Morphologic studies of bladder tumors treated with hematoporphyrin derivative photochemotherapy

The morphologic changes that occurred in transplanted rat bladder tumors after treatment with hematoporphyrin derivative (HPD) and/or phototherapy were investigated. Transitional cell bladder tumors were initiated subcutaneously in male F344 rats by injection of AY27 cells. When tumors reached 1 cm in diameter, the rats received either HPD (10 mg/kg body weight) photochemotherapy, HPD only, phototherapy only, or no treatment. Tumors were sampled immediately (0 time), 1/2, 1, 2, 4, and 24 hours after phototreatment for light and electron microscopy. Tumors receiving HPD-photochemotherapy displayed progressive injury to both tumor cells and endothelial cells. Early changes (0-2 hours) included focal tumor and endothelial cell vacuolation and swelling as well as sloughing of tumor cells into papillary spaces. Tumor cells and endothelial cells displayed vacuolization and damage to cell mitochondria immediately after phototreatment. Intercellular spaces also increased in size. Lethally injured cells were apparent in papillary spaces. At 4 hours after phototherapy, tumor cells and endothelial cells exhibited extensive cell damage, including mitochondrial destruction, endoplasmic reticulum swelling, polyribosome disaggregation, and plasma membrane blebbing. By 24 hours after phototherapy, the majority of cells within the tumor were necrotic. Untreated tumors and those treated with phototherapy-only did not exhibit these changes. Tumors that received HPD only exhibited focal areas of cell swelling and focal mitochondrial vacuolization in both tumor and endothelial cells. These changes, unlike the HPD-light-treated group did not progress and were reversible.