Further Studies on the Radiation-Induced Expression of a Tumor-Specific Antigen in Human Cell Hybrids

Abstract

The neoplastic transformation of human cell hybrids (HeLa x skin fibroblasts) is accompanied by the expression of a cell surface protein for which monoclonal antibodies have been raised. The gamma-radiation-induced neoplastic transformation of these cells has been studied where the expression of this cell surface protein, as detected by immunoperoxidase staining, has been used as an end point. The yield of foci of positively staining cells has been shown to increase with increasing time postirradiation at which the assay is done and decrease with increasing density of viable cells plated postirradiation. The time of plating postirradiation is also an important parameter with transformation frequencies increasing over the first 6 h of postirradiation holding at confluence, followed by a gradual decrease.

Identification of the HeLa tumor-associated antigen, p75/150, as intestinal alkaline phosphatase and evidence for its transcriptional regulation.

“…In all cases, the various isolates expressing p75/150 were found to be tumorigenic in athymic nude mice (ref. 11; E.J.S. and J. L. Redpath, unpublished data).…”

“…p75/150 was abundantly expressed on the cell surfaces of the tumorigenic HeLa parents and the tumorigenic segregants; however, it was not detected on either the fibroblast parents or the nontumorigenic cell hybrids. In radiobiological studies involving the H/F cell hybrids, nontumorigenic hybrid cells were treated with ionizing y-radiation and screened for p75/150 expression (10,11). In all cases, the various isolates expressing p75/150 were found to be tumorigenic in athymic nude mice (ref.…”

Isolation of human cell hybrids (HeLa × skin fibroblast) expressing a radiation-induced tumour-associated antigen

“…We have recently developed a new quantitative assay for application to studies of radiation-induced neoplastic transformation in vitro (Redpath et al, 1987;Sun et al, 1988). This assay utilises a human cell hybrid system (HeLaxskin fibroblasts) (Stanbridge et al, 1982) and the end-point measured is the expression of a Mr=75,000 cell surface dimeric protein (p75/150) which is uniformly associated with the expression of tumorigenicity (Der & Stanbridge,198 1).…”

“…The cell line CGL3 is a p75 expressing tumorigenic segregant that arose spontaneously in a mass culture of the original fusion (ESH5) after more than 200 population doublings . Stock maintenance procedures have been described (Sun et al, 1988).…”

“…The cell line CGL1 was obtained from the third serial subclone of the above fusion in methylcellulose (Stanbridge & Wilkinson, 1980 non-tumorigenic when inoculated into nude mice Der & Stanbridge, 1981) and is very stable against spontaneous reversion to the tumorigenic phenotype (5 x 10-6 to 1X 10-5) which expresses the p75 cell surface protein (Redpath et al, 1987;Sun et al, 1988). The cell line CGL3 is a p75 expressing tumorigenic segregant that arose spontaneously in a mass culture of the original fusion (ESH5) after more than 200 population doublings .…”