There is evidence that neutrophil production is a balance between the proliferative action of granulocyte-colony-stimulating factor (G-CSF) and a negative feedback from mature neutrophils (the chalone). Two neutrophil serine proteases have been implicated in granulopoietic regulation: pro-proteinase 3 inhibits granulocyte macrophage-colony-forming unit (CFU-GM) growth, and elastase mutations cause cyclic and congenital neutropenia. We further studied the action of the neutrophil serine proteases (proteinase 3, elastase, azurocidin, and cathepsin G) on granulopoiesis in vitro. Elastase inhibited CFU-GM in methylcellulose culture. In serum-free suspension cultures of CD34 ؉ cells, elastase completely abrogated the proliferation induced by G-CSF but not that of GM-CSF or stem cell factor (SCF). The blocking effect of elastase was prevented by inhibition of its enzymatic activity with phenylmethylsulfonyl fluoride (PMSF) or heat treatment. When exposed to enzymatically active elastase, G-CSF, but not GM-CSF or SCF, was rapidly cleaved and rendered inactive. These results support a role for neutrophil elastase in providing negative feedback to granulopoiesis by direct antagonism of

G-CSF primed CD34 cells cultured for 2-3 weeks in IL-2 and stem cell factor generate CD56 high cells with phenotypic and morphologic features of NK cells, and a novel adherent CD56 low CD16À population expressing myeloid markers (CD33 and HLA-DR). We hypothesized that similar cells might also occur in peripheral blood. In 13/13 normal individuals, we found a circulating population of CD56 low , CD33 þ , FccRI þ , FccRII þ , HLA-DR þ , CD11b high , CD14 þ monocytes closely resembling the cultured CD56 low CD33 þ cells. They may represent a normal counterpart of the CD56 þ CD33 þ hybrid myeloid/natural killer cell leukemia. Their mean frequency was 1.371% (standard deviation), range 0.16-3.5%, of total mononuclear cells. CD56 low CD33 þ cells, primed with cytomegalovirus antigen, induced autologous T-lymphocyte proliferation comparably to CD56À, CD14 þ peripheral blood monocytes (PBM). Conversely, CD56 low cells induced greater T-cell proliferation than CD56À PBM when lymphocyte responders were HLA mismatched. Unstimulated CD56 low CD33 þ cells showed a low antiproliferative effect on K562, which was increased upon LPS stimulation. The pattern of cytokine production by CD56 low CD33 þ cells and PBM largely overlapped; however, they produced detectable levels of IL-6 and IL-1b. These results define a minor monocyte population with distinct phenotypic and functional features.

Purpose There is growing evidence that interaction between stromal and tumor cells is pivotal in breast cancer progression and response to therapy. Based on earlier research suggesting that during breast cancer progression, striking changes occur in CD10+ stromal cells, we aimed to better characterize this cell population and its clinical relevance. Experimental Design We developed a CD10+ stroma gene expression signature (using HG U133 Plus 2.0) on the basis of the comparison of CD10 cells isolated from tumoral (n = 28) and normal (n = 3) breast tissue. We further characterized the CD10+ cells by coculture experiments of representative breast cancer cell lines with the different CD10+ stromal cell types (fibroblasts, myoepithelial, and mesenchymal stem cells). We then evaluated its clinical relevance in terms of in situ to invasive progression, invasive breast cancer prognosis, and prediction of efficacy of chemotherapy using publicly available data sets. Results This 12-gene CD10+ stroma signature includes, among others, genes involved in matrix remodeling (MMP11, MMP13, and COL10A1) and genes related to osteoblast differentiation (periostin). The coculture experiments showed that all 3 CD10+ cell types contribute to the CD10+ stroma signature, although mesenchymal stem cells have the highest CD10+ stroma signature score. Of interest, this signature showed an important role in differentiating in situ from invasive breast cancer, in prognosis of the HER2+ subpopulation of breast cancer only, and potentially in nonresponse to chemotherapy for those patients. Conclusions Our results highlight the importance of CD10+ cells in breast cancer prognosis and efficacy of chemotherapy, particularly within the HER2+ breast cancer disease.