Disruption of tumor cell adhesion promotes angiogenic switch and progression to micrometastasis in RAF-driven murine lung cancer

The role and clinical significance of tumor-associated macrophages in the epithelial-mesenchymal transition of lung cancer

Lung cancer remains the leading cause of cancer-related mortality worldwide. Tumor-associated macrophages (TAMs) and epithelial-mesenchymal transition (EMT) are key drivers of lung cancer metastasis and drug resistance. M2-polarized TAMs dominate the immunosuppressive tumor microenvironment (TME) and promote EMT through cytokines such as TGF-β, IL-6, and CCL2. Conversely, EMT-transformed tumor cells reinforce TAM recruitment and M2 polarization through immunomodulatory factors such as CCL2 and ZEB1, thereby establishing a bidirectional interplay that fuels tumor progression. Current evidence on this interaction remains fragmented, and a comprehensive review of the TAM-EMT regulatory network and its therapeutic implications is lacking. This review systematically integrates the bidirectional regulatory mechanisms between TAMs and EMT, highlighting their roles in lung cancer progression. It also summarizes emerging therapeutic strategies targeting TAM polarization and the EMT process, emphasizing their potential for clinical translation. This study fills the gap in systematic reviews on the interaction between TAMs and EMT, providing a comprehensive theoretical foundation for future research and the development of novel lung cancer therapies.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

Dysregulation of E-cadherin in pulmonary cell damage related with COPD contributes to emphysema

Air pollution, especially at chronic exposure to high concentrations, is a respiratory risk factor for the development of chronic obstructive pulmonary disease (COPD). E-cadherin, a cell–cell adhesion protein, is involved in the integrity of the alveolar epithelium. Causes of E-cadherin decreases in emphysematous areas with pulmonary cell damage related to COPD are not well understood. We aimed to determine the molecules causing the decrease of E-cadherin and interactions between these molecules. In emphysematous and non-emphysematous areas of lungs from COPD patients (n = 35), levels of E-cadherin, HDACs, Snail, Zeb1, active-β-catenin, p120ctn, and Kaiso were determined by using Western Blot. The interactions of HDAC1, HDAC2, and p120ctn with transcription co-activators and Kaiso were examined by co-immunoprecipitation experiments. The methylation status of the CDH1 promoter was investigated. E-cadherin, Zeb1, Kaiso, and active-β-catenin were decreased in emphysema, while HDAC1, HDAC2, and p120ctn2 were increased. Snail, Zeb1, Twist, active-β-catenin, Kaiso, and p120ctn co-precipitated with HDAC1 and HDAC2. E-cadherin, Kaiso, and active-β-catenin co-precipitated with p120ctn. HDAC1–Snail and HDAC2–Kaiso interactions were increased in emphysema, but p120ctn-E-cadherin interaction was decreased. The results show that HDAC1–Snail and HDAC2–Kaiso interactions are capable of decreasing the E-cadherin in emphysema. The decreased interaction of p120ctn/E-cadherin leads to E-cadherin destruction. The decreased E-cadherin and its induced degradation in pneumocytes cause impaired repair and disintegrity of the epithelium. Approaches to suppress HDAC1–Snail and HDAC2–Kaiso interactions may help the protection of alveolar epithelial integrity by increasing the E-cadherin stability in pneumocytes.

Lung cancer and epithelial-mesenchymal transition

Lung cancer (LC) is a leading cause of cancer-related death worldwide. Epithelial-mesenchymal transition (EMT) is a well-known phenomenon that promotes the invasive and metastatic capabilities of LC. Especially, EMT is assumed to be a pivotal mechanism for tumor cell invasion and metastasis, thereby limiting the efficacy of surgery and medical treatments, resulting in poor patient prognoses. Thus, the elucidation and reversal of EMT could provide changes in therapeutic strategies for LC. To overcome the limitations of currents treatment regimens for LC, it is important for surgeons to be familiar with this complex tumor characteristic. In this review, the activating signaling pathways underlying EMT and the associated tumor phenotypes are briefly described.

Metastasis-Associated Protein 2 Represses NF-κB to Reduce Lung Tumor Growth and Inflammation

Although NF-κB is known to play a pivotal role in lung cancer, contributing to tumor growth, microenvironmental changes, and metastasis, the epigenetic regulation of NF-κB in tumor context is largely unknown. Here we report that the IKK2/NF-κB signaling pathway modulates metastasis-associated protein 2 (MTA2), a component of the nucleosome remodeling and deacetylase complex (NuRD). In triple transgenic mice, downregulation of IKK2 (Sftpc-cRaf-IKK2DN) in cRaf-induced tumors in alveolar epithelial type II cells restricted tumor formation, whereas activation of IKK2 (Sftpc-cRaf-IKK2CA) supported tumor growth; both effects were accompanied by altered expression of MTA2. Further studies employing genetic inhibition of MTA2 suggested that in primary tumor growth, independent of IKK2, MTA2/NuRD corepressor complex negatively regulates NF-κB signaling and tumor growth, whereas later dissociation of MTA2/NuRD complex from the promoter of NF-κB target genes and IKK2-dependent positive regulation of MTA2 leads to activation of NF-κB signaling, epithelial-mesenchymal transition, and lung tumor metastasis. These findings reveal a previously unrecognized biphasic role of MTA2 in IKK2/NF-κB-driven primary-to-metastatic lung tumor progression. Addressing the interaction between MTA2 and NF-κB would provide potential targets for intervention of tumor growth and metastasis. SIGNIFICANCE: These findings strongly suggest a prominent role of MTA2 in primary tumor growth, lung metastasis, and NF-κB signaling modulatory functions.

MicroRNAs in breast cancer: New maestros defining the melody

MicroRNAs, short non-coding single-stranded RNAs, are important regulators and gatekeepers of the coding genes in the human genome. MicroRNAs are highly conserved among species and expressed in different tissues and cell types. They are involved in almost all the biological processes as apoptosis, proliferation, cell cycle arrest and differentiation. Playing all these roles, it is not surprising that the deregulation of the microRNA profile causes a number of diseases including cancer. Breast cancer, the most commonly diagnosed malignancy in women, accounts for the highest cancer-related deaths worldwide. Different microRNAs were shown to be up or down regulated in breast cancer. MicroRNAs can function as oncogenes or tumor suppressors according to their targets. In this review, the most common microRNAs implicated in breast cancer are fully illustrated with their targets. Besides, the review highlights the effect of exosomal microRNA on breast cancer and the effect of microRNAs on drug and therapies resistance as well as the miRNA-based therapeutic strategies used until today.

