Long Non-coding RNA LINC00941 as a Potential Biomarker Promotes the Proliferation and Metastasis of Gastric Cancer

Long noncoding RNAs (lncRNA) have been implicated in human cancer but their mechanisms of action are mainly undocumented. In this study, we investigated lncRNA alterations that contribute to gastric cancer through an analysis of The Cancer Genome Atlas RNA sequencing data and other publicly available microarray data. Here we report the gastric cancer-associated lncRNA HOXA11-AS as a key regulator of gastric cancer development and progression. Patients with high HOXA11-AS expression had a shorter survival and poorer prognosis. In vitro and in vivo assays of HOXA11-AS alterations revealed a complex integrated phenotype affecting cell growth, migration, invasion, and apoptosis. Strikingly, high-throughput sequencing analysis after HOXA11-AS silencing highlighted alterations in cell proliferation and cell-cell adhesion pathways. Mechanistically, EZH2 along with the histone demethylase LSD1 or DNMT1 were recruited by HOXA11-AS, which functioned as a scaffold. HOXA11-AS also functioned as a molecular sponge for miR-1297, antagonizing its ability to repress EZH2 protein translation. In addition, we found that E2F1 was involved in HOXA11-AS activation in gastric cancer cells. Taken together, our findings support a model in which the EZH2/HOXA11-AS/LSD1 complex and HOXA11-AS/miR-1297/EZH2 cross-talk serve as critical effectors in gastric cancer tumorigenesis and progression, suggesting new therapeutic directions in gastric cancer. Cancer Res; 76(21); 6299-310. ©2016 AACR.

Breast cancers are highly heterogeneous but can be grouped into subtypes based on several criteria, including level of expression of certain markers. Claudin-low breast cancer (CLBC) is associated with early metastasis and resistance to chemotherapy, while gene profiling indicates it is characterized by the expression of markers of epithelial-mesenchymal transition (EMT) - a phenotypic conversion linked with metastasis. Although the epigenetic program controlling the phenotypic and cellular plasticity of EMT remains unclear, one contributor may be methylation of the E-cadherin promoter, resulting in decreased E-cadherin expression, a hallmark of EMT. Indeed, reduced E-cadherin often occurs in CLBC and may contribute to the early metastasis and poor patient survival associated with this disease. Here, we have determined that methylation of histone H3 on lysine 9 (H3K9me2) is critical for promoter DNA methylation of E-cadherin in three TGF-β-induced EMT model cell lines, as well as in CLBC cell lines. Further, Snail interacted with G9a, a major euchromatin methyltransferase responsible for H3K9me2, and recruited G9a and DNA methyltransferases to the E-cadherin promoter for DNA methylation. Knockdown of G9a restored E-cadherin expression by suppressing H3K9me2 and blocking DNA methylation. This resulted in inhibition of cell migration and invasion in vitro and suppression of tumor growth and lung colonization in in vivo models of CLBC metastasis. Our study not only reveals a critical mechanism underlying the epigenetic regulation of EMT but also paves a way for the development of new treatment strategies for CLBC.

Long noncoding RNA HOTTIP plays important roles in the generation and progression of human cancers. Exosomes participate in cellular communication by transmitting moleculars between cells and are regarded as suitable candidates for non-invasive diagnosis. However, the existence of HOTTIP in the circulating exosomes and the potential roles of exosomal HOTTIP in gastric cancer (GC) was poorly understood. This study aims at investigating the clinical roles of exosomal HOTTIP in GC. Serum exosomal HOTTIP from 246 subjects (126 GC patients and 120 healthy people) were detected by reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR). Our results showed that expression levels of exosomal HOTTIP were typically upregulated in GC than in normal control (P < 0.001). And its expression levels were significantly correlated with invasion depth (P = 0.0298) and TNM stage (P < 0.001). The AUC for exosomal HOTTIP was 0.827, which demonstrated a higher diagnostic capability than CEA, CA 19–9 and CA72–4 (AUC = 0.653, 0.685 and 0.639, respectively) (P < 0.001). The Kaplan–Meier analysis showed a correlation between increased exosomal HOTTIP levels and poor overall survival (OS) (logrank P < 0.001). And univariate and multivariate COX analysis revealed exosomal HOTTIP overexpression was an independent prognostic factor in GC patients (P = 0.027). These findings demonstrated that exosomal HOTTIP may be a potential biomarker for GC in diagnosis and prognosis. Electronic supplementary material The online version of this article (10.1186/s12943-018-0817-x) contains supplementary material, which is available to authorized users.