Steroid hormone receptors and antineoplastic chemotherapy in human breast cancer

Several clinical and experimental investigations suggest that the action of antineoplastic chemotherapy in premenopausal women influences the menopause. Such hormonal reactions are mediated via specific steroid hormone receptors. Therefore, connections between hormone receptors and antineoplastic chemotherapy can be assumed making possible to predict success of chemotherapy on the basis of receptor status. Nevertheless, clinical experiences and animal and cell culture experiments yielded controversial results. This was related to the predictive value of receptor status as well as to the benefits of combined hormone and chemotherapy treatments in concurrent or sequential form. It is undeniable that a displacing of steroidal ligand from its receptors by the usual antineoplastic drugs does not occur. Furthermore, the receptor levels remain unchanged after a treatment with antineoplastic drugs. Thus, the mechanism of action of chemotherapeutic drugs is not related directly to the presence or absence of steroid hormone receptors. Despite this fact the receptor status in chemotherapeutic regimes seems to be helpful to define low or high risk patients. Influences on the ER de-novo-synthesis, actions related to parameters representing reduced tumor growth rates, down-regulation of the receptor gene expression or via receptor mediated hormonal actions to other genes, like the apoptosis-related gene bcl-2, are thought to be possible mechanisms of action of antineoplastic drugs on steroid hormone receptors. Future investigations should monitor the ratios between exon lacking receptor variants and the wild-type receptor during chemotherapy or the control of a ligand uptake during chemotherapy by means of the positron emission tomography.