Regulation of miRNA expression by Src and contact normalization: effects on nonanchored cell growth and migration

Independent effects of Src kinase and podoplanin on anchorage independent cell growth and migration

The Src tyrosine kinase is a strong tumor promotor. Over a century of research has elucidated fundamental mechanisms that drive its oncogenic potential. Src phosphorylates effector proteins to promote hallmarks of tumor progression. For example, Src associates with the Cas focal adhesion adaptor protein to promote anchorage independent cell growth. In addition, Src phosphorylates Cas to induce Pdpn expression to promote cell migration. Pdpn is a transmembrane receptor that can independently increase cell migration in the absence of oncogenic Src kinase activity. However, to our knowledge, effects of Src kinase activity on anchorage independent cell growth and migration have not been examined in the absence of Pdpn expression. Here, we analyzed the effects of an inducible Src kinase construct in knockout cells with and without exogenous Pdpn expression on cell morphology migration and anchorage independent growth. We report that Src promoted anchorage independent cell growth in the absence of Pdpn expression. In contrast, Src was not able to promote cell migration in the absence of Pdpn expression. In addition, continued Src kinase activity was required for cells to assume a transformed morphology since cells reverted to a nontransformed morphology upon cessation of Src kinase activity. We also used phosphoproteomic analysis to identify 28 proteins that are phosphorylated in Src transformed cells in a Pdpn dependent manner. Taken together, these data indicate that Src utilizes Pdpn to promote transformed cell growth and motility in complementary, but parallel, as opposed to serial, pathways.

Heterocellular N-cadherin junctions enable nontransformed cells to inhibit the growth of adjacent transformed cells

BACKGROUND

The Src tyrosine kinase phosphorylates effector proteins to induce expression of the podoplanin (PDPN) receptor in order to promote tumor progression. However, nontransformed cells can normalize the growth and morphology of neighboring transformed cells. Transformed cells must escape this process, called "contact normalization", to become invasive and malignant. Contact normalization requires junctional communication between transformed and nontransformed cells. However, specific junctions that mediate this process have not been defined. This study aimed to identify junctional proteins required for contact normalization.

METHODS

Src transformed cells and oral squamous cell carcinoma cells were cultured with nontransformed cells. Formation of heterocellular adherens junctions between transformed and nontransformed cells was visualized by fluorescent microscopy. CRISPR technology was used to produce cadherin deficient and cadherin competent nontransformed cells to determine the requirement for adherens junctions during contact normalization. Contact normalization of transformed cells cultured with cadherin deficient or cadherin competent nontransformed cells was analyzed by growth assays, immunofluorescence, western blotting, and RNA-seq. In addition, Src transformed cells expressing PDPN under a constitutively active exogenous promoter were used to examine the ability of PDPN to override contact normalization.

RESULTS

We found that N-cadherin (N-Cdh) appeared to mediate contact normalization. Cadherin competent cells that expressed N-Cdh inhibited the growth of neighboring transformed cells in culture, while cadherin deficient cells failed to inhibit the growth of these cells. Results from RNA-seq analysis indicate that about 10% of the transcripts affected by contact normalization relied on cadherin mediated communication, and this set of genes includes PDPN. In contrast, cadherin deficient cells failed to inhibit PDPN expression or normalize the growth of adjacent transformed cells. These data indicate that nontransformed cells formed heterocellular cadherin junctions to inhibit PDPN expression in adjacent transformed cells. Moreover, we found that PDPN enabled transformed cells to override the effects of contact normalization in the face of continued N-Cdh expression. Cadherin competent cells failed to normalize the growth of transformed cells expressing PDPN under a constitutively active exogenous promoter.

CONCLUSIONS

Nontransformed cells form cadherin junctions with adjacent transformed cells to decrease PDPN expression in order to inhibit tumor cell proliferation. Cancer begins when a single cell acquires changes that enables them to form tumors. During these beginning stages of cancer development, normal cells surround and directly contact the cancer cell to prevent tumor formation and inhibit cancer progression. This process is called contact normalization. Cancer cells must break free from contact normalization to progress into a malignant cancer. Contact normalization is a widespread and powerful process; however, not much is known about the mechanisms involved in this process. This work identifies proteins required to form contacts between normal cells and cancer cells, and explores pathways by which cancer cells override contact normalization to progress into malignant cancers. Video Abstract.

Epigenetic Silencing of MicroRNA-126 Promotes Cell Growth in Marek's Disease

During latency, herpesvirus infection results in the establishment of a dormant state in which a restricted set of viral genes are expressed. Together with alterations of the viral genome, several host genes undergo epigenetic silencing during latency. These epigenetic dysregulations of cellular genes might be involved in the development of cancer. In this context, Gallid alphaherpesvirus 2 (GaHV-2), causing Marek’s disease (MD) in susceptible chicken, was shown to impair the expression of several cellular microRNAs (miRNAs). We decided to focus on gga-miR-126, a host miRNA considered a tumor suppressor through signaling pathways controlling cell proliferation. Our objectives were to analyze the cause and the impact of miR-126 silencing during GaHV-2 infection. This cellular miRNA was found to be repressed at crucial steps of the viral infection. In order to determine whether miR-126 low expression level was associated with specific epigenetic signatures, DNA methylation patterns were established in the miR-126 gene promoter. Repression was associated with hypermethylation at a CpG island located in the miR-126 host gene epidermal growth factor like-7 (EGFL-7). A strategy was developed to conditionally overexpress miR-126 and control miRNAs in transformed CD4+ T cells propagated from Marek’s disease (MD) lymphoma. This functional assay showed that miR-126 restoration specifically diminishes cell proliferation. We identified CT10 regulator of kinase (CRK), an adaptor protein dysregulated in several human malignancies, as a candidate target gene. Indeed, CRK protein levels were markedly reduced by the miR-126 restoration.

Environmental control of mammary carcinoma cell expansion by acidification and spheroid formation in vitro

Breast cancer is the leading cause of cancer death among women worldwide. Like other cancers, mammary carcinoma progression involves acidification of the tumor microenvironment, which is an important factor for cancer detection and treatment strategies. However, the effects of acidity on mammary carcinoma cell morphology and phenotype have not been thoroughly characterized. Here, we evaluated fundamental effects of environmental acidification on mammary carcinoma cells in standard two-dimensional cultures and three-dimensional spheroids. Acidification decreased overall mammary carcinoma cell viability, while increasing their resistance to the anthracycline doxorubicin. Environmental acidification also increased extracellular vesicle production by mammary carcinoma cells. Conditioned media containing these vesicles appeared to increase fibroblast motility. Acidification also increased mammary carcinoma cell motility when cultured with fibroblasts in spheroids. Taken together, results from this study suggest that environmental acidification induces drug resistance and extracellular vesicle production by mammary carcinoma cells that promote tumor expansion.

