Id1 promotes lung cancer cell proliferation and tumor growth through Akt-related pathway

RGMb impacts partial epithelial-mesenchymal transition and BMP2-Induced ID mRNA expression independent of PD-L2 in nonsmall cell lung cancer cells

PD-1/PD-ligand-axis immunotherapy-mediated activation of T-cells for cancer cell elimination is a promising treatment of nonsmall cell lung cancer (NSCLC). However, the effect of immunotherapy on intracellular signaling pathways in cancer cells still needs further delineation. Repulsive Guidance Molecule b (RGMb), a regulator of Bone Morphogenetic Proteins (BMPs) signaling, interacts with the PD-ligand, PD-L2, at cancer cell membranes. Accordingly, a clarification of the functions of RGMb and its relation to PD-L2 might provide insight into NSCLC cell signaling responses to PD-1/PD-ligand-axis immunotherapy. In this study, the functions of RGMb and PD-L2 were examined using the two NSCLC cell lines HCC827 and A549. CRISPR/Cas9 was used to decrease the expression of RGMb and PD-L2, while lentiviral vectors were used to increase their expression. Downstream effects were examined by RT-qPCR and immunoassays. Ectopic expression of RGMb impacted BMP2-induced expression of ID1 and ID2 messenger RNA (mRNA) independently of PD-L2, while RGMb depletion by CRISPR/Cas9 did not affect the BMP2-mediated induction of ID1, ID2, and ID3 mRNA. However, depletion of RGMb resulted in a partial epithelial-mesenchymal transition (EMT) gene expression profile in HCC827 cells, which was not mimicked by PD-L2 depletion. The results show that RGMb is a coregulator of BMP signaling and hence, ID mRNA expression and that RGMb can control the EMT balance in NSCLC cells. However, RGMb appears to exert these functions independently of PD-L2, and accordingly, the PD-1/PD-ligand axis for immune surveillance in NSCLC cells.

Orai3 Calcium Channel Contributes to Oral/Oropharyngeal Cancer Stemness through the Elevation of ID1 Expression

Emerging evidence indicates that intracellular calcium (Ca2+) levels and their regulatory proteins play essential roles in normal stem cell proliferation and differentiation. Cancer stem-like cells (CSCs) are subpopulations of cancer cells that retain characteristics similar to stem cells and play an essential role in cancer progression. Recent studies have reported that the Orai3 calcium channel plays an oncogenic role in human cancer. However, its role in CSCs remains underexplored. In this study, we explored the effects of Orai3 in the progression and stemness of oral/oropharyngeal squamous cell carcinoma (OSCC). During the course of OSCC progression, the expression of Orai3 exhibited a stepwise augmentation. Notably, Orai3 was highly enriched in CSC populations of OSCC. Ectopic Orai3 expression in non-tumorigenic immortalized oral epithelial cells increased the intracellular Ca2+ levels, acquiring malignant growth and CSC properties. Conversely, silencing of the endogenous Orai3 in OSCC cells suppressed the CSC phenotype, indicating a pivotal role of Orai3 in CSC regulation. Moreover, Orai3 markedly increased the expression of inhibitor of DNA binding 1 (ID1), a stemness transcription factor. Orai3 and ID1 exhibited elevated expression within CSCs compared to their non-CSC counterparts, implying the functional importance of the Orai3/ID1 axis in CSC regulation. Furthermore, suppression of ID1 abrogated the CSC phenotype in the cell with ectopic Orai3 overexpression and OSCC. Our study reveals that Orai3 is a novel functional CSC regulator in OSCC and further suggests that Orai3 plays an oncogenic role in OSCC by promoting cancer stemness via ID1 upregulation.

Inhibitor of DNA binding/differentiation proteins as IDs for pancreatic cancer: Role in pancreatic cancer initiation, development and prognosis

A family of inhibitors of cell differentiation or DNA-binding proteins, known as ID proteins (ID1-4), function as mighty transcription factors in various cellular processes, such as inhibiting differentiation, promoting cell-cycle progression, senescence, angiogenesis, tumorigenesis, and metastasis in cancer. Pancreatic cancer represents the deadliest cancer with the lowest survival rate of 10% due to the diagnosis at an advanced fatal stage and therapeutic resistance. Modestly, the only curative option for this lethal cancer is surgery but is done in less than 15-20% of patients because of the locally aggressive and early metastatic nature. Finding the earliest biomarkers and targeting the various hallmarks of pancreatic cancer can improve the treatment and survival of pancreatic cancer patients. Therefore, herein in this review, we explore in depth the potential roles of ID proteins function in hallmarks of pancreatic cancer, signaling pathways, and its oncogenic and tumor-suppressive effects. Hence, understanding the roles of dysregulated ID proteins would provide new insights into its function in pancreatic cancer tumorigenesis.

