therefore, our data provide a mechanism by which ovarian cancer-intrinsic FASN oncogenic pathway induce the impaired anti-tumor immune response through lipid accumulation in TIDCs and subsequently T-cells exclusion and dysfunction. These results could further indicate that targeting the FASN oncogenic pathway concomitantly enhance anti-tumor immunity, thus offering a unique approach to ovarian cancer immunotherapy.