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Modulating the activity of miRNAs provides opportunities for novel cancer interventions. However, low bioavailability and poor cellular uptake are major challenges for delivering miRNA mimetics specifically to tumor cells. Here, we took advantage of the spontaneous enhanced endocytic activity of ovarian cancer-associated dendritic cells (DC) to selectively supplement the immunostimulatory miRNA miR-155. In vivo processing of nanoparticles carrying oligonucleotide duplexes mimicking the bulged structure of endogenous pre-miRNA (but not siRNA-like oligonucleotides) dramatically augmented miR-155 activity without saturating the RNA-induced silencing complex. Endogenous processing of synthetic miR-155 favored Ago2 and, to a lesser extent, Ago4 loading, resulting in genome-wide transcriptional changes that included silencing of multiple immunosuppressive mediators. Correspondingly, tumor-infiltrating DCs were transformed from immunosuppressive to highly immunostimulatory cells capable of triggering potent antitumor responses that abrogated the progression of established ovarian cancers. Our results show both the feasibility and therapeutic potential of supplementing/replenishing miRNAs in vivo using nonviral approaches to boost protective immunity against lethal tumors. Thus, we provide a platform, an optimized design, and a mechanistic rationale for the clinical testing of nonviral miRNA mimetics., (©2012 AACR.)

Heparin/heparan sulfate interacting protein (HIP) is a recently identified protein expressed by many normal epithelia and epithelial cell lines. In the present study, we examined expression and potential functions of this protein in a series of human breast cancer cells and in sections of normal and malignant human breast tissue. Four of the five breast cancer cell lines studied (MCF-7, T-47D, MDA-MB468, and BT-549) expressed HIP protein and mRNA at similar levels. In contrast, MDA-MB-231 cells failed to display reactivity with HIP-specific probes in any assay. Cell aggregation assays and cell surface antibody binding studies demonstrated that HIP was expressed on the cell surface. However, HIP expression did not correlate with the number of cell surface [3H]heparin (HP) binding sites. The K(Dapp)s for cell surface HP binding sites were similar in all breast cancer cell lines studied and ranged from 112 to 298 nM. In contrast, cell surface HP binding capacity varied greatly, ranging from 2.3 x 10(5) (MDA-MB-231 and MDA-MB-468) to 99 x 10(5) sites/cell (BT-549). All cell lines tested displayed the ability to bind to a heparan sulfate (HS)-binding synthetic peptide motif of HIP in a HP-inhibitable fashion. Binding to this motif was not inhibited by other glycosaminoglycans including hyaluronic acid, chondroitin sulfates, or keratan sulfate. Furthermore, cell binding to HIP peptide was almost completely lost when intact cells were predigested with heparinases but not chondroitinases. Cell surface HS from breast cancer cells as well as normal human breast epithelia binded to HIP peptide in a HP-inhibitable fashion, demonstrating the ability of these cell surface components to directly interact. HIP was detected in both normal breast epithelia and breast tumors in situ. It is suggested that HIP mediates aspects of HS-dependent interactions of both normal and malignant breast epithelia with other cells and extracellular matrix components.