C1QTNF6 promotes oral squamous cell carcinoma by enhancing proliferation and inhibiting apoptosis

BACKGROUND

C1QTNF6 (CTRP6), a member of the CTRP family, has recently been implied to play a role in the tumorigenesis of for a variety of cancer types. However, the role of C1QTNF6 in oral squamous cell carcinoma (OSCC) and its potential molecular remains unclear.

METHODS

C1QTNF6 expression was detected by qRT-PCR and western blot analysis. Lentiviral vectors were constructed to knockdown C1QTNF6 in CaL27 and SCC-9 human OSCC cell lines. Cell viability, cell cycle and cell apoptosis analyses were performed by MTT assay, PI/Annexin V staining, and flow cytometry. The effect of C1QTNF6 knockdown on in vivo tumorigenicity of OSCC cells in vivo was evaluated using nude mouse xenograft tumor model. Downstream signaling mechanisms were identified by microarray and Ingenuity Pathway Analysis.

RESULTS

Immunohistochemistry of OSCC tissue and data from TCGA demonstrate that C1QTNF6 was overexpressed in OSCC tissues, and that cellular proliferation was significantly decreased after C1QTNF6 was knockdown in CaL27 and SCC-9 cell lines. Knockdown of C1QTNF6 also resulted in cell cycle arrest at the G2/M phase and enhanced cell apoptosis in in CaL27 and SCC-9 cell lines. Furthermore, knockdown of C1QTNF6 in Cal-27 cells inhibited tumor growth of OSCC in vivo. Microarray analysis revealed that C1QTNF6 silencing resulted in significant alterations of gene expression, with the Acute Phase Response signaling pathway significantly activated following C1QTNF6 silencing.

CONCLUSIONS

These results suggest that C1QTNF6 plays an important role in promoting OSCC tumorigenesis, which indicates that C1QTNF6 may comprise a promising therapeutic target for OSCC treatment.

The Role of Non-Coding RNAs in the Regulation of the Proto-Oncogene MYC in Different Types of Cancer

Alterations in the expression level of the MYC gene are often found in the cells of various malignant tumors. Overexpressed MYC has been shown to stimulate the main processes of oncogenesis: uncontrolled growth, unlimited cell divisions, avoidance of apoptosis and immune response, changes in cellular metabolism, genomic instability, metastasis, and angiogenesis. Thus, controlling the expression of MYC is considered as an approach for targeted cancer treatment. Since c-Myc is also a crucial regulator of many cellular processes in healthy cells, it is necessary to find ways for selective regulation of MYC expression in tumor cells. Many recent studies have demonstrated that non-coding RNAs play an important role in the regulation of the transcription and translation of this gene and some RNAs directly interact with the c-Myc protein, affecting its stability. In this review, we summarize current data on the regulation of MYC by various non-coding RNAs that can potentially be targeted in specific tumor types.

Comprehensive analysis of inhibitor of differentiation/DNA-binding gene family in lung cancer using bioinformatics methods

The inhibitor of differentiation/DNA-binding (ID) is a member of the helix-loop-helix (HLH) transcription factor family, and plays a role in tumorigenesis, invasiveness and angiogenesis. The aims were to investigate the expression patterns and prognostic values of individual ID family members in lung cancer, and the potential functional roles. The expression levels of ID family were assessed using the Oncomine online database and GEPIA database. Furthermore, the prognostic value of ID family members was evaluated using the Kaplan-Meier plotter database. The genetic mutations of ID family members were investigated using the cBioPortal database. Moreover, enrichment analysis was performed using STRING database and Funrich software. It was found that all the ID family members were significantly down-regulated in lung cancer. Prognostic results indicated that low mRNA expression levels of ID1 or increased mRNA expression levels of ID2/3/4 were associated with improved overall survival, first progression and post progression survival. Additionally, genetic mutations of ID family members were identified in lung cancer, and it was suggested that amplification and deep deletion were the main mutation types. Furthermore, functional enrichment analysis results suggested that ID1/2/4 were significantly enriched in 'regulation of nucleobase, nucleoside, nucleotide and nucleic acid metabolism' for biological process, 'transcription factor activity' for molecular function and 'HLH domain' for protein domain. However, it was found that ID3 was not enriched in the above functions. The aberrant expression of ID family members may affect the occurrence and prognosis of lung cancer, and may be related to cell metabolism and transcriptional regulation.

