Analysis of malignancy in human cells: malignant and transformed phenotypes are under separate genetic control.

Abstract

Human cell hybrids derived from malignant HeLa and normal fibroblast parental cells expressed man of the transformed properties of the HeLa parent but their tumor-producing capability was suppressed. Hybrids derived from HeLa/HeLa fusions retained both their transformed and malignant henotypes. Thus, an apparent separation of the control of the transformed versus malignant phenotype is indicated. Furthermore, several transformed properties-including lack of density-dependent inhibition of growth, lectin agglutination, lowered requirement for serum growth factors, and anchorage independence-are expressed coordinately in the nontumorigenic hybrids. This finding suggests that none of these properties by themselves, or in concert, endows a cell with tumorigenic potential.The transition of a normal cell to a neoplastic one is reflected by a complex array of phenotype changes that are amenable to study. Many of these changes-which include lack of contact inhibition of division or topoinhibition (1, 2), reduced requirement for serum growth factors (3, 4), agglutination of cells by lectins (5, 6), anchorage independence (7, 8), altered cyclic nucleotide levels (9, 10), increased protease activity (11), and surface membrane changes such as altered ganglioside profiles (12) and fluctuations in the expression of glycoproteins [e.g., large external transformation sensitive glycoprotein (LETS)] (13, 14)-have been the subjects of intense investigation. Apparent correlations between one or more of these properties and the neoplastic (malignant) state of transformed* cells have been suggested (3-18), but in most cases the dependence of the malignant state on any one of these properties has been questioned (19)(20)(21)(22). In many of these investigations, cells of differing origins, including different animal species, have been used for comparative purposes.We report here our findings with intraspecific human hybrids, in which malignancy (defined here as the capacity of cells to produce a progressively growing tumor in a suitable host) is suppressed, whereas many of the in vitro properties that have been associated with malignant transformation continue to be expressed. Our results indicate that these two functional states-that is, the malignant and transformed phenotypes-are under separate genetic control in this cell system. MATERIALS AND METHODSParental and Hybrid Cells. The parental and hybrid cell lines are presented in Table 1. Details of hybridization procedure and selection of hybrids have been presented elsewhere (23). All cell populations were regularly tested for the presence of mycoplasma contaminants by cultural methods, uridine/ uracil ratio (24), and 4',6-diamidino-2-phenylindole assay (25).The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertuement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.The only cell line that was contaminated with mycoplasmas was ESH6.Growth Curves. Topoinhibition wa...

Progression of colorectal cancer is associated with multiple tumor suppressor gene defects but inhibition of tumorigenicity is accomplished by correction of any single defect via chromosome transfer.

“…The observation that growth of the SW480.7-chromosome 5 hybrids is not inhibited by TGF-1l indicates that responsiveness to TGF-pl is not necessary for cells to revert to a nontumorigenic state. It should also be noted that these experiments again prove that the anchorage-independent phenotype is not universally correlated with tumorigenic behavior of human cells, a finding reported elsewhere (43)(44)(45) (34,52). Certainly, by rendering SW480.7 more responsive to the growth-inhibitory effects of TGF-1l, the introduction of chromosome 18 has resulted in cells which are more similar to colorectal adenomatous cell lines, which is very interesting, considering that the loss of TGF-1I responsiveness, like alterations of chromosome 18, is an event associated with the later stages of colorectal tumor progression.…”

“…All chromosome 18-SW480.7 hybrids had RNA levels similar to that shown in lanes 1 to 3. (39,44,45). The observation that growth of the SW480.7-chromosome 5 hybrids is not inhibited by TGF-1l indicates that responsiveness to TGF-pl is not necessary for cells to revert to a nontumorigenic state.…”

The free cytoplasmic calcium concentration of tumorigenic and non-tumorigenic human somatic cell hybrids

“…In addition, the tumorigenic parental cell line D98-AH2 was studied. The parental non-tumorigenic fibrobast used in the original cell fusion (Stanbridge et al, 1982) was difficult to obtain so a non-tumorigenic foetal fibroblast cell line of similar type (MRC-5) was also included in the study. The tumorigenic status of these cells was reported by Stanbridge et al (1982) and has been confirmed in this laboratory (Gowing et al, 1984 …”

“…In this system, tumorigenicity of the cell lines is defined by the ability of the hybrids to grow progressively in nude mice and not by in vitro characteristics associated with transformed cells; like anchorage independent growth, lectin agglutination and dependence on serum growth factors (Stanbridge et al, 1982). One of the few in vitro characteristics which does correlate with tumorigenicity in these cells is the disruption of the microfilaments (Gowing et al, 1984), a complex process which may be influenced by the activity of calcium-dependent regulatory proteins.…”

“…In view of the involvement of Ca2 + in cell transformation and the lack of information concerning the relative cytosolic free calcium concentration ([Ca2+]i) of normal and transformed cells, we have measured the level of [Ca2 + ], in normal cells and somatic cell hybrids of tumorigenic and non-tumorigenic phenotypes (Stanbridge & Wilkinson, 1978). In this system, tumorigenicity of the cell lines is defined by the ability of the hybrids to grow progressively in nude mice and not by in vitro characteristics associated with transformed cells; like anchorage independent growth, lectin agglutination and dependence on serum growth factors (Stanbridge et al, 1982).…”