Reduced N-Myc downstream-regulated gene 2 expression is associated with CD24 upregulation and poor prognosis in patients with lung adenocarcinoma

The Function of N-Myc Downstream-Regulated Gene 2 (NDRG2) as a Negative Regulator in Tumor Cell Metastasis

N-myc downstream-regulated gene 2 (NDRG2) is a tumor-suppressor gene that suppresses tumorigenesis and metastasis of tumors and increases sensitivity to anti-cancer drugs. In this review, we summarize information on the clinicopathological characteristics of tumor patients according to NDRG2 expression in various tumor tissues and provide information on the metastasis inhibition-related cell signaling modulation by NDRG2. Loss of NDRG2 expression is a prognostic factor that correlates with TNM grade and tumor metastasis and has an inverse relationship with patient survival in various tumor patients. NDRG2 inhibits cell signaling, such as AKT-, NF-κB-, STAT3-, and TGF-β-mediated signaling, to induce tumor metastasis, and induces activation of GSK-3β which has anti-tumor effects. Although NDRG2 operates as an adaptor protein to mediate the interaction between kinases and phosphatases, which is essential in regulating cell signaling related to tumor metastasis, the molecular mechanism of NDRG2 as an adapter protein does not seem to be fully elucidated. This review aims to assist the research design regarding NDRG2 function as an adaptor protein and suggests NDRG2 as a molecular target to inhibit tumor metastasis and improve the prognosis in tumor patients.

CD24, A Review of its Role in Tumor Diagnosis, Progression and Therapy

CD24, is a mucin-like GPI-anchored molecules. By immunohistochemistry, it is widely detected in many solid tumors, such as breast cancers, genital system cancers, digestive system cancers, neural system cancers and so on. The functional roles of CD24 are either fulfilled by combination with ligands or participate in signal transduction, which mediate the initiation and progression of neoplasms. However, the character of CD24 remains to be intriguing because there are still opposite voices about the impact of CD24 on tumors. In preclinical studies, CD24 target therapies, including monoclonal antibodies, target silencing by RNA interference and immunotherapy, have shown us brighten futures on the anti-tumor application. Nevertheless, evidences based on clinical studies are urgently needed. Here, with expectancy to spark new ideas, we summarize the relevant studies about CD24 from a tumor perspective.

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.

Low NDRG2 expression predicts poor prognosis in solid tumors: A meta-analysis of cohort study

BACKGROUND

As a member of the N-myc down-regulated gene family, N-Myc downstream-regulated gene 2 (NDRG2) contributes to the tumorigenesis of various types of cancers. However, the correlation between NDRG2 expression and the prognosis of solid tumor remains to be elucidated because of small sample sizes and inconsistent results in previous studies. In the present study, we conducted a systematic review and meta-analysis to explore the prognostic significance of NDRG2 in human solid tumors.

METHODS

PubMed, Web of Science, Embase, Chinese National Knowledge Infrastructure, and WanFang databases (up to April 2020) were searched for relevant studies that evaluated the impact of NDRG2 on clinical outcomes, including overall survival (OS), and disease-free survival (DFS), in solid tumors. Hazard ratios (HRs) with 95% confidence intervals (CIs) were pooled to assess the association between NDRG2 expression and the survival of patients with solid tumors. Odds ratios (ORs) with 95% CIs were pooled to estimate the correlation between NDRG2 expression and clinicopathologic characteristics in the patients.

RESULTS

A total of 13 eligible studies with 1980 patients were included in this meta-analysis. Low NDRG2 expression was significantly associated with poor OS (HR = 1.96, 95% CI: 1.60-2.40, P < .001) and DFS (HR = 2.70, 95% CI: 1.42-5.13, P = .002) in solid tumor. Furthermore, low NDRG2 expression was related to some phenotypes of tumor aggressiveness, such as clinical stage (OR = 3.21, 95% CI: 1.96-5.26, P < .001), lymph node metastasis (OR = 2.14, 95% CI: 1.49-3.07, P < .001), and degree of differentiation (OR = 0.60, 95% CI: 0.45-0.81, P = .001).

