AKT inhibitor suppresses hyperthermia-induced Ndrg2 phosphorylation in gastric cancer cells

Identification of a novel MYC target gene set signature for predicting the prognosis of osteosarcoma patients

Osteosarcoma is a primary malignant tumor found mainly in teenagers and young adults. Patients have very little long-term survival. MYC controls tumor initiation and progression by regulating the expression of its target genes; thus, constructing a risk signature of osteosarcoma MYC target gene set will benefit the evaluation of both treatment and prognosis. In this paper, we used GEO data to download the ChIP-seq data of MYC to obtain the MYC target gene. Then, a risk signature consisting of 10 MYC target genes was developed using Cox regression analysis. The signature indicates that patients in the high-risk group performed poorly. After that, we verified it in the GSE21257 dataset. In addition, the difference in tumor immune function among the low- and high-risk populations was compared by single sample gene enrichment analysis. Immunotherapy and prediction of response to the anticancer drug have shown that the risk signature of the MYC target gene set was positively correlated with immune checkpoint response and drug sensitivity. Functional analysis has demonstrated that these genes are enriched in malignant tumors. Finally, STX10 was selected for functional experimentation. STX10 silence has limited osteosarcoma cell migration, invasion, and proliferation. Therefore, these findings indicated that the MYC target gene set risk signature could be used as a potential therapeutic target and prognostic indicator in patients with osteosarcoma.

CDK6 is stimulated by hyperthermia and protects gastric cancer cells from hyperthermia‑induced damage

Hyperthermia is one of the most widely employed adjuvant treatments for cancer, especially for hyperthermic intraperitoneal chemotherapy, and has few side effects. Gastric cancer has various hyperthermia sensitivities, but the exact molecular mechanisms remain to be elucidated. In the present study, western blotting was performed to detect differential expression of proteins that have been reported to be upregulated in gastric cancer. Following knockdown of these proteins, apoptosis was measured by Annexin V-FITC/propidium iodide (PI) double staining and hyperthermia treatment was applied. To evaluate the effect of cyclin-dependent kinase 6 (CDK6) on hyperthermia-induced apoptosis, CDK6 was knocked down or inhibited by the addition of a specific inhibitor and subsequent PI staining and cell proliferation, migration and invasion assays were performed. Hyperthermia-induced protein kinase B (AKT) expression and phosphorylation inhibition were detected. As demonstrated in the present study, the hyperthermia-induced proteins kinesin family member 11 (KIF11), cyclin-dependent kinase 6 (CDK6), stromal antigen 2, NIMA-related kinase 2 and karyopherin subunit α 4 were highly expressed in gastric cancer cells, including SH-10-TC and HGC-27 cells. Knockdown of KIF11 significantly increased apoptosis without hyperthermia treatment and CDK6 significantly increased hyperthermia-induced apoptosis, prompting the present study to focus on CDK6. It was further confirmed that CDK6 activity was critical for decreasing hyperthermia-induced apoptosis and for cell proliferation. Hyperthermia-induced AKT expression and phosphorylation inhibition is potentially the main cause of CDK6 transcriptional upregulation. Taken together, these findings demonstrated that CDK6 is upregulated via hyperthermia-induced AKT inhibition and subsequently protected gastric cancer cells from hyperthermia-induced apoptosis, indicating that it is a potential therapeutic target to sensitize gastric cancer cells to hyperthermia-based therapy.

Radiation-induced gastrointestinal syndrome is alleviated in NDRG2-deficient mice

Background

Radiation-induced gastrointestinal syndrome (GIS) often occurs after therapeutic or accidental exposure to high doses of radiation. Unfortunately, there are still no effective medical treatments for GIS. N-Myc downstream regulated gene 2 (NDRG2), is a tumor suppressor gene and promotes cell apoptosis and differentiation. The aim of our study was to identify the role of NDRG2 in the progression of GIS and explore the potential mechanism.

Methods

We generated Ndrg2^ΔG mice, lacking NDRG2 specifically in the intestinal epithelium. Survival analysis was performed to validate the effect of NDRG2 on GIS, and other common indicators (body weight loss and diarrhea) were used for the assessment of GIS. Enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) were conducted to obtain the expression of pro-inflammatory interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α). TUNNEL and western blotting were further adopted to determine the relationship between NDRG2 and apoptosis. Finally, we performed histology and immunohistochemistry assays to explore the morphological alternations and changes of proliferation-related molecules, including Ki-67 and proliferating cell nuclear antigen (PCNA).

Results

We found that after 8 gray of total body ɤ-irradiation (TBI), the deletion of NDRG2 in the intestine revealed longer survival time, considerably milder symptoms of GIS, and milder damage to jejunal tissue, compared with the WT mice. Moreover, the Ndrg2^ΔG mice significantly inhibited the expression of pro-inflammatory IL-1β, IL-6, and TNF-α, which were typically increased by irradiation. Apoptosis of the epithelial cells in the Ndrg2^ΔG mice was significantly milder while the ratio of proliferation cells was larger in the epithelium of mice 8 days after TBI when compared with the WT mice.