The Anticancer Peptide CIGB-552 Exerts Anti-Inflammatory and Anti-Angiogenic Effects through COMMD1

CIGB-552 is a synthetic anti-tumor peptide capable of reducing tumor size and increasing the lifespan of tumor-bearing mice. Part of its anti-cancer effects consists of inducing apoptosis, modulating NF-kB signaling pathway, and the angiogenesis process. Although one of its major mediators, the COMMD1 protein, has been identified, the mechanism by which CIGB-552 exerts such effects remains elusive. In the present study, we show the role of COMMD1 in CIGB-552 mechanism of action by generating the COMMD1 knock-out from the human lung cancer cell line NCI-H460. A microarray was performed to analyze both wild-type and KO cell lines with regard to CIGB-552 treatment. Additionally, different signaling pathways were studied in both cell lines to validate the results. Furthermore, the interaction between CIGB-552 and COMMD1 was analyzed by confocal microscopy. By signaling pathway analysis we found that genes involved in cell proliferation and apoptosis, oncogenic transformation, angiogenesis and inflammatory response are potentially regulated by the treatment with CIGB-552. We then demonstrated that CIGB-552 is capable of modulating NF-kB in both 2D and 3D cell culture models. Finally, we show that the ability of CIGB-552 to negatively modulate NF-kB and HIF-1 pathways is impaired in the COMMD1 knock-out NCI-H460 cell line, confirming that COMMD1 is essential for the peptide mechanism of action.

Organoids Model Transcriptional Hallmarks of Oncogenic KRAS Activation in Lung Epithelial Progenitor Cells

Mutant KRAS is a common driver in epithelial cancers. Nevertheless, molecular changes occurring early after activation of oncogenic KRAS in epithelial cells remain poorly understood. We compared transcriptional changes at single-cell resolution after KRAS activation in four sample sets. In addition to patient samples and genetically engineered mouse models, we developed organoid systems from primary mouse and human induced pluripotent stem cell-derived lung epithelial cells to model early-stage lung adenocarcinoma. In all four settings, alveolar epithelial progenitor (AT2) cells expressing oncogenic KRAS had reduced expression of mature lineage identity genes. These findings demonstrate the utility of our in vitro organoid approaches for uncovering the early consequences of oncogenic KRAS expression. This resource provides an extensive collection of datasets and describes organoid tools to study the transcriptional and proteomic changes that distinguish normal epithelial progenitor cells from early-stage lung cancer, facilitating the search for targets for KRAS-driven tumors.

Inhibitor of Differentiation 1 (Id1) in Cancer and Cancer Therapy

The inhibitor of DNA binding (Id) proteins are regulators of cell cycle and cell differentiation. Of all Id family proteins, Id1 is mostly linked to tumorigenesis, cellular senescence as well as cell proliferation and survival. Id1 is a stem cell-like gene more than a classical oncogene. Id1 is overexpressed in numerous types of cancers and exerts its promotion effect to these tumors through different pathways. Briefly, Id1 was found significantly correlated with EMT-related proteins, K-Ras signaling, EGFR signaling, BMP signaling, PI3K/Akt signaling, WNT and SHH signaling, c-Myc signaling, STAT3 signaling, RK1/2 MAPK/Egr1 pathway and TGF-β pathway, etc. Id1 has potent effect on facilitating tumorous angiogenesis and metastasis. Moreover, high expression of Id1 plays a facilitating role in the development of drug resistance, including chemoresistance, radiation resistance and resistance to drugs targeting angiogenesis. However, controversial results were also obtained. Overall, Id1 represent a promising target of anti-tumor therapeutics based on its potent promotion effect to cancer. Numerous drugs were found exerting their anti-tumor function through Id1-related signaling pathways, such as fucoidan, berberine, tetramethylpyrazine, crizotinib, cannabidiol and vinblastine.

