EXPRESSION OF NEOPLASIA-RELATED PROTEINS OF CHEMICALLY TRANSFORMED HUT FIBROBLASTS IN HUMAN OSTEO-SARCOMA HOS FIBROBLASTS AND MODULATION OF ACTIN EXPRESSION UPON ELEVATION OF TUMORIGENIC POTENTIAL

  • 1 January 1985
    • journal article
    • research article
    • Vol. 45  (7) , 3256-3261
Abstract
Two sets of abundant cytoplasmic transformation-specific polypeptides, p788/p789and p219/p220, were identified by comparing in vitro-transformed human fibroblasts with diploid human fibroblasts. These polypeptides are also expressed by the human fibrosarcoma and osteosarcoma cell lines HT1080 and HOS, respectively. HOS cells, however, synthesize only 1 of the 2 electrophoretic forms of each marker set, p789 and p219, at greatly reduced rates compared to the rates of synthesis found for HT1080 cells and the in vitro-transformed cell lines. Induction of expression of these neoplastic marker polypeptides is independent of the activation of a transforming gene that will induce focus formation in confluent mouse 3T3 cell monolayers. Activation of the met oncogene in MNNG-HOS cells and simultaneous elevation of tumorigenic potential did not lead to a significant change in the rate of the 600 most abundant polypeptide species with the exception of 1 of the 2 cytoplasmic actin polypeptides. While the normal ratio of .beta.- to .gamma.-actin which is approximately 2:1 was expressed in untransformed HOS cells, MNNG-HOS cells synthesized 50% less .beta.-actin resulting in a 1:1 ratio of .beta.-actin to .gamma.-actin. Apparently 1 of 2 functional .beta.-actin genes expressed in HOS cells has been inactivated in MNNG-HOS cells by either a regulatory or structural gene mutation.