MicroRNAs are important regulators of gene expression in normal development and 
disease. miR-9 is overexpressed in several cancer forms, including brain 
tumours, hepatocellular carcinomas, breast cancer and Hodgkin lymphoma (HL). 
Here we demonstrated a relevance for miR-9 in HL pathogenesis and identified two 
new targets Dicer1 and HuR. HL is characterized by a massive infiltration of 
immune cells and fibroblasts in the tumour, whereas malignant cells represent 
only 1% of the tumour mass. These infiltrates provide important survival and 
growth signals to the tumour cells, and several lines of evidence indicate that 
they are essential for the persistence of HL. We show that inhibition of miR-9 
leads to derepression of DICER and HuR, which in turn results in a decrease in 
cytokine production by HL cells followed by an impaired ability to attract 
normal inflammatory cells. Finally, inhibition of miR-9 by a systemically 
delivered antimiR-9 in a xenograft model of HL increases the protein levels of 
HuR and DICER1 and results in decreased tumour outgrowth, confirming that miR-9 
actively participates in HL pathogenesis and points to miR-9 as a potential 
therapeutic target.