HMGA2 maintains oncogenic RAS-induced epithelial-mesenchymal transition in human pancreatic cancer cells

Prevalence and significance of HMGA2 expression in oesophageal adenocarcinoma

AIMS

Oesophageal adenocarcinoma (EAC) tumorigenesis has been linked primarily to loss-of-function mutations in tumour suppressor genes. Knowledge of specific oncogenes that drive tumour progression, and their relationship to outcomes, is limited. High mobility group AT-hook 2 (HMGA2) has been reported to be amplified in a subset of EACs, but the clinicopathological and prognostic implications of HMGA2 expression in EAC are unknown.

METHODS AND RESULTS

We performed HMGA2 immunohistochemistry and fluorescence in-situ hybridization (FISH) in EAC to determine its clinicopathological and prognostic significance. Ninety-one primary EAC resections without neoadjuvant treatment were identified and immunohistochemistry for HMGA2 was performed. The presence or absence of nuclear staining was evaluated and correlated with predetermined clinicopathological parameters and patient outcomes. A selected subset of tumours was subjected to FISH to identify alterations at the HMGA2 locus. HMGA2 expression was present in 25 of 91 (27.4%) tumours. HMGA2-expressing cells were present in solid, poorly differentiated areas of the tumours at the invasive front, or as single infiltrating cells. FISH showed that three to four copies of HMGA2 are frequently present in EAC irrespective of HMGA2 protein expression and that high level HMGA2 amplification is a rare event. HMGA2 expression was associated with numerous adverse clinicopathological parameters, including higher T- and N-stage, the presence of lymphovascular invasion and with a worse recurrence-free and overall survival.

CONCLUSION

Our data suggest that HMGA2 is regulated in EAC primarily through non-chromosomal-level alterations that lead to increased HMGA2 expression. HMGA2-positive EAC correlates with adverse pathological features and worse patient outcomes.

RUNX1 promote invasiveness in pancreatic ductal adenocarcinoma through regulating miR-93

Runt-related transcription factor 1(RUNX1), a key factor in hematopoiesis that mediates specification and homeostasis of hematopoietic stem and progenitor cells (HSPCs), is also overexpressed in several solid human cancers, and correlated with tumor progression. However, the expression and function of RUNX1 in pancreatic ductal adenocarcinoma were still unclear. Here, we show that RUNX1 is highly expressed in pancreatic adenocarcinoma tissues and knocking down of RUNX1 attenuated aggressiveness in pancreatic cell lines. Moreover, we found that RUNX1 could negatively regulate the expression of miR-93. Bioinformatics method showed that there are two binding sites in the the promotor region of miR-93 precursor and through ChIP-qPCR and firefly luciferase reporter assay, we vertified that these two binding sites each have transcriptive activity in one pancreatic cell lines. This result supported our presumption that RUNX1 regulate miR-93 through binding to the promotor region of miR-93. Besides, the expression and function of miR-93 is quite the opposite, miR-93 overexpression suppresses migration and invasiveness in pancreatic cell lines supporting that RUNX1 negatively regulated miR-93. Our findings provided evidence regarding the role of RUNX1 as an oncogene through the inhibition of miR-93. Targeting RUNX1 can be a potential therapeutic strategy in pancreatic cancer.

HMGA2 regulates lung cancer proliferation and metastasis

BACKGROUND

This study aimed to explore the effects of HMGA2 on cell proliferation and metastases in lung cancer and its underlying mechanism.

METHODS

HMGA2 expression in lung cancer tissues and its association with overall survival were analyzed based on data from a public database. The roles of HMGA2 were validated via loss-of-function and gain-of-function experiments in vitro. HMGA2 regulation by microRNA-195 (miR-195) was validated by real time-PCR, Western blotting, and luciferase reporter assays.

RESULTS

HMGA2 was upregulated and associated with reduced overall survival in patients with lung adenocarcinoma. HMGA2 knockdown suppressed the proliferation and motility of H1299 cells, while HMGA2 ectopic expression in A549 cells increased cell proliferation and migration. HMGA2 affected cell apoptosis through caspase 3/9 and Bcl-2, and regulated epithelial-to-mesenchymal transition by targeting Twist 1. Moreover, miR-195 was found to directly target the 3' untranslated region of HMGA2 messenger RNA and suppress its expression in lung cancer.

CONCLUSION

This study demonstrated that HMGA2, regulated by miR-195, played important roles in proliferation, metastases, and epithelial-to-mesenchymal transition in lung cancer. HMGA2 might serve as a biomarker and potential therapeutic target for lung cancer treatment.

Development of Phosphorothioate DNA and DNA Thioaptamers

Nucleic acid aptamers are short RNA- or DNA-based affinity reagents typically selected from combinatorial libraries to bind to a specific target such as a protein, a small molecule, whole cells or even animals. Aptamers have utility in the development of diagnostic, imaging and therapeutic applications due to their size, physico-chemical nature and ease of synthesis and modification to suit the application. A variety of oligonucleotide modifications have been used to enhance the stability of aptamers from nuclease degradation in vivo. The non-bridging oxygen atoms of the phosphodiester backbones of RNA and DNA aptamers can be substituted with one or two sulfur atoms, resulting in thioaptamers with phosphorothioate or phosphorodithioate linkages, respectively. Such thioaptamers are known to have increased binding affinity towards their target, as well as enhanced resistance to nuclease degradation. In this review, we discuss the development of phosphorothioate chemistry and thioaptamers, with a brief review of selection methods.

miR-509-5p and miR-1243 increase the sensitivity to gemcitabine by inhibiting epithelial-mesenchymal transition in pancreatic cancer

The epithelial-mesenchymal transition (EMT) contributes to various processes in cancer progression, such as metastasis and drug resistance. Since we have already established a cell-based reporter system for identifying EMT-suppressive microRNAs (miRNAs) in the pancreatic cancer cell line Panc1, we performed a function-based screening assay by combining this reporter system and a miRNA library composed of 1,090 miRNAs. As a result, we identified miR-509-5p and miR-1243 as EMT-suppressive miRNAs, although the mechanisms for EMT-suppression induced by these miRNAs have yet to be clarified. Herein, we demonstrated that overexpression of miR-509-5p and miR-1243 increased the expression of E-cadherin through the suppression of EMT-related gene expression and that drug sensitivity increased with a combination of each of these miRNAs and gemcitabine. Moreover, miR-509-5p was associated with worse overall survival in patients with pancreatic cancer and was identified as an independently selected predictor of mortality. Our findings suggest that miR-509-5p and miR-1243 might be novel chemotherapeutic targets and serve as biomarkers in pancreatic cancer.

Stroma-regulated HMGA2 is an independent prognostic marker in PDAC and AAC

Background:

The HMGA2 protein has experimentally been linked to EMT and cancer stemness. Recent studies imply that tumour–stroma interactions regulate these features and thereby contribute to tumour aggressiveness.

Methods:

We analysed 253 cases of pancreatic ductal adenocarcinoma (PDAC) and 155 cases of ampullary adenocarcinoma (AAC) for HMGA2 expression by IHC. The data were correlated with stroma abundance and supplemented by experimental studies.

Results:

HMGA2 acts as an independent prognostic marker associated with a significantly shorter overall survival in both tumour types. Overall, HMGA2-positivity was more frequent in patients with PDAC than with AAC. The HMGA2 status in tumour cells significantly correlated with the abundance of PDGFRβ-defined stroma cells. In vivo co-injection of Panc-1 cancer cells with pancreatic stellate cells increased tumour growth in a manner associated with increased HMGA2 expression. Furthermore, in vitro treatment of Panc-1 with conditioned media from PDGF-BB-activated stellate cells increased their ability to form tumour spheroids.

