β-Catenin expression is regulated by an IRES-dependent mechanism and stimulated by paclitaxel in human ovarian cancer cells

Upregulated Apelin Signaling in Pancreatic Cancer Activates Oncogenic Signaling Pathways to Promote Tumor Development

Despite decades of effort in understanding pancreatic ductal adenocarcinoma (PDAC), there is still a lack of innovative targeted therapies for this devastating disease. Herein, we report the expression of apelin and its receptor, APJ, in human pancreatic adenocarcinoma and its protumoral function. Apelin and APJ protein expression in tumor tissues from patients with PDAC and their spatiotemporal pattern of expression in engineered mouse models of PDAC were investigated by immunohistochemistry. Apelin signaling function in tumor cells was characterized in pancreatic tumor cell lines by Western blot as well as proliferation, migration assays and in murine orthotopic xenograft experiments. In premalignant lesions, apelin was expressed in epithelial lesions whereas APJ was found in isolated cells tightly attached to premalignant lesions. However, in the invasive stage, apelin and APJ were co-expressed by tumor cells. In human tumor cells, apelin induced a long-lasting activation of PI3K/Akt, upregulated β-catenin and the oncogenes c-myc and cyclin D1 and promoted proliferation, migration and glucose uptake. Apelin receptor blockades reduced cancer cell proliferation along with a reduction in pancreatic tumor burden. These findings identify the apelin signaling pathway as a new actor for PDAC development and a novel therapeutic target for this incurable disease.

The Effect of Nano Albumin Combined with Paclitaxel on Drug Resistance of Breast Cancer Through Regulating ATP Binding Cassette Subfamily B Member 1 (ABCB1)

The paclitaxel is a common-used chemotherapy drug and its combination with nano albumin reduces drug side effect. However, whether nab-paclitaxel affects drug resistance of breast cancer remains unclear. This study intends to discuss the mechanism of drug resistance induced by nab-paclitaxel. The drug resistance of MCF-7/nab-paclitaxel in MCF-7 cell and cell proliferation was detected by MTT along with analysis of ABCB1 expression, cell cycle, and apoptosis. There was stronger drug resistance of nab-paclitaxel in the MCF-7/nab-paclitaxel cell group through be adopted with different concentration of nab-paclitaxel at the 0th hour, 24th hour and 48th hour. There was remarkable abnormal expression of the ABCB1 in the MCF-7/nab-paclitaxel cell group. The si-ABCB1 could release the quantity of the MCF-7/nab-paclitaxel cell blocked at S period. And the si-ABCB1 could reduce the expression of cyclin D1 and CDK2 in the MCF-7/nab-paclitaxel cell notably. But the expression level of p21 was increased when there was high concentration of si-ABCB1. The si-ABCB1 could increase the quantity of the MCF-7/nab-paclitaxel cell at the later period of cell apoptosis notably. The rat’s tumor growth was delayed obviously at the MCF-7/nabpaclitaxel cell group treated by si-ABCB1. But the inhibiting effect of the MCF-7/nab-paclitaxel cell on tumor growth was less. There was stronger drug resistance of cell for the nano albumin combined with paclitaxel. The function of cell proliferation in breast cancer was restrained by the nano albumin combined with paclitaxel mainly through inducing the expression of ABCB1, adjusting the growth of cell cycle and the expression of P21/BCL-2 protein.

CIRP promotes the progression of non-small cell lung cancer through activation of Wnt/β-catenin signaling via CTNNB1

BACKGROUND

Cold-inducible RNA binding protein (CIRP) is a newly discovered proto-oncogene. In this study, we investigated the role of CIRP in the progression of non-small cell lung cancer (NSCLC) using patient tissue samples, cultured cell lines and animal lung cancer models.

METHODS

Tissue arrays, IHC and HE staining, immunoblotting, and qRT-PCR were used to detect the indicated gene expression; plasmid and siRNA transfections as well as viral infection were used to manipulate gene expression; cell proliferation assay, cell cycle analysis, cell migration and invasion analysis, soft agar colony formation assay, tail intravenous injection and subcutaneous inoculation of animal models were performed to study the role of CIRP in NSCLC cells; Gene expression microarray was used to select the underlying pathways; and RNA immunoprecipitation assay, biotin pull-down assay, immunopurification assay, mRNA decay analyses and luciferase reporter assay were performed to elucidate the mechanisms. The log-rank (Mantel-Cox) test, independent sample T-test, nonparametric Mann-Whitney test, Spearman rank test and two-tailed independent sample T-test were used accordingly in our study.