Conclusions

These findings all indicated that NDRG2 deficiency in the intestine protects mice against radiation-induced GIS mainly through promoting proliferation and suppressing apoptosis of epithelial cells.

Pathophysiological significance of N-myc downstream-regulated gene 2 in cancer development through protein phosphatase 2A phosphorylation regulation

N-myc downstream-regulated gene 2 (NDRG2) is a candidate tumor suppressor in various cancers, including adult T-cell leukemia/lymphoma (ATLL). NDRG2, as a stress-responsive protein, is induced by several stress-related signaling pathways and NDRG2 negatively regulates various signal transduction pathways. Although it has not been found to function alone, NDRG2 binds serine/threonine protein phosphatase 2A (PP2A), generating a complex that is involved in the regulation of various target proteins. The main function of NDRG2 is to maintain cell homeostasis by suppressing stress-induced signal transduction; however, in cancer, genomic deletions and/or promoter methylation may inhibit the expression of NDRG2, resulting in enhanced tumor development through overactivated signal transduction pathways. A wide variety of tumors develop in Ndrg2-deficient mice, including T-cell lymphoma, liver, lung and other tumors, the characteristics of which are similar to those in Pten-deficient mice. In particular, PTEN is a target molecule of the NDRG2/PP2A complex, which enhances PTEN phosphatase activity by dephosphorylating residues in the PTEN C-terminal region. In ATLL cells, loss of NDRG2 expression leads to the failed recruitment of PP2A to PTEN, resulting in the inactivation of PTEN phosphatase with phosphorylation, ultimately leading to the activation of PI3K/AKT. Thus, NDRG2, as a PP2A adaptor, regulates the global phosphorylation of important signaling molecules. Moreover, the downregulation of NDRG2 expression by long-term stress-induced methylation is directly correlated with the development of ATLL and other cancers. Thus, NDRG2 might be important for the development of stress-induced leukemia and other cancers and has become an important target for novel molecular therapies.

Astrocyte-specific NDRG2 gene: functions in the brain and neurological diseases

In recent years, the roles of astrocytes of the central nervous system in brain function and neurological disease have drawn increasing attention. As a member of the N-myc downstream-regulated gene (NDRG) family, NDRG2 is principally expressed in astrocytes of the central nervous system. NDRG2, which is involved in cell proliferation and differentiation, is commonly regarded as a tumor suppressor. In astrocytes, NDRG2 affects the regulation of apoptosis, astrogliosis, blood-brain barrier integrity, and glutamate clearance. Several preclinical studies have revealed that NDRG2 is implicated in the pathogenesis of many neurological diseases not limited to tumors (mostly glioma in the nervous system), such as stroke, neurodegeneration (Alzheimer's disease and Parkinson's disease), and psychiatric disorders (depression and attention deficit hyperactivity disorder). This review summarizes the biological functions of NDRG2 under physiological and pathological conditions, and further discusses the roles of NDRG2 during the occurrence and development of neurological diseases.

Characterization of the prognostic values of the NDRG family in gastric cancer

BACKGROUND

The N-myc downstream-regulated gene (NDRG) family, NDRG1-4, has been involved in a wide spectrum of biological functions in multiple cancers. However, their prognostic values remain sparse in gastric cancer (GC). Therefore, it is crucial to systematically investigate the prognostic values of the NDRG family in GC.

METHODS

The prognostic values of the NDRG family were evaluated by Kaplan-Meier Plotter and SurvExpress. The mRNA of the NDRG family was investigated in The Cancer Genome Atlas (TCGA). Transcription factors (TFs) and miRNAs associated with the NDRG family were predicted by NetworkAnalysis. The prognostic values of DNA methylation levels were analyzed by MethSurv. The correlation between immune cells and the NDRG family was evaluated by the Tumor Immune Estimation Resource (TIMER) database.

