Establishment of recipient cells for oncogene detection and analysis of transformation-associated cell surface antigen expression

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The detail of anti-tumor surveillance mechanisms by the hosts is still unknown. Surface phenotypes and the ontogeny of NK cells have been widely studied, and there is considerable heterogeneity among NK cell populations. However, little is known about the target structures of tumor cells that are recognized by NK cells. It is also essential to investigate how these structures could be associated with the cell transformation process.We have demonstrated two different candidates of the NK target molecules, namely 86 kd and 62 kd protein composed of a single polypeptide chain. These were defined by monoclonal antibodies (mabs), #109 and #061, respectively, and were highly associated with the activated H-ras oncogene-induced transformation of WKA rat fetus-derived fibroblast WFB. It is also strongly suggested that the expression of 86 kd and not that of the 62 kd molecule was enhanced on nontumorigenic WFD cells which were stimulated by PDGF. The data suggest that these two different molecules are directly involved in the NK-target cell interactions as the target strucutres. These molecules may play an important role in the antitumor surveillance by the hosts.On the other hand, another mab #067 recognizing 67 kd single polypeptide reacted selectively with W31 but not with w14 and other EKras-WFB or PyMt-WFB transformants as well as parental WFB. The expression of this antigen was enhanced on W31 by treatment with heat, superoxide and cAMP or cholera toxin. Furthermore, it was induced by these treatment on W14 and other EKras WFB transformants that did not show constitutively this antigen under the regular culture conditions. These data suggested that this antigen is a novel heat-inducible molecule, and might be a tumor specific antigen of WFB cells.