Scutellaria Flavonoids Effectively Inhibit the Malignant Phenotypes of Non-small Cell Lung Cancer in an Id1-dependent Manner

Non-small cell lung cancer (NSCLC) is the leading cause of cancer death in the world. Inhibitor of differentiation 1 (Id1) is overexpressed in NSCLC and involved in promoting its progression and metastasis. Identifying natural compounds targeting Id1 may have utility in NSCLC treatment. Here, we sought to determine whether the anti-tumor activities of Scutellaria flavonoids (SFs) were related to Id1. We reported that three SFs (baicalin, baicalein and wogonin) exhibited strong antitumor activity in NSCLC cells in vitro and in vivo. Id1 played a pivotal role on blockage of migration and invasion by SFs. Abrogation of invasion and migration mediated by baicalin, baicalein and wogonin were totally abolished by ectopic overexpression of Id1. Mechanistically, baicalin, baicalein and wogonin activated Rap1-GTP binding and dephosphorylated Akt and Src by suppressing a7nAChR, consequently triggering inhibition of Id1. Then attenuation of its downstream mediators, VEGF-A, N-cadherin, vimentin, combined with augment of E-cadherin led to the blockage of proliferation, EMT and angiogenesis of NSCLC. Overall, our data shed light on heretofore-undescribed role of SFs as modulators of Id1, which may be a useful strategy in the treatment of NSCLC.

ID1 contributes to cell growth invasion and migration in salivary adenoid cystic carcinoma

Previous studies have reported that inhibitor of DNA binding 1 (ID1) exerts an oncogenic role in a number of tumors. In the present study, the role of ID1 in the growth, invasion and migration of salivary adenoid cystic carcinoma (SACC) cells was investigated. ID1 expression in clinical SACC samples was compared with that in normal salivary tissues using immunohistochemical staining, and the correlation between ID1 expression and clinical pathological characteristics was then determined. Subsequently, ID1 was overexpressed or silenced to investigate the effects of ID1 expression on SACC cell proliferation, invasion and migration. In addition, the gene expression levels of known ID1 target genes, including S100A9, CDKN2A and matrix metalloproteinase 1 (MMP1) was measured using reverse transcription-quantitative polymerase chain reaction to elucidate the potential mechanisms of ID1 in SACC. The results of the present study indicated that the protein expression levels of ID1 were significantly increased in the SACC tissues compared with that in the normal salivary tissues (P<0.001), and a positive correlation between ID1 expression and tumor stage (P=0.001), tumor invasion (P=0.002) and metastasis (P=0.019) in SACC was observed. Knockdown of ID1 in SACC cells significantly inhibited cell growth, invasion and migration (all P<0.01), whereas overexpression of ID1 promoted cell proliferation, invasion and migration (all P<0.01). The gene expression level of MMP1 was significantly reduced following ID1 knockdown in SACC-83 cells when compared with negative controls (P<0.05), whereas S100A9 and CDKN2A expression levels were significantly upregulated (both P<0.05). The results suggest that ID1 may regulate the growth, invasion and migration of SACC cells, and that MMP1, S100A9 and CDKN2A may serve as target genes of ID1 and mediate the effects of ID1 in SACC cells. Therefore, ID1 may present a potential target gene for the treatment of patients with SACC to inhibit cancer cell growth and metastasis.

A Genome-Wide Identification and Analysis of the Basic Helix-Loop-Helix Transcription Factors in Brown Planthopper, Nilaparvata lugens

The basic helix-loop-helix (bHLH) transcription factors in insects play essential roles in multiple developmental processes including neurogenesis, sterol metabolism, circadian rhythms, organogenesis and formation of olfactory sensory neurons. The identification and function analysis of bHLH family members of the most destructive insect pest of rice, Nilaparvata lugens, may provide novel tools for pest management. Here, a genome-wide survey for bHLH sequences identified 60 bHLH sequences (NlbHLHs) encoded in the draft genome of N. lugens. Phylogenetic analysis of the bHLH domains successfully classified these genes into 40 bHLH families in group A (25), B (14), C (10), D (1), E (8) and F (2). The number of NlbHLHs with introns is higher than many other insect species, and the average intron length is shorter than those of Acyrthosiphon pisum. High number of ortholog families of NlbHLHs was found suggesting functional conversation for these proteins. Compared to other insect species studied, N. lugens has the highest number of bHLH members. Furthermore, gene duplication events of SREBP, Kn(col), Tap, Delilah, Sim, Ato and Crp were found in N. lugens. In addition, a putative full set of NlbHLH genes is defined and compared with another insect species. Thus, our classification of these NlbHLH members provides a platform for further investigations of bHLH protein functions in the regulation of N. lugens, and of insects in general.