Downregulation of microRNA-126 is inversely correlated with insulin receptor substrate-1 protein expression in colorectal cancer and is associated with advanced stages of disease

Colorectal cancer (CRC) is a common human malignant tumor, and the fourth most common cause of cancer-associated mortality in China. However, the pathogenesis of CRC is not yet fully understood. The present study aimed to investigate the expression and clinical significance of microRNA (miR)-126 and insulin receptor substrate-1 (IRS-1), as well as the role of miR-126 in the prognosis of patients with CRC. A total of 86 colorectal tissue specimens, including 40 CRC and adjacent normal tissue, 26 colorectal adenoma tissue and 20 normal colorectal tissue samples, were collected for the present study. Reverse transcription-quantitative PCR analysis was performed to determine miR-126 and IRS-1 mRNA expression levels, while western blotting and immunohistochemistry (IHC) analyses were performed to determine IRS-1 protein expression levels. The correlation between miR-126 and IRS-1 expression, as well as the association between altered miR-126 and IRS-1 expression levels and clinicopathological characteristics, and the overall survival time of patients with CRC were assessed. The results demonstrated that miR-126 expression was significantly downregulated, while IRS-1 protein expression was upregulated in CRC tissues compared with that in adjacent normal tissues, colorectal adenoma tissues and normal colorectal tissues, respectively. IHC analysis exhibited strong positive staining of IRS-1 protein in CRC tissues, while absent or weak staining of IRS-1 protein was detected in adjacent normal tissues, colorectal adenoma tissues and normal colorectal tissues. miR-126 expression was inversely correlated with IRS-1 protein expression in CRC tissues (r=−0.420; P<0.05). Furthermore, downregulated miR-126 expression was associated with advanced clinicopathological characteristics of the disease and a shorter overall survival time in patients with CRC. Taken together, the results of the present study suggest that miR-126 downregulation may be a candidate molecular marker predictive of poor prognosis of patients with CRC.

MicroRNA-126 Inhibit Viability of Colorectal Cancer Cell by Repressing mTOR Induced Apoptosis and Autophagy

OBJECTIVE

Colorectal cancer (CRC) is a fatal disease, and tumor development is a complex cellular event involving a multistep cascade process involving proliferation, invasion, and migration. In recent years, it has been shown that microRNA-126 (miR-126) plays a key role in the tumorigenesis of CRC, but further studies are required to investigate the regulatory mechanisms through which this miRNA affects cell viability, autophagy, and apoptosis in CRC. We aimed to study the effect of miR-126 in gene regulation in CRC HCT116 cells.

METHODS

CRC biopsy samples and normal colorectal tissue samples were used for miRNA profiling. Real-time quantitative PCR and WB were utilized to detect RNA and protein levels. MTT and colony formation assays were performed to examine cell viability. Furthermore, an immunofluorescence assay and Annexin V/PI flow cytometry were performed to detect autophagy and apoptosis, respectively.

RESULTS

The expression of miR-126 was downregulated in CRC biopsies and cell lines compared with that in normal cells and tissues. The upregulation of miR-126 resulted in impaired viability and growth of CRC cells. Furthermore, with the overexpression of miR-126, cell autophagy was increased, as evidenced by LC3-I/II transformation and p62 degradation. Meanwhile, apoptosis induction was also observed because of the increased miR-126 levels. The autophagy inhibitor Bafilomycin A1 (BafA1) repressed both autophagy and apoptosis, indicating that miR-126 induced autophagy was responsible for the induction of apoptosis. A dual-luciferase reporter assay (DLRA) and bioinformatics prediction revealed that miR-126 silenced the mTOR gene by targeting the 3'-UTR. mTOR mRNA levels in CRC biopsy tissues and cell lines were upregulated to a greater extent than that in normal cells and tissues. Furthermore, HCT116 cells transfected with an miR-126 mimic showed a decreased expression of mTOR. In addition, the overexpression of mTOR counteracted miR-126 on autophagy and apoptosis.

CONCLUSION

Our study demonstrated that miR-126-induced can regulate the activity of CRC cells via autophagy and apoptosis and suggested a new mechanism of miR-126-mTOR interaction in CRC pathogenesis.

AGO2 phosphorylation by c-Src kinase promotes tumorigenesis

Numerous studies have reported that c-Src is highly expressed with high tyrosine kinase activity in a variety of tumors. However, it remains unclear whether c-Src contributes to the miRNA pathway. Here, we report that c-Src can interact with and phosphorylate AGO2, a core component of RISC complex, at tyr 393, tyr 529 and tyr749. Mechanistically, it is confirmed that c-Src phosphorylation of AGO2 at tyr393 reduces its binding to DICER, thereby suppressing the maturation of long-loop pre-miR-192. However, the other two phosphorylation sites don’t work on this function. Significantly, Ectopic expression of wild-type AGO2, but not the three tyrosine site mutants, has an obvious tumor-promoting effect in vitro and in vivo, which function could be blocked thoroughly by treatment with c-Src kinase inhibitor, Saracatinib. Our findings identify AGO2 as c-Src target and c-Src phosphorylation of AGO2 may therefore play a potential role during tumor progress.

Regulation of expression of microRNAs by DNA methylation in lung cancer

Differential expression of miRNAs has been linked with lung carcinogenesis. Recent studies have indicated that DNA hypermethylation can lead to silencing of tumor suppressor miRNA-encoding genes. Restoration of tumor suppressor miRNAs using inhibitors of DNA methyltransferases has been shown to suppress cell proliferation, angiogenesis, invasion and metastasis implying that modulation of methylation of specific miRNAs can be used as novel therapeutic targets in lung cancer. In this review, we highlight tremendous progress which has been made in the identification of methylation-mediated silencing of miRNAs and their contribution in lung carcinogenesis along with the clinical utility of methylated miRNAs.

Mechanisms of environmental chemicals that enable the cancer hallmark of evasion of growth suppression

As part of the Halifax Project, this review brings attention to the potential effects of environmental chemicals on important molecular and cellular regulators of the cancer hallmark of evading growth suppression. Specifically, we review the mechanisms by which cancer cells escape the growth-inhibitory signals of p53, retinoblastoma protein, transforming growth factor-beta, gap junctions and contact inhibition. We discuss the effects of selected environmental chemicals on these mechanisms of growth inhibition and cross-reference the effects of these chemicals in other classical cancer hallmarks.

Regulation of RPTPα-c-Src signalling pathway by miR-218

Receptor protein tyrosine phosphatase alpha (RPTPα), an activator of Src family kinases, is found significantly overexpressed in human cancer tissues. However, little is known about the regulation of RPTPα expression. miRNAs target multiple genes and play important roles in many cancer processes. Here, we identified a miRNA, miR-218 that binds directly to the 3'-UTR of RPTPα. Ectopic overexpression of miR-218 decreased RPTPα protein leading to decreased dephosphorylation of c-Src and decreased tumour growth in vitro and in vivo. A feedback loop between c-Src and miR-218 was revealed where c-Src inhibits transcription of SLIT2, which intronically hosts miR-218. These results show a novel regulatory pathway for RPTPα-c-Src signalling.

MicroRNAs as the fine-tuners of Src oncogenic signalling

The cellular Src (c-Src) tyrosine kinase is upregulated and believed to play a pivotal role in various human cancers. However, the molecular mechanism underlying c-Src-mediated tumour progression remains elusive. Recent studies have revealed that several microRNAs (miRNAs) function as tumour suppressors by regulating the malignant expression of signalling molecules. Aberrant expression of miRNAs is frequently observed in human cancers and should be exploited to seek related molecular targets. In this review, we focus on miRNAs found to be involved in Src signalling in various cancers. We summarize recent findings on Src-related miRNAs, their target genes, mechanisms behind their interplay and their implications for cancer therapeutics.

