Metastasis is a multistep process involving modification of morphology to suit migration, reduction of tumor cell adhesion to the extracellular matrix, increase of cell mobility, tumor cell resistance to anoikis, and other steps. MicroRNAs are well-suited to regulate tumor metastasis due to their capacity to repress numerous target genes in a coordinated manner, thereby enabling their intervention at multiple steps of the invasion-metastasis cascade. In this study, we identified a microRNA exemplifying these attributes, miR-124, whose expression was reduced in aggressive MDA-MB-231 and SK-3rd breast cancer cells. Down-regulation of miR-124 expression in highly aggressive breast cancer cells contributed in part to DNA hypermethylation around the promoters of the three genes encoding miR-124. Ectopic expression of miR-124 in MDA-MB-231 cells suppressed metastasis-related traits including formation of spindle-like morphology, migratory capacity, adhesion to fibronectin, and anoikis. These findings indicate that miR-124 suppresses multiple steps of metastasis by diverse mechanisms in breast cancer cells and suggest a potential application of miR-124 in breast cancer treatment.
A previous study indicated that C–C chemokine(C–C motif)ligand 18(CCL18)is capable of inducing tumor cell invasion and metastasis by interacting with receptor membrane-associated phosphatidylinositol transfer protein 3(PITPNM3)in breast cancer cells.The present study aims to investigate the correlation between the PITPNM3 expression and metastasis in hepatocellular carcinoma(HCC).Real-time quantitative polymerase chain reaction and Western blot were performed to detect the expression pattern of PITPNM3 in patient samples and HCC cell lines.Wound-healing and transwell chamber assays were performed to assess the migration and invasiveness of HCC cells,and the activation of the signaling protein downstream of PITPNM3 was also detected by Western blot and immunofluorescence.The results revealed that PITPNM3 was upregulated in HCC tissue compared to matched normal liver tissue.Silencing the expression of PITPNM3 by specific siRNAs markedly attenuated the invasive and metastatic abilities of HCC cells,whereas the upregulation of PITPNM3 significantly increased HCC cell mobility.Furthermore,inhibiting the expression of PITPNM3 suppressed the activation of Pyk2,FAK,and Src,while overexpression of PITPNM3enhanced the phosphorylation of FAK and Src in HCC cells.Besides,suppression of Pyk2 can also impair the clustering of integrin.These results imply that PITPNM3 is a vital determinant of HCC migration and invasion.
Tumor metastasis is one of the most serious challenges for human cancers as the majority of deaths caused by cancer are associated with metastasis,rather than the primary tumor.Recent studies have demonstrated that tumor cell plasticity plays a critical role in tumor metastasis by giving rise to various cell types which is necessary for tumor to invade adjacent tissues and form distant metastasis.These include differentiation of cancer stem cells(CSCs),or epithelial-mesenchymal transition(EMT)and its reverse process,mesenchymal-epithelial transition(MET).A growing body of evidence has demonstrated that the biology of tumor cell plasticity is tightly linked to functions of non-coding RNAs(ncRNAs),especially microRNAs(miRNAs)and long non-coding RNAs(lncRNAs).Therefore,understanding the mechanisms how non-coding RNAs regulate tumor cell plasticity is essential for discovery of new diagnostic markers and therapeutic targets to overcome metastasis.
It is clear that RNA is more than just a messenger between gene and protein.The mammalian genome is pervasively transcribed,giving rise to tens of thousands of non-coding transcripts.Whether all of these transcripts are functional remains to be elucidated,but it is evident that there are many functional long non-coding RNAs(lncRNAs).Recent studies have set out to decode the regulatory role and functional diversity of lncRNAs.Here we organize these studies to highlight the significant involvements of lncRNAs in regulation of gene expression and human physiological and pathological processes,which are achieved by their interaction with DNA,RNA or protein.
