Progenitor gene DLK1 might be an independent prognostic factor of liver cancer

Single-Cell Profiling Comparisons of Tumor Microenvironment between Primary Advanced Lung Adenocarcinomas and Brain Metastases and Machine Learning Algorithms in Predicting Immunotherapeutic Responses

Brain metastasis (BM) occurs commonly in patients with lung adenocarcinomas. Limited evidence indicates safety and efficacy of immunotherapy for this metastatic tumor, though immune checkpoint blockade has become the front-line treatment for primary advanced non-small cell lung cancer. We aim to comprehensively compare tumor microenvironments (TME) between primary tumors (PT) and BM at single-cell resolution. Single-cell RNA transcriptomics from tumor samples of PT (N = 23) and BM (N = 16) and bulk sequencing data were analyzed to explore potential differences in immunotherapeutic efficacy between PT and BM of lung adenocarcinomas. Multiple machine learning algorithms were used to develop and validate models that predict responses to immunotherapy using the external cohorts. We found obviously less infiltration of immune cells in BM than PT, characterized specifically by deletion of anti-cancer CD8+ Trm cells and more dysfunctional CD8+ Tem cells in BM tumors. Meanwhile, macrophages and dendritic cells within BM demonstrated more pro-tumoral and anti-inflammatory effects, represented by distinct distribution and function of SPP1+ and C1Qs+ tumor-associated microphages, and inhibited antigen presentation capacity and HLA-I gene expression, respectively. Besides, we also found the lack of inflammatory-like CAFs and enrichment of pericytes within BM tumors, which may be critical factors in shaping inhibitory TME. Cell communication analysis further revealed mechanisms of the immunosuppressive effects associated with the activation of some unfavorable pathways, such as TGFβ signaling, highlighting the important roles of stromal cells in the anti-inflammatory microenvironment, especially specific pericytes. Furthermore, pericyte-related genes were identified to optimally predict immunotherapeutic responses by machine learning models with great predictive performance. Overall, various factors contribute to the immunosuppressive TME within BM tumors, represented by the lack of critical anti-cancer immune cells. Meanwhile, pericytes may help shape the TME and targeting the associated mechanisms may enhance immunotherapy efficacy for BM tumors in patients with lung adenocarcinomas.

Pituitary Tumor-Transforming Gene 1/Delta like Non-Canonical Notch Ligand 1 Signaling in Chronic Liver Diseases

The management of chronic liver diseases (CLDs) remains a challenge, and identifying effective treatments is a major unmet medical need. In the current review we focus on the pituitary tumor transforming gene (PTTG1)/delta like non-canonical notch ligand 1 (DLK1) axis as a potential therapeutic target to attenuate the progression of these pathological conditions. PTTG1 is a proto-oncogene involved in proliferation and metabolism. PTTG1 expression has been related to inflammation, angiogenesis, and fibrogenesis in cancer and experimental fibrosis. On the other hand, DLK1 has been identified as one of the most abundantly expressed PTTG1 targets in adipose tissue and has shown to contribute to hepatic fibrosis by promoting the activation of hepatic stellate cells. Here, we extensively analyze the increasing amount of information pointing to the PTTG1/DLK1 signaling pathway as an important player in the regulation of these disturbances. These data prompted us to hypothesize that activation of the PTTG1/DLK1 axis is a key factor upregulating the tissue remodeling mechanisms characteristic of CLDs. Therefore, disruption of this signaling pathway could be useful in the therapeutic management of CLDs.

Delta-like Factor 1 as a Possible Therapeutic Target for Sarcomas

Backgroud

Cancer stem cells (CSCs) are cells characterized by their self-renewal and tumorigenic potential. The purpose of this study was to discover the role of the delta-like factor 1 (DLK1) in sarcoma.

Methods

mRNA expression of DLK1 from 13 sarcoma cell lines was examined. Isolated CSCs from the tumors were examined using fluorescence-activated cell sorting (FACS) with CD133, the CSC marker, or sphere-forming assay. The relationship between DLK1 and CSCs in sarcoma was examined using cell proliferation and cell invasion assays after they were treated with DLK1 short interfering RNA (siRNA).

