Interleukin-like EMT inducer (ILEI) promotes melanoma invasiveness and is transcriptionally up-regulated by upstream stimulatory factor-1 (USF-1)

Human FAM3C restores memory-based thermotaxis of Caenorhabditis elegans famp-1/m70.4 loss-of-function mutants

The family with sequence similarity 3 (FAM3) superfamily represents a distinct class of signaling molecules that share a characteristic structural feature. Mammalian FAM3 member C (FAM3C) is abundantly expressed in neuronal cells and released from the synaptic vesicle to the extracellular milieu in an activity-dependent manner. However, the neural function of FAM3C has yet to be fully clarified. We found that the protein sequence of human FAM3C is similar to that of the N-terminal tandem domains of Caenorhabditis elegans FAMP-1 (formerly named M70.4), which has been recognized as a tentative ortholog of mammalian FAM3 members or protein-O-mannose β-1,2-N-acetylglucosaminyltransferase 1 (POMGnT1). Missense mutations in the N-terminal domain, named Fam3L2, caused defects in memory-based thermotaxis but not in chemotaxis behaviors; these defects could be restored by AFD neuron-specific exogenous expression of a polypeptide corresponding to the Fam3L2 domain but not that corresponding to the Fam3L1. Moreover, human FAM3C could also rescue defective thermotaxis behavior in famp-1 mutant worms. An in vitro assay revealed that the Fam3L2 and FAM3C can bind with carbohydrates, similar to the stem domain of POMGnT1. The athermotactic mutations in the Fam3L2 domain caused a partial loss-of-function of FAMP-1, whereas the C-terminal truncation mutations led to more severe neural dysfunction that reduced locomotor activity. Overall, we show that the Fam3L2 domain-dependent function of FAMP-1 in AFD neurons is required for the thermotaxis migration of C. elegans and that human FAM3C can act as a substitute for the Fam3L2 domain in thermotaxis behaviors.

A Novel ER Stress Mediator TMTC3 Promotes Squamous Cell Carcinoma Progression by Activating GRP78/PERK Signaling Pathway

During tumor progression, tumor cells are exposed to various stress conditions, which result in endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) to restore ER homeostasis. Accumulating evidence reported the orchestrating role of ER stress in epithelial-mesenchymal transition (EMT) progress, but the detailed mechanism was unclear. Here, we identified ectopic expression of TMTC3 in cells undergoing ER stress and verified the association with EMT markers through the cellular model of ER stress and database analysis. TMTC3 was abnormally highly expressed in squamous cell carcinomas (SCCs), and regulated by TP63, an SCCs-specific transcription factor. Biological function experiments indicated that TMTC3 promoted a malignant phenotype in vitro, and accelerated tumor growth and metastasis in vivo. RNA-seq analyses and further experiments revealed that TMTC3 promoted the expression of EMT markers via interleukin-like EMT inducer (ILEI, FAM3C). Further studies on the mechanism showed that TMTC3 disrupted the interaction between PERK and GRP78 to activate the PERK pathway and promote the nuclear translocation of ATF4, which increased the transcriptional activity of ILEI. These findings indicated that TMTC3 activates GRP78/PERK signaling pathway during ER stress-induced EMT, which might serve as a potential therapeutic target in SCCs.

The ILEI/LIFR complex induces EMT via the Akt and ERK pathways in renal interstitial fibrosis

BACKGROUND

Chronic kidney disease (CKD) is characterized by high morbidity and mortality and is difficult to cure. Renal interstitial fibrosis (RIF) is a major determinant of, and commonly occurs within, CKD progression. Epithelial mesenchymal transition (EMT) has been identified as a crucial process in triggering renal interstitial fibrosis (RIF). Interleukin-like EMT inducer (ILEI) is an important promotor of EMT; this study aims to elucidate the mechanisms involved.

METHODS

Male C57BL6/J mouse were randomly divided into 6 groups: sham (n = 10), sham with negative control (NC) shRNA (sham + NC, n = 10), sham with ILEI shRNA (sham + shILEI, n = 10), unilateral ureteral obstruction (UUO, n = 10), UUO with NC (UUO + NC, n = 10) and UUO with ILEI shRNA (UUO + shILEI, n = 10). Hematoxylin and eosin (H&E), Masson, and immunohistochemical (IHC) staining and western blotting (WB) were performed on murine kidney tissue to identify the function and mechanism of ILEI in RIF. In vitro, ILEI was overexpressed to induce EMT in HK2 cells and analyzed via transwell, WB, real-time PCR, and co-immunoprecipitation. Finally, tissue from 12 pediatric CKD patients (seven with RIF and five without RIF) were studied with H&E, Masson, and IHC staining.

RESULTS

Our in vitro model revealed that ILEI facilitates RIF in the UUO model via the Akt and ERK pathways. Further experiments in vivo and in vitro revealed that ILEI promotes renal tubular EMT by binding and activating leukemia inhibitory factor receptor (LIFR), in which phosphorylation of Akt and ERK is involved. We further find markedly increased expression levels of ILEI and LIFR in kidneys from pediatric CKD patients with RIF.