Clinical and prognostic association of oncogene cadherin 11 in gastric cancer

The abnormal expression of cadherin-11 (CDH11) affects the progression of several types of cancer. However, the expression pattern and prognostic value of CDH11 in gastric cancer (GC) have not been reported. In the present study, the expression of CDH11 in patients with GC and its effect on their survival were analyzed using public cancer databases. The expression of CDH11 in GC tissues was significantly higher compared with that in normal gastric tissues. The expression of CDH11 was higher in advanced GC compared with early GC, and increased CDH11 was associated with tumor progression and poor prognosis in patients with GC. The high level of methylation in the promoter of CDH11 in GC tissues was not sufficient to reverse the upregulation of CDH11 caused by transcriptional activation. Finally, the expression pattern and prognostic significance of CDH11 in GC were validated using data from patients with GC recruited for the present study. Collectively, the present results demonstrated that CDH11 was upregulated in GC tissues, and suggested that high CDH11 expression may be associated with progression and poor prognosis in GC.

Dulcitol suppresses proliferation and migration of hepatocellular carcinoma via regulating SIRT1/p53 pathway

BACKGROUND

Hepatocellular carcinoma (HCC) spreads further with continuance and increasing incidence due to its high-grade malignancy and metastasis. More effectual strategies on blocking proliferation and metastasis of cancer cells should be studied in HCC. Dulcitol, a natural product extracted from euonymus alatus, was reported that it could induce apoptosis of C6 glioma cells. However, the underlying mechanism of Dulcitol on HCC remains unclea.

PURPOSE

In this study, we aimed to reveal the effect and potential mechanisms of Dulcitol on hepatocellular carcinoma in vitro and in vivo. Study design and methods The cell proliferation and apoptosis were evaluated by MTT, Ki-67 and Hoechst 33258/PI double staining. The migratory and invasive abilities of HepG2 cells were measured by wound-healing and transwell assays. Pathological changes of tumor tissue were observed by HE staining and IHC methods. The expression levels of protein were detected using Western Blot analysis.

RESULTS

The results showed that Dulcitol inhibited HepG2 cells proliferation by down-regulating the protein expression of SIRT1, Bcl-2, along with up-regulating p53, acetylated-p53 (K382), cleaved-caspase9, cleaved-caspase3, Bax, and cytochrome c in a dose-dependent manner. Furthermore, Dulcitol surpressed the migration and invasion of HepG2 cells through decreasing the levels of MMP-2, uPA and MMP-9 and increasing E-cadherin associated with tumor invasion. In vivo, Dulcitol distinctly inhibited the growth of HepG2 cancer xenograft tumors via inhibiting SIRT1/p53 pathway.

CONCLUSIONS

Our findings suggested that Dulcitol acted as a SIRT1 inhibitor, inducing apoptosis and inhibiting proliferation, migration and invasion of HepG2 cells and its modulatory mechanism seemed to be associated with regulation of MMPs, SIRT1/p53 pathways.

Muse cells and Neurorestoratology

Multilineage-differentiating stress-enduring (Muse) cells were discovered in 2010 as a subpopulation of mesenchymal stroma cells (MSCs). Muse cells can self-renew and tolerate severe culturing conditions. These cells can differentiate into three lineage cells spontaneously or in induced medium but do not form teratoma in vitro or in vivo. Central nervous system (CNS) diseases, such as intracerebral hemorrhage (ICH), cerebral infarction, and spinal cord injury are normally disastrous. Despite numerous therapy strategies, CNS diseases are difficult to recover. As a novel kind of pluripotent stem cells, Muse cells have shown great regeneration capacity in many animal models, including acute myocardial infarction, hepatectomy, and acute cerebral ischemia (ACI). After injection into injury sites, Muse cells survived, migrated, and differentiated into functional neurons with synaptic junctions to local neurons and contributed to recovery of function. Furthermore, Muse cell differentiation did not need to be induced pre-transplantation and no tumors were observed post- transplantation. The Muse cell population is promising and may lead to a revolution in regenerative medicine. This review focuses on recent advances regarding the Muse cells therapies in Neurorestoratology and discusses future perspectives in this field.

Pancreatic Exocrine Tissue Architecture and Integrity are Maintained by E-cadherin During Postnatal Development

Cadherin-mediated cell-cell adhesion plays an important role in organ development and changes in cadherin expression are often linked to morphogenetic and pathogenic events. Cadherins interact with other intracellular components to form adherens junctions (AJs) and provide mechanical attachments between adjacent cells. E-cadherin (Cdh1) represents an integral component of these intercellular junctions. To elucidate the function of E-cadherin in the developing pancreas, we generated and studied pancreas-specific Cdh1-knockout (Cdh1^ΔPan/ΔPan) mice. Cdh1^ΔPan/ΔPan mice exhibit normal body size at birth, but fail to gain weight and become hypoglycemic soon afterward. We found that E-cadherin is not required for the establishment of apical-basal polarity or pancreatic exocrine cell identity at birth. However, four days after birth, the pancreata of Cdh1^ΔPan/ΔPan mutants display progressive deterioration of exocrine architecture and dysregulation of Wnt and YAP signaling. At this time point, the acinar cells of Cdh1^ΔPan/ΔPan mutants begin to exhibit ductal phenotypes, suggesting acinar-to-ductal metaplasia (ADM) in the E-cadherin-deficient pancreas. Our findings demonstrate that E-cadherin plays an integral role in the maintenance of exocrine architecture and regulation of homeostatic signaling. The present study provides insights into the involvement of cadherin-mediated cell-cell adhesion in pathogenic conditions such as pancreatitis or pancreatic cancer.

Characterization of a lung epithelium specific E-cadherin knock-out model: Implications for obstructive lung pathology

The airway epithelium regulates responses to aeroallergens, acting as a physical and immunological barrier. In asthma, epithelial barrier function and the expression of adherens junction protein E-cadherin is compromised, but it is unknown whether this is cause or consequence of the disease. We hypothesized that airway epithelial loss of E-cadherin is a critical step in the development of manifestations of asthma. We generated a transgenic mouse model with conditional loss of E-cadherin in lung epithelial cells at birth and onwards. We observed normal lung development at the time of birth in mice lacking E-cadherin in the lung epithelium. However, E-cadherin deficiency led to progressive epithelial damage in mice growing into adulthood, as evidenced by airway epithelial denudation, decreased zonula occludens (ZO)-1 expression, loss of ciliated cells, and enlarged alveolar spaces. In addition, spontaneous goblet cell metaplasia with mucus production was observed. These epithelial changes were accompanied by elevated levels of the epithelial-derived chemokine CCL17, infiltration of eosinophils and dendritic cells, and mucus production. In conclusion, loss of E-cadherin induces features in the lung reminiscent of those observed in asthma, indicating that the disruption of E-cadherin-mediated cell-cell contacts may play a key role in the development of asthma manifestations.