Results

A high expression of DLK1 mRNA was observed in all sarcoma cell lines. However, CSCs were isolated from over expressed sarcomas of the DLK1 gene, and they have shown to be expressed lower than the wild type. The anti-cancer effects of DLK1 siRNA inhibited cell proliferation and invasion in U2OS, A204, and sw872. In addition, treatment with DLK1 siRNA inhibited cell invasion in sw872 CSCs. DLK1 gene induces tumorigenesis in various sarcoma cells and regulates the invasiveness of liposarcoma. These results suggest that DLK1 could serve as a possible therapeutic target for sarcoma.

Conclusions

Our study showed that the DLK1 gene induces tumorigenesis in various sarcomas and is associated with invasive mechanism in sarcoma. These results suggest DLK1 could serve as a possible therapeutic target in a variety of sarcomas.

Progress in research of surface markers of liver cancer stem cells

In recent years, cancer stem cell theory, in which a tumor is considered to consist of a handful of tumor stem cells and most common tumor cells, has been put forward by many scientists, which helps researchers to understand cancer from a new perspective. Isolating tumor stem cells is based mainly on their markers and in this way, many kinds of cancer stem cell markers have been confirmed, including live cancer stem cells. Isolating and identifying live cancer stem cells will provide a new hope for curing cancer. This paper mainly discusses seven liver cancer stem cell surface markers and their clinical significance.

The Progress and Prospects of Putative Biomarkers for Liver Cancer Stem Cells in Hepatocellular Carcinoma

Accumulating evidence suggests that hepatocellular carcinoma (HCC) is organized by liver cancer stem cells (LCSCs), which are a subset of cells with “stem-like” characteristics. Identification of the LCSCs is a fundamental and important problem in HCC research. LCSCs have been investigated by various stem cell biomarkers. There is still lack of consensus regarding the existence of a “global” marker for LCSCs in HCC. In this review article, we summarize the progress and prospects of putative biomarkers for LCSCs in the past decades, which is essential to develop future therapies targeting CSCs and to predict prognosis and curative effect of these therapies.

Tissue- and Serum-Associated Biomarkers of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), one of the leading causes of cancer deaths in the world, is offering a challenge to human beings, with the current modes of treatment being a palliative approach. Lack of proper curative or preventive treatment methods encouraged extensive research around the world with an aim to detect a vaccine or therapeutic target biomolecule that could lead to development of a drug or vaccine against HCC. Biomarkers or biological disease markers have emerged as a potential tool as drug/vaccine targets, as they can accurately diagnose, predict, and even prevent the diseases. Biomarker expression in tissue, serum, plasma, or urine can detect tumor in very early stages of its development and monitor the cancer progression and also the effect of therapeutic interventions. Biomarker discoveries are driven by advanced techniques, such as proteomics, transcriptomics, whole genome sequencing, micro- and micro-RNA arrays, and translational clinics. In this review, an overview of the potential of tissue- and serum-associated HCC biomarkers as diagnostic, prognostic, and therapeutic targets for drug development is presented. In addition, we highlight recently developed micro-RNA, long noncoding RNA biomarkers, and single-nucleotide changes, which may be used independently or as complementary biomarkers. These active investigations going on around the world aimed at conquering HCC might show a bright light in the near future.

IMP2/p62 induces genomic instability and an aggressive hepatocellular carcinoma phenotype

Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related deaths and commonly develops in inflammatory environments. The IGF2 mRNA-binding protein IMP2-2/IGF2BP2-2/p62 was originally identified as an autoantigen in HCC. Aim of this study was to investigate a potential pathophysiological role of p62 in hepatocarcinogenesis. Human HCC tissue showed overexpression of IMP2, which strongly correlated with the fetal markers AFP and DLK1/Pref-1/FA-1 and was particularly elevated in tumors with stem-like features and hypervascularization. Molecular classification of IMP2-overexpressing tumors revealed an aggressive phenotype. Livers of mice overexpressing the IMP2 splice variant p62 highly expressed the stem cell marker DLK1 and secreted DLK1 into the blood. p62 was oncogenic: diethylnitrosamine (DEN)-treated p62 transgenic mice exhibited a higher tumor incidence and multiplicity than wild types. Tumors of transgenics showed a more aggressive and stem-like phenotype and displayed more oncogenic chromosomal aberrations determined with aCGH analysis. DEN-treated p62 transgenic mice exhibited distinct signs of inflammation, such as inflammatory cytokine expression and oxidative stress markers, that is, thiobarbituric acid-reactive substance (TBARS) levels. Reactive oxygen species (ROS) production was elevated in HepG2 cells, which either overexpressed p62 or were treated with DLK1. p62 induced this ROS production by a DLK1-dependent induction and activation of the small Rho-GTPase RAC1, activating NADPH oxidase and being overexpressed in human HCC. Our data indicate that p62/IMP2 promotes hepatocarcinogenesis by an amplification of inflammation.

Serum DLK1 is a potential prognostic biomarker in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the third most frequent cause of cancer-related death in developing countries, especially in East Asia and South Africa, and the identification of new biomarkers for early diagnosis and prognosis is needed. Delta-like 1 homologue (Drosophila) (DLK1) is expressed in malignancies and promotes cancer cell stemness and tumourigenicity, which makes this molecule a potential target for therapies directed against cancer stem/progenitor cells. Here, we aimed to assess the predictive value of DLK1 as a diagnostic and prognostic biomarker in HCC. With this purpose, serum DLK1 levels were detected using an enzyme-linked immunosorbent assay (ELISA) in serum specimens from 397 HCC patients, 114 healthy individuals, 43 patients with chronic hepatitis B virus (HBV) infection and 24 cirrhotic liver patients with HBV infection, and the correlation between DLK1 levels and clinical features was evaluated. Our data showed that the serum DLK1 level was significantly higher in HCC patients than in healthy individuals or patients with chronic HBV infection (HBV carriers) (P < 0.05). Moreover, the serum DLK1 levels were positively correlated with tumour size and α-fetoprotein (AFP) levels, but not with gender, age, histological grade, HBV infection, intrahepatic metastasis or cirrhosis in HCC patients. Kaplan-Meier analysis indicated that higher DLK1 levels were associated with shorter survival in HCC patients. These results suggest that the serum levels of DLK1 may serve as a prognostic biomarker for HCC patients.

Dysregulated methylation at imprinted genes in prostate tumor tissue detected by methylation microarray

Background

Imprinting is an important epigenetic regulator of gene expression that is often disrupted in cancer. While loss of imprinting (LOI) has been reported for two genes in prostate cancer (IGF2 and TFPI2), disease-related changes in methylation across all imprinted gene regions has not been investigated.

Methods

Using an Illumina Infinium Methylation Assay, we analyzed methylation of 396 CpG sites in the promoter regions of 56 genes in a pooled sample of 12 pairs of prostate tumor and adjacent normal tissue. Selected LOI identified from the array was validated using the Sequenom EpiTYPER assay for individual samples and further confirmed by expression data from publicly available datasets.

Results

Methylation significantly increased in 52 sites and significantly decreased in 17 sites across 28 unique genes (P < 0.05), and the strongest evidence for loss of imprinting was demonstrated in tumor suppressor genes DLK1, PLAGL1, SLC22A18, TP73, and WT1. Differential expression of these five genes in prostate tumor versus normal tissue using array data from a publicly available database were consistent with the observed LOI patterns, and WT1 hypermethylation was confirmed using quantitative DNA methylation analysis.

Conclusions

Together, these findings suggest a more widespread dysregulation of genetic imprinting in prostate cancer than previously reported and warrant further investigation.

Tumor markers for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a high rate of morbidity and mortality. HCC affects approximately one million individuals annually worldwide, with the incidence equal to the mortality rate. In 2008, HCC was listed as the third most lethal cancer. Thus, early diagnosis is crucial for improving the survival rate for patients. α-fetoprotein (AFP) together with iconography and pathology detection are commonly used in the clinical early diagnosis of liver cancer. However, the specificity and sensitivity of AFP used in screening for liver cancer are not satisfactory. Athough the development of molecular biology has led to the identification of new tumor markers, including proteantigens, cytokines, enzymes and isoenzymes, as well as related genes that can be used in the treatment and prognosis of liver cancer, more tumor markers are required for effective early diagnosis of diseases and monitoring of the curative effect.

