Role of tumor­derived extracellular vesicles in cancer progression and their clinical applications (Review).

Extracellular vesicles (EVs), including micro­vesicles and exosomes, are heterogeneous small membranous vesicles shed from the surface of myriad cells and are crucial in mediating intercellular communication. The vertical trafficking of cargo to the plasma membrane and subsequent redistribution of surface lipids may contribute to EV formation. Tumor­derived extracellular vesicles (TD­EVs) can carry complex, bioactive cargo, such as nucleic acids and proteins, during tumor metastasis. Paracrine information gets relayed by TD­EVs to adjacent tumor cells and this allows a crosstalk between malignant cells. These structures may even move to a distant metastatic lesion and modulate the tumor microenvironment to form a premetastatic niche. Thus, TD­EVs might be potential biomarkers for tumor development and metastasis. Additionally, EVs are promising candidates for use as cell­free vaccines or as vehicles for the delivery of specific tumor therapeutic molecules. Genetically modified microvesicles and engineered exosomes have shed light on a novel strategy for tumor­targeted gene therapy. This review focuses on the role of EVs in tumor development and metastasis and their possible applications in the advanced diagnosis and therapy of cancer and personalized medicine.

The role of adrenomedullin in the pathogenesis of gastric cancer.

Adrenomedullin has been shown to be overexpressed in many tumors, including gastric cancer tumors; however, its mechanism of action remains unclear. In this study, we examined the role of adrenomedullin in the pathogenesis of gastric cancer. Using clinical specimens and immunohistochemistry, we found that the expression levels of adrenomedullin and its receptors are inordinately elevated as compared to the adjacent non-tumor gastric tissues. We used siRNA gene silencing, in BGC-823 gastric cancer cell lines, to target adrenomedullin genes, and found that increased adrenomedullin expression results in the proliferation of tumor cells, tumor invasion, and metastasis. Furthermore, we found that under hypoxic conditions, gastric cancer BGC-823 cells exhibit higher expression levels of adrenomedullin and various other related proteins. Our results indicate the involvement of adrenomedullin in microvessel proliferation and partially in the release of hypoxia in solid tumors. Knockdown of adrenomedullin expression, at the protein level, reduced the levels of phosphoprotein kinase B and B-cell lymphoma 2 but increased the levels of cleaved-caspase3 and Bcl 2 associated x protein (Bax). Therefore, we hypothesized siRNA targeting of adrenomedullin genes inhibits various serine/threonine kinases via a signaling pathway that induces cell apoptosis. SiRNA targeting of adrenomedullin genes and green fluorescent control vectors were used to transfect BGC-823 cells, and western blot analyses were used to detect changes in the rates of autophagy in related proteins using confocal laser scanning microscopy. No significant changes were detected. Therefore, the knockdown of adrenomedullin and its receptors may represent a novel treatment strategy for gastric cancer.

Microvesicles released from human embryonic stem cell derived-mesenchymal stem cells inhibit proliferation of leukemia cells.

Human embryonic stem cell derived-mesenchymal stem cells (hESC­MSCs) are able to inhibit proliferation of leukemia cells. Microvesicles released from human embryonic stem cell derived-mesenchymal stem cells (hESC­MSC­MVs) might play an important part in antitumor activity. Microvesicles were isolated by ultracentrifugation and identified under a scanning electron microscopy and transmission electron microscope separately. After 48-h cocultured with hESC­MSCs and hESC­MSC­MVs, the number of K562 and HL60 was counted and tumor cell viability was measured by CCK8 assay. The expression of proteins Bcl-2 and Bax were estimated by western blotting. Transmission electron microscope and western blot analysis were adopted to evaluate the autophagy level. Results showed that both hESC­MSCs and hESC­MSC­MVs inhibited proliferation of leukemia cells in a concentration-dependent manner. hESC­MSC­MVs reduced the ratio of Bcl/Bax, enhanced the protein level of Beclin-1 and LC3-II conversion, thus upregulating autophagy and apoptosis. In conclusion, microvesicles released from human embryonic stem cell derived-mesenchymal stem cells inhibited tumor growth and stimulated autophagy and excessive autophagy might induce apoptosis.

High expression of long non-coding RNA NEAT1 indicates poor prognosis of human cancer.

The nuclear paraspeckle assembly transcript 1 (NEAT1) is a long non-coding RNA. Many studies have reported that NEAT1 plays critical oncogenic roles and facilitates tumorigenesis of various human cancers. High NEAT1 expression is associated with a poor prognosis in cancer patients. This meta-analysis was conducted to assess the association between NEAT1 levels and survival times of cancer patients. Overall survival (OS) was the primary endpoint. Thirteen publications with 1,496 cancer patients from 5 databases (PubMed, EMBASE, Cochrane Library, Wiley Online Library, and Medline) met the criteria for this meta-analysis. Results of the analysis showed that NEAT1 expression in human cancer was significantly associated with OS (hazard ratio [HR]=1.53, 95% confidence interval [CI]: 1.39-1.68), including digestive system tumor (HR=1.54, 95% CI: 1.37-1.73) and respiratory carcinomas (HR=1.44, 95% CI: 1.11-1.85). The results also indicated that NEAT1 expression was highly associated with tumor size (>3 cm vs. ≤3 cm; odds ratio [OR]=2.51, 95% CI: 1.27-4.99; p=0.009), TNM stage (III+IV vs. I+II; OR=4.17, 95% CI: 2.42-7.18; p=0.00001), and distant metastasis (OR=2.73, 95% CI: 1.28-5.79; p=0.01). However, there was no significant association with differentiation (poor vs. well + moderate, OR=1.45, 95% CI: 0.72-2.91) and lymph node metastasis (OR=1.39, 95% CI: 0.54-3.60). This meta-analysis showed that NEAT1 expression may be a useful biomarker for predicting a poor prognosis in patients with cancer.