MicroRNA-224 targets ERG2 and contributes to malignant progressions of meningioma

MicroRNA-224 is overexpressed in various malignant tumors with poor prognosis, which plays a critical role in biological processes including cell proliferation, apoptosis and several developmental and physiological progressions. However, the potential association between miR-224 and clinical outcome in patients with meningiomas remains unknown. Here, we investigate miR-224 expression and biological functions in meningiomas. MiR-224 expression was measured by Northern blot analysis and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in meningioma and normal brain tissues. Kaplan-Meier analysis and Cox regression analysis were used to exam its correlation with clinicopathological features and prognostic value. The biological effects of miR-224 on the cell proliferation and apoptosis in meningioma cells were examined by MTT assay and apoptosis assay. We found the expression levels of miR-224 were significantly higher in meningioma tissues than that in normal brain, positively correlated with advanced pathological grade. Kaplan-Meier analysis indicated that meningioma patients with low miR-224 expression exhibited significantly prolonged overall and recurrence-free survival. Furthermore, we demonstrated that ERG2 was an identical candidate target gene of MiR-224 in vitro. Our results indicated that downregulation of miR-224 suppressed cell growth and resulted in the enhancement of cell apoptosis through activation of the ERG2-BAK-induced apoptosis pathway. Our findings imply the miR-224 expression could predict the overall survival and recurrence-free survival of patients with meningioma and it might be a promising therapeutic target for treating malignant meningiomas.

The role of microRNA in castration-resistant prostate cancer

INTRODUCTION

Castration-resistant prostate cancer (CRPC) has a historically low median survival rate, but recent advances and discoveries in microRNAs (miRNAs) have opened the potential for new prognostication modalities to enhance therapeutic success. As new chemotherapies and immunotherapies are developed, there is an increasing need for precision and stratification of CRPC to allow for optimization and personalization of therapy.

METHODS

A systematic literature review was conducted via electronic database resulting in the selection of 42 articles based on title, abstract, study format, and content by a consensus of all participating authors. Most selected articles were published between 2002 and 2013. In this review, we discuss the robustness of miRNAs as a biomarker platform, miRNAs associated with prostate cancer, and recent discoveries of miRNA associations with CRPC.

RESULTS

The associations discovered have been of interest owing to the ability to differentiate between CRPC and localized prostate cancer. With the evaluation of multiple miRNAs, it is possible to provide a profile regarding tumor characteristics. Furthermore, actions of miRNAs on CRPC tumor cells have the ability to suppress metastatic phenotypes.

CONCLUSION

miRNAs may have a growing role in CRPC prognostication and may potentially transform into a therapeutic potential.

miR-224 overexpression is a strong and independent prognosticator of short-term relapse and poor overall survival in colorectal adenocarcinoma

Colorectal adenocarcinoma constitutes the most frequent form of colorectal cancer and a serious cause of cancer-related deaths. The expression of multiple miRNAs, including miR-224, is deregulated in colorectal adenocarcinoma. The aim of this study was the investigation of the prognostic value of miR-224 in colorectal adenocarcinoma. For this purpose, total RNA was isolated from 115 colorectal adenocarcinomas and 66 adjacent non-cancer mucosae. Total RNA (2 µg) was polyadenylated and reverse transcribed. A quantitative PCR method based on SYBR-Green chemistry was developed and applied for the quantification of miR-224 levels, followed by extensive biostatistical analysis. miR-224 levels in malignant colorectal adenocarcinomas ranged between 1.81 and 187.75 RQU (miR-224 copies/1,000 SNORD48 copies) with a median of 34.27, and were significantly elevated, compared to miR-224 levels in adjacent non-cancer mucosae (p<0.001). Enhanced miR-224 expression constitutes a rather strong prognosticator in colorectal adenocarcinoma, predicting short-term relapse and poor overall survival in these patients (p=0.012 and p=0.005, respectively), independent of established clinicopathological parameters. In conclusion, miR-224 is significantly upregulated in malignant colorectal tumors compared to adjacent non-cancer mucosae, and its enhanced expression constitutes an independent predictor of short-term relapse and poor overall survival in colorectal adenocarcinoma patients.

Crk at the quarter century mark: perspectives in signaling and cancer

The Crk adaptor protein, discovered 25 years ago as the transforming gene (v-crk) product encoded by the CT10 avian retrovirus, has made a great impact on the field of signal transduction. By encoding an oncoprotein that contained a viral gag protein fused to only SH2 and SH3 domains, v-Crk demonstrated the significance of SH2 and SH3 domains in oncogenic signaling by their virtue of binding in a sequence-specific context to organize and assemble protein networks. In more recent years, the cellular homologs of Crk (Crk II, Crk I, and CrkL) have been extensively studied, and shown to have critical functions in a wide spectrum of biological and pathological processes that include cell motility, invasion, survival, bacterial pathogenesis, and the efferocytosis of apoptotic cells. Clinically, Crk proteins are implicated in the aggressive behavior of human cancers, including adenocarcinomas of the lung, breast, and stomach, as well as in sarcomas and gliomas. Over-expression of Crk proteins in human cancers has led to a renewed interest in both their signal transduction pathways and mechanisms of up-regulation. This prospect summarizes recent developments in Crk biology, including new structural and biochemical roles for the atypical carboxyl-terminal SH3 (SH3C) domain, revelations regarding the molecular differences between Crk II and Crk L, and the significance of Crk expression in stratified human tumor samples.

A molecular signaling map and its application

Cancer research over the past decades has revealed a number of molecular, biochemical, and cellular events that reflect progressive transformation of normal human cells into their malignant derivatives. These findings help to better understand the complexity of human tumorigenesis. In our study, molecular information is organized to chart a comprehensive map of the signaling network for human cancer. It includes transcriptional and translational regulation and diverse feedback-control loops. It is demonstrated that applying this signaling network map allows predicting the effect of targeted therapy before it can be applied into practice to reduce clinical trial risks. Hence, the proposed map with prognosticating potential effect might become part of drug discovery programs for targeted therapy. Applied in individual patient care it helps to reduce the current reliance of cancer treatment on chemotherapies with low therapeutic indices. This study also demonstrates that continuing elucidation of tumorigenesis will not only need heterotypic organ culture systems in vitro and increasingly refined animal models in vivo, but also computationally calculable virtual cell models in silico.

Suppressive effect of microRNA-126 on oral squamous cell carcinoma in vitro

MicroRNA-126 (miR-126), an endothelial-specific miRNA located within intron 7 of epidermal growth factor‑like domain 7 (EGFL7), has been demonstrated to act as a tumor suppressor in various types of human cancer. However, its role in oral squamous cell carcinoma (OSCC) remains unclear. In the present study, we revealed that the expression of miR-126 was significantly decreased in OSCC tissues, when compared with that in their matched adjacent tissues, and its expression level was also reduced in Tca8113, OSCC-15 and CAL27 cell lines compared with normal tissues. The protein expression of EGFL7 was upregulated in OSCC tissues compared with their matched adjacent tissues as well as normal tissues, and Tca8113, OSCC-15 and CAL27 cells additionally demonstrated a positive expression of EGFL7. The overexpression of miR-126 significantly reduced the protein expression of EGFL7 in OSCC-15 cells, while transfection with the miR-126 inhibitor upregulated the EGFL7 protein level in OSCC-15 cells. Furthermore, transfection with an miR-126 mimic into OSCC-15 cells markedly suppressed cell proliferation, cell cycle progression, cell invasion and colony formation, while inducing cell apoptosis, which contrasted with the effects of transfection with an miR-126 inhibitor. The overexpression of miR-126 suppressed the secretion of two key regulators of angiogenesis, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), which was also reversed by miR-126 inhibitor transfection. In conclusion, the present study demonstrated that miR-126 acts as a tumor suppressor in OSCC cells, partially at least via the downregulation of EGFL7. Thus, miR-126 may serve as a promising candidate for the treatment of OSCC.

