Finally, we introduce methods to study TGF-β-regulated miRNAs and their functions in tumor progression and metastasis using an example of publication from our lab demonstrating the presence of a TGF-β-miR-34a-CCL22 signaling axis, which serves as a potent etiological pathway for the development of hepatocellular carcinoma venous metastases.
We also showed that HOTAIR recruiting and binding to PRC2 epigenetically represses miR34a, which controls the targets C-Met (HGF/C-Met/Snail pathway) and Snail, thus contributing to GC cell-EMT process and accelerating tumor metastasis.
Collectively, these findings suggested a plausible role of CD44v/SYNE1/miR34a axis as non-invasive salivary biomarkers to diagnose this disease at an early stage and predict the early onset of metastasis.
A vast number of miRNAs, including the well-studied miR-21, miR-155 and miR-34, has been shown to regulate PDAC growth, invasion and metastasis in vitro and in vivo by targeting members of key signaling pathways.
Mechanistic investigations demonstrated that MALAT1, as a competing endogenous RNA (ceRNA), regulated osteosarcoma proliferation and metastasis through competitively binding to miR-34a/c-5p and miR-449a/b.
The expression of shrimp miR-34 in breast cancer cells and in mice suppressed the growth and metastasis of breast cancer by targeting human CCND1, CDK6, CCNE2, E2F3, FOSL1, and MET genes in a cross-phylum manner.
Here, we provide an overview of the function of miR-34a in tumor-associated EMT. ceRNA hypothesis plays an important role in miR-34a regulation in EMT, cancer progression, and metastasis.
Combined inactivation of the microRNA 34a gene (MIR34A, by methylation) and the TP53 gene (by mutation or deletion) is observed in 50% of colorectal tumors that progress to distant metastases.
Ectopic expression of miR-34a-5p in p53 wild-type colon cancer cell HCT116 significantly inhibited cell growth, migration, invasion and metastasis. miR-34a-5p induced cell apoptosis, cell cycle arrest at G1 phase and p53 transcription activity in HCT116 cells, but not in the HCT116 p53 knockout (p53(-/-)) cells. miR-34a-5p significantly suppressed the HCT116 growth in vivo, whereas it showed no effect on the HCT116 p53(-/-) xenograft, indicating that the growth-inhibiting effect by miR-34a-5p was dependent on p53.
Further results indicated that SNHG7 facilitated the proliferation and metastasis as a competing endogenous RNA to regulate GALNT7 expression by sponging miR-34a in CRC cell lines.
Ectopic over expression of miR-34a restrained cell growth, tube formation and migration/invasion, and significantly suppressed the growth of renal carcinoma xenografts and metastasis in nude mice.
Moreover, miR‑34 has been identified as a tumour‑suppressor in GC. p53‑induced miR‑34 regulates several different target genes and signalling pathways, inducing apoptosis, senescence, and cell cycle arrest and repressing GC cell proliferation, migration and metastasis, thus contributing to the suppression of carcinogenesis and GC cancer progression.
Here, we studied miR-34a-5p expression, and Met-receptor expression and localization in bone metastases from ductal breast carcinomas, and in ductal carcinomas without history of metastasis (20 cases). miR-34a-5p was elevated in non-metastatic breast carcinoma, intermediate in the adjacent tissue and practically absent in bone metastases, opposite to pair-matched carcinoma.
We previously reported that IL-6R, STAT3 and miR-34a form a positive feedback-loop, which promotes epithelial to mesenchymal transition (EMT), invasion, and metastasis of colorectal cancer (CRC) [1].
Esophageal squamous cell carcinoma (ESCC), one of the most common gastrointestinal tumors, is known for its high mortality rate. microRNAs (miRNAs) have been reported to play important regulatory roles in cancer metastasis and progression. miR-34a has been demonstrated to be associated with the development of and metastasis in certain types of cancer via various target genes, but its function and targets in ESCC are unknown.
The expressions of miR-34a/34b/34c were significantly lower in TNBC patients than in HC (p<0.001, p=0.027, p<0.001, respectively). miR-34a was correlated with tumor grade (p=0.038), lymph node positive (p=0.027), distant metastasis (p=0.004), and surgery (p=0.023); miR-34b was correlated with lymph node positivity (p=0.027); and miR-34c was correlated with tumor grade (p=0.017) and distant metastasis (p<0.001).
Taken together, the results of the present study suggested that the overexpression of miR-34a may have suppressed HCC metastasis via inhibited cell migration and invasion.
The results presented in this study demonstrated that over-expression of miR-34a could inhibit the tumor growth and metastasis of osteosarcoma probably through down regulating c-Met.
Decreased miR-34a expression was associated with upregulation of c-Met, Snail, and β-catenin protein levels (P = 0.031, 0.132, and 0.004), which were associated with distant metastases (P = 0.001, 0.017, and 0.005).
MRX34, a liposome-formulated mimic of miR-34 for treatment of metastatic cancer with liver involvement and unresectable primary liver cancer, has also entered in clinical trial.