Epigenetically downregulated Semaphorin 3E contributes to gastric cancer

Axon guidance protein Semaphorin 3E (Sema3E) promotes tumor metastasis and suppresses tumor cell death. Here, we demonstrated that Sema3E was decreased in gastric cancer. Its levels were inversely associated with tumor progression. Levels of Sema3E were associated with low p300 and high class I histone deacetylase (class I HDAC). Ectopic expression of Sema3E inhibited proliferation and colony formation of gastric cancer cell lines in vitro and xenografts in vivo. Sema3E overexpression inhibited migration and invasion of gastric cancer cells, which was associated with induction of E-cadherin and reduction of Akt and ERK1/2 phosphorylation. We suggest that silencing of Sema3E contributes to the pathogenesis of gastric cancer.

Sustained delivery of siRNA/PEI complex from in situ forming hydrogels potently inhibits the proliferation of gastric cancer

Background

Gastric cancer remains a major cause of mortality and morbidity worldwide. In recent years, gene-based therapeutic strategies were confirmed promising in cancer inhibition and attracted great attention. RNA interference (RNAi) is a powerful tool for gene therapy and has been widely employed to aid in treatment for various diseases, especially cancers. However, effective delivery of small interfering RNA (siRNA) to target cells in vivo remains a challenge for that it is prone to degradation and only lasts a few days in rapidly dividing cells.

Methods

Due to its biocompatibility and well-established safety profile, collagen represents a favourable matrix for in-site drug delivery. In the study, collagen hydrogel was used as carriers to test the feasibility of localized and sustained delivery of Id1-targeted siRNA for in vivo gastric cancer inhibition. To enhance the siRNA delivery, cationic polyethylenimine (PEI) was further emplored for scallold modification. The efficacy of siRNA delivery and cancer inhibition were evaluated with multimodality of mehods in vitro and in vivo.

Results

Our results showed that addition of polyethylenimine (PEI) to collagen can facilitate entry of Id1-siRNA into target cells, prolong the silencing effect, and further inhibit tumor growth both in vitro and in vivo.

Conclusion

This collagen-based delivery system may facilitate the pathogenesis elucidation and design of effective therapies against gastric cancer.

Identification of Id1 as a downstream effector for arsenic-promoted angiogenesis via PI3K/Akt, NF-κB and NOS signaling

Exposure to arsenic is known to be a risk factor for various types of cancer. Apart from its carcinogenic activity, arsenic also shows promoting effects on angiogenesis, a crucial process for tumor growth. Yet, the mechanism underlying arsenic-induced angiogenesis is not fully understood. In this study, we aimed at investigating the involvement of inhibitor of DNA binding 1 (Id1) and the associated signal molecules in the arsenic-mediated angiogenesis. Our initial screening revealed that treatment with low concentrations of arsenic (0.5-1 μM) led to multiple cellular responses, including enhanced endothelial cell viability and angiogenic activity as well as increased protein expression of Id1. The arsenic-induced angiogenesis was suppressed in the Id1-knocked down cells compared to that in control cells. Furthermore, arsenic-induced Id1 expression and angiogenic activity were regulated by PI3K/Akt, NF-κB, and nitric oxide synthase (NOS) signaling. In summary, our current data demonstrate for the first time that Id1 mediates the arsenic-promoted angiogenesis, and Id1 may be regarded as an antiangiogenesis target for treatment of arsenic-associated cancer.

High Id1 expression, a generally negative prognostic factor, paradoxically predicts a favorable prognosis for adjuvant paclitaxel plus cisplatin therapy in surgically treated lung cancer patients

Adjuvant chemotherapy is commonly given to surgically treated non-small-cell lung cancer (NSCLC) patients. However, the prerequisite for chemotherapy needs to be scrutinized in order to maximize the benefits to patients. In this study, we observed that NSCLC cells with high Id1 protein expression were vulnerable to the treatment of paclitaxel and cisplatin. In addition, paclitaxel and cisplatin caused Id1 protein degradation through ubiquitination. In the nude mice xenograft model, the tumor growth was reduced to a large degree in the Id1-overexpressing group upon treatment with paclitaxel and cisplatin. Furthermore, immunohistochemical staining for Id1 followed by Kaplan-Meier survival analysis showed that surgically treated NSCLC patients with high Id1 expression in primary tumor tissues had better disease-free and overall survivals after adjuvant paclitaxel and cisplatin chemotherapy. In summary, our current data suggest that Id1, a generally negative prognostic factor, predicts a favorable prognosis in the case of surgically treated NSCLC patients receiving the definitive adjuvant chemotherapy. The distinct role of Id1 reported in this study may arise from the phenomenon of Id1 dependence of NSCLC cells for survival, which renders the cancer cells additionally susceptive to the adjuvant chemotherapy with paclitaxel and cisplatin.

