Retrogenic expression of receptors for growth factors in neoplasia.

Hormone-dependent tumors have a decreased requirement for growth stimulating hormones compared with the normal tissues from which the tumors originate. This property of hormone-dependent tumors is due to an inappropriate expression of hormone receptors in and by cancer cells making these cells highly sensitive to growth stimulating effects of hormones, and a variety of growth factors, compared with their normal counterparts. In the early stages of tumor development, the ectopic receptors for hormones are inappropriately expressed in cancer cells. The expression of multiple ectopic receptors for hormones and growth factors confers an apparent autonomy on cancer cells. In some instances, cancer cells have been found to exhibit hormonal sensitivity and hormone receptor content as do their normal counterparts at earlier developmental stages.