Human cytomegalovirus US7 is regulated synergistically by two virally encoded microRNAs and by two distinct mechanisms.

Human cytomegalovirus (HCMV) encodes at least 14 microRNAs (miRNAs) that act posttranscriptionally to repress gene expression. Although several HCMV miRNA targets of both cellular and viral origin have been identified, our knowledge of their function remains limited. HCMV miRNA targets, as well as phenotypes associated with HCMV miRNA mutants, have been difficult to identify since the downregulation of targets by a single miRNA is often less than 2-fold. Several factors can contribute to the strength of repression, including the mechanism of translational inhibition, the degree of complementarity between the miRNA and target mRNA, the number of binding sites for one miRNA, and cooperativity or antagonism between miRNAs. To determine the effect of multiple miRNAs on one gene, we examined the repression of a viral gene, US7. Here we demonstrate that the HCMV-encoded miRNAs miR-US5-1 and miR-US5-2 function in a highly synergistic manner to regulate US7, even at very low miRNA concentrations. Regulation of US7 involves three functional miRNA binding sites: two that are completely complementary to the 3' untranslated region (3'UTR) and one that is imperfectly matched. Surprisingly, we observed equal contributions to inhibition from both complete and partially complementary sites, and repression was not completely abrogated until all three sites were mutated simultaneously. We also observed that the miRNA binding sites did not follow the spacing constraints for corepressive miRNAs observed in earlier reports. These results underscore the importance of evaluating the contribution of multiple miRNAs on gene regulation and shed new insight into miRNA:mRNA interactions.

A randomized phase 2 trial of neoadjuvant chemotherapy in resectable pancreatic cancer: gemcitabine alone versus gemcitabine combined with cisplatin.

BACKGROUND: Survival after surgery for pancreas cancer remains low. This improves with adjuvant chemotherapy, but up to 30% patients do not receive the prescribed treatment. Neoadjuvant therapy may increase the proportion of patients who receive all treatment components, may downstage disease before surgery, and may provide early treatment of micrometastases. This randomized phase 2 study compares gemcitabine-based chemotherapy regimens to identify the most promising regimen for future study. METHODS: Fifty patients with potentially resectable pancreas lesions were enrolled onto the study. Twenty-four patients were randomized to gemcitabine (1000 mg/m(2)) every 7 days for 43 days; 26 patients were randomized to gemcitabine (1000 mg/m(2)) and cisplatin (25 mg/m(2)), 7 to the original schedule (omitting day 22) and 19 to a revised schedule due to neutropenia (omitting days 15 and 36). The primary outcome measure was resection rate. RESULTS: Patients who were allocated to gemcitabine received a median of 85% of the planned dose. Patients who were allocated to combination treatment received a median of 88% and 92% of the planned gemcitabine and cisplatin doses, respectively. There were 10 episodes of grade III/IV hematological toxicity in each group. Twenty-seven patients (54%) underwent pancreatic resection, 9 (38%) in the gemcitabine arm and 18 (70%) in the combination arm, with no increase in surgical complications. To date, 34 patients (68%) have died. Twelve-month survival for the gemcitabine and combination groups was 42% and 62%. CONCLUSIONS: Chemotherapy can be safely administered before pancreatic surgery. Combination therapy with gemcitabine and cisplatin is associated with a high resection rate and an encouraging survival rate, suggesting that further study is warranted.