The control of differentiation and proliferation in normal stem cells is complex and is mediated by both positive and negative signals. The expression of defects in the coupling or integrated control of cellular differentiation and proliferation are of etiological significance in neoplastic transformation. Carcinogenesis is a multistep process that involves the development of defects in a variety of regulatory mechanisms in the affected cell. In some cases, the autonomy of cancer cell growth is known to be caused, at least in part, by the aberrant production and response to growth factors, i.e., autocrine stimulation of proliferation. Recent studies suggest that one of the potential mechanisms by which differentiation is abrogated or inhibited in neoplastic cells is the autocrine secretion of differentiation-inhibiting factors. These studies have shown that transforming growth factor type-beta (TGF-beta) and cachectin/tumor necrosis factor (TNF), both of which are known to be anomalously secreted by some tumor cells, are potent inhibitors of distinct steps of differentiation in 3T3 T mesenchymal stem cells as well as other cell types. We hypothesize that the development of some cancers and their inability to differentiate properly involves the aberrant production and response to differentiation-inhibiting factors as well as growth factors. We propose to further define the mechanisms of carcinogenesis by determining how the activation of autoregulatory growth and differentiation control mechanisms contribute to aberrant proliferation and/or differentiation in cancer cells. First, we will determine if TGF-beta or cachectin/TNF exert their effect by inhibiting the expression of known differentiation-specific genes. Second, the aberrant expression of TGF-beta and cachectin/TNF will be characterized in nontransformed cells with single differentiation defects or fully transformed cells with cannot differentiate. Third, the potential existence of other differentiation-inhibiting factors will be determined by testing serum-free conditioned media from these same cells for the ability to inhibit differentiation of the parental 3T3 T cells. In addition, the autocrine production of growth factors will be characterized to provide a better understanding of autocrine differentiation and/or proliferation defects in cancer. Differentiation-specific gene expression, TGF-beta and cachectin/TNF expression, and growth factor expression will be studied by Northern blot analysis, Western blot analysis, or by the measurements of activity present in conditioned medium. Neutralizing antibodies are available for some of these factors and will be used to block their actions on the secreting cells and verify autocrine activity. We anticipate obtaining information which will provide new insight into the mechanisms regulating growth and differentiation control of normal and tranformed cells.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29CA046683-06
Application #
3458710
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1988-04-01
Project End
1994-03-31
Budget Start
1992-04-01
Budget End
1994-03-31
Support Year
6
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Tulane University
Department
Type
Schools of Medicine
DUNS #
City
New Orleans
State
LA
Country
United States
Zip Code
70118
Sparks, R L; Strauss, E E; Manga, A V (1994) Regulation of differentiation and protein kinase C expression in 3T3 T proadipocytes: effects of TGF-beta and transformation. Cell Prolif 27:139-51
Smyth, M J; Sparks, R L; Wharton, W (1993) Proadipocyte cell lines: models of cellular proliferation and differentiation. J Cell Sci 106 ( Pt 1):1-9
Sparks, R L; Allen, B J; Zygmunt, A I et al. (1993) Loss of differentiation control in transformed 3T3 T proadipocytes. Cancer Res 53:1770-6
Sparks, R L; Allen, B J; Strauss, E E (1992) TGF-beta blocks early but not late differentiation-specific gene expression and morphologic differentiation of 3T3 T proadipocytes. J Cell Physiol 150:568-77
Sparks, R L; Strauss, E E; Zygmunt, A I et al. (1991) Antidiabetic AD4743 enhances adipocyte differentiation of 3T3 T mesenchymal stem cells. J Cell Physiol 146:101-9
Choudhury, C; Sparks, R (1991) Cell cycle status of stromal cells in long-term haematopoietic cultures. Cell Prolif 24:461-8
Sparks, R L; Zschunke, M A; Seibel-Ross, E I et al. (1990) Specific expression of proteins and phosphoproteins in 3T3 T mesenchymal stem cells at distinct growth arrest and differentiation states. Cell Tissue Kinet 23:71-87