Down-regulation of miR-203 induced by Helicobacter pylori infection promotes the proliferation and invasion of gastric cancer by targeting CASK

Methylation-mediated repression of potential tumor suppressor miR-203a and miR-203b contributes to esophageal squamous cell carcinoma development

MiRNAs regulate gene expression and play pivotal roles in biological processes. MiRNAs can be inactivated by epigenetic mechanisms, such as DNA hypermethylation of CpG sites within CpG islands. Here, we investigated the role and methylation status of miR-203a and miR-203b in esophageal cancer cell lines and primary esophageal squamous cell carcinoma (ESCC) tumors and further elucidate the role of both miRNAs in the prognosis of ESCC. The present study revealed a strong downregulation of miR-203a and miR-203b in esophageal cancer cell lines and primary ESCC samples. Treatment of esophageal cancer cells with demethylating agent 5-Aza-dC led to increased miR-203a and miR-203b expression, confirming the epigenetic regulation of both miRNAs. The inhibition of proliferation and invasiveness in esophageal cancer cells after treated with 5-Aza-dC or transfected with miR-203a or miR-203b mimics, suggesting the tumor suppressor role of both miRNAs in esophageal cancer. Furthermore, the critical CpG sites of miR-203a and miR-203b were found to be located in proximal promoter region, and the proximal promoter hypermethylation of both miRNAs was found to influence transcriptional activity. Downregulation and hypermethylation of miR-203a and miR-203b were associated with TNM stage, pathological differentiation, and lymph node metastasis. ESCC patients in stages III and IV, with reduced expression of miR-203a or hypermethylation of miR-203a or miR-203b, demonstrated poor patient survival. In summary, our results suggest that miR-203a and miR-203b may function as tumor-suppressive miRNAs that are inactivated through proximal promoter hypermethylation and miR-203a expression and methylation may be useful prognostic marker in ESCC patients.

miR-221 and miR-222 Simultaneously Target RECK and Regulate Growth and Invasion of Gastric Cancer Cells

BACKGROUND

Although Helicobacter pylori infection is necessary for development of gastric adenocarcinoma (GAC), the underlying mechanism remains poorly defined. This study aimed to explore how miR-221 and miR-222 are dysregulated after H. pylori infection and how these 2 miRNAs are involved in pathological development of gastric cancer.

MATERIAL AND METHODS

qRT-PCR analysis was performed to quantify miR-221 and miR-222 expression in patients with H. pylori - induced chronic gastritis, H. pylori-negative healthy controls, and in gastric cancer tissues and the corresponding adjacent normal tissues. Cell models were used to verify the expression profile. Dual luciferase assay was performed to verify putative binding between miR-221 or miR-222 and RECK. A loss-and-gain function study was performed to assess the miR-221/miR-222-RECK axis in gastric cancer cells.

RESULTS

H. pylori infection leads to significantly higher miR-221 and miR-222 expression. MiR-221 and miR-222 can bind the same sequence of RECK 3'UTR, thereby modulating its expression. Through simultaneous regulation over RECK, miR-221 and miR-222 can promote gastric cancer cell growth and invasion.

CONCLUSIONS

The miR-221/miR-222-RECK axis might be an important path modulating H. pylori infection-related gastric cancer development.

miR-221 and miR-222 Simultaneously Target RECK and Regulate Growth and Invasion of Gastric Cancer Cells

BACKGROUND

Although Helicobacter pylori infection is necessary for development of gastric adenocarcinoma (GAC), the underlying mechanism remains poorly defined. This study aimed to explore how miR-221 and miR-222 are dysregulated after H. pylori infection and how these 2 miRNAs are involved in pathological development of gastric cancer.

MATERIAL AND METHODS

qRT-PCR analysis was performed to quantify miR-221 and miR-222 expression in patients with H. pylori - induced chronic gastritis, H. pylori-negative healthy controls, and in gastric cancer tissues and the corresponding adjacent normal tissues. Cell models were used to verify the expression profile. Dual luciferase assay was performed to verify putative binding between miR-221 or miR-222 and RECK. A loss-and-gain function study was performed to assess the miR-221/miR-222-RECK axis in gastric cancer cells.

RESULTS

H. pylori infection leads to significantly higher miR-221 and miR-222 expression. MiR-221 and miR-222 can bind the same sequence of RECK 3'UTR, thereby modulating its expression. Through simultaneous regulation over RECK, miR-221 and miR-222 can promote gastric cancer cell growth and invasion.

CONCLUSIONS

The miR-221/miR-222-RECK axis might be an important path modulating H. pylori infection-related gastric cancer development.