RESULTS

High levels of mRNA expression of NDRG2 and NDRG3 were associated with a favorable prognosis in all GCs. In HER2 ^- GC, NDRG1 was significantly associated with a poor prognosis of GC [hazard ratio (HR) = 1.65, 95% confidence interval (CI) = 1.16-2.33, p = 0.0046]. In HER2 ⁺ GC, NDRG4 showed a poor prognosis (HR = 1.4, 95% CI: 1.06-1.85, p = 0.017). NDRG4 was an independent prognostic factor in recurrence-free survival by TCGA cohort. The low-risk NDRG-signature group displayed a significantly favorable survival outcome than the high-risk group (HR = 1.76, 95% CI: 1.2-2.59, p = 0.00385). The phosphorylated protein NDRG1 (NDRG1_pT346) displayed a favorable overall survival and was significantly associated with HER2 and phosphorylated HER2. Epidermis development was the top biological process (BP) for coexpressed genes associated with NDRG1 and NDRG4, while mitotic nuclear division and mitotic cell processes were the top BPs for NDRG2 and NDRG3, respectively. Overall, 6 CpGs of NDRG1, 4 CpGs of NDRG2, 3 CpGs of NDRG3 and 24 CpGs of NDRG4 were associated with significant prognosis. CD4⁺ T-cells showed the highest correlation with NDRG4 (correlation = 0.341, p = 2.14e^-11). Furthermore, BCL6 in follicular helper T-cells (Tfh) cells showed the highest association with NDRG4 (correlation = 0.438, p = 00e⁺00).

CONCLUSIONS

This study analyzed the multilevel prognostic values and biological roles of the NDRG family in GC.

Synergistic action of microwave-induced mild hyperthermia and paclitaxel in inducing apoptosis in the human breast cancer cell line MCF-7

Microwave mild hyperthermia and paclitaxel have been reported to be involved in variety of solid tumors. However, rare related researches have been accomplished via directly killing tumor cells using thermochemotherapy. In order to clarify the potential synergy between microwave-induced hyperthermia at temperatures <41°C and paclitaxel chemotherapy for inhibiting the growth of the human breast cancer cell line MCF-7, an MTT assay was used. The MCF-7 cells cultured in vitro were treated with paclitaxel alone, treated with microwave-induced hyperthermia for 2 h alone (at 40, 40.5 or 41°C), or treated with a combination of paclitaxel and 2 h of hyperthermia (at 40, 40.5 or 41°C). Flow cytometry was used to determine the cell apoptosis rate and it was demonstrated that paclitaxel decreased cell viability in a dose-dependent manner. Alone, hyperthermia for 2 h at 41°C induced apoptosis in MCF-7 cells, to a greater extent compared with hyperthermia for 2 h at 40.0 or 40.5°C (P<0.05). Together, paclitaxel and 2 h of hyperthermia at 40.5°C induced significantly increased apoptosis compared with either treatment alone (P<0.05). Increasing the temperature to 41°C in combination with paclitaxel increased the apoptotic ratio from 12.21±1.02% to 16.36±2.39%. The apoptotic ratio correlated positively with hyperthermia temperature and duration following hyperthermia, as did the synergistic effect obtained by combining hyperthermia and paclitaxel. Notably, the combination of 5 µg/ml paclitaxel and 2 h of hyperthermia at 40°C enhanced MCF-7 cell proliferation. Mild hyperthermia may exert anti-tumor effects by inducing apoptosis, and combining hyperthermia with paclitaxel synergistically induces apoptosis. Paclitaxel dose and hyperthermia temperature require careful optimization, as low-dose paclitaxel combined with hyperthermia at an insufficient temperature may enhance breast cancer proliferation.

Clinical and pathological significance of N-Myc downstream-regulated gene 2 (NDRG2) in diverse human cancers

Human N-Myc downstream-regulated gene 2 (NDRG2), located at chromosome 14q11.2, has been reported to be down-regulated and associated with the progression and prognosis of diverse cancers. Collectively, previous studies suggest that NDRG2 functions as a candidate tumor-suppressor gene; thus, up-regulation of NDRG2 protein might act as a promising therapeutic strategy for malignant tumors. The aim of this review was to comprehensively present the clinical and pathological significance of NDRG2 in human cancers.

Association between integrin-linked kinase and hyperthermia in oral squamous cell carcinoma

The present study aimed to observe the effect of the biological functions of integrin-linked kinase (ILK) silencing combined with hyperthermia on Tca8113 cells. Lentivirus-mediated short hairpin RNA (shRNA)-targeting ILK was transfected into oral squamous cell carcinoma (OSCC) Tca8113 cells and, combined with hyperthermia, several experimental methods were used to detect their biological behavior in vitro. On the basis of in vitro experiments, Tca8113 cells were transplanted into nude mice models, and ILK-shRNA-lentivirus was injected into the nude mice transplanted tumor and combined with hyperthermia. Tumor morphology and the associated protein expression changes were determined. Subsequent to ILK silencing combined with hyperthermia, the growth, migration and proliferation of Tca8113 cells were significantly inhibited. Flow cytometry revealed that the cells were blocked in the S phase, and western blot analysis demonstrated that ILK, phosphorylated (p)-RAC-alpha serine/threonine-protein kinase (Akt), p-glycogen synthase kinase-3β and p-heat shock factor 1 protein expression levels were significantly decreased, while apoptosis-associated protein B-cell lymphoma-2-associated X protein expression and the efficacy of hypothermia were significantly increased. By ILK silencing combined with hyperthermia, a significant therapeutic effect on transplanted tumors was observed in nude mice. Immunohistochemistry revealed the same results as the in vitro experiments. ILK silencing combined with hyperthermia can inhibit the growth, proliferation and migration of Tca8113 cells, promote Tca8113 cell apoptosis, inhibit the phosphatidylinositol-3-kinase/Akt signaling pathway and increase hyperthermia sensitivity; the combination therapy exhibits a synergistic sensitizing effect. Therefore, ILK silencing combined with hypothermia may serve as a novel combination therapy strategy against OSCC.

