Multisequential transformation of a pig cell line (PFT): correlations between tumorigenicity and chromosome and ultrastructural markers.

Cells from representative subcultures of a continuous cell line of pig uterine tube (PFT) and carrying none, one, or two chromosome markers were inoculated in athymic nude mice (RCN) to determine the occurrence of the malignant transformation in this line. No tumors developed in mice after implantation of cells from either the 16th and 65th subcultures (no chromosome markers) or the 106th subculture (one chromosome marker, anchorage-dependent). Three adenomas (11.1%) were found in 27 mice that had been inoculated with anchorage-independent cells having one chromosome marker. Of 27 mice inoculated with cells showing two chromosome markers and gap junctions, 23 mice (85.1%) developed undifferentiated carcinomas. Ultrastructural traits and karyotypes of tumors were generally similar to those of the PFT cell inocula. However, annulate lamellae were found in 8 of 13 tumors examined by electron microscopy but were not seen in PFT cell inocula. The occurrence of a multisequential transformation was indicated by serial examination of the first 400 subcultures of the line and by comparison of the markers observed in three successive populations of cells differing in their genetic constitution.