Upregulated miR-182 increases drug resistance in cisplatin-treated HCC cell by regulating TP53INP1

Chemotherapy plays a crucial role in hepatocellular carcinoma (HCC) treatment especially for patients with advanced HCC. Cisplatin is one of the commonly used chemotherapeutic drugs for the treatment of HCC. However, acquisition of cisplatin resistance is common in patients with HCC, and the underlying mechanism of such resistance is not fully understood. In the study, we focused on identifying the role of miRNAs in chemotherapy resistance after cisplatin-based combination chemotherapy. We assayed the expression level of miR-182 after cisplatin-based chemotherapy in patients with advanced HCC, and defined the biological functions by real-time PCR analysis and CCK-8 assay. We found that miR-182 levels were significantly increased in HCC patients treated with cisplatin-based chemotherapy. miR-182 levels were also higher in cisplatin-resistant HepG2 (HepG2-R) cells than in HepG2 cells. Upregulated miR-182 significantly increased the cell viability, whereas miR-182 knockdown reduced the cell viability during cisplatin treatment. miR-182 inhibition also partially overcame cisplatin resistance in HepG2-R cell. Furthermore, we found that upregulated miR-182 inhibited the expression of tumor suppressor gene TP53INP1 (tumor protein 53-induced nuclear protein1) in vitro. In vivo, miR-182 and TP53INP1 expression was negatively correlated. We finally demonstrated that miR-182 increased cisplatin resistance of HCC cell, partly by targeting TP53INP1. These data suggest that miR-182/TP53INP1 signaling represents a novel pathway regulating chemoresistance, thus offering a new target for chemotherapy of HCC.     

Cisplatin-induced downregulation of miR-199a-5p increases drug resistance by activating autophagy in HCC cell

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Systemic chemotherapy plays an important role in the treatment of patients with advanced liver cancer. However, chemoresistance to cisplatin is a major limitation of cisplatin-based chemotherapy in the clinic, and the underlying mechanism of such resistance is not fully understood. In the study, we found that miR-199a-5p levels were significantly reduced in HCC patients treated with cisplatin-based chemotherapy. Cisplatin treatment also resulted in decreased miR-199a-5p levels in human HCC cell lines. Forced expression of miR-199a-5p promoted cisplatin-induced inhibition of cell proliferation. Cisplatin treatment activated autophagy in Huh7 and HepG2 cells, which increased cell proliferation. We further demonstrated that downregulated miR-199a-5p enhanced autophagy activation by targeting autophagy-associated gene 7 (ATG7). More important, autophagy inhibition abrogated miR-199a-5p downregulation-induced cell proliferation. These data demonstrated that miR-199a-5p/autophagy signaling represents a novel pathway regulating chemoresistance, thus offering a new target for chemotherapy of HCC.     

GATA6 activates Wnt signaling in pancreatic cancer by negatively regulating the Wnt antagonist Dickkopf-1

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease characterized by late diagnosis and treatment resistance. Recurrent genetic alterations in defined genes in association with perturbations of developmental cell signaling pathways have been associated with PDAC development and progression. Here, we show that GATA6 contributes to pancreatic carcinogenesis during the temporal progression of pancreatic intraepithelial neoplasia by virtue of Wnt pathway activation. GATA6 is recurrently amplified by both quantitative-PCR and fluorescent in-situ hybridization in human pancreatic intraepithelial neoplasia and in PDAC tissues, and GATA6 copy number is significantly correlated with overall patient survival. Forced overexpression of GATA6 in cancer cell lines enhanced cell proliferation and colony formation in soft agar in vitro and growth in vivo, as well as increased Wnt signaling. By contrast siRNA mediated knockdown of GATA6 led to corresponding decreases in these same parameters. The effects of GATA6 were found to be due to its ability to bind DNA, as forced overexpression of a DNA-binding mutant of GATA6 had no effects on cell growth in vitro or in vivo, nor did they affect Wnt signaling levels in these same cells. A microarray analysis revealed the Wnt antagonist Dickopf-1 (DKK1) as a dysregulated gene in association with GATA6 knockdown, and direct binding of GATA6 to the DKK1 promoter was confirmed by chromatin immunoprecipitation and electrophoretic mobility shift assays. Transient transfection of GATA6, but not mutant GATA6, into cancer cell lines led to decreased DKK1 mRNA expression and secretion of DKK1 protein into culture media. Forced overexpression of DKK1 antagonized the effects of GATA6 on Wnt signaling in pancreatic cancer cells. These findings illustrate that one mechanism by which GATA6 promotes pancreatic carcinogenesis is by virtue of its activation of canonical Wnt signaling via regulation of DKK1.     

