Human monocytes selectively bind to cells expressing the tumorigenic phenotype

Summary The characteristics of the binding of human monocytes to tumor cells were studied by a newly developed microassay. First, we determined the kinetics and optimal conditions of the binding. Monocytes recognized and bound to tumor cells very rapidly within 10–20 min of cellular interaction. Binding was also more efficient at 37°C suggesting that active metabolism of monocytes is required. Second, we determined that selective binding of monocytes to cells with tumorigenic phenotypes occurs. For this purpose, lymphocytic leukemia cell lines versus normal lymphocytes, and tumorigenic versus nontumorigenic hybrids from the same parental lines were compared as the targets of the binding assay. In both cases, neoplastic cells were selectively bound by monocytes. Although tumor cells were bound rapidly and selectively by monocytes, initial recognition and binding did not necessarily lead to subsequent tumor cell lysis. This is based on the observation that some tumorigenic parental and hybrid lines were avidly bound by monocytes yet not subsequently killed in a cytotoxicity assay.This work was supported in part by a grant from the National Institutes of Health CA42992 and a grant from the Kleberg foundation Abbreviations used: [¹²⁵I]IdUrd [¹²⁵I]iododeoxyuridine; rIFN-, recombinant human interferon ; IL-1, interleukin 1; rTNF, recombinant human tumor necrosis factor     

The fibronectin receptor is organized by extracellular matrix fibronectin: implications for oncogenic transformation and for cell recognition of fibronectin matrices

Cells interact with extracellular fibronectin (FN) via adhesive fibronectin receptors (FNRs) that are members of the very late antigens (VLAs) subgroup of the integrin family. In stationary fibroblasts, the FNR is highly organized and distributed identically to extracellular FN fibrils. However, in highly migratory neural crest cells and embryonic somatic fibroblasts, this organization is lost and the FNR appears diffuse. Similarly, oncogenic transformation typically leads to disorganization of the FN receptor and loss of matrix FN. Two models can account for these observations. First, the FN matrix may organize the FN receptor at extracellular matrix contacts on the cell surface. Motile cells not depositing FN matrices thus lack organized receptors. Alternatively, as the FNR is required for optimal FN matrix assembly, (McDonald, J. A., B. J. Quade, T. J. Broekelmann, R. LaChance, K. Forseman, K. Hasegawa, and S. Akiyama. 1987. J. Biol. Chem. 272:2957-2967; Roman, J. R. M. LaChance, T. J. Broekelmann, C. J. R. Kennedy, E. A. Wayner, W. G. Carter, J. A. McDonald. 1989. J. Cell Biol. 108:2529-2543) and has putative cytoskeletal links, it could be organized from within the cell helping to position newly forming FN fibrils. To study this question, we developed peptide antibodies specifically recognizing the alpha 5 subunit of the FNR. Using these antibodies, we examined the organization of FN and of the FNR in normal, matrix assembly inhibited, and SV40-transformed human fibroblasts. On FN-coated substrates, the FNR is found in focal contacts rather than diffusely on the basal cell surface, suggesting FNR interaction with intracellular components. However, when FN fibrils are deposited, the FNR is co-distributed with these fibrils. Preventing FN matrix assembly prevents organization of the FNR. Moreover, when fibroblasts with well established FN matrices and co-distributed FNR are incubated briefly with monoclonal antibodies that block FNR binding to FN, the FNR is no longer co-distributed with the FN matrix. Thus, the FN receptor is organized in fibrils on the cell surface in response to extracellular FN. Because exogenous FN restores a FN matrix and receptor organization to SV40-transformed cells, the diffuse FN receptor phenotype appears to be related to loss of the FN matrix rather than to impaired FNR function. These results explain diffusely distributed FNRs in migratory neural crest and embryonic fibroblasts lacking well organized FN matrices and emphasize the existence of separate but related systems controlling FN deposition and recognition by receptor-armed cells.     

Differentiation of staphylococcal species and strains by ribosomal RNA gene restriction patterns

Staphylococcal DNA was digested with endonucleases and probed with labelled ribosomal RNA (rRNA) from Escherichia coli. Reproducible restriction patterns containing between seven and 22 bands were obtained for seven different species of staphylococci. These profiles were species-specific with different strains of a particular species sharing an identical or similar restriction pattern. The results reported here indicate that rRNA gene restriction pattern analyses have an application in the taxonomy of staphylococci.     

Relationship between Freezing Tolerance of Root-Tip Cells and Cold Stability of Microtubules in Rye (Secale cereale L. cv Puma)

The response of cortical microtubules to low temperature and freezing was assessed for root tips of cold-acclimated and non-acclimated winter rye (Secale cereale L. cv Puma) seedlings using indirect immunofluorescence microscopy with antitubulin antibodies. Roots cooled to 0 or −3°C were fixed for immunofluorescence microscopy at these temperatures or after an additional hour at 4°C. Typical arrays of cortical microtubules were present in root-tip cells of seedlings exposed to the cold-acclimation treatment of 4°C for 2 days. Microtubules in these cold-acclimated cells were more easily depolymerized by a 0°C treatment than microtubules in root-tip cells of nonacclimated, 22°C-grown seedlings. Microtubules were still present in some cells of both nonacclimated and cold-acclimated roots at 0 and −3°C; however, the number of microtubules in these cells was lower than in controls. Microtubules remaining during the −3°C freeze were shorter than microtubules in unfrozen control cells. Repolymerization of microtubules after both the 0 and −3°C treatments occurred within 1 h. Root tips of nonacclimated seedlings had an LT-50 of −9°C. Cold acclimation lowered this value to −14°C. Treatment of 22°C-grown seedlings for 24 h with the microtubule-stabilizing drug taxol caused a decrease in the freezing tolerance of root tips, indicated by a LT-50 of −3°C. Treatment with D-secotaxol, an analog of taxol that was less effective in stabilizing microtubules, did not alter the freezing tolerance. We interpret these data to indicate that a degree of depolymerization of microtubules is necessary for realization of maximum freezing tolerance in root-tip cells of rye.