MicroRNA-224 suppresses colorectal cancer cell migration by targeting Cdc42. Dis Markers. 2014;2014:617150. [PMID: 24817781 PMCID: PMC4004168 DOI: 10.1155/2014/617150]

The metastatic spread of tumor cells is the major risk factor affecting the clinical prognosis of colorectal cancer (CRC) patients. The metastatic phenotype can be modulated by dysregulating the synthesis of different structural and functional proteins of tumor cells. Micro(mi)RNAs are noncoding RNAs that recognize their cognate messenger (m)RNA targets by sequence-specific interactions with the 3′ untranslated region and are involved in the multistep process of CRC development. The objective of this study was to investigate the expression and biological roles of miR-224 in CRC. The miR-224 expression level was assessed by a quantitative real-time PCR in 79 CRC and 18 nontumor tissues. Expression levels of miR-224 in CRC tissues were significantly lower than those in nontumor tissues. Its expression level was associated with the mutation status of the APC gene. Ectopic expression of miR-224 suppressed the migratory ability of CRC cell line, but cell proliferation was less affected. Increased miR-224 diminished Cdc42 and SMAD4 expressions at both the protein and mRNA levels and inhibited the formation of actin filaments. Overall, this study indicated a role of miR-224 in negatively regulating CRC cell migration. The expression level of miR-224 may be a useful predictive biomarker for CRC progression.

Prometastatic GPCR CD97 is a direct target of tumor suppressor microRNA-126

Tumor suppressor microRNA-126 (miR-126) is often down-regulated in cancer cells, and its overexpression is found to inhibit cancer metastasis. To elucidate the mechanism of tumor suppression by miR-126, we analyzed the proteomic response to miR-126 overexpression in the human metastatic breast cancer cell line MDA-MB-231. To acquire quantitative, time-resolved information, we combined two complementary proteomic methods, BONCAT and SILAC. We discovered a new direct target of miR-126: CD97, a pro-metastatic G-protein-coupled receptor (GPCR) that has been reported to promote tumor cell invasion, endothelial cell migration, and tumor angiogenesis. This discovery establishes a link between down-regulation of miR-126 and overexpression of CD97 in cancer and provides new mechanistic insight into the role of miR-126 in inhibiting both cell-autonomous and non-cell-autonomous cancer progression.

miR-218 regulates focal adhesion kinase-dependent TGFβ signaling in fibroblasts

Unlike other tissues in the body, the oral cavity does not scar. Myofibroblasts are the essential cell type in scar tissue formation; gingival fibroblasts are relatively unable to differentiate into myofibroblasts in response to TGFβ. This differential response is attributed to the relative lack of miR-218 in gingival fibroblasts.

Scarring, which occurs in essentially all adult tissue, is characterized by the excessive production and remodeling of extracellular matrix by α-smooth muscle actin (SMA)–expressing myofibroblasts located within connective tissue. Excessive scarring can cause organ failure and death. Oral gingivae do not scar. Compared to dermal fibroblasts, gingival fibroblasts are less responsive to transforming growth factor β (TGFβ) due to the reduced expression, due to the reduced expression and activity of focal adhesion kinase (FAK) by this cell type. Here we show that, compared with dermal fibroblasts, gingival fibroblasts show reduced expression of miR-218. Introduction of pre–miR-218 into gingival fibroblasts elevates FAK expression and, via a FAK/src-dependent mechanism, results in the ability of TGFβ to induce α-SMA. The deubiquitinase cezanne is a direct target of miR-218 and has increased expression in gingival fibroblasts compared with dermal fibroblasts. Knockdown of cezanne in gingival fibroblasts increases FAK expression and causes TGFβ to induce α-smooth muscle actin (α-SMA). These results suggest that miR-218 regulates the ability of TGFβ to induce myofibroblast differentiation in fibroblasts via cezanne/FAK.

MicroRNA-224 inhibits progression of human prostate cancer by downregulating TRIB1

Our previous microarray data showed that microRNA-224 (miR-224) was downregulated in human prostate cancer (PCa) tissues compared with adjacent benign tissues. However, the underlying mechanisms by which miR-224 is involved in PCa remain unclear. In this study, we identified TRIB1 as a target gene of miR-224. Forced expression of miR-224 suppressed PCa cell proliferation, invasion and migration, and promoted cell apoptosis by downregulating TRIB1. Moreover, the expression level of miR-224 in PCa tissues was negatively correlated with that of TRIB1. miR-224 downregulation was frequently found in PCa tissues with metastasis, higher PSA level and clinical stage, whereas TRIB1 upregulation was significantly associated with metastasis. Both miR-224 downregulation and TRIB1 upregulation were significantly associated with poor biochemical recurrence-free survival of patients with PCa. In conclusion, these findings reveal that the aberrant expression of miR-224 and TRIB1 may promote PCa progression and have potentials to serve as novel biomarkers for PCa prognosis.

MicroRNA-224 targets SMAD family member 4 to promote cell proliferation and negatively influence patient survival

MicroRNA-224 (miR-224) is frequently over-expressed in liver and colorectal cancers. We and others have previously described the role of miR-224 over-expression in cell proliferation in vitro but we have yet to identify the relevant miR-224 direct target. In this study, we further demonstrated that miR-224 up-regulation promotes cell proliferation using both in vitro assays and in vivo tumor growth models. We systematically screened for high confidence miR-224 targets by overlapping in silico predicted targets from multiple algorithms and significantly down-regulated genes in miR-224-expressing cells from whole genome expression microarrays. A total of 72 high confidence miR-224 targets were identified and found to be enriched in various cancer-related processes. SMAD family member 4 (SMAD4) is experimentally validated as the direct cellular target through which miR-224 promotes cell proliferation. The clinical relevance of our experimental observations was supported by a statistically significant inverse correlation between miR-224 and SMAD4 transcript expression in tumor versus paired adjacent non-tumorous tissues from HCC patients (p<0.001, r = −0.45, R² = 0.122). Furthermore, miR-224 up-regulation and SMAD4 down-regulation is significantly associated with poorer patient survival (p<0.05). In summary, miR-224/SMAD4 pathway is a clinically relevant pathway to provide new insights in understanding HCC. (191 words).

miR-30 as a tumor suppressor connects EGF/Src signal to ERG and EMT

Src tyrosine kinase (Src) is implicated in the development of bone metastasis and castration resistance of prostate cancer. Src inhibitors are currently being tested in clinical trials for such diseases. Understanding the molecular and cellular actions of Src inhibitors holds the key to future improvement of this line of therapy. Here we describe the microRNA expression profiles modulated by two Src inhibitors and demonstrate that the miR-30 family members are the most prominently induced species. Consistent with its tumor suppressor role, miR-30 is downmodulated by oncogenic signals such as epidermal growth factor (EGF) and hepatocyte growth factor, and is generally underexpressed in prostate cancer specimens. A number of epithelial-to-mesenchymal transition (EMT)-associated genes are predicted targets of miR-30. Among these genes the Ets-related gene (ERG) is the most frequently overexpressed oncogene in prostate cancer activated by genomic fusion events between promoter upstream sequences of the TMPRSS2 and coding sequences of ERG. We showed by ERG 3' untranslated region reporter and mutagenesis assays that ERG is a direct target of miR-30. Overexpression of miR-30 in prostate cancer cells suppresses EMT phenotypes and inhibits cell migration and invasion. It also inhibits the in vitro and in vivo growth of VCaP cells, which depends on TMPRSS2-ERG for proliferation. TMPRSS2-ERG is generally regulated by androgen at the transcriptional level. Our finding reveals a new post-transcriptional mechanism of TMPRSS2-ERG regulation by Src and growth signals via miR-30 providing a rationale for targeting ERG-positive castration-resistant tumors with Src inhibitors.

