RAB31 and breast carcinoma: Since uPAR as well as rab31 mRNA are known to be regulated by the RNA binding protein HuR both in vitro and in vivo[10,50], the observed elevated uPAR-del4/5 as well as rab31 expression in metastasizing breast cancer may be due to increased HuR expression in these tumors and points to a possible link between rab31 and the uPA/uPAR system in cancer cells.