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

Abstract

Summary-3H-thymidine labelling and autoradiography were used to compare density dependent inhibition of growth in the cultures of two transformed lines of hamster fibroblasts and in primary cultures of their parent normal cells. Similar manifestations of density dependent inhibition were found in the isolated cultures of normal and neoplastic cells: at saturation densities these cultures had low labelling indices; these indices considerably increased when the cells migrated into the wound from the dense sheet, prelabelled cells seeded on the dense sheets of unlabelled homologous cells did not proliferate. However, proliferation of neoplastic cells was not inhibited when they were seeded on the dense sheet of normal fibroblasts. Thus, neoplastic hamster fibroblasts of both lines retained sensitivity to the inhibiting effect of homologous neoplastic cells but completely lost sensitivity to the inhibiting effect of normal fibroblasts. The possible significance of this selective loss of the sensitivity to normal cells is discussed briefly.INSENSITIVITY to the local inhibiting effect of homologous cells (loss ofthe homologous density dependent inhibition of growth) is usually regarded as one of the characteristic traits of transformed fibroblasts. At the same time, certain lines of transformed cells retain sensitivity to heterologous inhibition: their growth is inhibited by normal fibroblasts (Stoker, 1964;Ponten and MacIntyre, 1968;Weiss and Njeuma, 1971 The cells were grown in small (10 ml)

Properties of cell lines derived from altered‐cell foci in baby mouse skin cultures

“…Figure 4 shows that in a checkerboard consisting of y-irradiated monolayers of BMS, Cl4, CZl, and C23 cells (rows) overlaid with no cells or lo4 BMS,C14,C21,or C23 cells (columns), all cell types could form colonies on all others, except for BMS, C14, and C23 cells on C23 monolayers. The reasons for such selective growth abilities are unknown, hut several similar instances have been reported from which no clear pattern has emerged (Stoker, 1964;Ponten and MacIntyre, 1968;Eagle et al, 1968;Weiss, 1970;Pletyushkina et al, 1975;Sakiyama et al, 1978).…”

Serum dependence of expression of the transformed phenotype: Experiments with subline of mouse L fibroblasts adapted to growth in serum‐free medium

“…It is known that sensitivity to topoinhibition by homologous cells is not always completely lost after transformation (Westermark, 1973;Risser and Pollack, 1974;Pletyushkina et al, 1975) although the saturation density at which topoinhibition is observed may increase after transformation. I n particular, L-cells, the parent strain of LSF subline, were found to be sensitive to topoinhibition (Domnina et al, 1972).…”