THE superfamily of low molecular mass GTP-binding proteins, for which the ras proteins are prototypes, has been implicated in the regulation of diverse biological activities including protein trafficking, secretion, and cell growth and differentiation. One member of this family, CDC42Hs (originally referred to as Gp or G25K), seems to be the human homologue of the Saccharomyces cerevisiae cell-division-cycle protein, CDC42Sc. A second S. cerevisiae protein, CDC24, which is known from complementation studies to act with CDC42Sc to regulate the development of normal cell shape and the selection of nonrandom budding sites in yeast, contains a region with sequence similarity to the dbl oncogene product. Here we show that dbl specifically catalyses the dissociation of GDP from CDC42Hs and thereby qualifies as a highly selective guanine nucleotide exchange factor for the GTP-binding protein. Although guanine nucleotide exchange activities have been previously described for other members of the Ras-related GTP-binding protein family, this is the first demonstration, to our knowledge, of the involvement of a human oncogenic protein in catalysing exchange activity.

Total cellular poly(A)-enriched RNA from.a variety of fresh human leukemic blood cells and hematopoietic cell lines was analyzed for homology with molecularly cloned DNA probes containing the one sequence of Abelson. murine leukemia virus (Ab-MuLV), Harvey murine sarcoma virus (Ha-MuSV), simian sarcoma virus (SSV), and avian myelocytomatosis virus strain MC29. Results with the fresh blood cells paralleled those obtained with the cell lines. With Ab-MuLV and Ha,-MuSV, multiple RNA bands were visualized in all cell types examined without significant variation in the relative intensities of the bands. When SSV was used as the probe, expression of related one sequences was absent in all of the hematopoietic cell types examined except for one neoplastic T-cell line (HUT 102), which produces the human T-cell leukemia (lymphoma) retrovirus HTLV. In this cell line, a single band (4.2 kilobases) was -observed. With MC29 as the probe, a single band of 2.7 kilobases was visualized in all cell types examined with only a 1-to 2-fold-variation in intensity-of hybridization. An exception was the promyelocytic cell line, HL60, which expressed approximately 10-fold more MC29-related one sequences. With induction of differentiation of HL60 with either dimethyl sulfoxide or retinoic acid, a marked diminution in the amount of the MC29-related, but not the Ab-MuLV-related, onc message was observed.

We have developed an efficient expression cloning system that allows rapid isolation of complementary DNAs able to induce the transformed phenotype. We searched for molecules expressed in epithelial cells and possessing transforming potential to fibroblasts, and cloned a cDNA for the normal receptor of a growth factor secreted by NIH/3T3 cells. Here we report a second novel transforming gene, ect2. The isolated cDNA is activated by amino-terminal truncation of the normal product. The Ect2 protein has sequence similarity within a central core of 255 amino acids with the products of the breakpoint cluster gene, bcr (ref. 5), the yeast cell cycle gene, CDC24 (ref. 6), and the dbl oncogene. Each of these genes encodes regulatory molecules or effectors for Rho-like small GTP-binding proteins. The baculovirus-expressed Ect2 protein could bind highly specifically to Rho and Rac proteins, whereas the dbl product showed broader binding specificity to Rho family proteins. Thus ect2 is a new member of an expanding family, whose products have transforming properties and interact with Rho-like proteins of the Ras superfamily.

Total cellular RNAs from a variety of fresh and culture-derived human hematopoietic neoplastic cell types at various stages of differentiation and human sarcoma, carcinoma, melanoma, and glioblastoma cell lines were enriched for poly(A)-containing sequences, fractionated by gel electrophoresis, and blot hybridized to a cloned DNA probe containing the transforming sequences (v-amv) of avian myeloblastosis virus (AMV), a virus known to cause myeloid leukemias in chickens. Expression of RNA sequences homologous to AMV was detected in all immature myeloid and lymphoid T cells in addition to the single erythroid cell line examined, but not in mature T cells or in B cells, including lymphoblast cell lines derived from patients with Burkitt lymphoma. In addition, induction of the cell line HL60, a promyelocytic leukemia line, to differentiate with dimethyl sulfoxide or retinoic acid resulted in a reduction of the level of expression of the human cellular gene c-amy homologous to v-amy. There was no detectable c-amv mRNA in any of the solid tumor cell lines examined. Thus, expression of the human c-amy gene could be correlated with the stage ofdifferentiation ofdifferent hematopoietic cell types determined by morphologic and marker studies. Expression ofc-amy could not be correlated with the extent ofmethylation in HL60 and in HL60 induced to differentiate with dimethyl sulfoxide.

Macrophages (Mf) are a heterogeneous population of tissue-resident professional phagocytes and a major component of the leukocyte infiltrate at sites of inflammation, infection, and tumor growth. They can undergo diverse forms of activation in response to environmental factors, polarizing into specialized functional subsets. A common hallmark of the pathologic environment is represented by hypoxia. The impact of hypoxia on human Mf polarization has not been fully established. The objective of this study was to elucidate the effects of a hypoxic environment reflecting that occurring in vivo in diseased tissues on the ability of human Mf to polarize into classically activated (proinflammatory M1) and alternatively activated (anti-inflammatory M2) subsets. We present data showing that hypoxia hinders Mf polarization toward the M1 phenotype by decreasing the expression of T cell costimulatory molecules and chemokine homing receptors and the production of proinflammatory, Th1-priming cytokines typical of classical activation, while promoting their acquisition of phenotypic and secretory features of alternative activation. Furthermore, we identify the triggering receptor expressed on myeloid cells (TREM)-1, a member of the Ig-like immunoregulatory receptor family, as a hypoxia-inducible gene in Mf and demonstrate that its engagement by an agonist Ab reverses the M2-polarizing effect of hypoxia imparting a M1-skewed phenotype to Mf. Finally, we provide evidence that Mf infiltrating the inflamed hypoxic joints of children affected by oligoarticular juvenile idiopatic arthritis express high surface levels of TREM-1 associated with predominant M1 polarization and suggest the potential of this molecule in driving M1 proinflammatory reprogramming in the hypoxic synovial environment.