Dibutyryl cyclic AMP treatment of 3T3 and SV40 virus-transformed 3T3 cells in aggregates. Effects on mobility and cell contact ultrastructure

Cellular interactions between 3T3 cells and interleukin-3-dependent multipotent haemopoietic cells: a model system for stromal-cell-mediated haemopoiesis

With the aid of a multipotent stem cell line (FDCP-mix cells) co-cultured with either normal or irradiated Swiss 3T3, cellular interactions between stromal cells and haemopoietic stem cells were studied by electron microscopy and time-lapse video microscopy. When cultured in the presence of interleukin 3 (IL-3) but in the absence of stromal cells, the FDCP-mix cells have a characteristic blast morphology. In the absence of IL-3, the cells die unless they are co-cultured with marrow stromal cells or 3T3 cells. In the latter case, they attach, proliferate, and differentiate on both normal and irradiated Swiss 3T3 cell layers without the addition of extrinsic growth factor (IL-3). At the initial attachment sites of these two cell lines, cellular recognition seemed to be mediated by the formation of microvillus cytoplasmic projections and extracellular matrix. These areas may well be the sites of plasma-membrane-bound signalling/adhesional molecules between the interacting cells.

Heterogeneity of murine mammary adenocarcinoma cell subpopulations. In vitro and in vivo resistance to macrophage cytotoxicity and its association with metastatic capacity

Properties of Ts, a long-term tissue culture line of T1699 mammary adenocarcinoma of DBA/2 mice, and two of its sublines - TR2 and TLI-1-were comparatively studied. Ts tumors produced no spontaneous metastases, nor did i.v. injection of up to 1 X 10(6) Ts cells produce a lung tumor nodule. Ts cells were susceptible to macrophage cytotoxicity in vitro and i.v. injected cells were rapidly destroyed in the lungs. TLI-1 tumors spontaneously metastasized to the lungs, and i.v. injection of 1 X 10(3) TLI-1 cells produced approximately 15 lung nodules per animal. TLI-1 cells were least susceptible to both macrophage-mediated cytolysis in vitro and in vivo host antitumor mechanisms. TR2 cells were intermediate with respect to all these properties. Differences in their susceptibility to macrophage cytotoxicity were recognized not only by normal peritoneal macrophages but also by murine macrophage lines. On the other hand, all the subpopulations were uniformly resistant to NK activity in vitro. These findings suggest that resistance of tumor cells in vitro to macrophage cytotoxicity corresponds with their in vivo metastatic potential.

Cell cycle parameters of 3T3 cells cultured as aggregates

BALB/c3T3 cells cultured as aggregates were examined by two independent techniques to determine whether or not cells accumulated at a specific point in the cell cycle, and if so to determine the point at which they accumulate. Replating cells onto dishes followed by pulse labeling with [3H]thymidine and autoradiography indicated that aggregate-cultured cells were in the same phase of the cell cycle as cells cultured as confluent monolayers. Flow microfluorometry confirmed that 75% of the aggregate-maintained cells were arrested in G(0) or G(1), with 25% distributed throughout the rest of the cell cycle. Labeling and mitotic indices of cells in aggregates were also consistent with about 20 to 25% of the cells being in S + G(2) = M phases of the cell cycle at any time.

Hemicyst formation stimulated by cyclic AMP in dog kidney cell line MDCK

Certain epithelial cell lines have morphologic, physiologic, biochemical and pharmacologic characteristics of transporting epithelia from intact organs. In this paper we show that dibutyryl cyclic AMP, 5' AMP, adenosine and cyclic AMP phosphodiesterase inhibitors stimulate hemicyst formation by the dog kidney cell line MDCK. It is suggested that this effect is explained by elevation of intracellular cyclic AMP levels by means of an exogenous non-metabolizable source of cyclic AMP, phosphodiesterase inhibition or adenyl cyclase stimulation. Since hemicyst formation is in part due to transepithelial fluid transport, these findings raise the possibility that this fraction might be modulated by cAMP in an established cell line. We believe that cultured epithelial cells may provide an exploitable model system to investigate at the cellular and subcellular levels, the mechanism by which cyclic AMP modifies water and solute movements across epithelia.

Induction of some features of glial differentiation in primary cultures of human gliomas by treatment with dibutyrl cyclic AMP

Explants from 18 gliomas were cultured for periods up to 7 weeks and studied by light microscopy scanning and transmission electron microscopy. Well-differentiated tumor tissue gave rise to early outgrowths of stellate cells showing process orientation. Poorly-differentiated tissue produced a more haphazard out-growth of pleomorphic cells with few processes and flattened pseudopodia. Mean circadian cell displacement was several times greater in poorly-differentiated cells, but was significantly and reversibly reduced by treatment and dibutyryl cAMP (5 X 10(-4)M) for 48 h. Reduction in motility was directly correlated with a change in cell morphology to a more stellate form. Well-differentiated cells had a smooth surface with ruffling restricted to the ends of processes and highly orientated glial filament and microfilament bundles. The poorly-differentiated cell surface had a microvillous, blebbed appearance and ruffling regularly occurred around the edge of the cytoplasm. Glial filaments and microfilaments were fewer and less well orientated in the poorly-differentiated cells; sites of adhesion to the substratum were fewer than in well-differentiated cells. Treatment of malignant cultures with dibutyryl cAMP resulted in smoothing of the cell surface, retraction of processes into thin pseudopodia and the appearance of microfilament bundles within the cells. These features marked the apparent cyto-differentiation. However, there was a loss of attachment, disappearance of microtubules and loss of glial filaments in the cytoplasm which was not compatible with differentiation. Intracellular recordings of membrane potentials gave a significantly higher mean value for well-differentiated cells. The mean membrane potential and input resistance of poorly-differentiated cells was unchanged by the addition of dibutyryl cAMP. The results of this study suggest that some, but not all, features of mature glia are restored in malignant tumour cells by cAMP treatment.

Mobility of cells from solid tumors

The mobility of cells from two established cell lines of hamster origin, NIL B and its SV40 virus-transformant SV-NIL, was studied in cellular aggregates maintained in agitated liquid medium. Subcutaneous injection of 5 x 10(6) NIL B or SV-NIL cells into Syrian hamsters resulted in a high frequency of tumor formation - 1.00 for SV-NIL cells and 0.93 for NIL B cells. Cells from five different tumors of NIL B origin were grown in tissue culture and their mobility in cellular aggregates was also studied. The mobilities of the tumor-derived cells were similar to each other and to that of the SV-NIL cells, but slightly higher than that of the NIL B cells. In addition, the plating efficiency, saturation density and doubling time of NIL B, SV-NIL and the tumor-derived cells were determined in conventional flat culture. No consistent pattern of saturation density or doubling time was observed in the tumor-derived cells with respect to each other or to the established lines; however, the plating efficiencies of the tumor-derived cells were all considerably lower than those of NIL B and SV-NIL cells. It was concluded that selection for the ability to divide and survive in vivo (i.e. to form tumors) was accompanied by a modest increase in cell mobility in vitro.