E-cadherin bridges cell polarity and spindle orientation to ensure prostate epithelial integrity and prevent carcinogenesis in vivo

Cell polarity and correct mitotic spindle positioning are essential for the maintenance of a proper prostate epithelial architecture, and disruption of the two biological features occurs at early stages in prostate tumorigenesis. However, whether and how these two epithelial attributes are connected in vivo is largely unknown. We herein report that conditional genetic deletion of E-cadherin, a key component of adherens junctions, in a mouse model results in loss of prostate luminal cell polarity and randomization of spindle orientations. Critically, E-cadherin ablation causes prostatic hyperplasia which progresses to invasive adenocarcinoma. Mechanistically, E-cadherin and the spindle positioning determinant LGN interacts with the PDZ domain of cell polarity protein SCRIB and form a ternary protein complex to bridge cell polarity and cell division orientation. These findings provide a novel mechanism by which E-cadherin acts an anchor to maintain prostate epithelial integrity and to prevent carcinogenesis in vivo.

Luminal cells are the most abundant type of the prostate epithelial cells. Most prostate cancers also display a luminal phenotype. Horizontal cell division of luminal cells allows the surface expansion of the secretory prostate lumen and meanwhile maintains the monolayer and polarized epithelial architecture. Disruption of the epithelial integrity and appearance of multilayer epithelia are early events in prostate adenocarcinoma development. However, the molecular mechanism that ensures the horizontal division in luminal cells remains largely unknown. Here, we generated a genetically engineered mouse model in which E-cadherin, a key component of the adherens junction that serves to connect the lateral plasma membrane of neighboring epithelial cells, was knocked out in the prostate luminal cells. E-cadherin deletion leads to loss of cell polarity and disoriented cell division, which subsequently causes dysregulated cell proliferation and strongly predisposes mice for prostate tumorigenesis. Importantly, we revealed that E-cadherin acts as an anchor to recruit cell polarity protein SCRIB and spindle positioning determinant LGN to the lateral cell membrane, thereby ensure a proper alignment of the cell division plane. All these findings uncover a novel mechanism by which E-cadherin links cell polarity and spindle orientation to keep prostate epithelial integrity and prevent carcinogenesis.

E-Cadherin Loss Accelerates Tumor Progression and Metastasis in a Mouse Model of Lung Adenocarcinoma

Metastatic disease is the primary cause of death of patients with lung cancer, but the mouse models of lung adenocarcinoma do not accurately recapitulate the tumor microenvironment or metastatic disease observed in patients. In this study, we conditionally deleted E-cadherin in an autochthonous lung adenocarcinoma mouse model driven by activated oncogenic Kras and p53 loss. Loss of E-cadherin significantly accelerated lung adenocarcinoma progression and decreased survival of the mice. Kras;p53;E-cadherin mice had a 41% lung tumor burden, invasive grade 4 tumors, and a desmoplastic stroma just 8 weeks after tumor initiation. One hundred percent of the mice developed local metastases to the lymph nodes or chest wall, and 38% developed distant metastases to the liver or kidney. Lung adenocarcinoma cancer cell lines derived from these tumors also had high migratory rates. These studies demonstrate that the Kras;p53;E-cadherin mouse model better emulates the tumor microenvironment and metastases observed in patients with lung adenocarcinoma than previous models and may therefore be useful for studying metastasis and testing new lung cancer treatments in vivo.

WNT signaling - lung cancer is no exception

Since the initial discovery of the oncogenic activity of WNT ligands our understanding of the complex roles for WNT signaling pathways in lung cancers has increased substantially. In the current review, the various effects of activation and inhibition of the WNT signaling pathways are summarized in the context of lung carcinogenesis. Recent evidence regarding WNT ligand transport mechanisms, the role of WNT signaling in lung cancer angiogenesis and drug transporter regulation and the importance of microRNA and posttranscriptional regulation of WNT signaling are also reviewed.

Relationships of MMP-9, E-cadherin, and VEGF expression with clinicopathological features and response to chemosensitivity in gastric cancer

The matrix metalloproteinase-9, E-cadherin, and vascular endothelial growth factor play an important role in behavior of tumor cell growth, invasion, and metastasis. In this study, we investigated the relationships of matrix metalloproteinase-9, E-cadherin, and vascular endothelial growth factor expression with clinicopathological features and results of chemosensitivity tested by collagen gel droplet–embedded culture–drug sensitivity test in gastric cancer. Fresh specimens were used for collagen gel droplet–embedded culture–drug sensitivity test and paired fixed specimens were used for immunohistochemistry. Positive expression of matrix metalloproteinase-9 was associated with poorly differentiated carcinoma (p = 0.032), lymph node metastasis (p = 0.022), and tumor stage (p = 0.023). Negative expression of E-cadherin was associated with poorly differentiated carcinoma (p = 0.007), lymph node metastasis (p = 0.012), and tumor stage (p = 0.007). Positive expression of vascular endothelial growth factor was associated with tumor size (p = 0.040) and stage (p = 0.007). Collagen gel droplet–embedded culture–drug sensitivity test was successfully evaluated in 56 patients. Among them, 29 (51.7%) patients were resistant to TS-1 and 31 (55.3%) patients were resistant to L-OHP. The L-OHP resistance rate in vascular endothelial growth factor positive patients was significantly higher than that in negative patients (p = 0.031). The L-OHP resistance rate in E-cadherin negative patients was significantly higher than that in positive patients (p = 0.014). In conclusion, matrix metalloproteinase-9, E-cadherin, and vascular endothelial growth factor were involved in tumor invasion and metastasis. Positive expression of matrix metalloproteinase-9 and vascular endothelial growth factor and negative expression of E-cadherin were malignant markers for gastric cancer. Positive expression of vascular endothelial growth factor and negative expression of E-cadherin were associated with L-OHP resistance.

MTA1-activated Epi-microRNA-22 regulates E-cadherin and prostate cancer invasiveness

We have previously shown that metastasis-associated protein 1 (MTA1), a chromatin remodeler, plays an important role in prostate cancer invasiveness, likely through regulation of epithelial-to-mesenchymal transition. Here, we identified miR-22 as an epigenetic-microRNA (Epi-miR) directly induced by MTA1 and predicted to target E-cadherin. Loss-of-function and overexpression studies of MTA1 reinforced its regulatory role in miR-22 expression. MiR-22 directly targets the 3'-untranslated region of E-cadherin, and ectopic overexpression of miR-22 diminishes E-cadherin expression. Overexpression of miR-22 in prostate cancer cells promotes cell invasiveness and migration. Meta-analysis of patient tumor samples indicates a positive correlation between MTA1 and miR-22, supporting their inhibitory effect on E-cadherin expression. Our findings implicate the MTA1/Epi-miR-22/E-cadherin axis as a new epigenetic signaling pathway that promotes tumor invasion in prostate cancer.

