DESCRIPTION: The objective of this revised proposal is to explore the mechanisms by which neoplastic transformation abrogates the control of cellular differentiation. The investigator proposes to further characterize normal regulatory events controlling 3T3 T proadipocyte cell differentiation and to determine if defects in these processes are involved in the loss of differentiation control associated with carcinogenesis. Both positive and negative regulatory mechanisms controlling differentiation will be examined. Specifically, the idea that regulation occurs via a pathway/cascade of events which involve the C/EBP transcription factors, TGF-beta and c-myc will be examined. Signal transduction pathways leading to induction of C/EBP-alpha and other differentiation events as well as the TGF-beta inhibitory pathways blocking these events will be characterized. The first specific aim will be to determine the temporal relationships of expression of C/EBP-alpha, beta and gamma and c-myc and to characterize their basic regulation during differentiation of 3T3 T proadipocytes and in transformed 3T3 T cells. Both mRNA expression and protein will be examined. The second aim will be to determine the effects of the differentiation agonist TGF-beta on expression of C/EBP-alpha, beta and gamma and on c-myc. Studies will be performed to identify which events are RNA or protein synthesis dependent and if the regulation occurs via kinase or phosphatase dependent pathways. The third aim is to determine the potential role of the transcription factors C/EBP-alpha, beta, and gamma in regulating proliferation and differentiation of normal and transformed 3T3 T cells using overexpression and antisense strategies.