Emerging role of N-myc downstream-regulated gene 2 (NDRG2) in cancer

N-myc downstream-regulated gene 2 (NDRG2) is a tumor suppressor and cell stress-related gene. NDRG2 is associated with tumor incidence, progression, and metastasis. NDRG2 regulates tumor-associated genes and is regulated by multiple conditions, treatments, and protein/RNA entities, including hyperthermia, trichostatin A and 5-aza-2'-deoxycytidine, which are promising potential cancer therapeutics. In this review, we discuss the expression as well as the clinical and pathological significance of NDRG2 in cancer. The pathological processes and molecular pathways regulated by NDRG2 are also summarized. Moreover, mechanisms for increasing NDRG2 expression in tumors and the potential directions of future NDRG2 research are discussed. The information reviewed here should assist in experimental design and increase the potential of NDRG2 as a therapeutic target for cancer.

Lipocalin 2 (LCN2) is a promising target for cholangiocarcinoma treatment and bile LCN2 level is a potential cholangiocarcinoma diagnostic marker

Cholangiocarcinoma (CCA) is a devastating disease due to resistance to traditional chemotherapies and radiotherapies. New therapeutic strategies against CCA are urgently needed. This study investigated the role of lipocalin-2 (LCN2) in human cholangiocarcinoma as a potential therapeutic target and diagnostic marker. So far, the role of LCN2 in cancer is still controversial and studies regarding the role of LCN2 in CCA are limited. LCN2 knockdown inhibited CCA cell growth in vitro and in vivo through induction of cell cycle arrest at G0/G1 phases and decreased metastatic potential due to repression of epithelial-mesenchymal transition (EMT). Overexpression of LCN2 in CCA cells increased cell metastatic potential. We showed for the first time that the N-myc downstream regulated gene 1 (NDRG1) and NDRG2, known as tumor suppressor genes, are negatively regulated by LCN2 in CCA cells. LCN2 concentration in bile was higher in patients with CCA than that in patients with gallstones, with a cutoff value of 20.08 ng/ml making this a potential diagnostic marker. Higher LCN2 expression was associated with worse survival in patients with CCA. LCN2 is a promising target for CCA treatment and bile LCN2 level is a potential diagnostic marker for CCA.

Preparation of folic acid-conjugated, doxorubicin-loaded, magnetic bovine serum albumin nanospheres and their antitumor effects in vitro and in vivo

BACKGROUND

This study aimed to generate targeted folic acid-conjugated, doxorubicin-loaded, magnetic iron oxide bovine serum albumin nanospheres (FA-DOX-BSA MNPs) that lower the side effects and improve the therapeutic effect of antitumor drugs when combined with hyperthermia and targeting therapy. A new nanodrug using magnetic nanospheres for heating and addition of the folate receptor with cancer cell specificity was prepared. The characteristics of these nanospheres and their antitumor effects in nasopharyngeal carcinoma were explored.

METHODS

FA-DOX-BSA MNPs comprising encapsulated magnetic iron oxide nanoparticles were prepared using a desolvation cross-linking method. Activated folic acid (N-hydroxysuccinimide ester of folic acid) was conjugated to the surface of albumin nanospheres via amino groups.

RESULTS

Folic acid was successfully expressed on the surface of the nanospheres. Electron microscopy revealed that the FA-DOX-BSA MNPs were nearly spherical and uniform in size, with an average diameter of 180 nm. The nanomaterial could deliver doxorubicin at clinically relevant doses with an entrapment efficiency of 80%. An increasing temperature test revealed that incorporation of magnetic iron oxide into nanospheres could achieve a satisfactory heat treatment temperature at a significantly lower dose when placed in a high-frequency alternating magnetic field. FA-DOX-BSA MNPs showed greater inhibition of tumors than in the absence of folic acid in vitro and in vivo. Compared with chemotherapy alone, hyperthermia combined with chemotherapy was more effective against tumor cells.

CONCLUSION

Folic acid-conjugated bovine serum albumin nanospheres composed of mixed doxorubicin and magnetic iron oxide cores can enable controlled and targeted delivery of anticancer drugs and may offer a promising alternative to targeted doxorubicin therapy for nasopharyngeal carcinoma.