Assignment of two human epidermal squamous cell carcinoma cell lines to more than one complementation group for the immortal phenotype

Abstract

Two human cell lines derived from squamous cell carcinomas (SCCs) of the epidermis, SCC-12 clone F and SCC-13 clone Y, were made to be independent of the Swiss 3T3 feeder layer to perform somatic-cell genetic experiments. We fused these SCC lines with normal human fibroblasts, and all resulting hybrids senesced after completing 12-17 population doublings, suggesting that in part, immortalization of the keratinocyte during SCC development results from the loss of gene function. We also tested whether these two SCC lines mapped to known complementation groups for immortality by fusing them with representatives of groups A (GM847), B (HeLa), and C (143B), but most of these hybrids were indistinguishable from those derived from homotypic crosses set up as immortal hybrid controls. As reported by others, fusions of cell lines from different complementation groups-143B (group C) x HeLa (group B) or GM847 (group A) x Hela (group B)--resulted in predominantly senescent hybrids. Our results confirmed and extended previous observations by others that the phenomenon of senescence is dominant to that of immortality, but they did not allow us to assign either of the SCC lines we studied to a complementation group for immortality.

Experimental elongation of telomeres extends the lifespan of immortal x normal cell hybrids.

“…A classic observation in aging research is that hybrids between normal diploid fibroblasts and immortal cell lines show a limited proliferative capacity (Bunn and Tarrant, 1980;Muggleton-Harris and DeSimone, 1980;Smith, 1981, 1983;Berry et al, 1994;Ryan et al, 1994). In this report, we provide an explanation for this phenomenon by demonstrating that telomerase is repressed in these hybrids.…”

“…Telomerase is repressed in immortalx normal cell hybrids Cell hybrids between normal and immortal cells are mortal (Bunn and Tarrant, 1980;Muggleton-Harris and DeSimone, 1980;Smith, 1981, 1983;Berry et al, 1994;Ryan et al, 1994). If telomerase were repressed in such hybrids, telomeres would no longer be stable and should shorten with each cell division.…”

Critical pathways in cellular senescence and immortalization revealed by gene expression profiling

“…There are, however, many more chromosomes that can induce senescence than there are senescence complementation groups. Furthermore, there are some immortal cell lines that have been assigned to multiple complementation groups (Duncan et al ., 1993; Berry et al ., 1994). This indicates that in any one immortal cell line there are probably multiple senescence genes/pathways that are abrogated (Sasaki et al ., 1994; Vojta et al ., 1996).…”

Enhanced efficacy of Escherichia coli nitroreductase/CB1954 prodrug activation gene therapy using an E1B-55K-deleted oncolytic adenovirus vector

“…AC-3 keratinocytes (a subclone of SCC12F that is immortalized but otherwise retains the growth characteristics of normal cells) 44 were cultured in DME/HEPES containing 5% fetal calf serum, 2 mM glutamine and 0.4 mg/ml hydrocortisone. All cells were kept at 371C in a humiditycontrolled incubator with 5% CO 2 .…”