Cancer stem cell and embryonic development-associated molecules contribute to prognostic significance in ovarian cancer

OBJECTIVES

Embryonic molecules and cancer stem cell signaling resemble each other, and they organize cancer modality. We hypothesized that similar immunohistochemical expressions between tumor spheroids and patients' samples compared with clinical relevance would give an important clue in patients' prognosis.

METHODS

Immunohistochemical expression of c-kit, Notch1, Jagged1, and Delta1 in 50 cases of primary ovarian tumors (10 endometrioid, 10 serous, 10 mucinous adenocarcinoma, 10 borderline serous, and 10 borderline mucinous tumors) and MDAH-2774 spheroids were investigated. Results were compared in both spheroids and tumor samples with morphologic parameters (histological grade) and clinical data (age, stage, tumor size, and metastasis).

RESULTS

High c-kit and Notch1 immunoreactivity was shown in spheroids, but interestingly immunoreactivity of these molecules in tumor samples was different from patients' clinicopathological characteristics. In serous carcinoma, metastasis correlated with Notch1 immunoexpression; in mucinous carcinoma, Jagged1 immunohistochemistry correlated with grade, stage, and metastasis of tumor; in borderline serous and mucinous tumors, Jagged1 correlated with high grade. Moreover, Jagged1 correlated with stage and Notch1 with size in borderline mucinous tumor. Endometrioid carcinoma statistics showed that there was a correlation between age and Notch1 expression.

CONCLUSION

Notch1, Jagged1, and Delta1 expressions might be useful markers for clinical prognosis of ovarian carcinomas; and Notch pathway, one of the most intensively studied putative therapeutic targets, may be a useful marker for cancer. Consequently, Jagged1 could be a marker for tumor grades and Notch1 as a marker for metastases.

Rho/ROCK-dependent inhibition of 3T3-L1 adipogenesis by G-protein-deamidating dermonecrotic toxins: differential regulation of Notch1, Pref1/Dlk1, and β-catenin signaling

The dermonecrotic toxins from Pasteurella multocida (PMT), Bordetella (DNT), Escherichia coli (CNF1-3), and Yersinia (CNFY) modulate their G-protein targets through deamidation and/or transglutamination of an active site Gln residue, which results in activation of the G protein and its cognate downstream signaling pathways. Whereas DNT and the CNFs act on small Rho GTPases, PMT acts on the α subunit of heterotrimeric G_q, G_i, and G_12/13 proteins. We previously demonstrated that PMT potently blocks adipogenesis and adipocyte differentiation in a calcineurin-independent manner through downregulation of Notch1 and stabilization of β-catenin and Pref1/Dlk1, key proteins in signaling pathways strongly linked to cell fate decisions, including fat and bone development. Here, we report that similar to PMT, DNT, and CNF1 completely block adipogenesis and adipocyte differentiation by preventing upregulation of adipocyte markers, PPARγ and C/EBPα, while stabilizing the expression of Pref1/Dlk1 and β-catenin. We show that the Rho/ROCK inhibitor Y-27632 prevented or reversed these toxin-mediated effects, strongly supporting a role for Rho/ROCK signaling in dermonecrotic toxin-mediated inhibition of adipogenesis and adipocyte differentiation. Toxin treatment was also accompanied by downregulation of Notch1 expression, although this inhibition was independent of Rho/ROCK signaling. We further show that PMT-mediated downregulation of Notch1 expression occurs primarily through G_12/13 signaling. Our results reveal new details of the pathways involved in dermonecrotic toxin action on adipocyte differentiation, and the role of Rho/ROCK signaling in mediating toxin effects on Wnt/β-catenin and Notch1 signaling, and in particular the role of G_q and G_12/13 in mediating PMT effects on Rho/ROCK and Notch1 signaling.

