No abstract

Background: Gastric cancer (GC) is the third leading cause of cancer-related mortality globally. Long noncoding RNAs (lncRNAs) are dysregulated in obvious malignancies including GC and exploring the regulatory mechanisms underlying their expression is an attractive research area. However, these molecular mechanisms require further clarification, especially upstream mechanisms. Methods: LncRNA MNX1-AS1 expression in GC tissue samples was investigated via microarray analysis and further determined in a cohort of GC tissues via quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays. Cell proliferation and flow cytometry assays were performed to confirm the roles of MNX1-AS1 in GC proliferation, cell cycle regulation, and apoptosis. The influence of MNX1-AS1 on GC cell migration and invasion was explored with Transwell assays. A xenograft tumour model was established to verify the effects of MNX1-AS1 on in vivo tumourigenesis. The TEAD4-involved upstream regulatory mechanism of MNX1-AS1 was explored through ChIP and luciferase reporter assays. The mechanistic model of MNX1-AS1 in regulating gene expression was further detected by subcellular fractionation, FISH, RIP, ChIP and luciferase reporter assays. Results: It was found that MNX1-AS1 displayed obvious upregulation in GC tissue samples and cell lines, and ectopic expression of MNX1-AS1 predicted poor clinical outcomes for patients with GC. Overexpressed MNX1-AS1 expression promoted proliferation, migration and invasion of GC cells markedly, whereas decreased MNX1-AS1 expression elicited the opposite effects. Consistent with the in vitro results, MNX1-AS1 depletion effectively inhibited the growth of xenograft tumour in vivo. Mechanistically, TEAD4 directly bound the promoter region of MNX1-AS1 and stimulated the transcription of MNX1-AS1. Furthermore, MNX1-AS1 can sponge miR-6785-5p to upregulate the expression of BCL2 in GC cells. Meanwhile, MNX1-AS1 suppressed the transcription of BTG2 by recruiting polycomb repressive complex 2 to BTG2 promoter regions. Conclusions: Our findings demonstrate that MNX1-AS1 may be able to serve as a prognostic indicator in GC patients and that TEAD4-activatd MNX1-AS1 can promote GC progression through EZH2/BTG2 and miR-6785-5p/ BCL2 axes, implicating it as a novel and potent target for the treatment of GC.

No abstract

Sesquiterpene lactones (SLs) are plant-derived constituents that have been proved to have potential antitumour activity. However, the intracellular molecular targets of SLs and the underlying molecular mechanisms have not been well elucidated. Here, we report that F1012-2, a novel SL active fraction, isolated from Eupatorium lindleyanum DC., can significantly inhibit the growth of triple-negative breast cancer (TNBC) cells (MDA-MB-231 and MDA-MB-468) but has no obvious inhibitory effect on the growth of human mammary epithelial cells (MCF-10A). The related mechanisms on cell growth inhibition of F1012-2 were demonstrated by inducing apoptosis in a caspase-dependent manner through the intrinsic pathway and extrinsic pathway. F1012-2 could also activate autophagy in TNBC cells. Simultaneously, we found that F1012-2-induced apoptosis was enhanced by inhibition of autophagy. Furthermore, F1012-2 could induce cell cycle arrest at G2/M phase with decreasing expression of cyclin B1, cdc2, and upregulating p21, p-cdc2. Also, F1012-2 activated Akt and p38 signalling pathways. In vivo, F1012-2 exhibited a potential antitumour effect in MDA-MB-231 xenografts without apparent toxicity. Taken together, our results identified that F1012-2 inhibited cell growth via multiple signalling pathways in vitro and in vivo. These data suggest that F1012-2 may be a potential natural active fraction for the treatment of TNBC.