GCIP functions as a tumor suppressor in non-small cell lung cancer by suppressing Id1-mediated tumor promotion

Grap2 and cyclin D1 interacting protein (GCIP) has been recognized as a putative tumor suppressor, but the molecular mechanisms underlying its anti-tumor properties remain undefined. Here, we report that GCIP is frequently downregulated in non-small cell lung cancer (NSCLC) tissues. Binding assays indicated that inhibitor of DNA binding/differentiation 1 (Id1) interacts with GCIP in the nucleus. Ectopic GCIP expression in the highly invasive NSCLC cell line, H1299, inhibited proliferation, colony formation, invasion and migration, and increased susceptibility to anticancer drugs. Conversely, silencing GCIP expression in the minimally invasive NSCLS cell line, A549, increased proliferation, colony formation, invasion, and migration in vitro, and increased survival and resistance to anticancer drugs. GCIP also suppresses tumorigenicity of NSCLC cells in vivo and GCIP suppresses NSCLC progression is mediated in part by interfering with Id1 signaling, which was confirmed in conditionally induced stable cell lines. In addition, GCIP downregulates the expression of Id1, and GCIP and Id1 are inversely expressed in NSCLC cell lines and specimens. Taken together, these results suggest that GCIP is a potential tumor suppressor in NSCLC and that suppression of Id1-mediated oncogenic properties may be a key mechanism by which GCIP can potently suppress NSCLC tumor progression.

Chlorogenic acid inhibits hypoxia-induced angiogenesis via down-regulation of the HIF-1α/AKT pathway

BACKGROUND

The hypoxia-inducible factor-1 (HIF-1) is known to play an important role in cellular responses to hypoxia, including the transcriptional activation of a number of genes involved in tumor angiogenesis. Chlorogenic acid (CGA), one of the most abundant polyphenols in the human diet, has been reported to inhibit cancer cell growth. The effect of CGA on tumor angiogenesis and its underlying mechanisms are, as yet, unknown.

METHODS

The effect of CGA on HIF-1α expression was assessed by Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) assays in A549 lung cancer cells. The transcriptional activity of the HIF-1 complex was confirmed using a luciferase assay. To assess whether angiogenic factors are increased under hypoxic conditions in these cells, vascular endothelial growth factor (VEGF) expression levels were measured by RT-PCR and Western blotting. The direct effect of CGA on human vascular endothelial cells (HUVEC) under hypoxic conditions was analyzed using in vitro assays, including tube-formation, wound healing and Transwell invasion assays. To investigate the effect of CGA on angiogenesis in vivo, we performed a Matrigel plug assay in a mouse model. Finally, the effect of CGA on AKT and ERK activation (phosphorylation) as a putative mechanism underlying the effect of CGA on VEGF-mediated angiogenesis inhibition was assessed using Western blotting.

RESULTS

We found that CGA significantly decreases the hypoxia-induced HIF-1α protein level in A549 cells, without changing its mRNA level. CGA was, however, found to suppress the transcriptional activity of HIF-1α under hypoxic conditions, leading to a decrease in the expression of its downstream target VEGF. We also found that CGA can block hypoxia-stimulated angiogenesis in vitro and VEGF-stimulated angiogenesis in vivo using HUVEC cells. In addition, we found that CGA can inhibit the HIF-1α/AKT signaling pathway, which plays an important role in VEGF activation and angiogenesis.

CONCLUSIONS

Our data indicate that CGA plays a role in the suppression of angiogenesis via inhibition of the HIF-1α/AKT pathway. CGA may represent a novel therapeutic option for the treatment of (lung) cancer.

Inhibitor of DNA-binding protein 1 knockdown arrests the growth of colorectal cancer cells and suppresses hepatic metastasis in vivo

