1. Amounts of prostaglandin E and prostaglandin F have been measured by radioimmunoassay in extracts of renal cortical carcinoma and benign and malignant breast tumours after solvent extraction and column chromatography.
2. Substantial amounts of prostaglandin E were found in extracts of benign and malignant breast tumours and in renal tumours. Much lower amounts of prostaglandin F were present in all tumour types.
3. Co-cultivation of tumour explants with mouse calvaria led to significant bone resorption in 10 of 13 renal carcinomas, three of eight malignant breast tumours, and two of nine benign breast tumours. Tumours associated with bone resorption had higher concentrations of prostaglandin E in culture media at the end of incubation than did non-resorbers.
4. Indomethacin (14 μmol/l) greatly reduced bone resorption in the presence of the tumour, but this was not always complete, particularly with breast tumours. Indomethacin had no effect on prostaglandin-induced bone resorption. Theophylline (2·2 mmol/l) significantly increased prostaglandin E production and resorption by an effect on the tumour.
5. It is concluded that prostaglandins may be important in mediating the effects of renal cortical carcinoma and possibly breast cancer on bone destruction. A non-prostaglandin mechanism may also contribute to bone destruction by breast carcinoma.