RESULTS

Our data showed that CIRP was highly expressed in NSCLC tissue, and its level was negatively correlated with the prognosis of NSCLC patients. By manipulating CIRP expression in A549, H460, H1299, and H1650 cell lines, we demonstrated that CIRP overexpression promoted the transition of G1/G0 phase to S phase and the formation of an enhanced malignant phenotype of NSCLC, reflected by increased proliferation, enhanced invasion/metastasis and greater tumorigenic capabilities both in vitro and in vivo. Transcriptome sequencing further demonstrated that CIRP acted on the cell cycle, DNA replication and Wnt signaling pathway to exert its pro-oncogenic action. Mechanistically, CIRP directly bound to the 3'- and 5'-UTRs of CTNNB1 mRNA, leading to enhanced stability and translation of CTNNB1 mRNA and promoting IRES-mediated protein synthesis, respectively. Eventually, the increased CTNNB1 protein levels mediated excessive activation of the Wnt/β-catenin signaling pathway and its downstream targets C-myc, COX-2, CCND1, MMP7, VEGFA and CD44.

CONCLUSION

Our results support CIRP as a candidate oncogene in NSCLC and a potential target for NSCLC therapy.

MicroRNA-126 exerts antitumor functions in ovarian cancer by targeting EGFL7 and affecting epithelial-to-mesenchymal transition and ERK/MAPK signaling pathway

Ovarian cancer (OC) is a common gynecological malignant carcinoma worldwide. Accumulating research has revealed that multiple microRNAs (miRNAs) are abnormally expressed at different levels in various malignancies, playing vital roles in tumorigenesis. This study investigated the regulatory functions and potential mechanism of miR-126 in OC proliferation, invasion and migration. It was found that miR-126 was prominently downregulated in OC. Moreover, the decrease of miR-126 promoted the aggressive phenotypes and indicated poor prognosis of OC patients. Functional assays demonstrated that restoration of miR-126 dramatically repressed OC cell proliferation, migration and invasion. Furthermore, luciferase reporter assay was conducted to verify putative binding sites of miR-126 in the epidermal growth factor-like domain 7 (EGFL7) 3 untranslated region (3'UTR), indicating that EGFL7 was a target gene of miR-126 in OC cells. It was further discovered that miR-126 exerts its function on regulating ERK/MAPK pathway and epithelial-to-mesenchymal transition (EMT) in OC cells. The above findings suggested that miR-126 served as a cancer suppressor in OC, suggesting a promising application of miR-126 in the clinical diagnosis and therapeutics of OC.

Repurposing Potential of Riluzole as an ITAF Inhibitor in mTOR Therapy Resistant Glioblastoma

Internal ribosome entry site (IRES)-mediated protein synthesis has been demonstrated to play an important role in resistance to mechanistic target of rapamycin (mTOR) targeted therapies. Previously, we have demonstrated that the IRES trans-acting factor (ITAF), hnRNP A1 is required to promote IRES activity and small molecule inhibitors which bind specifically to this ITAF and curtail IRES activity, leading to mTOR inhibitor sensitivity. Here we report the identification of riluzole (Rilutek^®), an FDA-approved drug for amyotrophic lateral sclerosis (ALS), via an in silico docking analysis of FDA-approved compounds, as an inhibitor of hnRNP A1. In a riluzole-bead coupled binding assay and in surface plasmon resonance imaging analyses, riluzole was found to directly bind to hnRNP A1 and inhibited IRES activity via effects on ITAF/RNA-binding. Riluzole also demonstrated synergistic anti-glioblastoma (GBM) affects with mTOR inhibitors in vitro and in GBM xenografts in mice. These data suggest that repurposing riluzole, used in conjunction with mTOR inhibitors, may serve as an effective therapeutic option in glioblastoma.

Alternative Mechanisms of mRNA Translation Initiation in Cellular Stress Response and Cancer

Throughout evolution, eukaryotic cells have devised different mechanisms to cope with stressful environments. When eukaryotic cells are exposed to stress stimuli, they activate adaptive pathways that allow them to restore cellular homeostasis. Most types of stress stimuli have been reported to induce a decrease in overall protein synthesis accompanied by induction of alternative mechanisms of mRNA translation initiation. Here, we present well-studied and recent examples of such stress responses and the alternative translation initiation mechanisms they induce, and discuss the consequences of such regulation for cell homeostasis and oncogenic transformation.