miR-199b-5p enhances the proliferation of medullary thymic epithelial cells via regulating Wnt signaling by targeting Fzd6

Thymic epithelial cells (TECs) are essential regulators of T-cell development and selection. miRNAs play critical roles in regulating TEC proliferation during the process of thymic aging. Our previous studies revealed that miR-199b-5p was upregulated in TECs from 1- to 3-month-old mice. But its function and potential mechanism are not clear. We hypothesized that miR-199b-5p may play an important role in age-related thymus involution via targeting some genes. To confirm it, the murine thymic epithelial cell line 1 (MTEC1) cells were used. Our results showed that overexpression of miR-199b-5p can enhance MTEC1 cell proliferation. On the contrary, repression of miR-199b-5p can inhibit MTEC1 cell proliferation. Meanwhile, it was confirmed that frizzled receptor 6 (Fzd6) is the direct target gene of miR-199b-5p. Furthermore, overexpression of miR-199b-5p can upregulate the expressions of β-catenin, Tcf7, Wnt4, and C-myc to activate Wnt signaling and cell cycle signaling. Silence of Fzd6 and co-transfection with siFzd6 and miR-199b-5p mimic/inhibitor confirmed that the biological function of miR-199b-5p is indeed by targeting Fzd6 in medullary TECs. Overall, miR-199b-5p is an important regulator in medullary TEC proliferation through targeting Fzd6 to activate Wnt signaling and cell cycle signaling. Our data indicate that miR-199b-5p may block the process of thymic aging and be a potential therapeutic target for thymus involution.     

Tauroursodeoxycholic acid increases neural stem cell pool and neuronal conversion by regulating mitochondria-cell cycle retrograde signaling

The low survival and differentiation rates of stem cells after either transplantation or neural injury have been a major concern of stem cell-based therapy. Thus, further understanding long-term survival and differentiation of stem cells may uncover new targets for discovery and development of novel therapeutic approaches. We have previously described the impact of mitochondrial apoptosis-related events in modulating neural stem cell (NSC) fate. In addition, the endogenous bile acid, tauroursodeoxycholic acid (TUDCA) was shown to be neuroprotective in several animal models of neurodegenerative disorders by acting as an anti-apoptotic and anti-oxidant molecule at the mitochondrial level. Here, we hypothesize that TUDCA might also play a role on NSC fate decision. We found that TUDCA prevents mitochondrial apoptotic events typical of early-stage mouse NSC differentiation, preserves mitochondrial integrity and function, while enhancing self-renewal potential and accelerating cell cycle exit of NSCs. Interestingly, TUDCA prevention of mitochondrial alterations interfered with NSC differentiation potential by favoring neuronal rather than astroglial conversion. Finally, inhibition of mitochondrial reactive oxygen species (mtROS) scavenger and adenosine triphosphate (ATP) synthase revealed that the effect of TUDCA is dependent on mtROS and ATP regulation levels. Collectively, these data underline the importance of mitochondrial stress control of NSC fate decision and support a new role for TUDCA in this process.     

MicroRNA-106a induces multidrug resistance in gastric cancer by targeting RUNX3

Multidrug resistance (MDR) is the main barrier to the success of chemotherapy for gastric cancer (GC). miR-106a, which is highly expressed in GC, influences a variety of aspects of GC. However, the function of miR-106a in MDR of GC still remains unclear. In the present study, we found that miR-106a is elevated in MDR cell lines. miR-106a promotes chemo-resistance of GC cells, accelerates ADR efflux, and suppresses drug-induced apoptosis. Finally, we show that runt-related trans factor 3 (RUNX3) is the functional target of miR-106a. Collectively, these findings demonstrate that miR-106a may promote MDR in GC cells by targeting RUNX3.     