Beyond steroidogenesis: novel target genes for SF-1 discovered by genomics

Steroidogenic Factor-1 (SF-1) is a nuclear receptor transcription factor that has an essential role in the development of adrenal glands and gonads and in the regulation of steroidogenic gene expression. Recent studies using genomic approaches have revealed that SF-1 also has an important role in regulating proliferation of adrenocortical cells and have revealed its role in the control of a variety of biological processes as diverse as angiogenesis, adhesion to the extracellular matrix, cytoskeleton dynamics, transcriptional and post-transcriptional regulation of gene expression and apoptosis in the adrenal cortex. The identification of the complete set of SF-1 target genes will be of great importance to open new avenues for therapeutic intervention in adrenal diseases.

Role of microRNAs in breast cancer

MicroRNAs (miRNAs) are a class of post-transcriptional gene regulators with critical functions in normal cellular processes as well as disease processes. They are small molecules with 18~23 nucleotides in length. Since their early discovery in 1993, a large number of miRNAs have been characterized and analyzed to understand their pivotal role and their impact in a myriad of biological processes. Substantial research on miRNA highlights the involvement of these tiny RNAs in the etiopathogenesis of a variety of human diseases such as cancer, neuro-degenerative disorders, diabetes, cardiac hypertrophy and respiratory diseases. In this review, we update on recent advances of the emerging role of miRNAs in breast cancer and their clinical implications.

Up-regulation of microRNA-126 may contribute to pathogenesis of ulcerative colitis via regulating NF-kappaB inhibitor IκBα. PLoS One. 2012;7:e52782. [PMID: 23285182 PMCID: PMC3532399 DOI: 10.1371/journal.pone.0052782]

Background

MicroRNAs (miRNAs) are important post-transcriptional regulators. Altered expression of miRNAs has recently demonstrated association with human ulcerative colitis (UC). In this study, we attempted to elucidate the roles of miR-126 in the pathogenesis of UC.

Methods

Expression of miR-126, miR-21, miR-375 and the potential targets NF-κB inhibitor alpha (IκBα, IKBA or NFKBIA), Polo-like kinase 2 (PLK2) and v-Crk sarcoma virus CT10 oncogene homolog (CRK) were assessed in 52 colonic biopsies from patients with active UC, inactive UC, irritable bowel syndrome (IBS) and from healthy subjects by quantitative RT-PCR and immunofluorescence analyses. Regulation of gene expression by miR-126 was assessed using luciferase reporter construct assays and specific miRNA mimic transfection.

Results

We found that the expression of miR-126 and miR-21 were significantly increased in active UC group compared to the inactive UC, IBS and healthy control groups (P<0.05). In contrast, the expression of IKBA mRNA and protein was remarkably decreased in the active UC group compared with the other three groups (P<0.05). The expression of miR-126 and IKBA mRNA were inversely correlated in active UC patients (P<0.05). However the expression of miR-375, PLK2 and CRK showed no difference between each group. Furthermore, we demonstrate that endogenous miR-126 and exogenous miR-126 mimic can inhibit IκBα expression. Finally, mutating the miR-126 binding site of the IKBA 3′-UTR reporter construct restored reporter gene expression.

Conclusion

miR-126 may play roles in UC inflammatory activity by down-regulating the expression of IKBA, an important inhibitor of NF-κB signaling pathway.

Upregulation of microRNA-224 confers a poor prognosis in glioma patients

OBJECTIVE

MicroRNA-224 (miR-224) has been consistently reported to be dysregulated in various human malignancies and can potentially affect many cancer-related cellular processes, including transcription, cell differentiation, cell death, growth, and cell proliferation. However, its roles in human glioma have not been reported. The aim of this study was to explore the expression pattern, clinical significance, and prognostic value of miR-224 in glioma patients using large cohorts.

METHODS

Quantitative real-time polymerase chain reaction analysis was used to characterize the expression patterns of miR-224 in 108 glioma and 20 normal brain tissues. The associations of miR-224 expression with clinicopathological factors and prognosis of glioma patients were also statistically analyzed.

RESULTS

miR-224 expression is significantly upregulated in glioma tissues compared with normal brain tissues (P < 0.001). In addition, high expression of miR-224 was significantly associated with advanced pathological grade (P = 0.006) and low Karnofsky performance score (KPS, P = 0.01). Moreover, Kaplan-Meier survival analysis showed that high miR-224 expression group had significantly shorter disease-free survival (DFS) and overall survival (OS) rates than low miR-224 expression group (both P < 0.001). Multivariate analysis with the Cox's proportional hazards model revealed that high expression of miR-224 (P = 0.006 and P = 0.01, respectively) and advanced pathological grade (both P = 0.02) were independent factors for shorter DFS and OS. Furthermore, subgroup analyses showed that miR-224 expression was significantly associated with poor DFS and OS in glioma patients with high pathological grades (for grade III-IV: P < 0.001 and P = 0.005, respectively).

CONCLUSIONS

MiR-224 is upregulated and confers a poor prognosis in glioma patients.

SRC points the way to biomarkers and chemotherapeutic targets

The role of Src in tumorigenesis has been extensively studied since the work of Peyton Rous over a hundred years ago. Src is a non-receptor tyrosine kinase that plays key roles in signaling pathways controlling tumor cell growth and migration. Src regulates the activities of numerous molecules to induce cell transformation. However, transformed cells do not always migrate and realize their tumorigenic potential. They can be normalized by surrounding nontransformed cells by a process called contact normalization. Tumor cells need to override contact normalization to become malignant or metastatic. In this review, we discuss the role of Src in cell migration and contact normalization, with emphasis on Cas and Abl pathways. This paradigm illuminates several chemotherapeutic targets and may lead to the identification of new biomarkers and the development of effective anticancer treatments.

Downregulation and prognostic performance of microRNA 224 expression in prostate cancer

INTRODUCTION

The extensive use of prostate-specific antigen as a general prostate cancer biomarker has introduced the hazards of overdiagnosis and overtreatment. Recent studies have revealed the immense biomarker capacity of microRNAs (miRNAs) in prostate cancer. The aim of this study was to analyze the expression pattern of miR-224, a cancer-related miRNA, in prostate tumors and investigate its clinical utility.

METHODS

Total RNA was isolated from 139 prostate tissue samples. After the polyadenylation of total RNA by poly(A) polymerase, cDNA was synthesized with a suitable poly(T) adapter. miR-224 expression was assessed by quantitative real-time PCR and analyzed with the comparative quantification cycle method, C(q)(2(-ΔΔCq)). We performed comprehensive biostatistical analyses to explore the clinical value of miR-224 in prostate cancer.