Conclusions:

This study identifies HMGA2 expression in tumour cells as an independent prognostic marker in PDAC and AAC. Correlative data analysis gives novel tissue-based evidence for a heterotypic cross-talk with stroma cells as a possible mechanism for HMGA2 induction, which is further supported by experimental models.

Long Non-Coding RNAs: Key Regulators of Epithelial-Mesenchymal Transition, Tumour Drug Resistance and Cancer Stem Cells

Epithelial mesenchymal transition (EMT), the adoption by epithelial cells of a mesenchymal-like phenotype, is a process co-opted by carcinoma cells in order to initiate invasion and metastasis. In addition, it is becoming clear that is instrumental to both the development of drug resistance by tumour cells and in the generation and maintenance of cancer stem cells. EMT is thus a pivotal process during tumour progression and poses a major barrier to the successful treatment of cancer. Non-coding RNAs (ncRNA) often utilize epigenetic programs to regulate both gene expression and chromatin structure. One type of ncRNA, called long non-coding RNAs (lncRNAs), has become increasingly recognized as being both highly dysregulated in cancer and to play a variety of different roles in tumourigenesis. Indeed, over the last few years, lncRNAs have rapidly emerged as key regulators of EMT in cancer. In this review, we discuss the lncRNAs that have been associated with the EMT process in cancer and the variety of molecular mechanisms and signalling pathways through which they regulate EMT, and finally discuss how these EMT-regulating lncRNAs impact on both anti-cancer drug resistance and the cancer stem cell phenotype.

HMGA2 regulates CD44 expression to promote gastric cancer cell motility and sphere formation

High mobility group AT-hook 2 (HMGA2) is a transcriptional modulator that mediates motility and self-renewal in cancer stem cells. Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide. GC contains a population of stem-like cells that promote tumor invasion and resistance to therapy. In the current study, we investigated the expression of HMGA2 and the cancer stem cell marker CD44 in 200 GC samples and found that HMGA2 and CD44 were significantly associated with distant metastasis, histological differentiation and poor prognosis in GC patients. Positive clinical correlations of HMGA2 with CD44 were also observed in tissue sections. In vitro, overexpression of HMGA2 promoted GC sphere formation and migration in MKN74/MKN28 cells, whereas downregulation of HMGA2 decreased GC sphere formation and migration in MKN45/MGC803 cells. In addition, western blot and immunofluorescent analyses showed that HMGA2 increased the expression of the stem cell markers CD44, ALDH1, Sox2, and Oct4 and the EMT-related factors Snail and β-catenin. In a xenograft mouse model, overexpression of HMGA2 promoted tumor growth. Further immunohistochemical (IHC) analysis showed that HMGA2 increased the expression of CD44 and β-catenin, resulting in the promotion of tumor growth. Taken together, our findings indicate that HMGA2 promotes GC cancer stem cell induction and cell motility by regulating the expression of CD44. Therefore, targeting HMGA2 in GC may be therapeutically beneficial.

ΔNp63α and microRNAs: leveraging the epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) is a cellular reprogramming mechanism that is an underlying cause of cancer metastasis. Recent investigations have uncovered an intricate network of regulation involving the TGFβ, Wnt, and Notch signaling pathways and small regulatory RNA species called microRNAs (miRNAs). The activity of a transcription factor vital to the maintenance of epithelial stemness, ΔNp63α, has been shown to modulate the activity of these EMT pathways to either repress or promote EMT. Furthermore, ΔNp63α is a known regulator of miRNA, including those directly involved in EMT. This review discusses the evidence of ΔNp63α as a master regulator of EMT components and miRNA, highlighting the need for a deeper understanding of its role in EMT. This expanded knowledge may provide a basis for new developments in the diagnosis and treatment of metastatic cancer.

The transcriptional modulator HMGA2 promotes stemness and tumorigenicity in glioblastoma

Glioblastoma (GBM) contains a population of stem-like cells that promote tumor invasion and resistance to therapy. Identifying and targeting stem cell factors in GBM may lead to the development of more effective therapies. High Mobility Group AT-hook 2 (HMGA2) is a transcriptional modulator that mediates motility and self-renewal in normal and cancer stem cells. We identified increased expression of HMGA2 in the majority of primary human GBM tumors and cell lines compared to normal brain. Additionally, HMGA2 expression was increased in CD133+ GBM neurosphere cells compared to CD133- cells. Targeting HMGA2 with lentiviral short hairpin RNA (shRNA) led to decreased GBM stemness, invasion, and tumorigenicity. Ectopic expression of HMGA2 in GBM cell lines promoted stemness, invasion, and tumorigenicity. Our data suggests that targeting HMGA2 in GBM may be therapeutically beneficial.

HMGA2 promotes adipogenesis by activating C/EBPβ-mediated expression of PPARγ

Adipogenesis is orchestrated by a highly ordered network of transcription factors including peroxisome-proliferator activated receptor-gamma (PPARγ) and CCAAT-enhancer binding protein (C/EBP) family proteins. High mobility group protein AT-hook 2 (HMGA2), an architectural transcription factor, has been reported to play an essential role in preadipocyte proliferation, and its overexpression has been implicated in obesity in mice and humans. However, the direct role of HMGA2 in regulating the gene expression program during adipogenesis is not known. Here, we demonstrate that HMGA2 is required for C/EBPβ-mediated expression of PPARγ, and thus promotes adipogenic differentiation. We observed a transient but marked increase of Hmga2 transcript at an early phase of differentiation of mouse 3T3-L1 preadipocytes. Importantly, Hmga2 knockdown greatly impaired adipocyte formation, while its overexpression promoted the formation of mature adipocytes. We found that HMGA2 colocalized with C/EBPβ in the nucleus and was required for the recruitment of C/EBPβ to its binding element at the Pparγ2 promoter. Accordingly, HMGA2 and C/EBPβ cooperatively enhanced the Pparγ2 promoter activity. Our results indicate that HMGA2 is an essential constituent of the adipogenic transcription factor network, and thus its function may be affected during the course of obesity.

Heat shock protein 90 is involved in the regulation of HMGA2-driven growth and epithelial-to-mesenchymal transition of colorectal cancer cells

High Mobility Group AT-hook 2 (HMGA2) is a nonhistone chromatin-binding protein which acts as a transcriptional regulating factor involved in gene transcription. In particular, overexpression of HMGA2 has been demonstrated to associate with neoplastic transformation and tumor progression in Colorectal Cancer (CRC). Thus, HMGA2 is a potential therapeutic target in cancer therapy. Heat Shock Protein 90 (Hsp90) is a chaperone protein required for the stability and function for a number of proteins that promote the growth, mobility, and survival of cancer cells. Moreover, it has shown strong positive connections were observed between Hsp90 inhibitors and CRC, which indicated their potential for use in CRC treatment by using combination of data mining and experimental designs. However, little is known about the effect of Hsp90 inhibition on HMGA2 protein expression in CRC. In this study, we tested the hypothesis that Hsp90 may regulate HMGA2 expression and investigated the relationship between Hsp90 and HMGA2 signaling. The use of the second-generation Hsp90 inhibitor, NVP-AUY922, considerably knocked down HMGA2 expression, and the effects of Hsp90 and HMGA2 knockdown were similar. In addition, Hsp90 knockdown abrogates colocalization of Hsp90 and HMGA2 in CRC cells. Moreover, the suppression of HMGA2 protein expression in response to NVP-AUY922 treatment resulted in ubiquitination and subsequent proteasome-dependant degradation of HMGA2. Furthermore, RNAi-mediated silencing of HMGA2 reduced the survival of CRC cells and increased the sensitivity of these cells to chemotherapy. Finally, we found that the NVP-AUY922-dependent mitigation of HMGA2 signaling occurred also through indirect reactivation of the tumor suppressor microRNA (miRNA), let-7a, or the inhibition of ERK-regulated HMGA2 involved in regulating the growth of CRC cells. Collectively, our studies identify the crucial role for the Hsp90-HMGA2 interaction in maintaining CRC cell survival and migration. These findings have significant implications for inhibition HMGA2-dependent tumorigenesis by clinically available Hsp90 inhibitors.