A switch from canonical to noncanonical Wnt signaling mediates drug resistance in colon cancer cells

Butyrate, a fermentation product of fiber in the colon, acts as a histone deacetylase inhibitor (HDACi) and induces apoptosis in colon cancer (CC) cells in vitro. We have reported that the apoptotic effects of butyrate are dependent upon the hyperactivation of the Wnt/beta-catenin pathway. However, prolonged exposure of CC cells to increasing concentrations of butyrate results in the acquisition of resistance to the Wnt/beta-catenin- and apoptosis-inducing effects of this agent, as well as cross-resistance to structurally different HDACis. Here we report that one mechanism whereby HDACi resistance arises is through the increase of beta-catenin-independent (noncanonical) Wnt signaling. Compared to HDACi-sensitive HCT-116 CC cells, HDACi-resistant HCT-R cells exhibit higher levels of AKT/PKB cell survival signaling, which is in part induced by WNT5A and its receptor ROR2. The induction of AKT signaling by HDACis is also detected in other CC cell lines, albeit to a lesser extent than in the drug-resistant HCT-R cells. The observations suggested that the apoptotic effect of butyrate and other HDACis in CC cells can be augmented by inhibitors of pAKT. In agreement with the hypothesis, the combination of MK2206, a pAKT inhibitor, and a HDACi (butyrate or LBH589) induced higher apoptosis in CC cells compared to each agent alone. The exposure to both agents also re-sensitized the HCT-R cells to apoptosis. Finally, the concept of simultaneously inducing canonical Wnt activity and suppressing AKT signaling was translated into a combination of diet-derived agents. Diet-derived pAKT inhibitors (caffeic acid phethyl ester, sulforaphane, dilallyl trisulfide) suppressed the butyrate-induced levels of pAKT, and increased the apoptotic effects of butyrate in both drug-sensitive and drug-resistant CC cells.Our findings can be translated into (a) CC therapy employing combinations of synthetic HDACis and inhibitors of pAKT, as well as (b) CC prevention based upon diets that result in sufficient amounts of butyrate and pAKT inhibitors.     

Adult stem cell specification by Wnt signaling in muscle regeneration

Recently, we describe a biological role for endogenous CD45+ stem cells in maintaining muscle integrity by participating in regeneration. Our experiments further establish that Wnt-signaling is the mechanism by which resident CD45+ adult stem cells are induced to undergo myogenic specification during muscle regeneration. Importantly, our study suggests that targeting the Wnt-pathway represents a promising therapeutic approach for the treatment of neuromuscular degenerative diseases.     

Cell-cell signaling by direct contact increases cell proliferation via a PI3K-dependent signal

We report a novel mechanism of cellular growth control. Increasing the density of endothelial or smooth muscle cells in culture increased cell-cell contact and decreased cell spreading, leading to growth arrest. Using a new method to independently control cell-cell contact and cell spreading, we found that introducing cell-cell contact positively regulates proliferation, but that contact-mediated proliferation can be masked by changes in cell spreading: Round cells with many contacts proliferated less than spread cells with none. Physically blocking cell-cell contact or inhibiting PI3K signaling abrogated cell-cell induced proliferation, but inhibiting diffusible paracrine signaling did not. Thus, direct cell-cell contact induces proliferation in these cells.     

miR-106a confers cisplatin resistance by regulating PTEN/Akt pathway in gastric cancer cells

Recent studies have shown that microRNA-106a （miR-106a） is overexpressed in gastric cancer and contributes to tumor growth. In this study, we investigated whether miR-106a mediated resistance of the gastric cancer cell line SGC7901 to the chemotherapeutic agent cisplatin （DDP）. MiR-106a expression was up-regulated in the DDP resistant cell line SGC7901/DDP compared with its parental line SGC7901. Transfection of miR-106a induced DDP resist- ance in SGC7901, while suppression of miR-106a in SGC7901/DDP led to enhanced DDP cytotoxicity. Further study indicated that the mechanism of miR-106a-induced DDP resistance involved the expression of phosphatase and tensin homolog deleted from chromosome 10 （PTEN） protein and its downstream phosphatidylinositol 3 kinase （Pl3K）/protein kinase B （AKT） pathway. This study provides a novel mechanism of DDP resistance in gastric cancer.     

