NONRANDOM KARYOTYPIC CHANGES IN A SPONTANEOUSLY IMMORTALIZED AND TUMORIGENIC SYRIAN-HAMSTER EMBRYO CELL-LINE

Syrian hamster embryo (SHE) cells were used as a model system to study genetic changes during the rare spontaneous progression from normal t o immortalized and then to neoplastically transformed cells. Cultures were established for immortalized and/or neoplastically transformed ce lls by inoculating 2-5 x 10(5) primary cells into 75 cm(2) culture fla sks and subsequent subculture at subconfluence. We examined the karyot ypic changes in the spontaneously transformed and tumourigenic SHE cel ls. Chromosome analyses were performed on mitotic cells with the quina crine banding technique. The primary SHE cell stock (82-6) was karyoty pically normal, but cells that had overcome senescence exhibited chrom osome abnormalities. More than 90% of cells from passages 18-85 carrie d the same deletion in the short arm of chromosome 2 (2p-). This delet ion was also found in about 70% of cells analysed at passage 15. 2p- w as never found in cells at passage 4. We further observed a variety of numeric and structural chromosome changes in addition to 2p-, but the se were seen only in transformed cells at high passage numbers and in cell lines derived from nude mice tumours. Our findings suggest that 2 p- predisposed SHE cells either to immortalization and/or to progressi on to tumourigenicity.