The role of the oncofetal H19 lncRNA in tumor metastasis: orchestrating the EMT-MET decision

Long non-coding RNA (lncRNA) genes are emerging as key players in the metastatic cascade. Current evidence indicate that H19 lncRNA and the microRNA(miRNA) miR-675, which is processed from it, play crucial roles in metastasis, through the regulation of critical events specifically the epithelial to mesenchymal (EMT) and the mesenchymal to epithelial transitions (MET). This review summarizes recent mechanistic pathways and tries to put together seemingly conflicting data from different reports under one proposed general scheme underlying the various roles of H19/miR-675 in the metastatic cascade. We propose several approaches to harnessing this knowledge for translational medicine.

Hmga2 is required for neural crest cell specification in Xenopus laevis

HMGA proteins are small nuclear proteins that bind DNA by conserved AT-hook motifs, modify chromatin architecture and assist in gene expression. Two HMGAs (HMGA1 and HMGA2), encoded by distinct genes, exist in mammals and are highly expressed during embryogenesis or reactivated in tumour progression. We here addressed the in vivo role of Xenopus hmga2 in the neural crest cells (NCCs). We show that hmga2 is required for normal NCC specification and development. hmga2 knockdown leads to severe disruption of major skeletal derivatives of anterior NCCs. We show that, within the NCC genetic network, hmga2 acts downstream of msx1, and is required for msx1, pax3 and snail2 activities, thus participating at different levels of the network. Because of hmga2 early effects in NCC specification, the subsequent epithelial-mesenchymal transition (EMT) and migration of NCCs towards the branchial pouches are also compromised. Strictly paralleling results on embryos, interfering with Hmga2 in a breast cancer cell model for EMT leads to molecular effects largely consistent with those observed on NCCs. These data indicate that Hmga2 is recruited in key molecular events that are shared by both NCCs and tumour cells.

HDAC inhibition impedes epithelial-mesenchymal plasticity and suppresses metastatic, castration-resistant prostate cancer

PI3K/AKT and RAS/MAPK pathway co-activation in the prostate epithelium promotes both epithelial-mesenchymal transition (EMT) and metastatic castration-resistant prostate cancer (mCRPC), which is currently incurable. To study the dynamic regulation of the EMT process, we developed novel genetically-defined cellular and in vivo model systems from which epithelial, EMT, and mesenchymal-like tumor cells with Pten deletion and Kras activation can be isolated. When cultured individually, each population has the capacity to regenerate all three tumor cell populations, indicative of epithelial-mesenchymal plasticity. Despite harboring the same genetic alterations, mesenchymal-like tumor cells are resistant to PI3K and MAPK pathway inhibitors, suggesting that epigenetic mechanisms may regulate the EMT process, as well as dictate the heterogeneous responses of cancer cells to therapy. Among differentially expressed epigenetic regulators, the chromatin remodeling protein HMGA2 is significantly upregulated in EMT and mesenchymal-like tumors cells, as well as in human mCRPC. Knockdown of HMGA2, or suppressing HMGA2 expression with the histone deacetylase (HDAC) inhibitor LBH589, inhibits epithelial-mesenchymal plasticity and stemness activities in vitro and dramatically reduces tumor growth and metastasis in vivo through successful targeting of EMT and mesenchymal-like tumor cells. Importantly, LBH589 treatment in combination with castration prevents mCRPC development and significantly prolongs survival following castration by enhancing p53 and AR acetylation and in turn sensitizing castration-resistant mesenchymal-like tumor cells to ADT. Taken together, these findings demonstrate that cellular plasticity is regulated epigenetically, and that mesenchymal-like tumor cell populations in mCRPC that are resistant to conventional and targeted therapies can be effectively treated with the epigenetic inhibitor LBH589.

MiRNAs and Other Epigenetic Changes as Biomarkers in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is characterised by the lack of receptors for estrogen (ER), progesterone (PR), and human epidermal growth factor 2 (HER2). Since it cannot be treated by current endocrine therapies which target these receptors and due to its aggressive nature, it has one of the worst prognoses of all breast cancer subtypes. The only treatments remain chemo- and/or radio-therapy and surgery and because of this, novel biomarkers or treatment targets are urgently required to improve disease outcomes. MicroRNAs represent an attractive candidate for targeted therapies against TNBC, due to their natural ability to act as antisense interactors and regulators of entire gene sets involved in malignancy and their superiority over mRNA profiling to accurately classify disease. Here we review the current knowledge regarding miRNAs as biomarkers in TNBC and their potential use as therapeutic targets in this disease. Further, we review other epigenetic changes and interactions of these changes with microRNAs in this breast cancer subtype, which may lead to the discovery of new treatment targets for TNBC.

Brg1 promotes both tumor-suppressive and oncogenic activities at distinct stages of pancreatic cancer formation

Pancreatic Ductal Adenocarcinoma (PDA) develops predominantly through pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasm (IPMN) precursor lesions. Roy et al. identify critical antagonistic roles for Brg1, a catalytic subunit of the SWI/SNF complexes, during IPMN-PDA development. In mature duct cells Brg1 inhibits the dedifferentiation that precedes neoplastic transformation. In contrast, Brg1 promotes tumorigenesis in full-blown PDA by supporting a mesenchymal-like transcriptional landscape. JQ1 impairs PDA tumorigenesis by both mimicking some and inhibiting other Brg1-mediated functions.

Pancreatic ductal adenocarcinoma (PDA) develops predominantly through pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasm (IPMN) precursor lesions. Pancreatic acinar cells are reprogrammed to a “ductal-like” state during PanIN-PDA formation. Here, we demonstrate a parallel mechanism operative in mature duct cells during which functional cells undergo “ductal retrogression” to form IPMN-PDA. We further identify critical antagonistic roles for Brahma-related gene 1 (Brg1), a catalytic subunit of the SWI/SNF complexes, during IPMN-PDA development. In mature duct cells, Brg1 inhibits the dedifferentiation that precedes neoplastic transformation, thus attenuating tumor initiation. In contrast, Brg1 promotes tumorigenesis in full-blown PDA by supporting a mesenchymal-like transcriptional landscape. We further show that JQ1, a drug that is currently being tested in clinical trials for hematological malignancies, impairs PDA tumorigenesis by both mimicking some and inhibiting other Brg1-mediated functions. In summary, our study demonstrates the context-dependent roles of Brg1 and points to potential therapeutic treatment options based on epigenetic regulation in PDA.

Distinct E-cadherin-based complexes regulate cell behaviour through miRNA processing or Src and p120 catenin activity

E-cadherin and p120 catenin (p120) are essential for epithelial homeostasis, but can also exert pro-tumorigenic activities. Here, we resolve this apparent paradox by identifying two spatially and functionally distinct junctional complexes in non-transformed polarized epithelial cells: one growth suppressing at the apical zonula adherens (ZA), defined by the p120 partner PLEKHA7 and a non-nuclear subset of the core microprocessor components DROSHA and DGCR8, and one growth promoting at basolateral areas of cell-cell contact containing tyrosine-phosphorylated p120 and active Src. Recruitment of DROSHA and DGCR8 to the ZA is PLEKHA7 dependent. The PLEKHA7-microprocessor complex co-precipitates with primary microRNAs (pri-miRNAs) and possesses pri-miRNA processing activity. PLEKHA7 regulates the levels of select miRNAs, in particular processing of miR-30b, to suppress expression of cell transforming markers promoted by the basolateral complex, including SNAI1, MYC and CCND1. Our work identifies a mechanism through which adhesion complexes regulate cellular behaviour and reveals their surprising association with the microprocessor.

