MicroRNAs (miRNA) represent a novel class of genes that function as negative regulators of gene expression. Recently, miRNAs have been implicated in several cancers. However, aberrant miRNA expression and its clinicopathologic significance in human ovarian cancer have not been well documented. Here, we show that several miRNAs are altered in human ovarian cancer, with the most significantly deregulated miRNAs being miR-214, miR-199a*, miR-200a, miR-100, miR125b, and let-7 cluster. Further, we show the frequent deregulation of miR-

Natural killer cell (NK) receptors for major histocompatibility complex (MHC) class I influence engraftment and graft-versus-tumor effects after allogeneic bone marrow transplantation. We find that SH2-containing inositol phosphatase (SHIP) influences the repertoire of NK receptors. In adult SHIP-/- mice, the NK compartment is dominated by cells that express two inhibitory receptors capable of binding either self or allogeneic MHC ligands. This promiscuous repertoire has significant functional consequences, because SHIP-/- mice fail to reject fully mismatched allogeneic marrow grafts and show enhanced survival after such transplants. Thus, SHIP plays an important role in two processes that limit the success of allogeneic marrow transplantation: graft rejection and graft-versus-host disease.