Penfluridol overcomes paclitaxel resistance in metastatic breast cancer

Paclitaxel is a first line chemotherapeutic agent for the patients with metastatic breast cancer. But inherited or acquired resistance to paclitaxel leads to poor response rates in a majority of these patients. To identify mechanisms of paclitaxel resistance, we developed paclitaxel resistant breast cancer cell lines, MCF-7 and 4T1 by continuous exposure to paclitaxel for several months. Western blot analysis showed increased expression of HER2 and β-catenin pathway in resistant cell lines as compared to parent cells. Hence, we hypothesized that HER2/β-catenin mediates paclitaxel resistance in breast cancer and suppression of HER2/β-catenin signaling could overcome paclitaxel resistance. Our data showed that penfluridol (PFL) treatment significantly reduced the survival of paclitaxel-resistant cells. Western blot analysis revealed that PFL treatment suppressed HER2, as well as, β-catenin pathway. In vivo data confirmed that PFL significantly potentiated tumor growth suppressive effects of paclitaxel in an orthotropic breast cancer model. In addition, tumors from paclitaxel and PFL-treated mice showed reduced HER2 and β-catenin expression, along with increased apoptosis. Taken together our results demonstrate a novel role of HER2/β-catenin in paclitaxel resistance and open up new avenues for application of PFL as a therapeutic option for overcoming paclitaxel resistance.

Therapeutic Effects of Punicalagin Against Ovarian Carcinoma Cells in Association With β-Catenin Signaling Inhibition

AIM

The aim of this study was to investigate the effects of punicalagin, a polyphenol isolated from Punica granatum, on human A2780 ovarian cancer cells in vitro.

METHODS

The viability of human A2780 ovarian cells was evaluated using Cell Counting Kit-8 assay. Cell cycle was detected with flow cytometry analysis. The protein expression levels of Bcl-2, Bax, β-catenin, cyclin D1, survivin, tissue inhibitor of metalloproteinase (TIMP)-2, and TIMP-3 were measured using Western blot analysis. Matrix metalloproteinase (MMP)-2 and MMP-9 activity was determined with gelatin zymography. Wound healing assay was used to determine cell migration.

RESULTS

Punicalagin inhibited the cell viability of A2780 cells in a dose- and time-dependent manner, and the cell cycle of A2780 cells was arrested in G1/S phase transition. The treatment also induced apoptosis as shown by the up-regulation of Bax and down-regulation of Bcl-2. On the other hand, punicalagin treatment increased the expressions of TIMP-2 and TIMP-3, decreased the activities of MMP-2 and MMP-9, and inhibited cell migration. In addition, the β-catenin pathway was suppressed as shown by the down-regulations of β-catenin and its downstream factors including cyclin D1 and survivin.

CONCLUSIONS

Punicalagin may have cancer-chemopreventive as well as cancer-chemotherapeutic effects against human ovarian cancer in humans through the inhibition of β-catenin signaling pathway.

Low-dose paclitaxel downregulates MYC proto-oncogene bHLH transcription factor expression in colorectal carcinoma cells

Paclitaxel (PTX) has been commonly used to treat multiple types of tumor. Its anticancer mechanism differs based on different PTX concentrations and types of tumor cell. In the present study, MTT assays of HCT116 and LOVO cells treated with PTX revealed the chemosensitivity of the cell lines for different PTX concentrations. The half-maximal inhibitory concentration values of PTX for these cells were 2.46 and 2.24 nM, respectively. Cell morphology observation revealed that both cell lines exhibited rounded, wrinkled and damaged morphologies with increasing concentrations of PTX. Fluorescence-activated cell sorting analysis indicated that 1 nM PTX increased the proportion of cells in sub-G₁ phases and decreased the proportion of cells in G₀/G₁ phases, whereas the proportions of cells in S and G₂/M phases only slightly changed for both cell lines. Western blot analysis indicated that the total/nuclear protein expression of MYC proto-oncogene bHLH transcription factor (c-Myc) and phosphorylated (P)-c-Myc decreased in HCT116 cells in a dose-dependent manner, whereas the nuclear protein expression of P-c-Myc increased in LOVO cells in a dose-dependent manner. These results suggest that low-dose PTX downregulates c-Myc and P-c-Myc expression, subsequently inhibiting the cell cycle at G₀/G₁ in colorectal carcinoma.

