Cell Lines from grc Congenie Strains of Rats Having Different Susceptibilities to Chemical Carcinogens1

The growth and reproduction complex (grc~) strains of rats have a 70-kilobase deletion in the major histocompatibility complex (MHQlinked grc-GIC region that is associated with embryonic death, develop mental defects, and an increased susceptibility to chemical carcinogens. To study further the effects associated with the deletion, fibroblastic cell lines from grc~, grc*, and grc*'~ rat embryos were developed: BIL-derived cell lines are congenie for the MHC and grc, whereas R16-derived cell lines are congenie for the grc alone. In early passages, all cell lines expressed the MHC class I antigen RT1.A, had a diploid chromosome number, and did not display anchorage-independent growth or in vivo tumorigenicity. The grc~ cells [median population doubling time (PDT), 47 h] grew more slowly than the grc* (PDT, 30.5 h) and grc*1(PDT, 33 h) cells. All cells underwent crisis, but the crisis stage began earlier and lasted longer in the grc~ cells. The established grc~ cell lines (PDT, 32.5 h) grew faster than the grc* (PDT, 48.5 h) and grc*'~ (PDT, 54 h) cell lines. Two of the three BIL-derived grc~ lines that survived crisis became anchorage independent in tissue culture and tumorigenic in histocompatible Fl rats (highly ma lignant fibrosarcomas) at passages 33 and 48, respectively; by contrast, none of the R16-derived grc~ cell lines transformed. None of 8 grc* or 8 grc*'~ cell lines that survived crisis displayed anchorage-independent growth or tumorigenicity under the same conditions up to passage 50. All of the established cell lines, including the two tumorigenic ones, expressed MHC class I antigens. Southern and Northern blot analyses of BILderived cell lines before and after crisis showed that they all constitutively expressed ][-;«•> and Kb and that no cell line showed rearrangement, amplification, or overexpression of c-myc, H-ras, K-ras, Rb, and p53 either before or after crisis. These observations indicate that: (a) the homozygous grc' deletion is necessary but not sufficient for in vitro transformation; (b) another genetic factor(s) required for transformation is linked to, or pos sibly in, the MHC; and (c) passage through crisis, spontaneous transfor mation, or carcinogen treatment does not alter the cellular expression of MHC class I antigens or of several oncogenes and tumor suppressor genes.