CONCLUSION

Our results indicate that ILEI may be a useful biomarker for renal fibrosis and a potential therapeutic target for modulating RIF.

OUP accepted manuscript

BACKGROUND

Glioblastoma stem cells (GSCs) and their interplay with tumor-associated macrophages (TAMs) are responsible for malignant growth and tumor recurrence of glioblastoma multiforme (GBM), but the underlying mechanisms are largely unknown.

METHODS

Cell viability, stemness, migration, and invasion were measured in GSCs after the knockdown of upstream stimulating factor 1 (USF1). Luciferase assay and chromatin immunoprecipitation qPCR were performed to determine the regulation of CD90 by USF1. Immunohistochemistry and immunofluorescent staining were used to examine the expression of USF1 and GSC markers, as well as the crosstalk between GSCs and TAMs. In addition, the interaction between GSCs and TAMs was confirmed using in vivo GBM models.

RESULTS

We show that USF1 promotes malignant glioblastoma phenotypes and GSCs-TAMs physical interaction by inducing CD90 expression. USF1 predicts a poor prognosis for glioma patients and is upregulated in patient-derived GSCs and glioblastoma cell lines. USF1 overexpression increases the proliferation, invasion, and neurosphere formation of GSCs and glioblastoma cell lines, while USF1 knockdown exerts an opposite effect. Further mechanistic studies reveal that USF1 promotes GSC stemness by directly regulating CD90 expression. Importantly, CD90 of GSCs functions as an anchor for physical interaction with macrophages. Additionally, the USF1/CD90 signaling axis supports the GSCs and TAMs adhesion and immunosuppressive feature of TAMs, which in turn enhance the stemness of GSCs. Moreover, the overexpression of CD90 restores the stemness property in USF1 knockdown GSCs and its immunosuppressive microenvironment.

CONCLUSIONS

Our findings indicate that the USF1/CD90 axis might be a potential therapeutic target for the treatment of glioblastoma.

A dual role of human tRNA methyltransferase hTrmt13 in regulating translation and transcription

Since numerous RNAs and RBPs prevalently localize to active chromatin regions, many RNA-binding proteins (RBPs) may be potential transcriptional regulators. RBPs are generally thought to regulate transcription via noncoding RNAs. Here, we describe a distinct, dual mechanism of transcriptional regulation by the previously uncharacterized tRNA-modifying enzyme, hTrmt13. On one hand, hTrmt13 acts in the cytoplasm to catalyze 2'-O-methylation of tRNAs, thus regulating translation in a manner depending on its tRNA-modification activity. On the other hand, nucleus-localized hTrmt13 directly binds DNA as a transcriptional co-activator of key epithelial-mesenchymal transition factors, thereby promoting cell migration independent of tRNA-modification activity. These dual functions of hTrmt13 are mutually exclusive, as it can bind either DNA or tRNA through its CHHC zinc finger domain. Finally, we find that hTrmt13 expression is tightly associated with poor prognosis and survival in diverse cancer patients. Our discovery of the noncatalytic roles of an RNA-modifying enzyme provides a new perspective for understanding epitranscriptomic regulation.

Transcriptional downregulation of FAM3C/ILEI in the Alzheimer's brain

Amyloid-β (Aβ) accumulation in the brain triggers the pathogenic cascade for Alzheimer's disease (AD) development. The secretory protein FAM3C (also named ILEI) is a candidate for an endogenous suppressor of Aβ production. In this study, we found that FAM3C expression was transcriptionally downregulated in the AD brain. To determine the transcriptional mechanism of the human FAM3C gene, we delineated the minimal 5'-flanking sequence required for basal promoter activity. From a database search for DNA-binding motifs, expression analysis using cultured cells, and promoter DNA-binding assays, we identified SP1 and EBF1 as candidate basal transcription factors for FAM3C, and found that SMAD1 was a putative inducible transcription factor and KLF6 was a transcription repressor for FAM3C. Genomic deletion of the basal promoter sequence from HEK293 and Neuro-2a cells markedly reduced endogenous expression of FAM3C and abrogated SP1- or EBF1-mediated induction of FAM3C. Nuclear protein extracts from AD brains contained lower levels of SP1 and EBF1 than did those from control brains, although the relative mRNA levels of these factors did not differ significantly between the groups. Additionally, the ability of nuclear SP1 and EBF1 in AD brains to bind with the basal promoter sequence-containing DNA probe was reduced compared with the binding ability of these factors in control brains. Thus, the transcriptional downregulation of FAM3C in the AD brain is attributable to the reduced nuclear levels and genomic DNA binding of SP1 and EBF1. An expressional decline in FAM3C may be a risk factor for Aβ accumulation and eventually AD development.