RESULTS

miR-224 expression was significantly downregulated in malignant samples compared with benign samples (P < 0.001). Higher miR-224 expression levels were found in prostate tumors that were less aggressive (P = 0.017) and in an earlier disease stage (P = 0.018). Patients with prostate cancer who were positive for miR-224 had significantly enhanced progression-free survival intervals compared with miR-224-negative patients (P = 0.021). Univariate bootstrap Cox regression confirmed that miR-224 was associated with favorable prognosis (hazard ratio 0.314, P = 0.013); nonetheless, multivariate analysis, adjusted for conventional markers, did not identify miR-224 as an independent prognostic indicator.

CONCLUSIONS

miR-224 is aberrantly expressed in prostate cancer. Its assessment by cost-effective quantitative molecular methodologies could provide a useful biomarker for prostate cancer.

Identification of differentially expressed microRNAs and the possible role of miRNA-126* in Sprague-Dawley rats during fetal lung development

The aim of this study was to conduct a search for microRNAs (miRNAs) that are significant in fetal lung develop-ment to lay a foundation for further studies in the relevant fields. In this study, histological observation was performed in rats by hematoxylin and eosin (H&E) staining at three time points of fetal lung development [Embryo 21 (E21), E19 and E16, and designated as groups S1, S2 and S3, respectively]. An expression profile for fetal lung development was determined using the latest microarray technology. Furthermore, certain differentially expressed miRNAs were selected for further study by real‑time PCR. In total, 202 differentially expressed miRNAs were identified. Among them, miRNA-126* was selected for further study and validated by real-time PCR due to its higher expression levels in the microarrays. The results revealed that the relative expression of miRNA-126* differentially increased as embyronic development increased (P<0.05), which was consistent with the microarray results. In conclusion, we hypothesize that these newly identified miRNAs (including miRNA-126*) may be important in the physiological mechanisms during fetal lung development. These results may aid future studies of neonatal lung development.

MMSET stimulates myeloma cell growth through microRNA-mediated modulation of c-MYC

Multiple myeloma (MM) represents the malignant proliferation of terminally differentiated B cells, which, in many cases, is associated with the maintenance of high levels of the oncoprotein c-MYC. Overexpression of the histone methyltransferase MMSET (WHSC1/NSD2), due to t(4;14) chromosomal translocation, promotes the proliferation of MM cells along with global changes in chromatin; nevertheless, the precise mechanisms by which MMSET stimulates neoplasia remain incompletely understood. We found that MMSET enhances the proliferation of MM cells by stimulating the expression of c-MYC at the post-transcriptional level. A microRNA (miRNA) profiling experiment in t(4;14) MM cells identified miR-126* as an MMSET-regulated miRNA predicted to target c-MYC mRNA. We show that miR-126* specifically targets the 3'-untranslated region (3'-UTR) of c-MYC, inhibiting its translation and leading to decreased c-MYC protein levels. Moreover, the expression of this miRNA was sufficient to decrease the proliferation rate of t(4;14) MM cells. Chromatin immunoprecipitation analysis showed that MMSET binds to the miR-126* promoter along with the KAP1 corepressor and histone deacetylases, and is associated with heterochromatic modifications, characterized by increased trimethylation of H3K9 and decreased H3 acetylation, leading to miR-126* repression. Collectively, this study shows a novel mechanism that leads to increased c-MYC levels and enhanced proliferation of t(4;14) MM, and potentially other cancers with high MMSET expression.

miRNA-218 contributes to the regulation of D-glucuronyl C5-epimerase expression in normal and tumor breast tissues

microRNAs (miRNAs) are key posttranscriptional regulators of gene expression. In the present study, regulation of tumor-suppressor gene D-glucuronyl C5-epimerase (GLCE) by miRNA-218 was investigated. Significant downregulation of miRNA-218 expression was shown in primary breast tumors. Exogenous miRNA-218/anti-miRNA-218 did not affect GLCE mRNA but regulated GLCE protein level in MCF7 breast carcinoma cells in vitro. Comparative analysis showed a positive correlation between miRNA-218 and GLCE mRNA, and negative correlation between miRNA-218 and GLCE protein levels in breast tissues and primary tumors in vivo, supporting a direct involvement of miRNA-218 in posttranscriptional regulation of GLCE in human breast tissue. A common scheme for the regulation of GLCE expression in normal and tumor breast tissues is suggested.

Plant lectin can target receptors containing sialic acid, exemplified by podoplanin, to inhibit transformed cell growth and migration

Cancer is a leading cause of death of men and women worldwide. Tumor cell motility contributes to metastatic invasion that causes the vast majority of cancer deaths. Extracellular receptors modified by α2,3-sialic acids that promote this motility can serve as ideal chemotherapeutic targets. For example, the extracellular domain of the mucin receptor podoplanin (PDPN) is highly O-glycosylated with α2,3-sialic acid linked to galactose. PDPN is activated by endogenous ligands to induce tumor cell motility and metastasis. Dietary lectins that target proteins containing α2,3-sialic acid inhibit tumor cell growth. However, anti-cancer lectins that have been examined thus far target receptors that have not been identified. We report here that a lectin from the seeds of Maackia amurensis (MASL) with affinity for O-linked carbohydrate chains containing sialic acid targets PDPN to inhibit transformed cell growth and motility at nanomolar concentrations. Interestingly, the biological activity of this lectin survives gastrointestinal proteolysis and enters the cardiovascular system to inhibit melanoma cell growth, migration, and tumorigenesis. These studies demonstrate how lectins may be used to help develop dietary agents that target specific receptors to combat malignant cell growth.

Loss of miR-126 is crucial to pancreatic cancer progression

The tumor-suppressor miRNA 126 (miR-126) is downregulated in many tumors and has recently been placed at the heart of complex metastatic pathways. Hamada and colleagues have identified miR-126 as being downregulated in pancreatic ductal adenocarcinoma (PDAC) patient samples and cell lines. The protein ADAM9 has been implicated in the progression of various solid tumors including PDAC. ADAM9 is overexpressed in PDAC and also a direct target of miR-126. The miR-126/ADAM9 axis was subsequently established to control migration and invasion in PDAC, as well as reversal of epithelial-to-mesenchymal transition. miR-126 is also known to target other crucial oncogenes in PDAC such as KRAS and CRK. Replacing miR-126 in PDAC patients may be a novel strategy for preventing progression and metastasis.

miR-126 enhances the sensitivity of non-small cell lung cancer cells to anticancer agents by targeting vascular endothelial growth factor A

Increasing evidence suggests that hsa-miR-126 (miR-126) is down-regulated in non-small cell lung cancer (NSCLC) cell lines and the restoration of miR-126 impairs tumor cell proliferation, migration, invasion, and survival by targeting specific molecules. Here, we reported for the first time that miR-126 was involved in regulating the response of NSCLC cells to cancer chemotherapy. After transfected A549 cells with miR-126 mimic or inhibitor, we found that an elevated level of miR-126 was significantly associated with a decreased half maximal inhibitory concentration of adriamycin (ADM) and vincristine, an increased accumulation of ADM, down-regulation of vascular endothelial growth factor A (VEGFA) and multidrug resistance-associated protein 1 (MRP1), and inactivation of the Akt signaling pathway. Furthermore, enhanced expression of miR-126 suppressed the growth of A549 xenograft and inhibited the expression of VEGFA and MRP1. miR-126 could efficiently down-regulate VEGFA expression through the interaction with the VEGFA 3'-untranslated region, whereas restoration of VEGFA could partially attenuate the suppression of MRP1 by miR-126. However, LY294002, an inhibitor of the PI3K/Akt signaling pathway, diminished this effect, suggesting that enhanced expression of miR-126 increased the sensitivity of NSCLC cells to anticancer agents through negative regulation of a VEGF/PI3K/Akt/MRP1 signaling pathway.