MicroRNA Signaling Pathway Network in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is considered to be the most lethal and aggressive malignancy with high mortality and poor prognosis. Their responses to current multimodal therapeutic regimens are limited. It is urgently needed to identify the molecular mechanism underlying pancreatic oncogenesis. Twelve core signaling cascades have been established critical in PDAC tumorigenesis by governing a wide variety of cellular processes. MicroRNAs (miRNAs) are aberrantly expressed in different types of tumors and play pivotal roles as post-transcriptional regulators of gene expression. Here, we will describe how miRNAs regulate different signaling pathways that contribute to pancreatic oncogenesis and progression.

Downregulating HMGA2 attenuates epithelial-mesenchymal transition-induced invasion and migration in nasopharyngeal cancer cells

BACKGROUND

Epithelial-mesenchymal transition (EMT) is associated with invasion and metastasis of cancer cells. High-mobility group AT-hook 2 (HMGA2) has been found to play a critical role in EMT in a number of malignant tumors. However, whether HMGA2 regulates the EMT in human nasopharyngeal carcinoma (NPC) is unclear.

OBJECTIVE

The aim of this study was to investigate the effect and mechanism of HMGA2 in inducing invasion and migration in NPC.

METHODS

In NPC tissues samples, the association of HMGA2 mRNA expression with clinicopathological characteristics were estimated by real-time quantitative RT-PCR(qRT-PCR). In vitro, following the silencing of HMGA2 in CNE-1 and CNE-2 cell lines, the viability and metastatic ability were analyzed using Cell Counting Kit-8 (CCK8), colony formation assay, and transwell assay. EMT and transforming growth factor-beta (TGFβ)/Smad3 signaling pathway-related protein expression changes were evaluated using western blot.

RESULTS

HMGA2 was upregulated in NPC cell lines and clinical specimens (P < 0.01), and HMGA2 expression correlated significantly with metastasis (P = 0.02) and disease-free survival of NPC (hazard ratio: 3.52; 95% confidence interval: 1.34-7.79; P = 0.01). In addition, following in vitro knockdown of HMGA2, the aggressiveness of cells was markedly inhibited, Vimentin and Snail level was downregulated and E-cadherin expression was upregulated. Moreover, the expression of key proteins TGFβRII and p-Smad3 of the TGFβ/Smad3 signaling pathway was inhibited by the downregulation of HMGA2.

CONCLUSION

HMGA2 might maintain EMT-induced invasion and migration through the TGFβ/Smad3 signaling pathway in NPC cell lines.

High-mobility-group A2 overexpression provokes a poor prognosis of gastric cancer through the epithelial-mesenchymal transition

Tumor metastases are the ultimate target in cancer therapy. In epithelial malignancies, the expression of high-mobility-group A2 (HMGA2) is associated with disease progression and the epithelial-mesenchymal transition (EMT), which is involved in the metastatic process. The present study assessed the clinical and molecular effects of HMGA2 with the malignant tissues of 170 patients with gastric cancer and gastric cancer cells expressing HMGA2. HMGA2 expression was determined using immunohistochemistry and analyzed with respect to the clinicopathological data of patients with this tumor. In the gastric cancer cell line MKN28, in which HMGA2 was knocked down by two different short-hairpin RNAs, Transwell migration and invasion assays were conducted and western blotting was used to detect the altered expression of EMT markers. In patients with gastric cancer, HMGA2 overexpression correlated with tumor progression and was indicative of a significantly worse overall survival. Migration and invasion assays using HMGA2-knocked down MKN28 cells showed a reduction in cell migration and invasion. The upregulation of E-cadherin, an epithelial marker, and the downregulation of N-cadherin, a mesenchymal marker were observed in HMGA2-knocked down cells. In addition, expression of the transcriptional factors Snail and Zeb1 and of the EMT-pathway molecule β-catenin were decreased. HMGA2 overexpression, through its relationship to EMT, thus seems to aggravate invasion and metastasis in gastric cancer. It may therefore serve as a predictive marker in determining the clinical outcome of patients with gastric cancer and offer a promising therapeutic target.

Characterization of nanoparticle mediated laser transfection by femtosecond laser pulses for applications in molecular medicine

BACKGROUND

In molecular medicine, the manipulation of cells is prerequisite to evaluate genes as therapeutic targets or to transfect cells to develop cell therapeutic strategies. To achieve these purposes it is essential that given transfection techniques are capable of handling high cell numbers in reasonable time spans. To fulfill this demand, an alternative nanoparticle mediated laser transfection method is presented herein. The fs-laser excitation of cell-adhered gold nanoparticles evokes localized membrane permeabilization and enables an inflow of extracellular molecules into cells.

RESULTS

The parameters for an efficient and gentle cell manipulation are evaluated in detail. Efficiencies of 90% with a cell viability of 93% were achieved for siRNA transfection. The proof for a molecular medical approach is demonstrated by highly efficient knock down of the oncogene HMGA2 in a rapidly proliferating prostate carcinoma in vitro model using siRNA. Additionally, investigations concerning the initial perforation mechanism are conducted. Next to theoretical simulations, the laser induced effects are experimentally investigated by spectrometric and microscopic analysis. The results indicate that near field effects are the initial mechanism of membrane permeabilization.

CONCLUSION

This methodical approach combined with an automated setup, allows a high throughput targeting of several 100,000 cells within seconds, providing an excellent tool for in vitro applications in molecular medicine. NIR fs lasers are characterized by specific advantages when compared to lasers employing longer (ps/ns) pulses in the visible regime. The NIR fs pulses generate low thermal impact while allowing high penetration depths into tissue. Therefore fs lasers could be used for prospective in vivo applications.

The chromatin-modifying protein HMGA2 promotes atypical teratoid/rhabdoid cell tumorigenicity

Atypical teratoid/rhabdoid tumor (AT/RT) is an aggressive pediatric central nervous system tumor. The poor prognosis of AT/RT warrants identification of novel therapeutic targets and strategies. High-mobility Group AT-hook 2 (HMGA2) is a developmentally important chromatin-modifying protein that positively regulates tumor growth, self-renewal, and invasion in other cancer types. High-mobility group A2 was recently identified as being upregulated in AT/RT tissue, but the role of HMGA2 in brain tumors remains unknown. We used lentiviral short-hairpin RNA to suppress HMGA2 in AT/RT cell lines and found that loss of HMGA2 led to decreased cell growth, proliferation, and colony formation and increased apoptosis. We also found that suppression of HMGA2 negatively affected in vivo orthotopic xenograft tumor growth, more than doubling median survival of mice from 58 days to 153 days. Our results indicate a role for HMGA2 in AT/RT in vitro and in vivo and demonstrate that HMGA2 is a potential therapeutic target in these lethal pediatric tumors.

HMGA2 is associated with epithelial-mesenchymal transition and can predict poor prognosis in nasopharyngeal carcinoma

Objective

High-mobility group protein 2 (HMGA2) and epithelial–mesenchymal transition (EMT)-associated proteins play key roles in cancer progression and metastasis. However, the clinical significance of HMGA2 and its relationship with EMT markers in nasopharyngeal carcinoma (NPC) is unclear. This study aimed to assess the clinicopathological significance and prognostic value of HMGA2, E-cadherin, and vimentin in NPC.

Methods

Using immunohistochemistry, HMGA2, E-cadherin, and vimentin expression levels were evaluated in NPC (n=124) and non-tumoral inflammatory nasopharynx (n=20) tissues. The association of HMGA2 and EMT markers with clinicopathological characteristics and relationships between the protein levels and overall survival were analyzed.