FAM3C: an emerging biomarker and potential therapeutic target for cancer

FAM3C is a member of the FAM3 family. Recently, overexpression of FAM3C has been reported in numerous types of cancer, including breast and colon cancer. Increasing evidence suggests that elevated FAM3C and its altered subcellular localization are closely associated with tumor formation, invasion, metastasis and poor survival. Moreover, FAM3C has been found to be the regulator of various proteins that associate with cancer, including Ras, STAT3, TGF-β and LIFR. This review summarizes the current knowledge regarding FAM3C, including its structure, expression patterns, regulation, physiological roles and regulatory functions in various malignancies. These findings highlight the importance of FAM3C in cancer development and provide evidence that FAM3C is a novel biomarker and potential therapeutic target for various cancers.

The FAM3C locus that encodes interleukin-like EMT inducer (ILEI) is frequently co-amplified in MET-amplified cancers and contributes to invasiveness

BACKGROUND

Gene amplification of MET, which encodes for the receptor tyrosine kinase c-MET, occurs in a variety of human cancers. High c-MET levels often correlate with poor cancer prognosis. Interleukin-like EMT inducer (ILEI) is also overexpressed in many cancers and is associated with metastasis and poor survival. The gene for ILEI, FAM3C, is located close to MET on chromosome 7q31 in an amplification "hotspot", but it is unclear whether FAMC3 amplification contributes to elevated ILEI expression in cancer. In this study we have investigated FAMC3 copy number gain in different cancers and its potential connection to MET amplifications.

METHODS

FAMC3 and MET copy numbers were investigated in various cancer samples and 200 cancer cell lines. Copy numbers of the two genes were correlated with mRNA levels, with relapse-free survival in lung cancer patient samples as well as with clinicopathological parameters in primary samples from 49 advanced stage colorectal cancer patients. ILEI knock-down and c-MET inhibition effects on proliferation and invasiveness of five cancer cell lines and growth of xenograft tumors in mice were then investigated.

RESULTS

FAMC3 was amplified in strict association with MET amplification in several human cancers and cancer cell lines. Increased FAM3C and MET copy numbers were tightly linked and correlated with increased gene expression and poor survival in human lung cancer and with extramural invasion in colorectal carcinoma. Stable ILEI shRNA knock-down did not influence proliferation or sensitivity towards c-MET-inhibitor induced proliferation arrest in cancer cells, but impaired both c-MET-independent and -dependent cancer cell invasion. c-MET inhibition reduced ILEI secretion, and shRNA mediated ILEI knock-down prevented c-MET-signaling induced elevated expression and secretion of matrix metalloproteinase (MMP)-2 and MMP-9. Combination of ILEI knock-down and c-MET-inhibition significantly reduced the invasive outgrowth of NCI-H441 and NCI-H1993 lung tumor xenografts by inhibiting proliferation, MMP expression and E-cadherin membrane localization.

CONCLUSIONS

These novel findings suggest MET amplifications are often in reality MET-FAM3C co-amplifications with tight functional cooperation. Therefore, the clinical relevance of this frequent cancer amplification hotspot, so far dedicated purely to c-MET function, should be re-evaluated to include ILEI as a target in the therapy of c-MET-amplified human carcinomas.

LncRNA LOXL1-AS1 facilitates the tumorigenesis and stemness of gastric carcinoma via regulation of miR-708-5p/USF1 pathway

Objectives

As one of the most life‐threatening malignancies, gastric cancer is the third contributor of cancer mortalities globally. Increasing studies have proven the regulatory roles of lncRNAs in the development of diverse malignant tumours. But little is known about its function and molecular mechanism in gastric carcinoma.

Materials and methods

RT‐qPCR was performed to measure the expression pattern of LOXL1‐AS1 in gastric cancer. To ascertain its definite role, CCK‐8, EdU, Western blot, transwell and sphere formation assays were adopted. RNA pull‐down, RIP, ChIP and luciferase reporter assays were carried out to investigate the molecular mechanism of LOXL1‐AS1 in gastric carcinoma.

Results

LOXL1‐AS1 was highly expressed in tissues and cells of gastric cancer. The upregulation of LOXL1‐AS1 predicted poor prognosis in gastric carcinoma. Our findings demonstrated that LOXL1‐AS1 accelerated the deterioration of gastric cancer by inducing cell proliferation, migration, EMT and stemness. Moreover, the expression of USF1 in gastric cancer was higher than in normal control and LOXL1‐AS1 negatively modulated USF1. Functionally, LOXL1‐AS1 acted as a ceRNA to upregulate USF1 via sponging miR‐708‐5p. Besides, we confirmed USF1 promoted the transcription of stemness marker SOX2. Rescue experiments testified the stimulative role of LOXL1‐AS1/miR‐708‐5p/USF1 pathway in gastric cancer progression. It was also validated that LOXL1‐AS1 facilitated cell growth of gastric carcinoma in vivo.

Conclusions

Our study unravelled that LOXL1‐AS1/miR‐708‐5p/USF1 pathway contributed to the development of gastric cancer.