Converging miRNA functions in diverse brain disorders: a case for miR-124 and miR-126

A growing body of information on the biology of miRNAs has revealed new insight into their roles in normal homeostasis and pathology of disease. miRNAs control all steps of the cellular expression machinery acting through a "single miRNA/multiple targets" or "multiple miRNAs/single target" mechanism. They have profound impact on the regulation of signaling pathways, which govern common and specific functions across different cellular phenotypes. There is increasing evidence that various diseases share similar disturbances in gene expression networks. Since miRNAs have both common and varying effects in different cellular contexts, they might also influence overlapping signaling pathways in different organs and disease entities. Here, we review this concept for two miRNAs highly abundant in the brain, miR-124 and miR-126, and their potential role in diseases of the brain.

Role of miR-224 in hepatocellular carcinoma: a tool for possible therapeutic intervention?

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, characterized by high mortality rate and poor prognosis. Our understanding of the HCC pathology is still very much fragmented and little progress has been made to improve the clinical outcome of HCC patients. While recently discovered microRNA deregulation in HCC has added to the complexity of our understanding of HCC, it has also presented promising novel approaches to understand, diagnose and treat HCC. Here, we highlight one miRNA, miR-224, which has been more consistently reported to be upregulated in HCC than other miRNAs. We will discuss the validated and predicted functional roles of this miRNA in HCC, speculate on the possible mechanism for its upregulation in HCC and explore the potential of miR-224 as an exciting novel biomarker for the early detection of liver malignancies as well as a novel therapeutic target for HCC treatment.

MicroRNA-224 is up-regulated in hepatocellular carcinoma through epigenetic mechanisms

MicroRNA-224 (miR-224) is one of the most commonly up-regulated microRNAs in hepatocellular carcinoma (HCC), which affects crucial cellular processes such as apoptosis and cell proliferation. In this study, we aim to elucidate the molecular mechanism that leads to the overexpression of miR-224 in HCC. We examined the transcript expression of miR-224 and neighboring miR-452 and genes on chromosome Xq28 in tumor and paired adjacent nontumorous tissues from 100 patients with HCC and found that miR-224 is coordinately up-regulated with its neighboring microRNA (miRNA) and genes. This coordinated up-regulation of miRNAs and genes at the Xq28 locus can be mimicked in nontransformed immortalized human liver cells by the introduction of histone deacetylase (HDAC) inhibitors, which resulted in a corresponding increase in histone H3 acetylation in this region. This miR-224-residing locus in Xq28 is reciprocally regulated by HDAC1, HDAC3, and histone acetylase protein, E1A binding protein p300 (EP300). Notably, in HCC tumors that significantly overexpress microRNA-224, EP300 is also overexpressed and displays increased binding to the Xq28 locus. In transformed HCC cells, high miR-224 expression can be attenuated through the inhibition of EP300, using either siRNA or the specific drug C646. In summary, overexpression of EP300 may account, in part, for the up-regulation of miR-224 expression in patients with HCC.

MicroRNAs targeting oncogenes are down-regulated in pancreatic malignant transformation from benign tumors

BACKGROUND

MicroRNA (miRNA) expression profiles have been described in pancreatic ductal adenocarcinoma (PDAC), but these have not been compared with pre-malignant pancreatic tumors. We wished to compare the miRNA expression signatures in pancreatic benign cystic tumors (BCT) of low and high malignant potential with PDAC, in order to identify miRNAs deregulated during PDAC development. The mechanistic consequences of miRNA dysregulation were further evaluated.

METHODS

Tissue samples were obtained at a tertiary pancreatic unit from individuals with BCT and PDAC. MiRNA profiling was performed using a custom microarray and results were validated using RT-qPCR prior to evaluation of miRNA targets.

RESULTS

Widespread miRNA down-regulation was observed in PDAC compared to low malignant potential BCT. We show that amongst those miRNAs down-regulated, miR-16, miR-126 and let-7d regulate known PDAC oncogenes (targeting BCL2, CRK and KRAS respectively). Notably, miR-126 also directly targets the KRAS transcript at a "seedless" binding site within its 3'UTR. In clinical specimens, miR-126 was strongly down-regulated in PDAC tissues, with an associated elevation in KRAS and CRK proteins. Furthermore, miR-21, a known oncogenic miRNA in pancreatic and other cancers, was not elevated in PDAC compared to serous microcystic adenoma (SMCA), but in both groups it was up-regulated compared to normal pancreas, implicating early up-regulation during malignant change.

CONCLUSIONS

Expression profiling revealed 21 miRNAs down-regulated in PDAC compared to SMCA, the most benign lesion that rarely progresses to invasive carcinoma. It appears that miR-21 up-regulation is an early event in the transformation from normal pancreatic tissue. MiRNA expression has the potential to distinguish PDAC from normal pancreas and BCT. Mechanistically the down-regulation of miR-16, miR-126 and let-7d promotes PDAC transformation by post-transcriptional up-regulation of crucial PDAC oncogenes. We show that miR-126 is able to directly target KRAS; re-expression has the potential as a therapeutic strategy against PDAC and other KRAS-driven cancers.

Neuroimmune modulation following traumatic stress in rats: evidence for an immunoregulatory cascade mediated by c-Src, miRNA222 and PAK1

Background

Neuroimmune modulation following traumatic stress is accompanied by cortical upregulation of c-Src expression, but the mechanistic details of the potential regulatory link between c-Src expression and immunosuppression have not been established.

Methods

We used a combination of techniques to measure temporal changes in: (i) the parallel expression of c-Src and microRNA222; (ii) levels of PAK1 (p21-activated kinase 1); and (iii) the association between PAK1 and interleukin 1β signaling, both in cortex of rats following traumatic stress and in primary cortical neurons. Techniques included real-time PCR, immunoprecipitation, western blotting and subcellular fractionation by discontinuous centrifugation. We also measured lymphocyte proliferation and natural killer (NK) cell activity.

Results

We confirm robust upregulation of c-Src expression following traumatic stress. c-Src upregulation was accompanied by marked increases in levels of miRNA222; other studied miRNAs were not affected by stress. We also established that PAK1 is a primary target for miRNA222, and that increased levels of miRNA222 following traumatic stress are accompanied by downregulation of PAK1 expression. PAK1 was shown to mediate the association of IL-1RI with lipid rafts and thereby enhance IL-1 signaling. Detailed analyses in cultured neurons and glial cells revealed that PAK1-mediated enhancement of IL-1RI activation is governed to a large extent by c-Src/miRNA222 signaling; this signaling played a central role in the modulation of lymphocyte proliferation and NK cell activity.

Conclusions

Our results suggest that neuroimmune modulation following traumatic stress is mediated by a cascade that involves c-Src-mediated enhancement of miRNA222 expression and downregulation of PAK1, which in turn impairs signaling via IL-1β/IL1-RI, leading to immunosuppression. The regulatory networks involving c-Src/miRNA222 and PAK1/IL-1RI signaling have significant potential for the development of therapeutic approaches designed to promote recovery following traumatic injury.

