[Expression of long noncoding RNA STCAT3 in gastric cancer tissues and its effect on malignant phenotype of gastric cancer cells].

Objective: To detect the expression of long noncoding RNA(lncRNA)stomach cancer-associated transcript-3(STCAT3) in gastric cancer tissues, adjacent tissues, human gastric cancer cell lines and normal gastric epithelial cell lines, and to investigate the relationship between STCAT3 expression and clinicopathological features and malignant phenotype of gastric cancer. Methods: Quantitative fluorescent real-time polymerase chain reaction (qRT-PCR) was applied to detect the lncRNA STCAT3 expression levels in gastric cancer tissues, paired adjacent non-tumorous tissues, in order to explore the relationship between STCAT3 expression and clinicopathological features of gastric cancer. lncRNA STCAT3 low-expressing and high-expressing gastric cancer cell lines were transfected with expression plasmid to simulate gain-of-function, or interference plasmid to achieve loss-of-function. Cell proliferation was measured with CCK-8 and colony formation assay, cell migration with scratch assay, and cell invasion with Transwell migration assay. human gastric tumor were also transplanted to nude mice to detect the effect of lncRNA STCAT3 on tumorigenesis. Results: The expression of lncRNA STCAT3 was generally up-regulated in gastric cancer tissues compared with the adjacent tissues(12.55±0.16 vs 6.52±0.14), with median expression level in gastric cancer tissues being 6.03 higher (P<0.05). Meanwhile, the expression level of lncRNA STCAT3 in gastric cancer tissues was not correlated with age or gender (both P>0.05), while positively correlated with TNM stage (P<0.05). Interference of lncRNA STCAT3 expression in BGC-823 cells was found associated with significantly suppressed colony formation, proliferation, invasion, and migration (all P<0.05). Over-expression of lncRNA STCAT3 in AGS cells were also founded could promote the gastric cancer cells' proliferation, colony formation, migration, and invasion (all P<0.05). Conclusions: lncRNA STCAT3 may participate in the proliferation and invasion of gastric cancer cells, indicating that dysregulation of STCAT3 expression may play a role in occurrence and development of gastric cancer. lncRNA STCAT3 has the potential to be the biomarker of gastric cancer progression and target in treatment. The underlying mechanism is yet to be further studied.

MiR-630 inhibits proliferation by targeting CDC7 kinase, but maintains the apoptotic balance by targeting multiple modulators in human lung cancer A549 cells.

MicroRNAome analyses have shown microRNA-630 (miR-630) to be involved in the regulation of apoptosis. However, its apoptotic role is still debated and its participation in DNA replication is unknown. Here, we demonstrate that miR-630 inhibits cell proliferation by targeting cell-cycle kinase 7 (CDC7) kinase, but maintains the apoptotic balance by targeting multiple activators of apoptosis under genotoxic stress. We identified a novel regulatory mechanism of CDC7 gene expression, in which miR-630 downregulated CDC7 expression by recognizing and binding to four binding sites in CDC7 3'-UTR. We found that miR-630 was highly expressed in A549 and NIH3T3 cells where CDC7 was downregulated, but lower in H1299, MCF7, MDA-MB-231, HeLa and 2BS cells where CDC7 was upregulated. Furthermore, the induction of miR-630 occurred commonly in a variety of human cancer and immortalized cells in response to genotoxic agents. Importantly, downregulation of CDC7 by miR-630 was associated with cisplatin (CIS)-induced inhibitory proliferation in A549 cells. Mechanistically, miR-630 exerted its inhibitory proliferation by blocking CDC7-mediated initiation of DNA synthesis and by inducing G1 arrest, but maintains apoptotic balance under CIS exposure. On the one hand, miR-630 promoted apoptosis by downregulation of CDC7; on the other hand, it reduced apoptosis by downregulating several apoptotic modulators such as PARP3, DDIT4, EP300 and EP300 downstream effector p53, thereby maintaining the apoptotic balance. Our data indicate that miR-630 has a bimodal role in the regulation of apoptosis in response to DNA damage. Our data also support the notion that a certain mRNA can be targeted by several miRNAs, and in particular an miRNA may target a set of mRNAs. These data afford a comprehensive view of microRNA-dependent control of gene expression in the regulation of apoptosis under genotoxic stress.

Macrophage migration inhibitory factor is a direct target of HBP1-mediated transcriptional repression that is overexpressed in prostate cancer.

Macrophage migration inhibitory factor (MIF) is a well-described proinflammatory mediator. MIF overexpression has been observed in many tumors and is implicated in oncogenic transformation and tumor progression. However, the molecular mechanisms responsible for regulating MIF expression remain poorly understood. In this study, we showed that the transcriptional repressor HBP1 (HMG box-containing protein 1) negatively regulates MIF expression. We first identified a large high-affinity HBP1 DNA-binding element at positions -811 to -792 from the transcriptional start site within the MIF promoter by computer analysis. Reporter analyses showed that this element was required for HBP1-mediated transcriptional repression. Furthermore, HBP1 associated with the MIF promoter in vivo and repressed endogenous MIF gene expression. Consistent with HBP1-mediated repression of MIF, low levels of HBP1 expression were associated with high levels of MIF expression in prostate cancer samples. Importantly, HBP1-mediated repression of MIF inhibited tumorigenic growth and invasion, and the repressive effect of HBP1 on tumorigenic growth and invasion could be partially rescued by the addition of recombinant MIF to the culture medium. Finally, prostate tumor samples with low HBP1 and high MIF expression were associated with a significant decrease in relapse-free survival. Taken together, these results indicated that HBP1 directly inhibited MIF gene transcription, and suggested that the loss of HBP1 expression or activity may contribute to the upregulation of MIF expression in prostate tumor tissue.