Evaluation of models for steroid-protein interactions in malignancy.

Over the past two decades many model systems have been proposed for the steroid-protein interaction in target cells. The most widely used two-step model in malignant tissue is now seriously questioned. With the advent of advancing methodology and monoclonal antibodies the new models support nuclear localisation of the receptor, the clinical significance of this in cancer treatment is far from clear. These latter models are not without drawbacks themselves. Immunological, and immunocytochemical techniques in particular, cannot provide full binding parameters on receptor status, its affinity for a steroid, the number and nature of binding sites. Thus the ligand binding assay still remains useful and in combination with immunological techniques should provide information that neither technique can provide alone. This approach has great promise in the evaluation of receptor status in cancer. The interactions of steroids with intracellular non-steroid proteins and receptor-independent phenomena are indicative of the complexities that the designers of models will have to contend with.