A Brief Introduction

A high proportion of cancers arise in epithelial cells which are normally subject to endorine growth regulation. For this reason, for example, the best index of hormone dependence of a particular breast or gynaecological cancer has been the presence in the tumour biopsy of functional oestrogen receptors. In recent years, evidence has accumulated that hormonal regulation of epithelial cell growth may not be direct. It is likely that the direct stimulation of growth involves specific growth factors produced either by surrounding tissue (paracrine control) or by the epithelial cells themselves (autocrine control). Thus an understanding of the regulation of tumour growth requires consideration of both classical endocrine agents and locally produced growth factors. Recent observations have shown that certain oncogene products have extensive homology with known growth factors, growth factor receptors or hormone receptors. It is, therefore, appropriate to examine the relationship of hormones, growth factors and oncogene products.