Defective Formation of the Lamellar Cytoplasm by Neoplastic Fibroblasts

Abstract

ABSTRACTto as normal fibroblasts, and (b) fibroblasts of the L line (2). The subline of L cells kept in this Institute is weakly tumorigenic (all previously irradiated C3H mice injected with 106 cells developed tumors). Possibly the characteristics of this subline (e.g., sensitivity to topoinhibition) are somewhat different from those of L cells maintained in other laboratories (3); however, comparison is difficult as the detailed characteristics of other sublines are not published. Absence of pleuropneumonia-like organisms was checked by autoradiography with [3H]thymidine. Methods of cell culture, of wounding the confluent cultures, of autoradiography, of time-lapse microcinematography, and of transmission electron microscopy were described (4, 5). For scanning electron microscopy, cells cultured on coverslip were fixed in 5% glutaraldehyde, dehydrated in alcohols and in amylacetate, shadowed with silver, and examined with a Stereoscan microscope (Cambridge Instruments Ltd.).The aim of the experiments described in this paper was to find out why neoplastic fibroblasts of the L line grown together with their parent cells (mouse embryo fibroblasts) are sorted out from these cells and form the colonies above the normal monolayer. This ability to grow at the top of a sheet of normal cells is a characteristic property of many types of tumor cells, although there are few types of transformed cells that do not grow under these conditions (1).Data presented in the first part of this paper suggest that the behavior of L cells cannot be adequately described as due to loss of contact inhibition of movements or of topoinhibition of growth. Decreased attachment of L cells to the glass appears to be the main factor responsible for their abnormal interactions with embryo fibroblasts.The second part of the paper deals with the possible structural basis of this deficient attachment. The attachment of normal cells to the substratum is accompanied by formation at the cell periphery of a cytoplasmatic zone with certain special structural characteristics (lamellar cytoplasm); the lamellar cytoplasm of L cells is structurally abnormal and is smaller. Thus, decreased attachment of L cells to the substratum may result from a deficiency of reactions involved in the formation of lamellar cytoplasm. (a) Their rate of proliferation is density-dependent. The proportion of nuclei in the cultures pulse-labeled with [3H]dT that were fixed at 40 hr after change of medium gradually decreased as cell density increased. At 20-24 hr after wounding, the proportion of labeled nuclei in the wounded area of a confluent culture was much higher than in the surrounding cell sheet. The index of topoinhibition (6) for cultures in 0.2% serum-medium was 0.8-0.9. Saturation density was 6 X 105-10 X 105 cells/cm2, as compared with 4 X 105-5 X 105 cells/ cm2 for normal fibroblasts. Labeled L cells seeded upon the monolayer of the same cells were incorporated into this monolayer and did not increase in number (Fig. 1).(b) Contact inhibition of movement is obvious...

Effects of antitubulins on the redistribution of crosslinked receptors on the surface of fibroblasts and epithelial cells

“…The cleared peripheral zone reached a maximal width of about 10-25 ,um after 30-60 min of incubation. The internal margin of the cleared band was usually located near the internal margin of lamellar cytoplasm, as seen with the phase-contrast microscope (10) Transformed mouse fibroblasts of the L strain in control cultures usually had an elongated shape with narrow active parts of the edge and small lamellar zones. After incubation with ligands, only these zones were cleared of receptors (Fig.…”

“…The morphology and cultivation methods of these cells were described (4,(8)(9)(10) (4). The glycerol-sealed cultures were examined with the fluorescence microscope.…”

“…The morphology and cultivation methods of these cells were described (4,(8)(9)(10). The cells were grown on cover slips for 1-2 days before the treatment with ligands.…”

Adhesion defect of ascites cells corrected with membrane‐bound attachment molecules

“…Interference reflection microscopy reveals black contacts along the margin of the spread cells, typical of normal epithelial cells [4]. Thus it seems that binding of substrate-adhesive molecules allows the ascites cells to enter the normal physiological spreading.…”

Neoplastic fibroblasts sensitive to the growth inhibition by homologous cells but insensitive to inhibition by parent normal cells

“…8) Fig. 4 (Domnina et al, 1972). In the experiments of Weiss et al (1973) (Njeuma, 1971;Westermark, 1973); (2) certain neoplastic cells may retain sensitivity to the inhibiting effect of parent normal cells but lose sensitivity to homologous cells (Stoker, 1964;Ponten and Macintyre, 1968;Weiss and Njeuma, 1971 heterologous, and especially homologous, density dependent inhibition.…”