Galeterone and VNPT55 disrupt Mnk-eIF4E to inhibit prostate cancer cell migration and invasion

Metastatic castration-resistant prostate cancer (mCRPC) accounts for a high percentage of prostate cancer mortality. The proprietary compound galeterone (gal) was designed to inhibit proliferation of androgen/androgen receptor (AR)-dependent prostate cancer cell in vitro and in vivo and is currently in phase III clinical development. Additionally, clinical studies with gal revealed its superb efficacy in four different cohorts of patients with mCRPC, including those expressing splice variant AR-V7. Preclinical studies with gal show that it also exhibits strong antiproliferative activities against AR-negative prostate cancer cells and tumors through a mechanism involving phosphorylation of eIF2α, which forms an integral component of the eukaryotic mRNA translation complex. Thus, we hypothesized that gal and its new analog, VNPT55, could modulate oncogenic mRNA translation and prostate cancer cell migration and invasion. We report that gal and VNPT55 profoundly inhibit migration and invasion of prostate cancer cells, possibly by down-regulating protein expression of several EMT markers (Snail, Slug, N-cadherin, vimentin, and MMP-2/-9) via antagonizing the Mnk-eIF4E axis. In addition, gal/VNPT55 inhibited both NF-κB and Twist1 transcriptional activities, down-regulating Snail and BMI-1 mRNA expression, respectively. Furthermore, profound up-regulation of E-cadherin mRNA and protein expression may explain the observed significant inhibition of prostate cancer cell migration and invasion. Moreover, expression of self-renewal proteins, β-catenin, CD44, and Nanog, was markedly depleted. Analysis of gal/VNPT55-treated CWR22Rv1 xenograft tissue sections also revealed that observations in vitro were recapitulated in vivo. Our results suggest that gal/VNPT55 could become promising agents for the prevention and/or treatment of all stages of prostate cancer.

DNA methylation and not H3K4 trimethylation dictates the expression status of miR-152 gene which inhibits migration of breast cancer cells via DNMT1/CDH1 loop

MicroRNAs (miRNA) are small non-coding RNAs which targets most protein-coding transcripts (mRNA) and destroy them. Thus miRNA controls the abundance of those specific proteins and impact on developmental, physiological and pathological processes. Dysregulation of miRNA function thus may lead to various clinicopathological complications, including breast cancer. Silencing of miR-152 gene due to promoter DNA methylation alter the expression pattern of several other genes. E-cadherin (CDH1) forms the core of adherent junctions between surrounding epithelial cells, link with actin cytoskeleton and affects cell signaling. CDH1 gene is down regulated by promoter DNA methylation during cancer progression. In this investigation, we attempt to elucidate the correlation of miR-152 and CDH1 function, as it is well known that the loss of CDH1 function is one of the major reasons for cancer metastasis and aggressiveness of spreading. For the first time we have shown that loss of CDH1 expression is directly proportional to the loss of miR-152 function in breast cancer cells. mRNA and protein expression profile of DNMT1 implicate that miR-152 targets DNMT1 mRNA and inhibits its protein expression. Tracing the molecular marks on DNA and histone 3 for understanding the mechanism of gene regulation by ChIP analyses leads to a paradoxical result that shows DNA methylation adjacent to active histone marking (enrichment of H3K4me3) silence miR-152 gene. Further experiments revealed that DNMT1 plays crucial role for regulation of miR-152 gene. When DNMT1 protein function is blocked miR-152 expression prevails and destroys the mRNA of DNMT1; this molecular regulatory mechanism is creating a cyclic feedback loop, which is now focused as DNMT1/miR-152 switch for on/off of DNMT1 target genes. We discovered modulation of CDH1 gene expression by DNMT1/miR-152 switches. We have demonstrated further that DNMT1 down regulation mediated upregulation of CDH1 (hereafter, DNMT1/CDH1 loop) in presence of ectopic-excess of miR-152 prevents migration of cancer cells. Our data provides novel insights into the regulation mechanism of miRNA and mRNA/protein coding genes and enhances the amplitude of cancer epigenome.

WIP1 stimulates migration and invasion of salivary adenoid cystic carcinoma by inducing MMP-9 and VEGF-C

The wild-type p53 induced phosphatase 1 (WIP1) is an oncogene overexpressed in a variety of human cancers. Here, we demonstrated that WIP1 silencing reduced MMP-9 and VEGF-C expression as well as migration and invasion of salivary adenoid cystic carcinoma (ACC) cells. Overexpression of MMP-9 or VEGF-C restored migration and invasion in WIP1 knockdown cells, indicating that MMP-9 and VEGF-C are downstream targets of WIP1 signaling. Levels of cyclin D1 and c-Myc, targets of Wnt/β-catenin pathway, were significantly decreased by WIP1 silencing. In addition, WIP1 expression was positively associated with metastasis and prognosis of ACC patients as well as with MMP-9 or VEGF-C in ACC tissues.

MicroRNA-9 promotes tumor metastasis via repressing E-cadherin in esophageal squamous cell carcinoma

MicroRNAs (miRNAs) play a critical role in development and progression of cancers. Deregulation of MicroRNA-9 (miR-9) has been documented in many types of cancers but their role in the development of esophageal squamous cell carcinoma (ESCC) has not been studied. This study aimed to investigate the effect of miR-9 in esophageal cancer metastasis. The up-regulation of miR-9 was frequently detected in primary ESCC tumor tissue, which was significantly associated with clinical progression (P = 0.022), lymph node metastasis (P = 0.007) and poor overall survival (P < 0.001). Functional study demonstrated that miR-9 promoted cell migration and tumor metastasis, which were effectively inhibited when expression of miR-9 was silenced. Moreover, we demonstrated that miR-9 interacted with the 3'-untranslated region of E-cadherin and down-regulated its expression, which induced β-catenin nuclear translocation and subsequently up-regulated c-myc and CD44 expression. In addition, miR-9 induced epithelial-mesenchymal transition (EMT) in ESCC, a key event in tumor metastasis. Taken together, our study demonstrates that miR-9 plays an important role in ESCC metastasis by activating β-catenin pathway and inducing EMT via targeting E-cadherin. Our study also suggests miR-9 can be served as a new independent prognostic marker and/or as a novel potential therapeutic target for ESCC.

α5-nAChR modulates nicotine-induced cell migration and invasion in A549 lung cancer cells

Cigarette smoking is the most important risk factor in the development of human lung cancer. Nicotine, the major component in tobacco, not only contributes to carcinogenesis but also promotes tumor metastasis. By binding to nicotinic acetylcholine receptors (nAChRs), nicotine induces the proliferation and migration of non-small cell lung cancer. Recently studies have indicated that α5-nAChR is highly associated with lung cancer risk and nicotine dependence. Nevertheless, it is unclear whether nicotine promotes the migration and invasion through activation of α5-nAChR in lung cancer. In the present study, A549 cell was exposed to 1μN nicotine for 8, 24 or 48h. Wound-healing assay and transwell assay were used to evaluate the capability of A549 cell migration and cell invasion, respectively. Silencing of α5-nAChR was done by siRNA. Western blotting and PCR were used to detect α5-nAChR expression. Nicotine can induce activation of α5-nAChR in association with increased migration and invasion of human lung cancer A549 cell. Treatment of cells with α5-nAChR specific siRNA blocks nicotine-stimulated activation of α5-nAChR and suppresses A549 cell migration and invasion. Reduction of α5-nAChR resulted in upregulation of E-cadherin, consistent with E-cadherin being inhibitive of cancer cell invasion. These findings suggest that nicotine-induced migration and invasion may occur in a mechanism through activation of α5-nAChR, which can contribute to metastasis or development of human lung cancer.