MiRNA-203 Reduces Nasopharyngeal Carcinoma Radioresistance by Targeting IL8/AKT Signaling

Radioresistance poses a major challenge in nasopharyngeal carcinoma (NPC) treatment, but little is known about how miRNA (miR) regulates this phenomenon. In this study, we investigated the function and mechanism of miR-203 in NPC radioresistance, one of downregulated miRs in the radioresistant NPC cells identified by our previous microarray analysis. We observed that miR-203 was frequently downregulated in the radioresistant NPC tissues compared with radiosensitive NPC tissues, and its decrement significantly correlated with NPC radioresistance and poor patient survival, and was an independent predictor for reduced patient survival. In vitro radioresponse assays showed that miR-203 mimic markedly decreased NPC cell radioresistance. In a mouse model, therapeutic administration of miR-203 agomir dramatically sensitized NPC xenografts to irradiation. Mechanistically, we confirmed that IL8 was a direct target of miR-203, and found that reduced miR-203 promoted NPC cell radioresistance by activating IL8/AKT signaling. Moreover, the levels of IL8 and phospho-AKT were significantly increased in the radioresistant NPC tissues compared with radiosensitive NPC tissues, and negatively associated with miR-203 level. Our data demonstrate that miR-203 is a critical determinant of NPC radioresponse, and its decrement enhances NPC radioresistance through targeting IL8/AKT signaling, highlighting the therapeutic potential of the miR-203/IL8/AKT signaling axis in NPC radiosensitization.

MicroRNA and MET in lung cancer

MicroRNAs (miRNAs) are a class of small non-protein coding RNAs that modulate important cellular functions via their post-transcriptional regulation of messenger RNAs (mRNAs). Recent evidences from multiple tumor types and model systems implicate miRNA dysregulation as a common mechanism of tumorigenesis, cancer progression and resistance to therapy. Several miRNAs are dysregulated in cancers and a single miRNA can have multiple targets involved in different oncogenic pathways. MET, the tyrosine kinase receptor for hepatocyte growth factor (HGF), has a central role in lung cancer development and in acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors; it has been predicted and shown to be the target gene of multiple miRNAs, which play a crucial role in controlling its activity in a stimulatory or inhibitory sense. In this review we will focus on the most important and recent studies about the role of miRNAs in the control of MET expression, reporting also the progress made using miRNAs for therapy of lung cancer.

MicroRNA-126 inhibits cell proliferation in gastric cancer by targeting LAT-1

MicroRNA-126 (miR-126) is a pivotal post-transcriptional regulator, which has been validated as a suppressor in gastric cancer (GC). However, the downstream of its tumor inhibiting function has not been totally clear. L-type amino-acid transporter 1 (LAT-1) is a novel member of system L-type transporters involving in cell proliferation, and we have previously validated that LAT-1 played a role of promotor in GC. In this study, we further detected and confirmed that LAT-1 was exactly targeted by miR-126 in GC. We found LAT-1 was significantly downregulated in GC MKN-45 cell lines by using miR-126 mimics, along with an impairment on cell proliferation and cell cycle. Additionally, by overexpressing LAT-1 in MKN-45 cells which was firstly treated with miR-126 mimics, the ability of cell proliferation in MKN-45 cells was definitely rescued. Thus, our results suggests and consolidates the standpoint that miR-126 plays a pivotal role in GC suppressing the process of GC cell, and this function is at least partly taken to implement by miR-126s's post-transcriptional effect on LAT-1. This might provide us likely potential biomarkers and targets for GC prevention, diagnosis and therapeutic treatment.

MiR-203 inhibits melanoma invasive and proliferative abilities by targeting the polycomb group gene BMI1

Metastasis is the major problem in malignant melanoma, posing a therapeutic challenge to clinicians. The investigation of the underlying mechanism driving this progress remains a large unmet need. In this study, we revealed a miR-203-BMI1 axis that regulated melanoma metastasis. We found significantly deregulation of miR-203 and up-regulation of BMI1 in melanoma, particularly in metastatic melanoma. An inverse correlation between the levels of miR-203 and BMI1 was further observed in melanoma tissues and cell lines. We also identified BMI1 as a downstream target gene of miR-203, which bound to the 3'UTR of BMI1. Overexpression of miR-203 was associated with decreased BMI1 expression and impaired cell invasion and tumor sphere formation activities. Re-expression of BMI1 markedly rescued miR-203-mediated suppression of these events. Taken together, our results demonstrated that miR-203 regulated melanoma invasive and proliferative abilities in part by targeting BMI1, providing new insights into potential mechanisms of melanoma metastasis.