CONCLUSIONS

NDRG2 may be a meaningful biomarker of poor prognosis and a potential therapeutic target for human solid tumors.

NDRG2 gene expression pattern in ovarian cancer and its specific roles in inhibiting cancer cell proliferation and suppressing cancer cell apoptosis

Background

The cancer cell metastasis and the acquisition of chemotherapy resistance remain huge challenge for ovarian cancer treatment. Previously, N-myc downstream-regulated gene 2 (NDRG2) serves as a tumor suppressor for many cancers. Here, we attempted to investigate the specific roles of NDRG2 in ovarian cancer.

Methods

The expression levels of NDRG2 were detected by qRT-PCR or Immunoblotting. CCK-8 assay was employed to examine the cell viability of ovarian cancer cells. The colony formation ability was determined by colony formation assay. Flow cytometry analyses were performed to detect the cell apoptosis and cell cycle. Xenograft tumor assay was performed to detect the in vivo function of NDRG2.

Results

We revealed that NDRG2 mRNA expression and protein levels were downregulated within both ovarian cancer tissues and cell lines. The overexpression of NDRG2 dramatically inhibited the cell viability and colony formation and tumor growth, whereas promoted the cell apoptosis, cell cycle arrest in G1 phase within ovarian cancer cells. More importantly, NDRG2 overexpression significantly enhanced the suppressive roles of cisplatin (DDP) in ovarian cancer cell viability. On the contrary, NDRG2 silence exerted opposing effects on ovarian cancer cells.

Conclusions

In summary, we provide a solid experimental basis demonstrating the tumor-suppressive effects of NDRG2 in inhibiting the cell proliferation, enhancing the cell apoptosis, eliciting the cell cycle arrest in G1 phase, and promoting the suppressive effects of DDP on the viability of ovarian cancer cells. NDRG2 administration presents a potent adjuvant treatment for ovarian cancer therapy.

Adenovirus siMDM2 and NDRG2 Gene Therapy Inhibits Cell Proliferation and Induces Apoptosis of Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is one of the most common skin cancers. In the present study, we explored the effects of depletion of murine double minute gene 2 (MDM2) together with overexpression of N-myc downstream-regulated gene 2 (NDRG2) on cutaneous SCC. In order to achieve high efficiency of gene knockdown and overexpression in SCC-13 cells, recombinant adenovirus carrying siMDM2 and NDRG2 expression construct was produced. We found Ad-siMDM2, Ad-NDRG2, and Ad-siMDM2-NDRG2 infections inhibit the growth of SCC-13 cells in vitro, and Ad-siMDM2-NDRG2 infection has the highest inhibitory effect. Subcutaneous injections of Ad-siMDM2, Ad-NDRG2, and Ad-siMDM2-NDRG2 into SCC-13 xenograft nude mice resulted in the reduction of tumor volume. Moreover, we found that apoptosis protein caspase 3 was up-regulated in the Ad-siMDM2-, Ad-NDRG2-, and Ad-siMDM2-NDRG2-treated groups. Our data indicate that the adenovirus-mediated MDM2 silencing and NDRG2 overexpression can synergistically inhibit local cancer cell proliferation, induce apoptosis, and further prevent metastases of SCC. Our study provides a promising method that can be further developed as a new therapeutic approach against SCC.

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.

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.

Downregulation of CD99 and upregulation of human leukocyte antigen class II promote tumor aggravation and poor survival in patients with osteosarcomas

BACKGROUND

CD99 is involved in the intracellular transport of human leukocyte antigen class II (HLA-II) protein. The aim of this study was to clarify the clinical value of CD99 and HLA-II expression in primary osteosarcoma.

METHODS

One hundred and thirty pairs of osteosarcoma and matched noncancerous bone tissues were evaluated by immunohistochemistry for CD99 and HLA-II expression.

