Effect of pH on proteinase secretion by transformed fibroblast populations.

Effect of pH on secretion of proteolytic enzymes in cell cultures of three clonal lines of transformed fibroblasts (K2, T15 and K4) was studied by using 14C-labelled denatured proteins as substrate. One line of malignant macrophages derived from mouse reticulum cell sarcoma (J774.1) was used for comparison. The relative motility index of all cell lines was derived by computer analysis of quantitative estimations of cell dispersion in single-cell-derived colonies. Cultivation at pH 6.5 decreased the growth rate in most experiments as compared with that at pH 7.4, and stimulated cell motility to a different extent. The population of mouse malignant macrophages produced several-fold higher extracellular proteolytic activity than the fibroblast lines. Secretion of proteinases by the malignant macrophages was significantly stimulated by the lower pH. Enzyme secretion by two of the three fibroblast derivatives was also stimulated by acidic pH but to a lesser extent than the secretion of the malignant macrophages. The assessment of motility done by measurement of dispersion of cells in colony proved a positive correlation between motility and proteinase secretion in J774.1 cells and one transformed fibroblast clone (T15) but not in the two other clonal lines.

Patterns of in vitro behaviour characterizing cells of spontaneously metastasizing K2M rat sarcoma.

Cells of K2M rat sarcoma and their descendants (RP, RPS) form tumours in syngeneic inbred rat strain LEW/CUB. Thirty to fifty per cent of tumour-bearing rats develop metastases, preferentially in the lung. In vitro, a quasi-stellate dynamic morphotype was characteristic of K2M cells and their descendants (RP, RPS): a highly changeable round or spindle-shaped or multipolar rather thick cell body with two or more protrusions of various length, often branching, and broadened at the tips, where vivid membrane activity was observed. Changeability of appearance and directionality of locomotion were stimulated in medium of pH 6.5. The enhanced expression of this morphotype correlated with the increased metastatic potential. In vitro, in poor, slightly acid medium metastasizing cells preserved the quasi-stellate dynamic morphotype and survived longer than non-metastasizing cells. It is likely that the observed combination of traits, viz. the quasi-stellate dynamic morphotype and, under unfavourable conditions, prolonged survival, increased migratory activity and decreased mitotic rate could be of significance in the metastatic cascade, mainly for the escape from the primary site.

Behaviour of normal and neoplastic rat cells on grooved substrates.

The distribution and shape of rat cells cultivated on plastic surfaces containing cylindrical areas of various radii and grooves of various depths were studied. Normal embryo cells and two lines of neoplastic cells (LW13K2 and RsK4) were used. The nuclear shape, orientation of the nuclei and migration of cells from the bottom of the grooves were assessed by quantitative methods. All characteristics of the behaviour of both neoplastic cell lines on the grooved substrates were found to be different from those of normal cells: a) the nuclei of neoplastic cells, in contrast to those of the normal ones, did not undergo additional elongation on the cylindrical areas of the substrate; b) the orientation of neoplastic cells with regard to the axis of the cylindrical substrate was decreased or absent; c) the migration of neoplastic cells from certain types of the grooves was decreased. It is suggested that the different reaction to the geometry of the substrate may be a characteristic feature of transformed cells. Possible mechanisms of these alterations are discussed.

A contribution to the relationship between tumour cell social behaviour in vitro and malignancy in vivo.

Membrane activity of high malignant (grade IV in the immunogenetic test of malignancy) cells was found to continue along the contacting edge after random collision with normal cells in vitro, as demonstrated by the high resolution time-lapse cinemicrography. This preservation of surface activity was the main difference in social behaviour of high and low malignant rat tumour cells upon random collision with normal cells in four lines of tumour cells investigated.