Many retroviral oncogenes have been classified into one of several categories based on structure, enzymology and cellular localization. These genes originated from host cells and are probably derived from genes normally involved in the control of cell proliferation. The cellular counterparts of three oncogenes have been identified as a growth factor or growth factor receptor; related oncogenes include receptor-like membrane proteins which often express tyrosine kinase activity. These growth factor-related oncogenes are structurally and biochemically distinct from the membrane-associated ras gene family, which bind and hydrolyse GTP. Oncogenes localized primarily in the cytoplasm which probably have serine kinase activity, have also been identified. Although the structure and biochemistry of many oncogenes have been extensively studied, relatively little is known about the functional relationships of oncogene proteins within the cell. An opportunity to study such interaction is provided by the identification of a monoclonal antibody that neutralizes cellular ras proteins when microinjected into cells. It has been shown previously that the injected antibody inhibits the initiation of S-phase in NIH 3T3 cells. In the present study we injected this monoclonal antibody into NIH 3T3 cells transformed by a variety of oncogenes. The results show that transformation by three growth factor receptor-like oncogenes depends on c-ras proteins, while transformation by two cytoplasmic oncogenes appears to be independent of c-ras protein.

FK506, a neutral macrolide with immunosuppressive properties, was shown to selectively and rapidly inhibit the accumulation of IL-2 mRNA, as well as the mRNAs of other early (E) phase T cell activation genes such as IL-3, IL-4, GM-CSF, TNF alpha, IFN-gamma, and c-myc in activated human peripheral blood T cells. The activity of FK506, when compared to Cyclosporin A, another immunosuppressant, was 10 to 100x more potent in its ability to inhibit IL-2 mRNA synthesis. FK506 inhibited IL-2 mRNA accumulation in Con A, Con A plus PMA, Ionomycin plus PMA, anti-CD3, and anti-CD3 plus PMA activated T cells. Transcripts from other T cell gene classes such as the immediate early (IE) phase gene, c-fos, the late phase (L) genes, transferrin receptor, IL-2R alpha-chain, and TNF-beta, and the constitutive class genes glyceraldehyde-3-phosphate dehydrogenase and class I MHC HLA-B7 were not affected by FK506. The macrolide Rapamycin, which is structurally related to FK506, had no inhibitory effect on IE, E, L, or constitutive class mRNAs, but it appeared to increase the levels of the E-phase transcripts that were inhibited in FK506 treated T cells. The effect of FK506 on inducible genes in non-T and non-lymphoid human cells was studied in LPS-induced monocytes and PMA or IL-1 activated synovial fibroblasts. FK506 did not affect expression of the mRNAs for IL-1 alpha or IL-1 beta in human monocytes, or of stromelysin, collagenase, or TIMP in synovial fibroblasts. Nuclear run-off transcription studies indicate that FK506 inhibits transcription of the IL-2 gene. These studies suggest that Cyclosporin A and FK506 may effect a common early event in the T cell activation pathway.

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