Results

Compared with non-tumorous tissues, HMGA2 and vimentin levels were markedly increased in NPC tissues, whereas decreased E-cadherin levels were observed (P<0.001). Moreover, HMGA2 expression was positively correlated with vimentin levels (r=0.431, P<0.001) and negatively correlated with E-cadherin amounts (r=−0.413, P<0.001) in NPC tissues. The expression of all three proteins correlated significantly with tumor N stage, TNM stage, and 2-year metastasis. Furthermore, significant correlations were found for T stage, N stage, TNM stage, HMGA2, E-cadherin, and vimentin (all P<0.013) with poor prognosis (univariate analysis). However, multivariate analyses showed that only HMGA2 (hazard ratio [HR]: 2.683, 95% confidence interval [CI]: 1.185–6.077, P=0.018) and N stage (HR: 7.892, 95% CI: 2.731–22.807, P<0.001) were independent predictors of poor prognosis.

Conclusion

These results demonstrated that HMGA2, an independent prognostic factor, may promote NPC progression and metastasis, and is significantly associated with EMT proteins. Therefore, HMGA2 may be considered a potential therapeutic target in NPC.

Identification of genomic alterations in pancreatic cancer using array-based comparative genomic hybridization

Background

Genomic aberration is a common feature of human cancers and also is one of the basic mechanisms that lead to overexpression of oncogenes and underexpression of tumor suppressor genes. Our study aims to identify frequent genomic changes in pancreatic cancer.

Materials and Methods

We used array comparative genomic hybridization (array CGH) to identify recurrent genomic alterations and validated the protein expression of selected genes by immunohistochemistry.

Results

Sixteen gains and thirty-two losses occurred in more than 30% and 60% of the tumors, respectively. High-level amplifications at 7q21.3–q22.1 and 19q13.2 and homozygous deletions at 1p33–p32.3, 1p22.1, 1q22, 3q27.2, 6p22.3, 6p21.31, 12q13.2, 17p13.2, 17q21.31 and 22q13.1 were identified. Especially, amplification of AKT2 was detected in two carcinomas and homozygous deletion of CDKN2C in other two cases. In 15 independent validation samples, we found that AKT2 (19q13.2) and MCM7 (7q22.1) were amplified in 6 and 9 cases, and CAMTA2 (17p13.2) and PFN1 (17p13.2) were homozygously deleted in 3 and 1 cases. AKT2 and MCM7 were overexpressed, and CAMTA2 and PFN1 were underexpressed in pancreatic cancer tissues than in morphologically normal operative margin tissues. Both GISTIC and Genomic Workbench software identified 22q13.1 containing APOBEC3A and APOBEC3B as the only homozygous deletion region. And the expression levels of APOBEC3A and APOBEC3B were significantly lower in tumor tissues than in morphologically normal operative margin tissues. Further validation showed that overexpression of PSCA was significantly associated with lymph node metastasis, and overexpression of HMGA2 was significantly associated with invasive depth of pancreatic cancer.

Conclusion

These recurrent genomic changes may be useful for revealing the mechanism of pancreatic carcinogenesis and providing candidate biomarkers.

Nanoparticle delivery of an AKT/PDK1 inhibitor improves the therapeutic effect in pancreatic cancer

The K-ras mutation in pancreatic cancer can inhibit drug delivery and increase drug resistance. This is exemplified by the therapeutic effect of PH-427, a small molecule inhibitor of AKT/PDK1, which has shown a good therapeutic effect against a BxPC3 pancreatic cancer model that has K-ras, but has a poor therapeutic effect against a MiaPaCa-2 pancreatic cancer model with mutant K-ras. To increase the therapeutic effect of PH-427 against the MiaPaCa-2 pancreatic cancer model with mutant K-ras, we encapsulated PH-427 into poly(lactic-co-glycolic acid) nanoparticles (PNP) to form drug-loaded PH-427-PNP. PH-427 showed a biphasic release from PH-427-PNP over 30 days during studies in sodium phosphate buffer, and in vitro studies revealed that the PNP was rapidly internalized into MiaPaCa-2 tumor cells, suggesting that PNP can improve PH-427 delivery into cells harboring mutant K-ras. In vivo studies of an orthotopic MiaPaCa-2 pancreatic cancer model showed reduced tumor load with PH-427-PNP as compared with treatment using PH-427 alone or with no treatment. Ex vivo studies confirmed the in vivo results, suggesting that PNP can improve drug delivery to pancreatic cancer harboring mutant K-ras.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

MicroRNA expression as risk biomarker of breast cancer metastasis: a pilot retrospective case-cohort study

BACKGROUND

MicroRNAs (miRNAs) are small, non-coding RNA molecules involved in post-transcriptional gene regulation and have recently been shown to play a role in cancer metastasis. In solid tumors, especially breast cancer, alterations in miRNA expression contribute to cancer pathogenesis, including metastasis. Considering the emerging role of miRNAs in metastasis, the identification of predictive markers is necessary to further the understanding of stage-specific breast cancer development. This is a retrospective analysis that aimed to identify molecular biomarkers related to distant breast cancer metastasis development.

METHODS

A retrospective case cohort study was performed in 64 breast cancer patients treated during the period from 1998-2001. The case group (n = 29) consisted of patients with a poor prognosis who presented with breast cancer recurrence or metastasis during follow up. The control group (n = 35) consisted of patients with a good prognosis who did not develop breast cancer recurrence or metastasis. These patient groups were stratified according to TNM clinical stage (CS) I, II and III, and the main clinical features of the patients were homogeneous. MicroRNA profiling was performed and biomarkers related to metastatic were identified independent of clinical stage. Finally, a hazard risk analysis of these biomarkers was performed to evaluate their relation to metastatic potential.

RESULTS

MiRNA expression profiling identified several miRNAs that were both specific and shared across all clinical stages (p ≤ 0.05). Among these, we identified miRNAs previously associated with cell motility (let-7 family) and distant metastasis (hsa-miR-21). In addition, hsa-miR-494 and hsa-miR-21 were deregulated in metastatic cases of CSI and CSII. Furthermore, metastatic miRNAs shared across all clinical stages did not present high sensitivity and specificity when compared to specific-CS miRNAs. Between them, hsa-miR-183 was the most significative of CSII, which miRNAs combination for CSII (hsa-miR-494, hsa-miR-183 and hsa-miR-21) was significant and were a more effective risk marker compared to the single miRNAs.

CONCLUSIONS

Women with metastatic breast cancer, especially CSII, presented up-regulated levels of miR-183, miR-494 and miR-21, which were associated with a poor prognosis. These miRNAs therefore represent new risk biomarkers of breast cancer metastasis and may be useful for future targeted therapies.

HMGA2 induces transcription factor Slug expression to promote epithelial-to-mesenchymal transition and contributes to colon cancer progression

Epithelial-to-mesenchymal transition (EMT) is considered to play an essential role in progression and metastasis. This study aims to investigate the expression and underlying molecular targets of high-mobility group AT-hook 2 (HMGA2) in the progression of colon cancer. The expression of HMGA2 is upregulated by both active extracellular signal-regulated kinase (ERK)1/2 and TGF-β signaling in colon cancer cells through a series of lentiviral infection and pharmacological assays. HMGA2 knockdown by specific shRNAs attenuates proliferation, motility and invasion of colon cancer cells in vitro and in vivo. Besides, exogenous HMGA2 expression caused EMT in colon cancer cells, which was confirmed by the downregulation of the epithelial markers and the upregulation of the mesenchymal markers. Moreover, HMGA2 positively regulates the Slug expression by directly binding to the regulatory region in Slug promoter. Importantly, the knockdown of Slug could reverse the HMGA2-induced EMT and decrease the migration and invasion ability of colon cancer cells. Taken together, our results reveal a critical role for HMGA2 in promoting EMT, migration, invasion, and proliferation of colon cancer cells, suggesting HMGA2 as a potential molecular target to prevent colon cancer progression.

