Stromal fibroblast-derived miR-409 promotes epithelial-to-mesenchymal transition and prostate tumorigenesis.

Tumor-stromal interaction is a dynamic process that promotes tumor growth and metastasis via cell-cell interaction and extracellular vesicles. Recent studies demonstrate that stromal fibroblast-derived molecular signatures can be used to predict disease progression and drug resistance. To identify the epigenetic role of stromal noncoding RNAs in tumor-stromal interactions in the tumor microenvironment, we performed microRNA profiling of patient cancer-associated prostate stromal fibroblasts isolated by laser capture dissection microscopy and in bone-associated stromal models. We found specific upregulation of miR-409-3p and miR-409-5p located within the embryonically and developmentally regulated DLK1-DIO3 (delta-like 1 homolog-deiodinase, iodothyronine 3) cluster on human chromosome 14. The findings in cell lines were further validated in human prostate cancer tissues. Strikingly, ectopic expression of miR-409 in normal prostate fibroblasts conferred a cancer-associated stroma-like phenotype and led to the release of miR-409 via extracellular vesicles to promote tumor induction and epithelial-to-mesenchymal transition in vitro and in vivo. miR-409 promoted tumorigenesis through repression of tumor suppressor genes such as Ras suppressor 1 and stromal antigen 2. Thus, stromal fibroblasts derived miR-409-induced tumorigenesis, epithelial-to-mesenchymal transition and stemness of the epithelial cancer cells in vivo. Therefore, miR-409 appears to be an attractive therapeutic target to block the vicious cycle of tumor-stromal interactions that plagues prostate cancer patients.

Wrinkling of atomic planes in ultrathin Au nanowires.

A detailed understanding of structure and stability of nanowires is critical for applications. Atomic resolution imaging of ultrathin single crystalline Au nanowires using aberration-corrected microscopy reveals an intriguing relaxation whereby the atoms in the close-packed atomic planes normal to the growth direction are displaced in the axial direction leading to wrinkling of the (111) atomic plane normal to the wire axis. First-principles calculations of the structure of such nanowires confirm this wrinkling phenomenon, whereby the close-packed planes relax to form saddle-like surfaces. Molecular dynamics studies of wires with varying diameters and different bounding surfaces point to the key role of surface stress on the relaxation process. Using continuum mechanics arguments, we show that the wrinkling arises due to anisotropy in the surface stresses and in the elastic response, along with the divergence of surface-induced bulk stress near the edges of a faceted structure. The observations provide new understanding on the equilibrium structure of nanoscale systems and could have important implications for applications in sensing and actuation.