More than just scanning: the importance of cap-independent mRNA translation initiation for cellular stress response and cancer

The scanning model for eukaryotic mRNA translation initiation states that the small ribosomal subunit, along with initiation factors, binds at the cap structure at the 5' end of the mRNA and scans the 5' untranslated region (5'UTR) until an initiation codon is found. However, under conditions that impair canonical cap-dependent translation, the synthesis of some proteins is kept by alternative mechanisms that are required for cell survival and stress recovery. Alternative modes of translation initiation include cap- and/or scanning-independent mechanisms of ribosomal recruitment. In most cap-independent translation initiation events there is a direct recruitment of the 40S ribosome into a position upstream, or directly at, the initiation codon via a specific internal ribosome entry site (IRES) element in the 5'UTR. Yet, in some cellular mRNAs, a different translation initiation mechanism that is neither cap- nor IRES-dependent seems to occur through a special RNA structure called cap-independent translational enhancer (CITE). Recent evidence uncovered a distinct mechanism through which mRNAs containing N 6-methyladenosine (m6A) residues in their 5'UTR directly bind eukaryotic initiation factor 3 (eIF3) and the 40S ribosomal subunit in order to initiate translation in the absence of the cap-binding proteins. This review focuses on the important role of cap-independent translation mechanisms in human cells and how these alternative mechanisms can either act individually or cooperate with other cis-acting RNA regulons to orchestrate specific translational responses triggered upon several cellular stress states, and diseases such as cancer. Elucidation of these non-canonical mechanisms reveals the complexity of translational control and points out their potential as prospective novel therapeutic targets.

[Role of miR-206/CDK4 in modulating the growth and chemotlerapy sensitivity of ovarian cancer cells]

OBJECTIVE

To explore role of miR-206 in modulating the growth and chemotherapy sensitivity in ovarian cancer cells.

METHODS

Real-time PCR was used to detect the expression of miR-206 in ovarian cancer and normal ovarian tissues. Ovarian cancer SKOV3 cells were transfected with a miR-206 mimic or a specific inhibitor of miR-206, and MTT assay and flow cytometry were used to detect the changes in cell growth and cell cycle transition. Western blotting and luciferase reporter gene assay were employed to identify the target gene and signal pathways of miR-206. The effect of miR-206 on the sensitivity of ovarian cancer cells to 5-Fu was assessed.

RESULTS

miR-206 was down-regulated in ovarian cancer tissues compared to normal ovarian tissues. Transfection of SKOV3 cells with the miR-206 mimic resulted in obvious growth suppression and delayed cell cycle transition from G1 to S phase by suppressing CDK4, c-Myc, and CCND1 expressions. Transfection with the miR-206 inhibitor obviously promoted the cell growth and significantly increased CDK4 expression in the cells. Luciferase reporter gene assay indicated that miR-206 could directly bind to the 3'UTR of CDK4 gene and reduce the activity of luciferase. Transfection of SKOV3 cells with miR-206 significantly lowered the IC₅₀ of 5-Fu to enhance the chemotherapy sensitivity of the cells to 5-Fu.

CONCLUSION

As a potential tumor suppressor, miR-206 directly targets CDK4 to suppress the cell growth and enhance the chemotherapy sensitivity to 5-Fu in ovarian cancer cells in vitro.

Therapeutic Effects of Punicalagin Against Ovarian Carcinoma Cells in Association With β-Catenin Signaling Inhibition

Aim

The aim of this study was to investigate the effects of punicalagin, a polyphenol isolated from Punica granatum, on human A2780 ovarian cancer cells in vitro.

Methods

The viability of human A2780 ovarian cells was evaluated using Cell Counting Kit-8 assay. Cell cycle was detected with flow cytometry analysis. The protein expression levels of Bcl-2, Bax, β-catenin, cyclin D1, survivin, tissue inhibitor of metalloproteinase (TIMP)-2, and TIMP-3 were measured using Western blot analysis. Matrix metalloproteinase (MMP)-2 and MMP-9 activity was determined with gelatin zymography. Wound healing assay was used to determine cell migration.

Results

Punicalagin inhibited the cell viability of A2780 cells in a dose- and time-dependent manner, and the cell cycle of A2780 cells was arrested in G1/S phase transition. The treatment also induced apoptosis as shown by the up-regulation of Bax and down-regulation of Bcl-2. On the other hand, punicalagin treatment increased the expressions of TIMP-2 and TIMP-3, decreased the activities of MMP-2 and MMP-9, and inhibited cell migration. In addition, the β-catenin pathway was suppressed as shown by the down-regulations of β-catenin and its downstream factors including cyclin D1 and survivin.

Conclusions

Punicalagin may have cancer-chemopreventive as well as cancer-chemotherapeutic effects against human ovarian cancer in humans through the inhibition of β-catenin signaling pathway.