Role of miRNA let-7 and its major targets in prostate cancer

Prostate cancer is worldwide the sixth leading cause of cancer related death in men thus early detection and successful treatment are still of major interest. The commonly performed screening of the prostate-specific antigen (PSA) is controversially discussed, as in many patients the prostate-specific antigen levels are chronically elevated in the absence of cancer. Due to the unsatisfying efficiency of available prostate cancer screening markers and the current treatment outcome of the aggressive hormone refractory prostate cancer, the evaluation of novel molecular markers and targets is considered an issue of high importance. MicroRNAs are relatively stable in body fluids orchestrating simultaneously the expression of many genes. These molecules are currently discussed to bear a greater diagnostic potential than protein-coding genes, being additionally promising therapeutic drugs and/or targets. Herein we review the potential impact of the microRNA let-7 family on prostate cancer and show how deregulation of several of its target genes could influence the cellular equilibrium in the prostate gland, promoting cancer development as they do in a variety of other human malignant neoplasias.

RKIP inhibits gastric cancer cell survival and invasion by regulating the expression of HMGA2 and OPN

The objective of this study was to explore the mechanism via which Raf kinase inhibitor protein (RKIP) suppresses the invasion of gastric cancer cells and promote apoptosis, with an attempt to provide evidences for the application of RKIP in treating gastric cancer. The recombinant plasmid pcDNA3.1-RKIP or RKIP-shRNA was transfected into the gastric cancer cell line SGC-7901 using liposome. Then, the messenger RNA (mRNA) and protein expressions of RKIP, HMGA2, and OPN were detected using qPCR and Western blotting. The effects of HMGA2 on the proliferation, apoptosis, and invasion of SGC-7901 cells were detected using flow cytometry and Transwell assay. To further explore the regulatory effect of PKIP on the biological activities of HMGA2, we over-expressed or knock down RKIP and HMGA2 simultaneously and detected its effects on the proliferation, apoptosis, and invasion of SGC-7901 cells. As shown by qPCR and Western blotting, after over-expression of RKIP in SGC-7901 cells, the mRNA and protein expressions of RKIP significantly increased (P < 0.01), whereas the mRNA and protein expressions of HMGA2 and OPN significantly decreased (P < 0.01). In contrast, the transfection of RKIP-shRNA in the SGC-7901 cells resulted in opposite results. After over-expression of HMGA2 in SGC-7901 cells, the protein expression of HMGA2 significantly increased (P < 0.01); however, it significantly decreased after the transfection of HMGA2-shRNA (P < 0.01). As shown by Transwell assay and flow cytometry, After the over-expression of HMGA2 in SGC-7901 cells, the (G2 + S) phase fraction significantly increased (P < 0.01); also, the percentage of the apoptotic cells significantly declined (P < 0.05) and the number of invasive cells significantly increased (P < 0.05). However, the interference of the expression of HMGA2 resulted in opposite results. The simultaneous over-expression of RKIP and HMGA2 in SGC-7901 cells or the simultaneous interference of RKIP and HMGA2 showed no significant difference with the control group in terms of (G2 + S) phase fraction, percentage of apoptotic cells, and number of invasive cells (P > 0.05). In conclusion, RKIP can inhibit the survival and invasion of gastric cancer cells and promote apoptosis, possibly by regulating the expression of HMGA2 or OPN.

miRNA expression in anaplastic thyroid carcinomas

Anaplastic thyroid carcinoma (ATC) is the most lethal form of thyroid neoplasia and represents an end stage of thyroid tumor progression. No effective treatment exists so far. In this study, we analyzed the miRNA expression profiles of 11 ATC by microarrays and their relationship with the mRNA expression profiles of the same 11 ATC samples. ATC show distinct miRNA expression profiles compared to other less aggressive thyroid tumor types. ATC show 18 commonly deregulated miRNA compared to normal thyroid tissue (17 downregulated and 1 upregulated miRNA). First, the analysis of a combined approach of the mRNA gene expression and of the bioinformatically predicted mRNA targets of the deregulated miRNA suggested a role for these regulations in the epithelial to mesenchymal transition (EMT) process in ATC. Second, the direct interaction between one of the upregulated mRNA target, the LOX gene which is an EMT key player, and a downregulated miRNA, the miR-29a, was experimentally validated by a luciferase assay in HEK cell. Third, we confirmed that the ATC tissue is composed of about 50% of tumor associated macrophages (TAM) and suggested, by taking into account our data and published data, their most likely direct or paracrine intercommunication between them and the thyroid tumor cells, amplifying the tumor aggressiveness. Finally, we demonstrated by in situ hybridization a specific thyrocyte localization of 3 of the deregulated miRNA: let-7g, miR-29a and miR-30e and we pointed out the importance of identifying the cell type localization before drawing any conclusion on the physiopathological role of a given gene.

Stromal elements act to restrain, rather than support, pancreatic ductal adenocarcinoma

Sonic hedgehog (Shh), a soluble ligand overexpressed by neoplastic cells in pancreatic ductal adenocarcinoma (PDAC), drives formation of a fibroblast-rich desmoplastic stroma. To better understand its role in malignant progression, we deleted Shh in a well-defined mouse model of PDAC. As predicted, Shh-deficient tumors had reduced stromal content. Surprisingly, such tumors were more aggressive and exhibited undifferentiated histology, increased vascularity, and heightened proliferation--features that were fully recapitulated in control mice treated with a Smoothened inhibitor. Furthermore, administration of VEGFR blocking antibody selectively improved survival of Shh-deficient tumors, indicating that Hedgehog-driven stroma suppresses tumor growth in part by restraining tumor angiogenesis. Together, these data demonstrate that some components of the tumor stroma can act to restrain tumor growth.

Generation and characterisation of a canine EGFP-HMGA2 prostate cancer in vitro model

The architectural transcription factor HMGA2 is abundantly expressed during embryonic development. In several malignant neoplasias including prostate cancer, high re-expression of HMGA2 is correlated with malignancy and poor prognosis. The let-7 miRNA family is described to regulate HMGA2 negatively. The balance of let-7 and HMGA2 is discussed to play a major role in tumour aetiology. To further analyse the role of HMGA2 in prostate cancer a stable and highly reproducible in vitro model system is precondition. Herein we established a canine CT1258-EGFP-HMGA2 prostate cancer cell line stably overexpressing HMGA2 linked to EGFP and in addition the reference cell line CT1258-EGFP expressing solely EGFP to exclude EGFP-induced effects. Both recombinant cell lines were characterised by fluorescence microscopy, flow cytometry and immunocytochemistry. The proliferative effect of ectopically overexpressed HMGA2 was determined via BrdU assays. Comparative karyotyping of the derived and the initial CT1258 cell lines was performed to analyse chromosome consistency. The impact of the ectopic HMGA2 expression on its regulator let-7a was analysed by quantitative real-time PCR. Fluorescence microscopy and immunocytochemistry detected successful expression of the EGFP-HMGA2 fusion protein exclusively accumulating in the nucleus. Gene expression analyses confirmed HMGA2 overexpression in CT1258-EGFP-HMGA2 in comparison to CT1258-EGFP and native cells. Significantly higher let-7a expression levels were found in CT1258-EGFP-HMGA2 and CT1258-EGFP. The BrdU assays detected an increased proliferation of CT1258-HMGA2-EGFP cells compared to CT1258-EGFP and native CT1258. The cytogenetic analyses of CT1258-EGFP and CT1258-EGFP-HMGA2 resulted in a comparable hyperdiploid karyotype as described for native CT1258 cells. To further investigate the impact of recombinant overexpressed HMGA2 on CT1258 cells, other selected targets described to underlie HMGA2 regulation were screened in addition. The new fluorescent CT1258-EGFP-HMGA2 cell line is a stable tool enabling in vitro and in vivo analyses of the HMGA2-mediated effects on cells and the development and pathogenesis of prostate cancer.