PI3K/AKT pathway regulates E-cadherin and Desmoglein 2 in aggressive prostate cancer

Reduced expression of both classical and desmosomal cadherins has been associated with different types of carcinomas, including prostate cancer. This study aims to provide a comprehensive view of the role and regulation of cell-cell adhesion in prostate cancer aggressiveness by examining the functional implications of both E-cadherin and Desmoglein 2 (DSG2). E-cadherin expression was first examined using immunofluorescence in 50 normal prostate tissues and in a cohort of 414 prostate cancer patients. Correlation and survival analyses were performed to assess its clinical significance. In primary prostate cancer patients, reduced expression of both E-cadherin and DSG2 is significantly associated with an earlier biochemical recurrence. Transgenic DU145 E-cadherin knockdown and constitutively active AKT overexpression lines were generated. Functional implications of such genetic alterations were analyzed in vitro and in vivo, the latter by using tumorigenesis as well as extravasation and metastatic tumor formation assays. We observed that loss of E-cadherin leads to impaired primary and metastatic tumor formation in vivo, suggesting a tumor promoter role for E-cadherin in addition to its known role as a tumor suppressor. Activation of AKT leads to a significant reduction in E-cadherin expression and nuclear localization of Snail, suggesting a role for the PI3K/AKT signaling pathway in the transient repression of E-cadherin. This reduced expression may be regulated by separate mechanisms as neither the loss of E-cadherin nor activation of AKT significantly affected DSG2 expression. In conclusion, these findings illustrate the critical role of cell-cell adhesion in the progression to aggressive prostate cancer, through regulation by the PI3K pathway.

The Regulatory Role of MicroRNAs in EMT and Cancer

The epithelial to mesenchymal transition (EMT) is a powerful process in tumor invasion, metastasis, and tumorigenesis and describes the molecular reprogramming and phenotypic changes that are characterized by a transition from polarized immotile epithelial cells to motile mesenchymal cells. It is now well known that miRNAs are important regulators of malignant transformation and metastasis. The aberrant expression of the miR-200 family in cancer and its involvement in the initiation and progression of malignant transformation has been well demonstrated. The metastasis suppressive role of the miR-200 members is strongly associated with a pathologic EMT. This review describes the most recent advances regarding the influence of miRNAs in EMT and the control they exert in major signaling pathways in various cancers. The ability of the autocrine TGF-β/ZEB/miR-200 signaling regulatory network to control cell plasticity between the epithelial and mesenchymal state is further discussed. Various miRNAs are reported to directly target EMT transcription factors and components of the cell architecture, as well as miRNAs that are able to reverse the EMT process by targeting the Notch and Wnt signaling pathways. The link between cancer stem cells and EMT is also reported and the most recent developments regarding clinical trials that are currently using anti-miRNA constructs are further discussed.

Intracellular signals of lung cancer cells as possible therapeutic targets

In recent years, several molecularly targeted therapies have been developed as part of lung cancer treatment; they have produced dramatically good results. However, among the many oncogenes that have been identified to be involved in the development of lung cancers, a number of oncogenes are not covered by these advanced therapies. For the treatment of lung cancers, which is a group of heterogeneous diseases, persistent effort in developing individual therapies based on the respective causal genes is important. In addition, for the development of a novel therapy, identification of the lung epithelial stem cells and the origin cells of lung cancer, and understanding about candidate cancer stem cells in lung cancer tissues, their intracellular signaling pathways, and the mechanism of dysregulation of the pathways in cancer cells are extremely important. However, the development of drug resistance by cancer cells, despite the use of molecularly targeted drugs for the causal genes, thus obstructing treatment, is a well-known phenomenon. In this article, we discuss major causal genes of lung cancers and intracellular signaling pathways involving those genes, and review studies on origin and stem cells of lung cancers, as well as the possibility of developing molecularly targeted therapies based on these studies.

E-cadherin's role in development, tissue homeostasis and disease: Insights from mouse models: Tissue-specific inactivation of the adhesion protein E-cadherin in mice reveals its functions in health and disease

Recent studies uncovered critical roles of the adhesion protein E-cadherin in health and disease. Global inactivation of Cdh1, the gene encoding E-cadherin in mice, results in early embryonic lethality due to an inability to form the trophectodermal epithelium. To unravel E-cadherin's functions beyond development, numerous mouse lines with tissue-specific disruption of Cdh1 have been generated. The consequences of E-cadherin loss showed great variability depending on the tissue in question, ranging from nearly undetectable changes to a complete loss of tissue structure and function. This review focuses on these studies and discusses how they provided important insights into E-cadherin's role in cell adhesion, proliferation and differentiation, and its consequences for biological processes as epithelial-to-mesenchymal transition, vascularization, and carcinogenesis. Lastly, we present some perspectives and possible approaches for future research.

Tetracycline-regulated mouse models of cancer

Genetically engineered mouse models (GEMMs) have proven essential to the study of mammalian gene function in both development and disease. However, traditional constitutive transgenic mouse model systems are limited by the temporal and spatial characteristics of the experimental promoter used to drive transgene expression. To address this limitation, considerable effort has been dedicated to developing conditional and inducible mouse model systems. Although a number of approaches to generating inducible GEMMs have been pursued, several have been restricted by toxic or undesired physiological side effects of the compounds used to activate gene expression. The development of tetracycline (tet)-dependent regulatory systems has allowed for circumvention of these issues resulting in the widespread adoption of these systems as an invaluable tool for modeling the complex nature of cancer progression.

Restoration of miR-101 suppresses lung tumorigenesis through inhibition of DNMT3a-dependent DNA methylation

The deregulation of miR-101 and DNMT3a has been implicated in the pathogenesis of multiple tumor types, but whether and how miR-101 silencing and DNMT3a overexpression contribute to lung tumorigenesis remain elusive. Here we show that miR-101 downregulation associates with DNMT3a overexpression in lung cancer cell lines and patient tissues. Ectopic miR-101 expression remarkably abrogated the DNMT3a 3′-UTR luciferase activity corresponding to the miR-101 binding site and caused an attenuated expression of endogenous DNMT3a, which led to a reduction of global DNA methylation and the re-expression of tumor suppressor CDH1 via its promoter DNA hypomethylation. Functionally, restoration of miR-101 expression suppressed lung cancer cell clonability and migration, which recapitulated the DNMT3a knockdown effects. Interestingly, miR-101 synergized with decitabine to downregulate DNMT3a and to reduce DNA methylation. Importantly, ectopic miR-101 expression was sufficient to trigger in vivo lung tumor regression and the blockage of metastasis. Consistent with these phenotypes, examination of xenograft tumors disclosed an increase of miR-101, a decrease of DNMT3a and the subsequent DNA demethylation. These findings support that the loss or suppression of miR-101 function accelerates lung tumorigenesis through DNMT3a-dependent DNA methylation, and suggest that miR-101-DNMT3a axis may have therapeutic value in treating refractory lung cancer.