Inhibitor of DNA-binding protein 1 (ID1) is commonly abnormally overexpressed in colorectal cancer (CRC); yet, the functional significance of ID1 in the growth and invasive properties of CRC cells remains largely unclear. The present study investigated the effects of ID1 downregulation on the cell growth and metastatic features of CRC. Using lentiviral shRNA infection, stable ID1-knockdown (KD) HCT116 and SW620 cells, human metastatic CRC cell lines, were created. In vitro, the migration/invasion capacity of the ID1-KD CRC cells was assessed by a wound healing assay. The activities of MMP2 and MMP-9 were measured by gelatin zymography. The expression of CXC chemokine receptor 4 (CXCR4), PCNA and survivin were determined by immunoblot analysis and qRT-PCR. The effects of ID1 knockdown on tumor growth and hepatic metastasis were demonstrated by a xenograft study in mice. The results showed evident decreases in proliferation, migration and invasion and an increased apoptosis rate in the ID1-KD CRC cells. Similarly, ID1 knockdown significantly decreased mRNA and protein levels of PCNA, survivin, CXCR4, MMP2 and MMP9. Overexpression of CXCR4 antagonized the negative effect on the migration and invasion abilities of the ID1-KD cells. As compared with the control, ID1 knockdown prevented tumor growth and profoundly suppressed hepatic metastasis in vivo. The present study demonstrated the significance of ID1 in colon cancer progression, and its effect on tumor invasiveness and metastatic properties may be partly dependent on CXCR4.

ID1 regulates U87 human cell proliferation and invasion

Despite therapeutic advances, the prognosis of patients diagnosed with malignant glioma has not improved in recent years. In particular, the molecular mechanisms that mediate glioma invasion remain poorly understood. The importance of ID1 in promoting tumor invasion and metastasis has recently emerged and a role for ID1 as a possible molecular marker of tumor aggressiveness has been proposed. To investigate the biological function of ID1 in glioblastomas, ID1-silenced U87 glioblastoma multiforme (GBM) cells were constructed using a small hairpin RNA (shRNA) sequence. The effect of the knockdown of ID1 on proliferation and invasion in these cells was analyzed using the 5-bromo-2′-deoxy-uridine cell proliferation, Transwell invasion, scratch and cell adhesion assays. Compared with the controls, the U87 cells expressing ID1-shRNA exhibited a significantly decreased proliferation and invasion capacity (P<0.05), as well as increased cell adhesion. Furthermore, silencing ID1 reduced the expression of c-Myc, cyclin D1 and β-catenin, while increasing E-cadherin expression in U87 cells. This study showed that ID1 regulates the metastatic potential of GBM cells by controlling the epithelial-mesenchymal transition. Therefore, ID1 is a potential prognostic indicator and therapeutic target in glioblastomas.

TGM2 inhibition attenuates ID1 expression in CD44-high glioma-initiating cells

BACKGROUND

CD44 is a molecular marker associated with cancer stem cell populations and treatment resistance in glioma. More effective therapies will result from approaches aimed at targeting glioma cells high in CD44.

METHODS

Glioma-initiating cell lines were derived from fresh surgical glioblastoma samples. Expression of tissue transglutaminase 2 (TGM2) was attenuated through lentivirus-mediated short hairpin RNA knockdown. MTT assay [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] was used to evaluate the growth inhibition induced by TGM2 inhibitor. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling was used to evaluate cell apoptosis following TGM2 inhibition. CD44(+) glioma stem cells were sorted by flow cytometry. A nude mice orthotopic xenograft model was used to evaluate the in vivo effect of TGM2 inhibitor.

RESULTS

TGM2 was highly expressed in CD44-high glioblastoma tissues and tumor-derived glioma-initiating cell lines. TGM2 knockdown impaired cell proliferation and induced apoptosis in CD44-high glioma-initiating cell lines. Further studies indicated that expression of inhibitor of DNA binding 1 protein (ID1) is regulated by TGM2 and might be an important mediator for TGM2-regulated cell proliferation in CD44-high glioma-initiating cell lines. TGM2 inhibitor reduces ID1 expression, suppresses cell proliferation, and induces apoptosis in CD44-high glioma-initiating cell lines. Furthermore, TGM2 is highly expressed in CD44(+) glioma stem cells, while pharmacological inhibition of TGM2 activity preferentially eliminates CD44(+) glioma stem cells. Consistently, TGM2 inhibitor treatment reduced ID1 expression and induced apoptosis in our orthotopic mice xenograft model, which can be translated into prolonged median survival in tumor-bearing mice.

CONCLUSIONS

TGM2 regulates ID1 expression in glioma-initiating cell lines high in CD44. Targeting TGM2 could be an effective strategy to treat gliomas with high CD44 expression.

