The Clinton-Gore agenda: environmental pledges and economic puzzles.
نویسنده
چکیده
Multicellular tumour spheroids are cellular aggregates that can be prepared from many types of tumour cells. These three-dimensional structures provide a model for analysing the effects of cell-cell contact and intercellular microenvironments on phenomena such as autocrine regulation of growth factor synthesis. Autoregulation of the synthesis of transforming growth factor-a (TGF-a) was investigated at the message and protein levels in spheroid and monolayer cultures prepared from the A431 human squamous carcinoma cell line. The epidermal growth factor receptor (EGF-R) of these monolayer A431 cells had an average surface density of 2.2 x 106/cell. Constitutive expression of TGF-a mRNA was an average of 3-fold greater in A431 spheroids than in monolayers, even for densely packed, confluent monolayers. This effect did not depend on hypoxic stress within the spheroids. TGF-a protein sythesis was enhanced in comparison with that in monolayer culture, reaching a value of up to 2-fold greater on a per cell basis. These results are discussed in the context of a TGF-a/EGF-R autocrine loop operating within cells that produce high local concentrations of TGF-a in the three-dimensional architecture of a spheroid.
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عنوان ژورنال:
- Environmental Health Perspectives
دوره 101 شماره
صفحات -
تاریخ انتشار 1993