Elimination of B-RAF in oncogenic C-RAF-expressing alveolar epithelial type II cells reduces MAPK signal intensity and lung tumor growth

Tumors are often greatly dependent on signaling cascades promoting cell growth or survival and may become hypersensitive to inactivation of key components within these signaling pathways. Ras and RAF mutations found in human cancer confer constitutive activity to these signaling molecules thereby converting them into an oncogenic state. RAF dimerization is required for normal Ras-dependent RAF activation and is required for the oncogenic potential of mutant RAFs. Here we describe a new mouse model for lung tumor development to investigate the role of B-RAF in oncogenic C-RAF-mediated adenoma initiation and growth. Conditional elimination of B-RAF in C-RAF BxB-expressing embryonic alveolar epithelial type II cells did not block adenoma formation. However, loss of B-RAF led to significantly reduced tumor growth. The diminished tumor growth upon B-RAF inactivation was due to reduced cell proliferation in absence of senescence and increased apoptosis. Furthermore, B-RAF elimination inhibited C-RAF BxB-mediated activation of the mitogenic cascade. In line with these data, mutation of Ser-621 in C-RAF BxB abrogated in vitro the dimerization with B-RAF and blocked the ability to activate the MAPK cascade. Taken together these data indicate that B-RAF is an important factor in oncogenic C-RAF-mediated tumorigenesis.

Cooperation of tyrosine kinase receptor TrkB and epidermal growth factor receptor signaling enhances migration and dispersal of lung tumor cells

TrkB mediates the effects of brain-derived neurotrophic factor (BDNF) in neuronal and nonnneuronal cells. Based on recent reports that TrkB can also be transactivated through epidermal growth-factor receptor (EGFR) signaling and thus regulates migration of early neurons, we investigated the role of TrkB in migration of lung tumor cells. Early metastasis remains a major challenge in the clinical management of non-small cell lung cancer (NSCLC). TrkB receptor signaling is associated with metastasis and poor patient prognosis in NSCLC. Expression of this receptor in A549 cells and in another adenocarcinoma cell line, NCI-H441, promoted enhanced migratory capacity in wound healing assays in the presence of the TrkB ligand BDNF. Furthermore, TrkB expression in A549 cells potentiated the stimulatory effect of EGF in wound healing and in Boyden chamber migration experiments. Consistent with a potential loss of cell polarity upon TrkB expression, cell dispersal and de-clustering was induced in A549 cells independently of exogeneous BDNF. Morphological transformation involved extensive cytoskeletal changes, reduced E-cadherin expression and suppression of E-cadherin expression on the cell surface in TrkB expressing tumor cells. This function depended on MEK and Akt kinase activity but was independent of Src. These data indicate that TrkB expression in lung adenoma cells is an early step in tumor cell dissemination, and thus could represent a target for therapy development.

p120-catenin in cancer - mechanisms, models and opportunities for intervention

The epithelial adherens junction is an E-cadherin-based complex that controls tissue integrity and is stabilized at the plasma membrane by p120-catenin (p120, also known as CTNND1). Mutational and epigenetic inactivation of E-cadherin has been strongly implicated in the development and progression of cancer. In this setting, p120 translocates to the cytosol where it exerts oncogenic properties through aberrant regulation of Rho GTPases, growth factor receptor signaling and derepression of Kaiso (also known as ZBTB33) target genes. In contrast, indirect inactivation of the adherens junction through conditional knockout of p120 in mice was recently linked to tumor formation, indicating that p120 can also function as a tumor suppressor. Supporting these opposing functions are findings in human cancer, which show that either loss or cytoplasmic localization of p120 is a common feature in the progression of several types of carcinoma. Underlying this dual biological phenomenon might be the context-dependent regulation of Rho GTPases in the cytosol and the derepression of Kaiso target genes. Here, we discuss past and present findings that implicate p120 in the regulation of cancer progression and highlight opportunities for clinical intervention.

Molecular mechanisms of tissue inhibitor of metalloproteinase 2 in the tumor microenvironment

There has been a recent paradigm shift in the way we target cancer, drawing a greater focus on the role of the tumor microenvironment (TME) in cancer development, progression and metastasis. Within the TME, there is a crosstalk in signaling and communication between the malignant cells and the surrounding extracellular matrix. Matrix metalloproteinases (MMPs) are zinc-dependent endoproteases that have the ability to degrade the matrix surrounding a tumor and mediate tumor growth, angiogenesis and metastatic disease. Their endogenous inhibitors, the Tissue Inhibitors of Metalloproteinases (TIMPs), primarily function to prevent degradation of the ECM via inhibition of MMPs. However, recent studies demonstrate that TIMP family members also possess MMP-independent functions. One TIMP member in particular, TIMP-2, has many distinct properties and functions, that occur independent of MMP inhibition, including the inhibition of tumor growth and reduction of angiogenesis through decreased endothelial cell proliferation and migration. The MMP-independent molecular mechanisms and signaling pathways elicited by TIMP-2 in the TME are described in this review.

Molecular mechanisms of tissue inhibitor of metalloproteinase 2 in the tumor microenvironment

There has been a recent paradigm shift in the way we target cancer, drawing a greater focus on the role of the tumor microenvironment (TME) in cancer development, progression and metastasis. Within the TME, there is a crosstalk in signaling and communication between the malignant cells and the surrounding extracellular matrix. Matrix metalloproteinases (MMPs) are zinc-dependent endoproteases that have the ability to degrade the matrix surrounding a tumor and mediate tumor growth, angiogenesis and metastatic disease. Their endogenous inhibitors, the Tissue Inhibitors of Metalloproteinases (TIMPs), primarily function to prevent degradation of the ECM via inhibition of MMPs. However, recent studies demonstrate that TIMP family members also possess MMP-independent functions. One TIMP member in particular, TIMP-2, has many distinct properties and functions, that occur independent of MMP inhibition, including the inhibition of tumor growth and reduction of angiogenesis through decreased endothelial cell proliferation and migration. The MMP-independent molecular mechanisms and signaling pathways elicited by TIMP-2 in the TME are described in this review.

