Restoring expression of miR-16: a novel approach to therapy for malignant pleural mesothelioma.

BACKGROUND: Malignant pleural mesothelioma (MPM) is recalcitrant to treatment and new approaches to therapy are needed. Reduced expression of miR-15/16 in a range of cancer types has suggested a tumour suppressor function for these microRNAs, and re-expression has been shown to inhibit tumour cell proliferation. The miR-15/16 status in MPM is largely unknown. MATERIALS AND METHODS: MicroRNA expression was analysed by TaqMan-based RT-qPCR in MPM tumour specimens and cell lines. MicroRNA expression was restored in vitro using microRNA mimics, and effects on proliferation, drug sensitivity and target gene expression were assessed. Xenograft-bearing mice were treated with miR-16 mimic packaged in minicells targeted with epidermal growth factor receptor (EGFR)-specific antibodies. RESULTS: Expression of the miR-15 family was consistently downregulated in MPM tumour specimens and cell lines. A decrease of 4- to 22-fold was found when tumour specimens were compared with normal pleura. When MPM cell lines were compared with the normal mesothelial cell line MeT-5A, the downregulation of miR-15/16 was 2- to 10-fold. Using synthetic mimics to restore miR-15/16 expression led to growth inhibition in MPM cell lines but not in MeT-5A cells. Growth inhibition caused by miR-16 correlated with downregulation of target genes including Bcl-2 and CCND1, and miR-16 re-expression sensitised MPM cells to pemetrexed and gemcitabine. In xenograft-bearing nude mice, intravenous administration of miR-16 mimics packaged in minicells led to consistent and dose-dependent inhibition of MPM tumour growth. CONCLUSIONS: The miR-15/16 family is downregulated and has tumour suppressor function in MPM. Restoring miR-16 expression represents a novel therapeutic approach for MPM.

Use of a monoclonal antibody to ovine IgE for fly strike studies in sheep.

A new monoclonal raised against sheep IgE was used to examine sera and wound exudates from sheep which had been struck by Lucilia cuprina in the field. The antibody was also used to detect the presence of IgE in sera and skin sections from sheep which had been artificially infected with fly larvae 3 times. Neither total, nor L. cuprina specific circulating IgE could be detected in serum or wound exudates from struck sheep. Cell bound IgE was, however, identified by the monoclonal in skin sections from struck sheep and from a control sheep which had not been struck. No difference in the number of IgE positive cells was observed between the control and 2 of the 3 artificially infected sheep, and none of the latter showed an increase in IgE positive cells even after 3 infections. One sheep showed twice as many IgE positive cells as the other treated sheep and the third larval infection was difficult to establish and limited in size and severity. This suggests a relationship between innate resistance to strike and the number of IgE positive cells present in skin.

Characterization of Pseudomonas maltophilia Isolates from Fleece Rot.

A total of 286 isolates of Pseudomonas maltophilia was collected from sheep exhibiting brown or yellowish fleece rot and from fly-strike lesions. Enzyme activities for 10 of the isolates were examined by plate tests and with the API ZYM system and compared with the enzymatic profile of a human type strain of P. maltophilia. The fact that ovine isolates of P. maltophilia are biochemically similar to pathogenic human strains suggests there may be an association between this organism and the brown to yellow type of fleece rot.

Characterisation of isolates of Pseudomonas aeruginosa from sheep.

Fleece rot isolates of Pseudomonas aeruginosa were characterised in terms of biochemical reactions, serological typing and production of keratinase, lipase and the potentially dermal necrotic enzymes exotoxin A, protease, elastase phospholipase and lecithinase. The similarities generally obtained between these characteristics of isolates from sheep and man suggests a role for P. aeruginosa and mechanisms of pathogenesis in the development of the dermatitis associated with fleece rot.