LIN28A facilitates the transformation of human neural stem cells and promotes glioblastoma tumorigenesis through a pro-invasive genetic program

The cellular reprogramming factor LIN28A promotes tumorigenicity in cancers arising outside the central nervous system, but its role in brain tumors is unknown. We detected LIN28A protein in a subset of human gliomas observed higher expression in glioblastoma (GBM) than in lower grade tumors. Knockdown of LIN28A using lentiviral shRNA in GBM cell lines inhibited their invasion, growth and clonogenicity. Expression of LIN28A in GBM cell lines increased the number and size of orthotopic xenograft tumors. LIN28A expression also enhanced the invasiveness of GBM cells in vitro and in vivo. Increasing LIN28A was associated with down-regulation of tumor suppressing microRNAs let-7b and let-7g and up-regulation of the chromatin modifying protein HMGA2. The increase in tumor cell aggressiveness in vivo and in vitro was accompanied by an upregulation of pro-invasive gene expression, including SNAI1. To further investigate the oncogenic potential of LIN28A, we infected hNSC with lentiviruses encoding LIN28A together with dominant negative R248W-TP53, constitutively active KRAS and hTERT. Resulting subclones proliferated at an increased rate and formed invasive GBM-like tumors in orthotopic xenografts in immunodeficient mice. Similar to LIN28A-transduced GBM neurosphere lines, hNSC-derived tumor cells showed increased expression of HMGA2. Taken together, these data suggest a role for LIN28A in high grade gliomas and illustrate an HMGA2-associated, pro-invasive program that can be activated in GBM by LIN28A-mediated suppression of let-7 microRNAs.

Role of microRNA in epithelial to mesenchymal transition and metastasis and clinical perspectives

The microRNAs (miRNAs) are a class of small, 20–22 nucleotides in length, endogenously expressed noncoding RNAs that regulate multiple targets posttranscriptionally. Interestingly, miRNAs have emerged as regulators of most physiological and pathological processes, including metastatic tumor progression, in part by controlling a reversible process called epithelial-to-mesenchymal transition (EMT). The activation of EMT increases the migratory and invasive properties fundamental for tumor cell spread while activation of the reverse mesenchymal-to-epithelial transition is required for metastasis outgrowth. The EMT triggering leads to the activation of a core of transcription factors (EMT-TFs) – SNAIL1/SNAIL2, bHLH (E47, E2-2, and TWIST1/TWIST2), and ZEB1/ZEB2 – that act as E-cadherin repressors and, ultimately, coordinate EMT. Recent evidence indicates that several miRNAs regulate the expression of EMT-TFs or EMT-activating signaling pathways. Interestingly, some miRNAs and EMT-TFs form tightly interconnected negative feedback loops that control epithelial cell plasticity, providing self-reinforcing signals and robustness to maintain the epithelial or mesenchymal cell status. Among the most significant feedback loops, we focus on the ZEB/miR-200 and the SNAIL1/miR-34 networks that hold a clear impact in the regulation of the epithelial-mesenchymal state. Recent insights into the p53 modulation of the EMT-TF/miRNA loops and epigenetic regulatory mechanisms in the context of metastasis dissemination will also be discussed. Understanding the regulation of EMT by miRNAs opens new avenues for the diagnosis and prognosis of tumors and identifies potential therapeutic targets that might help to negatively impact on metastasis dissemination and increasing patient survival.

Molecular mechanisms of epithelial-mesenchymal transition

The transdifferentiation of epithelial cells into motile mesenchymal cells, a process known as epithelial-mesenchymal transition (EMT), is integral in development, wound healing and stem cell behaviour, and contributes pathologically to fibrosis and cancer progression. This switch in cell differentiation and behaviour is mediated by key transcription factors, including SNAIL, zinc-finger E-box-binding (ZEB) and basic helix-loop-helix transcription factors, the functions of which are finely regulated at the transcriptional, translational and post-translational levels. The reprogramming of gene expression during EMT, as well as non-transcriptional changes, are initiated and controlled by signalling pathways that respond to extracellular cues. Among these, transforming growth factor-β (TGFβ) family signalling has a predominant role; however, the convergence of signalling pathways is essential for EMT.

Probing into the biological processes influenced by ESC factor and oncoprotein HMGA2 using iPSCs

Induced pluripotent stem cells (iPSCs) are rapidly evolving into an important research tool due to their close resemblance with pluripotent embryonic stem cells (ESCs). Of particular interest at this point are iPSC applications in disease modeling and drug discovery/testing. The high mobility group AT-hook 2 (HMGA2) protein is a nonhistone chromatin factor normally expressed in ESCs and during early developmental stages. Aberrant HMGA2 expression is associated, for example, with abnormal body stature, diabetes mellitus, heart development and uterine leiomyomas. Furthermore, the protein is re-expressed in many primary tumor cells and plays an important role in metastasis. Here we used iPSC formation in conjunction with exogenous human HMGA2 expression to gain insight into biological functions of HMGA2. Gene expression profiling and gene ontology analyses showed that anatomical development and cell adhesion/differentiation processes are strongly affected by HMGA2. This could help to uncover, at the molecular level, some of the known phenotypic consequences of aberrant HMGA2 expression. Furthermore, our data showed that expression of key diabetes susceptibility genes is influenced by HMGA2, which revealed an interesting link to the recently indentified Lin28/let-7 pathway regulating mammalian glucose metabolism. Contrary to a previous report, our results indicate that HMGA2 is not involved in the regulation of telomerase gene expression. Finally, our data support a model in which tight regulation of intracellular HMGA2 levels is important both to maintain a pluripotent ESC state and to induce differentiation into certain cell lineages during later developmental stages.

Mechanisms of therapeutic resistance in cancer (stem) cells with emphasis on thyroid cancer cells

The two main reasons for death of cancer patients, tumor recurrence and metastasis, are multi-stage cellular processes that involve increased cell plasticity and coincide with elevated resistance to anti-cancer treatments. Epithelial-to-mesenchymal transition (EMT) is a key contributor to metastasis in many cancer types, including thyroid cancer and is known to confer stem cell-like properties onto cancer cells. This review provides an overview of molecular mechanisms and factors known to contribute to cancer cell plasticity and capable of enhancing cancer cell resistance to radio- and chemotherapy. We elucidate the role of DNA repair mechanisms in contributing to therapeutic resistance, with a special emphasis on thyroid cancer. Next, we explore the emerging roles of autophagy and damage-associated molecular pattern responses in EMT and chemoresistance in tumor cells. Finally, we demonstrate how cancer cells, including thyroid cancer cells, can highjack the oncofetal nucleoprotein high-mobility group A2 to gain increased transformative cell plasticity, prevent apoptosis, and enhance metastasis of chemoresistant tumor cells.

HMGA proteins as modulators of chromatin structure during transcriptional activation

High mobility group (HMG) proteins are the most abundant non-histone chromatin associated proteins. HMG proteins bind to DNA and nucleosome and alter the structure of chromatin locally and globally. Accessibility to DNA within chromatin is a central factor that affects DNA-dependent nuclear processes, such as transcription, replication, recombination, and repair. HMG proteins associate with different multi-protein complexes to regulate these processes by mediating accessibility to DNA. HMG proteins can be subdivided into three families: HMGA, HMGB, and HMGN. In this review, we will focus on recent advances in understanding the function of HMGA family members, specifically their role in gene transcription regulation during development and cancer.

