Effect of hematoporphyrin derivative 2 on estrogen receptors in experimental mammary tumors

This study reports the effect of hematoporphyrin derivative 2 (HPD2) on estrogen receptors (ER) in the animal model used to develop the clinical ER assay. Fifty 200-g female Sprague-Dawley rats were given 20 mg of dimethylbenzanthracene by gastric intubation. Spontaneous mammary tumors occurred in 35 animals. Animals were anesthetized and 50% of each tumor was removed when the tumors were 2 cm in diameter. Animals were then randomized to receive 5 mg/kg (group A), 10 mg/kg (group B), or 0 mg/kg (group C) HPD2 intravenously 48 hours after biopsy. The remaining tumor was excised 48 hours post HPD2 injection. All samples were weighed, placed on ice, and frozen to −70°C. ER assay was performed by batch run. Results (fmol/mg cytosol) were as follows: All animals (n=35) pre HPD2 34.2 ± 5.4, post HPD2 34.2 ± 5.8; group A: (n=11) pre HPD2 33.9 ± 7.9, post HPD2 37.1 ± 7.8; group B: (n=13) pre HPD2 29.2 ± 3.8, post HPD2 25.5 ± 3.6; group C: (n=11) pre HPD2 40.3 ± 5.2, post HPD2 41.5 ± 7.9. HPD2 does not affect ER in this animal model. Confirmatory studies with human tumor material must be completed.