Emerging roles for crk in human cancer

Adaptor proteins are named for their function in assembling complexes of cellular proteins to execute and facilitate transmission of signals. The Crk family of adaptors consists of 2 members, Crk and CrkL. Crk, which was originally isolated as an oncogene, v-Crk, that transforms CEFs, has at least 2 splice variants, CrkI and CrkII, with differing biological activities. All Crk family proteins serve to act as molecular bridges between tyrosine kinases and their substrates and also modulate the specificity and stoichiometry of signaling processes. Signaling via CrkII and CrkL can be negatively regulated via tyrosine phosphorylation-mediated autoinhibition, while such a mechanism is not known to exist for CrkI. Although v-Crk clearly functions as a bona fide oncogene, in recent years, an emerging body of evidence suggests that cellular Crk proteins are overexpressed in human tumors and the expression levels correlate with aggressive and malignant behavior of cancer cells. These properties of Crk proteins make them potential cancer prognosis markers and therapeutic targets.

MicroRNA-mediated breast cancer metastasis: from primary site to distant organs

The recent upsurge of interest in microRNA (miRNA) is partly attributed to the discovery of the novel roles of miRNAs in many physiological and pathological processes, including tumor development. Research on breast cancer metastasis has also focused on the concept of miRNA, which can act either as promoters or as suppressors of metastases. This review will focus on a series of recent studies that demonstrate the involvement of miRNAs in breast cancer metastasis and will briefly describe various pathways of miRNA-regulated metastasis. Finally, future prospects will be discussed for the potential role of miRNAs as predictive markers and therapeutic agents for patients with breast cancer metastases.

MicroRNA-mediated upregulation of integrin-linked kinase promotes Src-induced tumor progression

The tyrosine kinase c-Src is upregulated in various human cancers; however, the molecular mechanisms underlying c-Src-mediated tumor progression remain unclear. Here we show that downregulation of microRNA (miR)-542-3p is tightly associated with tumor progression via c-Src-related oncogenic pathways. In c-Src-transformed fibroblasts and human cancer cells that overexpress c-Src, miR-542-3p is substantially downregulated, and the ectopic expression of miR-542-3p suppresses tumor growth. We identified the integrin-linked kinase (ILK) as a conserved target of miR-542-3p. ILK upregulation promotes cell adhesion and invasion by activating the integrin-focal adhesion kinase (FAK)/c-Src pathway, and can also contribute to tumor growth via the AKT and glycogen synthase kinase 3β pathways. MiR-542-3p expression is downregulated by the activation of c-Src-related signaling molecules, including epidermal growth factor receptor, K-Ras and Ras/Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase. In human colon cancer tissues, downregulation of miR-542-3p is significantly correlated with the upregulation of c-Src and ILK. Our results suggest that the novel c-Src-miR-542-3p-ILK-FAK circuit plays a crucial role in controlling tumor progression.

The tumor suppressive microRNA miR-218 targets the mTOR component Rictor and inhibits AKT phosphorylation in oral cancer

The incidence of oral squamous cell carcinoma (OSCC) is rising rapidly in developed countries, posing a growing challenge due to the poor management of this type of malignancy at present. In this study, we profiled tumor suppressive microRNAs (miRNAs) that are silenced by DNA hypermethylation in OSCC using a function-based screening approach. This approach employed a cell proliferation assay for 327 synthetic miRNAs in two OSCC cell lines. Among the 110 miRNAs identified in this set that exhibited inhibitory properties, we compared DNA methylation and expression status in a wider panel of OSCC cell lines and primary tumor tissues, resulting in the identification of miR-218 and miR-585 as functionally significant miRNA genes that are frequently silenced in OSCC by DNA hypermethylation. Ectopic expression of miR-218 and miR-585 in OSCC cells lacking endogenous expression reduced cell growth in part through caspase-mediated apoptosis. Notably, miR-218 reduced levels of the rapamycin-insensitive component of mTOR, Rictor, in a manner associated with a suppression of Akt S473 phosphorylation. Together our findings define miR-585 as a tumor suppressive function that is often epigenetically silenced in OSCC, and they identify Rictor as a novel target of miR-218, suggesting that activation of the mTOR-Akt signaling pathway induced by Rictor contributes centrally to oral carcinogenesis.

miR-126 inhibits proliferation of small cell lung cancer cells by targeting SLC7A5

Despite intensive efforts to improve therapies, small cell lung cancer (SCLC) still has a dismal median survival of 18 months. Since miR-126 is under-expressed in the majority of SCLC tumors, we investigated the effect of miR-126 overexpression on the proliferation and cell cycle distribution of H69 cells. Our results demonstrate that miR-126 inhibits proliferation of H69 cells, by delaying the cells in the G1 phase. Short interfering RNA (siRNA) mediated suppression of SLC7A5, a predicted target of mir-126, has the same effect on H69 cells. We also show for the first time that SLC7A5 is a direct target of miR-126.

MicroRNA-mediated downregulation of mTOR/FGFR3 controls tumor growth induced by Src-related oncogenic pathways

The tyrosine kinase c-Src is upregulated in various human cancers, but the molecular mechanisms underlying c-Src-mediated tumor growth remain unclear. Here we examined the involvement of microRNAs in the c-Src-mediated tumor growth. Microarray profiling revealed that c-Src activation downregulates a limited set of microRNAs, including miR-99a, which targets oncogenic mammalian target of rapamycin (mTOR) and fibroblast growth factor receptor 3 (FGFR3). Re-expression of miR-99a suppressed tumor growth of c-Src-transformed cells, and this effect was restored by the overexpression of mTOR. The downregulation of miR-99a was also observed in epidermal growth factor- and Ras-transformed cells, and it was suppressed by inhibiting the mitogen-activated protein kinase (MAPK) pathway. Furthermore, miR-99a downregulation is associated with mTOR/FGFR3 upregulation in various human lung cancer cells/tissues. The tumorigenicity of these cells was suppressed by the introduction of miR-99a. These findings suggest that the miR-99a-mTOR/FGFR3 pathway is crucial for controlling tumor growth in a wide range of human cancers that harbor upregulation of the Src-related oncogenic pathways.

Src activates Abl to augment Robo1 expression in order to promote tumor cell migration

Cell migration is an essential step in cancer invasion and metastasis. A number of orchestrated cellular events involving tyrosine kinases and signaling receptors enable cancer cells to dislodge from primary tumors and colonize elsewhere in the body. For example, activation of the Src and Abl kinases can mediate events that promote tumor cell migration. Also, activation of the Robo1 receptor can induce tumor cell migration. However, while the importance of Src, Abl, and Robo1 in cell migration have been demonstrated, molecular mechanisms by which they collectively influence cell migration have not been clearly elucidated. In addition, little is known about mechanisms that control Robo1 expression. We report here that Src activates Abl to stabilize Robo1 in order to promote cell migration. Inhibition of Abl kinase activity by siRNA or kinase blockers decreased Robo1 protein levels and suppressed the migration of transformed cells. We also provide evidence that Robo1 utilizes Cdc42 and Rac1 GTPases to induce cell migration. In addition, inhibition of Robo1 signaling can suppress transformed cell migration in the face of robust Src and Abl kinase activity. Therefore, inhibitors of Src, Abl, Robo1 and small GTPases may target a coordinated pathway required for tumor cell migration.