MicroRNA-21 (miR-21) was reported to be overexpressed and contributes to invasion and gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC).
MiR-21 is a miRNA that is overexpressed in most tumor types, and acts as an oncogene by targeting many tumor suppressor genes related to proliferation, apoptosis, and invasion.
MiR-21 is one of the important microRNAs associated with tumor progression and metastasis, but the molecular mechanisms underlying EMT and CSC phenotype during miR-21 contributes to migration and invasion of breast cancer cells remain to be elucidated.
MicroRNA-21 has been proved to be associated with glioma proliferation and invasion; thus, we sought to clarify the clinical value of miR-21 expression in glioma tissues with WHO grade I to IV.
A co-culture system of normal fibroblasts and esophageal cancer cells was used to determine the effects of fibroblasts on miR-21 expression levels, and on SCC cell migration and invasion.
A total of 132 miRNAs were found to be altered in response to SS treatment, including miR-10b, miR-17, miR-21 and miR-9, which have been previously implicated in tumor invasion and metastasis.
Aberrantly expressed miR-21 might regulate the TCF21-KISS1-associated renal cell carcinoma cell invasion pathway, and this miRNA signature could offer a novel potential therapeutic strategy for renal cell carcinoma.
All seven esophageal squamous cell carcinoma cell lines also overexpressed microRNA-21, and anti-microRNA-21-transfected cells showed significant reduction in cellular proliferation and invasion.
Although the reasons for the high relapse are not fully understood, the presence of chemo- and radiotherapy-resistant cancer stem/stem-like cells, where many oncomirs like microRNA-21 (miR-21) are upregulated, could be one of the underlying causes. miR-21 regulates the processes of invasion and metastasis by downregulating multiple tumor/metastatic suppressor genes including PTEN (phosphatase and tensin homolog).
An in vitro study showed that CAFs with high miR-21 expression had elevated MMP-3, MMP-9, PDGF, and CCL-7 expression and promoted the invasion of PDAC cell lines. miR-21 overexpression also contributed to the activation of CAFs by regulating the PDCD4 gene.