result, we evaluated a possible role for miR-126 in regulating KRAS and found that it is able to directly regulate KRAS, inhibiting its protein translation by interacting with a ��seedless��site within its 39UTR. This suggests that its downregulation in PDAC could participate in the 7 MiRNAs in Benign vs. Malignant Pancreatic Tumors progression of PDAC because of the subsequent KRAS increase. MiR-126 expression was in fact down-regulated in PDAC compare to SMCA and previous studies have shown that these BCT lesions are devoid of the KRAS mutation. The high malignant potential BCT have been shown to have the mutated KRAS more frequently and we show these lesions had no significant difference in miR-126 expression when LY2109761 site compared to PDAC. Interestingly, for progression from PanIN to BCT to adenocarcinoma these mucinous lesions require KRAS, followed by loss of heterozygosity of SMAD4 and mutation of p53 or p16. As we show miR-126 up-regulation occurs in SMCA, this raises the possibility of replacement miRNA therapy for those patients with low miR-126 in their BCT at the time of pre-operative biopsy or even as adjuvant treatment after surgical resection to prevent recurrence or control disease. MiR-16 is often down-regulated in chronic lymphocytic leukaemia, gastric, ovarian and prostate cancers as a tumor suppressor that targets and down-regulates the antiapoptotic gene BCL2. MiR-126 is down-regulated in various tumors compared to non-cancerous tissues including breast, lung, stomach, cervix, bladder, and prostate. Recently, miR-126 has been shown to be a tumor suppressor PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22190001 in gastric cancer as it can inhibit tumor growth and metastasis in vivo and in vitro. This effect was partially mediated by down-regulation of CRK. SRC and CRK-associated substrate phosphorylation is an important promoter of PDAC anchorage-independence and tumor progression. SRC is able to repress miR-126 expression levels and furthermore miR-126 has been described as a suppressor of proliferation and metastasis in breast cancer. We have established that miR-16 targets BCL2 and miR-126 targets at least CRK and KRAS in PDAC cell-lines. As already shown, we did not observe any significant change in miR-16 and miR-126 expression comparing normal pancreas to PDAC using RTqPCR, but did find significant down-regulation of both miRNAs in PDAC compared to a low malignant potential BCT. Whilst the down-regulation of miR-16 has not been seen previously in PDAC compared to normal pancreas, the reduction of miR-126 in PDAC has recently been reported. As both are frequently down-regulated in several tumor types, their importance in tumorigenesis is 
clear. We could not see miR-21 as up-regulated in PDAC compared to SMCA. Croce’s group have also examined the oncomiR-21 in more detail in 80 PDAC specimens and found that it is significantly overexpressed in PDAC, but that its expression does not correlate with tumor size, nodal status or T stage. We observed that its up-regulation from normal tissue is almost certainly a very early event that occurs in the low malignant potential BCT we studied and this occurs even earlier than previously described. This suggests that miR-21 induces pancreatic cell proliferation, but it is not sufficient to induce malignant transformation. Since miR21 has recently been demonstrated to be up-regulated in PDAC compared to normal tissue and we show here that it is not deregulated in PDAC compared to pre-malignant BCT, this indicates that its up-regulation is l