RESULTS

Compared with the noncancerous bone tissues, the expression levels of CD99 (tumor versus normal: 2.96±0.09 versus 5.89±1.26, P<0.001) and HLA-II (tumor versus normal: 5.01±1.39 versus 1.92±0.06, P<0.001) proteins were respectively downregulated and upregulated in osteosarcoma tissues. CD99 and HLA-II were highly expressed in 49/130 (37.69%) and 107/130 (82.31%) of osteosarcoma tissues, respectively. In addition, the osteosarcoma patients with downregulation of CD99 and upregulation of HLA-II more frequently showed the presence of metastasis and recurrence and poor response to chemotherapy. Moreover, there was a negative correlation between CD99 and HLA-II expression in osteosarcoma tissues (r=-0.69, P=0.01). The patients with low CD99 expression correlated with poor prognosis of osteosarcoma, as opposed to HLA-II. Patients with CD99-low/HLA-II-high expression had the lowest overall and disease-free survival rates, and conjoined expression of CD99/HLA-II was an independent prognostic indicator of osteosarcoma.

CONCLUSION

These findings suggest for the first time that CD99 downregulation or HLA-II upregulation may be an important feature of human osteosarcoma. The combined detection of CD99/HLA-II coexpression may present a predictive and prognostic indicator in osteosarcoma.

CD24 induces the invasion of cholangiocarcinoma cells by upregulating CXCR4 and increasing the phosphorylation of ERK1/2

Cholangiocarcinoma is a malignant biliary tract tumor with an extremely poor prognosis. CD24 expression has been linked to the aggressiveness of cholangiocarcinoma cells and the adverse prognosis of cholangiocarcinoma patients. In the present study, the underlying mechanism of aggressive CD24⁺ cholangiocarcinoma cell behavior was elucidated. The magnetic-activated cell sorting system was used to isolate CD24⁺ and CD24^- cell populations from RMCCA1 cholangiocarcinoma cells. Using a human tumor metastasis PCR array, it was observed that numerous tumor-associated genes were upregulated in the CD24⁺ cells, including CXC chemokine receptor type 4 (CXCR4). In addition, an intracellular signaling array demonstrated the activation of extracellular signal-regulated kinase (ERK)1/2, which is downstream of the CXCR4 signaling cascade, in the CD24⁺ cells. Inhibition of CXCR4 or ERK1/2 significantly inhibited the motility and invasiveness of the CD24⁺ cells. The present study indicates that CXCR4 and ERK1/2 are induced by CD24 and that these proteins are associated with cholangiocarcinoma cell invasion.

Increased expression of CD24 is associated with tumor progression and prognosis in patients suffering osteosarcoma

OBJECTIVE

As a small heavily glycosylated mucin-like glycosyl-phosphatidylinositol-anchored cell surface protein, CD24 plays an important role in carcinogenesis of various human malignancies. However, its involvement in osteosarcoma is still unclear. The aim of this study was to investigate the expression pattern and the clinical significance of CD24 in human osteosarcoma.

METHODS

CD24 mRNA and protein expression levels were, respectively, detected by RT-PCR and Western blot assays using 30 pairs of osteosarcoma and noncancerous bone tissues. Then, immunohistochemistry was performed to analyze the association of CD24 expression in 166 osteosarcoma tissues with clinicopathological factors or survival of patients.

RESULTS

CD24 expression at mRNA and protein levels were both significantly higher in osteosarcoma tissues than those in corresponding noncancerous bone tissues (both P < 0.001). In addition, CD24 protein was positively expressed in 129 of 166 (77.7 %) osteosarcoma specimens with a cytoplasmic and membraneous staining, and also increased in the osteosarcoma specimens with advanced clinical stage (P = 0.01) and positive distant metastasis (P = 0.005). The univariate and multivariate analyses showed that osteosarcoma patients with high CD24 expression had poorer overall and disease-free survival, and high CD24 expression was an independent prognostic factor for both overall and disease-free survival.

CONCLUSION

The aforementioned findings offer convincing evidence for the first time that the increased expression of CD24 is correlated with tumor aggressiveness and tumor metastasis of osteosarcoma, and this molecule is an independent prognostic marker for osteosarcoma patients.