Insulin receptor tyrosine kinase substrate activates EGFR/ERK signalling pathway and promotes cell proliferation of hepatocellular carcinoma

Insulin receptor tyrosine kinase substrate (IRTKS) is closely associated with actin remodelling and membrane protrusion, but its role in the pathogenesis of malignant tumours, including hepatocellular carcinoma (HCC), is still unknown. In this study, we showed that IRTKS was frequently upregulated in HCC samples, and its expression level was significantly associated with tumour size. Enforced expression of IRTKS in human HCC cell lines significantly promoted their proliferation and colony formation in vitro, and their capacity to develop tumour xenografts in vivo, whereas knockdown of IRTKS resulted in the opposite effects. Furthermore, the bromodeoxyuridine (BrdU) incorporation analyses and propidium iodide staining indicated that IRTKS can promote the entry into S phase of cell cycle progression. Significantly, IRTKS can interact with epidermal growth factor receptor (EGFR), results in the phosphorylation of extracellular signal-regulated kinase (ERK). By contrast, inhibition of ERK activation can attenuate the effects of IRTKS overexpression on cellular proliferation. Taken together, these data demonstrate that IRTKS promotes the proliferation of HCC cells by enhancing EGFR-ERK signalling pathway.

Incorporating network structure in integrative analysis of cancer prognosis data

In high-throughput cancer genomic studies, markers identified from the analysis of single datasets may have unsatisfactory properties because of low sample sizes. Integrative analysis pools and analyzes raw data from multiple studies, and can effectively increase sample size and lead to improved marker identification results. In this study, we consider the integrative analysis of multiple high-throughput cancer prognosis studies. In the existing integrative analysis studies, the interplay among genes, which can be described using the network structure, has not been effectively accounted for. In network analysis, tightly connected nodes (genes) are more likely to have related biological functions and similar regression coefficients. The goal of this study is to develop an analysis approach that can incorporate the gene network structure in integrative analysis. To this end, we adopt an AFT (accelerated failure time) model to describe survival. A weighted least squares approach, which has low computational cost, is adopted for estimation. For marker selection, we propose a new penalization approach. The proposed penalty is composed of two parts. The first part is a group MCP penalty, and conducts gene selection. The second part is a Laplacian penalty, and smoothes the differences of coefficients for tightly connected genes. A group coordinate descent approach is developed to compute the proposed estimate. Simulation study shows satisfactory performance of the proposed approach when there exist moderate-to-strong correlations among genes. We analyze three lung cancer prognosis datasets, and demonstrate that incorporating the network structure can lead to the identification of important genes and improved prediction performance.

Reversal of aberrant cancer methylome and transcriptome upon direct reprogramming of lung cancer cells

Recent reports on direct reprogramming of cancer cells (iPCs) which results in reduced tumorigenic potential has attributed the importance of epigenetics in tumorigenesis, but lacked genome-wide analysis. Here we describe successful generation of iPCs from non-small cell lung cancer (NSCLC) cell lines. Following reprogramming, they resembled embryonic stem and induced pluripotent stem cells in pluripotency markers expression, gene expression patterns and in vitro differentiation ability. Genome-wide methylation analysis revealed that aberrantly methylated promoters which were mostly developmental-associated genes and tumor suppressors; as well as commonly upregulated genes in NSCLC i.e. KRT19 and S100P were reversed in iPCs upon reprogramming. Also, the reversal of oncogenes and tumor suppressors status were partially explainable by DNA methylation. These findings suggest that DNA methylation patterns explain the downstream transcriptional effects, which potentially caused the reduced tumorigenicity in iPCs, thus providing evidence that reprogramming reverses the aberrantly dysregulated genes in NSCLC both epigenetically and transcriptionally.

Downregulation of Id1 by small interfering RNA in gastric cancer inhibits cell growth via the Akt pathway

Inhibitor of differentiation or DNA binding (Id1) is a member of the helix-loop-helix transcription factor family that is overexpressed in various types of cancer, including gastric carcinoma. Previous studies showed that Id1 is a prognostic marker in patients with gastric cancer. However, the role of Id1 in the proliferation of human gastric cancer cells has yet to be clarified. In the present study, we downregulated the Id1 gene in SGC-7901 gastric cancer cells by RNA interference, and we also constructed a recombinant plasmid-expressing Id1 to investigate its effects on the proliferation of SGC-7901 cells. Results showed that the downregulation of Id1 inhibited proliferation of SGC-7901 cells, while the upregulation of Id1 had no effect on SGC-7901 cell proliferation. The potential mechanism was also investigated. The changes of certain proteins associated with cell proliferation, apoptosis and the cell cycle were detected by western blotting. Furthermore, we demonstrated a positive correlation between Id1 and phospho-Akt expression in SGC-7901 cells.