Reexpression of Let-7g microRNA inhibits the proliferation and migration via K-Ras/HMGA2/snail axis in hepatocellular carcinoma

Let-7 family microRNAs have been reported to be downregulated in human hepatocellular carcinoma in comparison with normal hepatic tissues. Among them, let-7g was identified as the lowest expression using real-time RT-PCR. However, the mechanism by which let-7g works in hepatocellular carcinoma remains unknown. Here, in our present study, we have had let-7g reexpressed in vitro in hepatocellular carcinoma cell lines MHCC97-H and HCCLM3 via transfection. The proliferation after reexpression of let-7g was assayed using MTT method; the migration and invasion after restoration were detected by wound-healing and Transwell assay, respectively. We found using Western-blotting that let-7g can regulate epithelial-mesenchymal transition (EMT) by downregulating K-Ras and HMGA2A after reexpresssion. Xenografted nude mice were used to observe whether or not reexpression of let-7g could have potential therapeutic ability. In vivo, to observe the association with let-7g expression and overall prognosis, 40 paired cases of hepatocellular carcinoma were analyzed using in situ hybridization (ISH). It was found that reexpression of let-7g can inhibit the proliferation, migration, and invasion significantly, and that low expression of let-7g was significantly associated with poorer overall survival. Taken together, let-7g could be used as a promising therapeutic agent in vivo in the treatment of hepatocellular carcinoma at the earlier stage.

Advances in serous tubal intraepithelial carcinoma: correlation with high grade serous carcinoma and ovarian carcinogenesis

Early serous carcinoma in fallopian tube or serous tubal intraepithelial carcinoma (STIC), an early lesion limited to the epithelium of the fallopian tube and firstly identified from specimen obtained by prophylactic salpingo-oophorectomy, has provided insight into pelvic high grade serous carcinoma (HGSC). Increasing evidence indicates that STIC is a likely precursor for HGSC and several studies have focused on this lesion and its clinical significance. This review addresses recent advances in recognizing STIC and its correlation with HGSC and ovarian carcinogenesis. It also describes evidence regarding the fallopian tube as a source of some HGSCs, the protocol for optimizing histological evaluation of the tubes, the spectrum of tubal lesions from benign to noninvasive carcinoma, changes in diagnostic criteria from purely morphologic characteristics to a combination of morphologic features and molecular biomarkers, and new studies about potential biomarkers. However, the direct evidence regarding STIC as the precursor of HGSC is still tantalizing due to other possibilities that may also explain the origin of pelvic HGSC. Further molecular genetic studies are required to address this important question.

MiR-200a inhibits epithelial-mesenchymal transition of pancreatic cancer stem cell

Background

Pancreatic cancer is one of the most aggressive cancers, and the aggressiveness of pancreatic cancer is in part due to its intrinsic and extrinsic drug resistance characteristics, which are also associated with the acquisition of epithelial-to-mesenchymal transition (EMT). Increasing evidence suggests that EMT-type cells share many biological characteristics with cancer stem-like cells. And miR-200 has been identified as a powerful regulator of EMT.

Methods

Cancer Stem Cells (CSCs) of human pancreatic cancer cell line PANC-1 were processed for CD24, CD44 and ESA multi-colorstaining, and sorted out on a BD FACS Aria II machine. RT-qPCR was performed using the miScript PCR Kit to assay the expression of miR-200 family. In order to find the role of miR-200a in the process of EMT, miR-200a mimic was transfected to CSCs.

Results

Pancreatic cancer cells with EMT phenotype displayed stem-like cell features characterized by the expression of cell surface markers CD24, CD44 and epithelial-specific antigen (ESA), which was associated with decreased expression of miR-200a. Moreover, overexpression of miR-200a was resulted in down-regulation of N-cadherin, ZEB1 and vimentin, but up-regulation of E-cadherin. In addition, miR-200a overexpression inhibited cell migration and invasion in CSCs.

Conclusion

In our study, we found that miR-200a played an important role in linking the characteristics of cancer stem-like cells with EMT-like cell signatures in pancreatic cancer. Selective elimination of cancer stem-like cells by reversing the EMT phenotype to mesenchymal-to-epithelial transition (MET) phenotype using novel agents would be useful for prevention and/or treatment of pancreatic cancer.

MicroRNAs (miRNAs) as biomarker(s) for prognosis and diagnosis of gastrointestinal (GI) cancers

Gastrointestinal (GI) cancers remain one of the most common malignancies and are the second common cause of cancer deaths worldwide. The limited effectiveness of therapy for patients with advanced stage and recurrent disease is a reflection of an incomplete understanding of the molecular basis of GI carcinogenesis. Major advancements have improved our understanding of pathology and pathogenesis of GI cancers, but high mortality rates, unfavorable prognosis and lack of clinical predictive biomarkers provide an impetus to investigate new sensitive and specific diagnostic and prognostic markers for GI cancers. MicroRNAs (miRNAs) are short (19-24 nucleotides) noncoding RNA molecules that regulate gene expression at the posttranscriptional level thus playing an important role in modulating various biological processes including, but not limited to developmental processes, proliferation, apoptosis, metabolism, differentiation, epithelial-mechenchymal transition and are involved in the initiation and progression of various human cancers. Unique miRNA expression profiles have been observed in various cancer types at different stages, suggesting their potential as diagnostic and prognostic biomarkers. Due to their tumor-specific and tissue-specific expression profiles, stability, robust clinical assays for detection in serum as well as in formalin-fixed tissue samples, miRNAs have emerged as attractive candidates for diagnostic and prognostic applications. This review summarizes recent research supporting the utility of miRNAs as novel diagnostic and prognostic tools for GI cancers.

Frequent overexpression of HMGA2 in human atypical teratoid/rhabdoid tumor and its correlation with let-7a3/let-7b miRNA

PURPOSE

Atypical teratoid/rhabdoid tumors (AT/RT) are highly aggressive pediatric malignancies characterized by biallelic inactivation of the SMARCB1 tumor suppressor gene. We searched for novel genomic aberrations by investigating the copy number and expression alterations of let-7a3/let-7b microRNA (miRNA) and correlated these with expression of high-mobility group AT-hook 2 (HMGA2) oncoprotein, a target of let-7 miRNA family, in 18 AT/RT samples to elucidate potential roles of HMGA2 in the pathogenesis of AT/RT.

EXPERIMENTAL DESIGN

Genomic aberrations, let-7a3/let-7b miRNA and HMGA2 expression in AT/RT tissues were identified using quantitative PCR, reverse transcription PCR (RT-PCR), and immunohistochemistry. The impact of let-7b miRNA on HMGA2 expression and the malignant potential of human rhabdoid tumor cell G401 (SMARCB1(-/-)) were investigated by antisense inhibition and ectopic overexpression studies.

RESULTS

The copy number of let-7a3/let-7b miRNA was substantially decreased in 4 of 11 AT/RT samples. A significantly inverse correlation between let-7a3/let-7b miRNA expression and HMGA2 mRNA expression was observed in AT/RT tissues (R = -0.34; P < 0.05). Immunohistochemistry analysis demonstrated that HMGA2 was highly overexpressed in 83.3% (15 of 18) of AT/RT tissues. Restoration of let-7 miRNA or knockdown of HMGA2 expression significantly suppressed proliferation and colony formation, and almost abolished the invasive potential of G401 cells.

CONCLUSION

Reduction of let-7a3/let-7b miRNA may be one of mechanisms leading to overexpression of HMGA2 in AT/RT tissues. HMGA2 oncoprotein plays critical roles in the pathogenesis of AT/RT development; and reconstitution of let-7 miRNA or knockdown of HMGA2 oncoprotein may provide a novel therapeutic strategy for the treatment of patients with AT/RT.