Enhancement of transforming growth factor-alpha synthesis in multicellular tumour spheroids of A431 squamous carcinoma cells

Br J Cancer. 1992 Feb;65(2):157-62. doi: 10.1038/bjc.1992.34.


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-alpha (TGF-alpha) 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 10(6)/cell. Constitutive expression of TGF-alpha 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-alpha protein synthesis 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-alpha/EGF-R autocrine loop operating within cells that produce high local concentrations of TGF-alpha in the three-dimensional architecture of a spheroid.

MeSH terms

  • Blotting, Northern
  • Carcinoma, Squamous Cell / metabolism*
  • Carcinoma, Squamous Cell / pathology
  • Cell Aggregation
  • Cell Communication*
  • Cell Count
  • Epidermal Growth Factor / pharmacology
  • Humans
  • RNA, Messenger / analysis*
  • Radioimmunoassay
  • Time Factors
  • Transforming Growth Factor alpha / biosynthesis*
  • Tumor Cells, Cultured


  • RNA, Messenger
  • Transforming Growth Factor alpha
  • Epidermal Growth Factor