[Study on the molecular mechanisms of dlk1 stimulated lung cancer cell proliferation]

背景与目的

印记基因dlk1因在多种肿瘤组织中出现异常表达而受到研究者越来越多的关注，但dlk1基因与肺癌的关系尚无报道。本研究首先在肺癌组织中检测了dlk1基因的表达，并进一步利用肺癌细胞系H520对dlk1基因促进细胞增殖的分子机制进行了初步研究。

方法

首先，采用RT-PCR在30对非小细胞肺癌肿瘤及其配对癌旁组织中检测dlk1基因的表达。然后，克隆人源dlk1基因，转染并筛选出稳定表达dlk1基因的肺癌细胞。最后，利用CCK8法研究dlk1基因对细胞增殖能力的影响，并用Western blot技术分析细胞周期蛋白CyclinB1的表达。

结果

RTPCR结果显示，dlk1基因在36.7%的非小细胞肺癌肿瘤组织中表达水平高于癌旁肺组织。在成功获得了稳定表达外源性dlk1基因的肺癌细胞H520-dlk1的基础上，CCK8实验及平板集落实验显示，稳定转染dlk1可以明显促进肺鳞癌细胞H520的增殖能力（P < 0.05）。同时，稳定表达DLK1蛋白可以上调细胞周期蛋白CyclinB1的表达水平（P < 0.05）。

结论

dlk1在非小细胞肺癌中存在异常高表达，它可以通过上调细胞周期蛋白CyclinB1的表达，促进肺鳞癌细胞H520的增殖。提示dlk1基因的异常表达可能在肺癌的发生演进中发挥作用。

Delta-like 1 contributes to cell growth by increasing the interferon-inducible protein 16 expression in hepatocellular carcinoma

BACKGROUND

Delta-like 1 (DLK1), a fetal liver stem cell marker, is strongly expressed in human and rodent fetal liver, but not in adult liver. Notably, dysregulation of DLK1 was found in some human hepatocellular carcinomas (HCC). However, the effect of DLK1 on HCC cell growth and its underlying mechanism are still largely unknown.

AIMS

To (i) assess the expression of DLK1 in human HCC and adjacent liver tissues and human HCC cell lines; (ii) evaluate the effect of DLK1 on SMMC-7721, Huh7 HCC cell growth in vitro and in vivo; and (iii) explore the potential mechanism of DLK1 that regulates HCC cell growth.

METHODS

The expression of DLK1 mRNA and protein were detected using reverse transcriptase-polymerase chain reaction and immunohistochemistry respectively. The effect of DLK1 on the proliferation of SMMC-7721 and Huh7 cells was evaluated by colony formation and tumour xenograft assay. The differential expression profiles of DLK1-overexpressing SMMC-7721 cells and control cells were compared using HG-U133 Plus 2 Genechip. The cell cycle distribution of DLK1 forced expressing cells was comparatively analysed.

RESULTS

Upregulation of DLK1 was observed in 41 of 57 (71.9%) human HCC samples. Ectopic expression of DLK1 promoted cell proliferation, colony formation and tumorigenicity in SMMC-7721 and Huh7 cells. DLK1 upregulated the expression of interferon-inducible protein 16 (IFI16) and its promoter transcriptional activity, decreased p21waf1/cip1 and induced cell cycle acceleration. However, silencing of IFI16 using small interfering RNA abrogated DLK1-induced proliferation in these cells.

CONCLUSIONS

IFI16 may be an essential downstream target of DLK1 in HCC cells and required for DLK1-induced cell proliferation.

An anti-DLK1 monoclonal antibody produced using ELISA and hybridoma techniques

DLK1 is a newly identified prognostic factor associated with liver cancer survival. To prepare specific monoclonal antibody (MAb) against DLK1, cDNA of DLK1 was cloned by RT-PCR and inserted into prokaryotic expression vector pGEX-4T1, respectively. The fusion proteins were expressed in Escherichia coli. Monoclonal antibody against DLK1 was obtained with hybridoma technique and specific ELISA screening. Western blotting and immunohistochemistry assays showed that MAb 6D6 had specific binding ability with DLK1 protein in eukaryotic cells and cancer tissues. This MAb will be a helpful tool for the detection of DLK1 protein in the tissues and serum of liver cancer and other cancer patients.