MYC and the art of microRNA maintenance

MYC is a noncanonical transcription factor that binds to thousands of genomic loci and affects >15% of the human transcriptome, with surprisingly little overlap between MYC-bound and -regulated genes. This discordance raises the question whether MYC chooses its targets based on their individual biological effects ("a la carte") or by virtue of belonging to a certain group of genes (on a "prix fixe" basis). This review presents evidence for a prix fixe, posttranscriptional model whereby MYC initially deregulates a select number of microRNAs. These microRNAs then target a broad spectrum of genes based solely on the presence in their 3' UTRs (untranslated regions) of distinct "seed" sequences. Existing evidence suggests that there are significant microRNA components to all key MYC-driven phenotypes, including cell-cycle progression, apoptosis, metabolism, angiogenesis, metastasis, stemness, and hematopoiesis. Furthermore, each of these cell-intrinsic and -extrinsic phenotypes is likely attributable to deregulation of multiple microRNA targets acting in different, yet frequently overlapping, pathways. The habitual targeting of multiple genes within the same pathway might account for the robustness and persistence of MYC-induced phenotypes.

MiR-612 suppresses the stemness of liver cancer via Wnt/β-catenin signaling

Previous research showed that microRNA-612 (miR-612) has inhibitory effects on cell proliferation, migration, invasion, and metastasis of hepatocellular carcinoma (HCC). AKT2 was confirmed to be a direct target of miR-612, through which the epithelial-mesenchymal transition (EMT) and metastasis of HCC were inhibited. Our present findings reveal that miR-612 is able to suppress the stemness of HCC by reducing the number and size of tumorspheres as well as clone formation in soft agar, and to relieve drug resistance to cisplatin and 5-fluorouracil. In addition, miR-612 hampered the capacity of tumorigenesis in NOD/SCID mice and redistributed the tumor invasive frontier of miR-612-modulating cells. Finally, our findings suggest that Wnt/β-catenin signaling is required in the regulation of EMT-associated stem cell-like traits by miR-612.

SWATH™- and iTRAQ-based quantitative proteomic analyses reveal an overexpression and biological relevance of CD109 in advanced NSCLC

To identify cancer-related proteins, we used isobaric tags in a relative and absolute quantitation (iTRAQ) proteomic approach and SWATH™ quantification approach to analyze the secretome of an isogenic pair of highly metastatic and low metastatic non-small-cell lung cancer (NSCLC) cell lines. In addition, we compared two groups of pooled serum samples (12 early-stage and 12 late-stage patients) to mine data for candidates screened by iTRAQ-labeled proteomic analysis. A total of 110 proteins and 71 proteins were observed to be significantly differentially expressed in the cell line secretome and NSCLC sera, respectively. Among these proteins, CD109 was found to be highly expressed in both the highly metastatic cell line secretome and the group of late-stage patients. A sandwich ELISA assay also demonstrated an elevation of serum CD109 levels in individual NSCLC patients (n=30) compared with healthy subjects (n=19). Furthermore, CD109 displayed higher expression in lung cancer tissues compared with their matched noncancerous lung tissues (n=72). In addition, the knockdown of CD109 influenced several NSCLC cell bio-functions, for instance, depressing cell growth, affecting cell cycle phases. These phenomena suggest that CD109 plays a critical role in NSCLC progression.

BIOLOGICAL SIGNIFICANCE

We simultaneously applied two quantitative proteomic approaches-iTRAQ-labeling and SWATH™-to analyze the secretome of metastatic cell lines, in order to explore the cancer-associated proteins in conditioned media. In this study, our results indicate that CD109 plays a critical role in non-small-cell lung cancer (NSCLC) progression, and is overexpressed in advanced NSCLC.

Human adipose tissue possesses a unique population of pluripotent stem cells with nontumorigenic and low telomerase activities: potential implications in regenerative medicine

In this study, we demonstrate that a small population of pluripotent stem cells, termed adipose multilineage-differentiating stress-enduring (adipose-Muse) cells, exist in adult human adipose tissue and adipose-derived mesenchymal stem cells (adipose-MSCs). They can be identified as cells positive for both MSC markers (CD105 and CD90) and human pluripotent stem cell marker SSEA-3. They intrinsically retain lineage plasticity and the ability to self-renew. They spontaneously generate cells representative of all three germ layers from a single cell and successfully differentiate into targeted cells by cytokine induction. Cells other than adipose-Muse cells exist in adipose-MSCs, however, do not exhibit these properties and are unable to cross the boundaries from mesodermal to ectodermal or endodermal lineages even under cytokine inductions. Importantly, adipose-Muse cells demonstrate low telomerase activity and transplants do not promote teratogenesis in vivo. When compared with bone marrow (BM)- and dermal-Muse cells, adipose-Muse cells have the tendency to exhibit higher expression in mesodermal lineage markers, while BM- and dermal-Muse cells were generally higher in those of ectodermal and endodermal lineages. Adipose-Muse cells distinguish themselves as both easily obtainable and versatile in their capacity for differentiation, while low telomerase activity and lack of teratoma formation make these cells a practical cell source for potential stem cell therapies. Further, they will promote the effectiveness of currently performed adipose-MSC transplantation, particularly for ectodermal and endodermal tissues where transplanted cells need to differentiate across the lineage from mesodermal to ectodermal or endodermal in order to replenish lost cells for tissue repair.

MicroRNA-23a promotes neuroblastoma cell metastasis by targeting CDH1

CDH1 inactivation is important in tumor metastasis. In the present study, it was suggested that the mRNA and protein levels of CDH1 decreased in metastatic neuroblastoma (NB) tissues compared with those in primary NB tissues. The aim of the study was to explore the regulatory mechanisms of CDH1 downregulation in metastatic NB. MicroRNAs are small non-coding RNAs (~22 nt in length) that negatively regulate target mRNAs and are involved in various cancer-related processes, including metastasis. In the current study, miR-23a was shown to be upregulated in human metastatic NB tissues compared with primary NB tissues. Inhibition of miR-23a may significantly suppress NB cell migration and invasion. In vitro reporter assay suggested that CDH1 is a direct target gene of miR-23a. Furthermore, blocking the expression of miR-23a partly restored the expression of CDH1 in NB cells. These findings provide evidence that miR-23a is key in promoting NB cell migration and invasion through targeting CDH1, and suggest that exogenous miR-23a may have therapeutic value in treating NB metastasis.

Dynamics and regulation of epithelial adherens junctions: recent discoveries and controversies

Adherens junctions (AJs) are evolutionarily conserved plasma-membrane structures that mediate cell-cell adhesions in multicellular organisms. They are organized by several types of adhesive integral membrane proteins, most notably cadherins and nectins that are clustered and stabilized by a number of cytoplasmic scaffolds. AJs are key regulators of tissue architecture and dynamics via control of cell proliferation, polarity, shape, motility, and survival. They are absolutely critical for normal tissue morphogenesis and their disruption results in pathological abnormalities in different tissues. Although the field of adherens-junction research dramatically progressed in recent years, a number of important questions remain controversial and poorly understood. This review outlines basic principles that regulate organization of AJs in mammalian epithelia and discusses recent advances and standing controversies in the field. A special attention is paid to the regulation of AJs by vesicle trafficking and the intracellular cytoskeleton as well as roles and mechanisms of adherens-junction disruption during tumor progression and tissue inflammation.