Involvement of miR-21 in resistance to daunorubicin by regulating PTEN expression in the leukaemia K562 cell line

Recent studies have shown microRNA-21 (miR-21) is overexpressed in several types of cancer and contributes to tumor resistance to chemotherapy. In this study, we investigated whether miR-21 mediated resistance of the leukaemia cell line K562 to the chemotherapeutic agent daunorubicin (DNR). miR-21 expression was upregulated in the DNR resistant cell line K562/DNR compared to its parental line K562. Stable transfection of miR-21 induced drug resistance in K562, while suppression of miR-21 in K562/DNR led to enhanced DNR cytotoxicity. Additional experiments indicate that the mechanism of miR-21 drug resistance involves the PI3K/Akt pathway and changes following PTEN protein expression. This study provides a novel mechanism for understanding leukaemia drug resistance.     

Neural crest stem cell maintenance by combinatorial Wnt and BMP signaling

Canonical Wnt signaling instructively promotes sensory neurogenesis in early neural crest stem cells (eNCSCs) (Lee, H.Y., M. Kleber, L. Hari, V. Brault, U. Suter, M.M. Taketo, R. Kemler, and L. Sommer. 2004. Science. 303:1020-1023). However, during normal development Wnt signaling induces a sensory fate only in a subpopulation of eNCSCs while other cells maintain their stem cell features, despite the presence of Wnt activity. Hence, factors counteracting Wnt signaling must exist. Here, we show that bone morphogenic protein (BMP) signaling antagonizes the sensory fate-inducing activity of Wnt/beta-catenin. Intriguingly, Wnt and BMP act synergistically to suppress differentiation and to maintain NCSC marker expression and multipotency. Similar to NCSCs in vivo, NCSCs maintained in culture alter their responsiveness to instructive growth factors with time. Thus, stem cell development is regulated by combinatorial growth factor activities that interact with changing cell-intrinsic cues.     

Targeting stem cell signaling pathways for drug discovery: advances in the Notch and Wnt pathways

Signaling pathways transduce extracellular stimuli into cells through molecular cascades to regulate cellular functions.In stem cells,a small number of pathways,notably those of TGF-?/BMP,Hedgehog,Notch,and Wnt,are responsible for the regulation of pluripotency and differentiation.During embryonic development,these pathways govern cell fate specifications as well as the formation of tissues and organs.In adulthood,their normal functions are important for tissue homeostasis and regeneration,whereas aberrations result in diseases,such as cancer and degenerative disorders.In complex biological systems,stem cell signaling pathways work in concert as a network and exhibit crosstalk,such as the negative crosstalk between Wnt and Notch.Over the past decade,genetic and genomic studies have identified a number of potential drug targets that are involved in stem cell signaling pathways.Indeed,discovery of new targets and drugs for these pathways has become one of the most active areas in both the research community and pharmaceutical industry.Remarkable progress has been made and several promising drug candidates have entered into clinical trials.This review focuses on recent advances in the discovery of novel drugs which target the Notch and Wnt pathways.     

Blocking circ_0014130 suppressed drug resistance and malignant behaviors of docetaxel resistance-acquired NSCLC cells via regulating miR-545-3p-YAP1 axis

Cytotechnology - Recent evidences have claimed that circular RNAs are deregulated in docetaxel (DTX) resistance in malignant tumors, including non-small-cell lung cancer (NSCLC). Hsa_circ_0014130...     

C. elegans AP-2 and retromer control Wnt signaling by regulating mig-14/Wntless

While endocytosis can regulate morphogen distribution, its precise role in shaping these gradients is unclear. Even more enigmatic is the role of retromer, a complex that shuttles proteins between endosomes and the Golgi apparatus, in Wnt gradient formation. Here we report that DPY-23, the C. elegans mu subunit of the clathrin adaptor AP-2 that mediates the endocytosis of membrane proteins, regulates Wnt function. dpy-23 mutants display Wnt phenotypes, including defects in neuronal migration, neuronal polarity, and asymmetric cell division. DPY-23 acts in Wnt-expressing cells to promote these processes. MIG-14, the C. elegans homolog of the Wnt-secretion factor Wntless, also acts in these cells to control Wnt function. In dpy-23 mutants, MIG-14 accumulates at or near the plasma membrane. By contrast, MIG-14 accumulates in intracellular compartments in retromer mutants. Based on our observations, we propose that intracellular trafficking of MIG-14 by AP-2 and retromer plays an important role in Wnt secretion.