E-cadherin controls bronchiolar progenitor cells and onset of preneoplastic lesions in mice

Although progenitor cells of the conducting airway have been spatially localized and some insights have been gained regarding their molecular phenotype, relatively little is known about the mechanisms regulating their maintenance, activation, and differentiation. This study investigates the potential roles of E-cadherin in mouse Clara cells, as these cells were shown to represent the progenitor/stem cells of the conducting airways and have been implicated as the cell of origin of human non-small cell lung cancer. Postnatal inactivation of E-cadherin affected Clara cell differentiation and compromised airway regeneration under injury conditions. In steady-state adult lung, overexpression of the dominant negative E-cadherin led to an expansion of the bronchiolar stem cells and decreased differentiation concomitant with canonical Wnt signaling activation. Expansion of the bronchiolar stem cell pool was associated with an incessant proliferation of neuroepithelial body.associated Clara cells that ultimately gave rise to bronchiolar hyperplasia. Despite progressive hyperplasia, only a minority of the mice developed pulmonary solid tumors, suggesting that the loss of E-cadherin function leads to tumor formation when additional mutations are sustained. The present study reveals that E-cadherin plays a critical role in the regulation of proliferation and homeostasis of the epithelial cells lining the conducting airways.

c-Myc suppressed E-cadherin through miR-9 at the post-transcriptional level

c-Myc oncoprotein is overexpressed in most human cancers and regulates different genes and pathways in different cell types. E-cadherin expression is repressed by MYC through a post-transcriptional mechanism, but the exact mechanism remains elusive. Since E-cadherin is a direct target of miR-9 and miR-9 can be activated by MYC and MYCN, this suggests that c-Myc negatively modulates E-cadherin through a microRNA pathway. We have established a c-Myc-inducible expression system in which the protein level and transcriptional activity of c-Myc is significantly upregulated upon doxycycline induction. Overexpressed c-Myc led to an EMT-like conversion in the T-REx-293 cells and resulted in a significant decrease in E-cadherin and an increase in Vimentin. Stem-loop RT-PCR showed elevated expression of miR-9 when c-Myc was induced to be overexpressed. Regarding the relationship of c-Myc, miR-9 and E-cadherin, the expression of miR-9 was curtailed by using antagomir-9 in induced overexpressing c-Myc. Restoration of E-cadherin expression became much stronger in the presence of c-Myc. Thus c-Myc represses E-cadherin at the post-transcriptional level through miR-9.

TIMP-2 modulates cancer cell transcriptional profile and enhances E-cadherin/beta-catenin complex expression in A549 lung cancer cells

Tissue Inhibitor of Metalloproteinase 2 (TIMP-2) plays an essential role in regulating matrix remodeling, cell growth, differentiation, angiogenesis and apoptosis in vitro and in vivo. We have recently shown that TIMP-2-mediated inhibition of tumor growth is independent of matrix metalloproteinase-mediated mechanisms, and is a consequence of modulating both the tumor cells and the tumor microenvironment. In the current study we aim to identify the molecular pathways associated with these effects. We analyzed the transcriptional profile of the human lung cancer cell line A549 upon overexpression of TIMP-2 and Ala+TIMP-2 (mutant that does not inhibit MMP activity), and we found changes in gene expression predominantly related to decreased tumor development and metastasis. Increased E-cadherin expression in response to both TIMP-2 and Ala+TIMP-2 expression was confirmed by real time quantitative RT-PCR and immunoblotting. A549 cells treated with epidermal growth factor (EGF) displayed loss of cobblestone morphology and cell-cell contact, while cells overexpressing TIMP-2 or Ala+TIMP-2 were resistant to EGF-induced morphological changes. Moreover, exogenous treatment with recombinant Ala+TIMP-2 blocked EGF induced down-regulation of E-cadherin. In vivo, immunohistochemistry of A549 xenografts expressing either TIMP-2 or Ala+TIMP-2 demonstrated increased E-cadherin protein levels. More importantly, transcriptional profile analysis of tumor tissue revealed critical pathways associated with effects on tumor-host interaction and inhibition of tumor growth. In conclusion, we show that TIMP-2 promotes an anti-tumoral transcriptional profile in vitro and in vivo, including upregulation of E-cadherin, in A549 lung cancer cells.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

Conditional expression of oncogenic C-RAF in mouse pulmonary epithelial cells reveals differential tumorigenesis and induction of autophagy leading to tumor regression

Here we describe a novel conditional mouse lung tumor model for investigation of the pathogenesis of human lung cancer. On the basis of the frequent involvement of the Ras-RAF-MEK-ERK signaling pathway in human non-small cell lung carcinoma (NSCLC), we have explored the target cell availability, reversibility, and cell type specificity of transformation by oncogenic C-RAF. Targeting expression to alveolar type II cells or to Clara cells, the two likely precursors of human NSCLC, revealed differential tumorigenicity between these cells. Whereas expression of oncogenic C-RAF in alveolar type II cells readily induced multifocal macroscopic lung tumors independent of the developmental state, few tumors with type II pneumocytes features and incomplete penetrance were found when targeted to Clara cells. Induced tumors did not progress and were strictly dependent on the initiating oncogene. Deinduction of mice resulted in tumor regression due to autophagy rather than apoptosis. Induction of autophagic cell death in regressing lung tumors suggests the use of autophagy enhancers as a treatment choice for patients with NSCLC.

Molecular networks that regulate cancer metastasis

Tumor metastases are responsible for approximately 90% of all cancer-related deaths. Although many patients can be cured, in the US and UK, cancer still causes 730,000 deaths every year, and it is second only to cardiovascular disease as a cause of death. The functional roles of many critical players involved in metastasis have been delineated in great detail in recent years, due to the draft of the human genome and to many associated discoveries. Here, we address several genetic events and critical factors that define the metastatic phenotype acquired during tumorigenesis. This involves molecular networks that promote local cancer-cell invasion, single-cell invasion, formation of the metastatic microenvironment of primary tumors, intravasation, lymphogenic metastasis, extravasation, and metastatic outgrowth. Altogether, these functional networks of molecules contribute to the development of a selective environment that promotes the seeding and malignant progression of tumorigenic cells in distant organs. We include here candidate target proteins and signaling pathways that are now under clinical investigation. Although many of these trials are still ongoing, they provide the basis for the development of new aspects in the treatment of metastatic cancers, which involves inhibition of these proteins and their molecular networks.

Adherens junctions and cancer

Cadherins and catenins are the central cell-cell adhesion molecules in adherens junctions (AJs). This chapter reviews the knowledge concerning the role of cadherins and catenins in epithelial cancer and examines the published literature demonstrating the changes in the expression and function of these proteins in human cancer and the association of these changes with patient outcomes. The chapter also covers the mechanistic studies aiming at uncovering the significance of changes in cadherin and catenin expression in cancer and potential molecular mechanisms responsible for the causal role of AJs in cancer initiation and progression.