Hematoporphyrin Monomethyl Ether Enhances the Killing Action of Ultrasound on Osteosarcoma In Vivo

Objectives. Osteosarcoma is one of the most common malignant cancers afflicting young adults. Ultrasound is a new therapeutic modality for controlling malignant cancers. Enhancing the efficacy of ultrasound treatment will improve clinical outcomes. The aim of this study was to investigate the killing action of ultrasound on osteosarcoma enhanced by hematoporphyrin monomethyl ether (HMME) in vivo. Methods. An animal model of an osteosarcoma xenograft was set up to investigate the inhibitory effect of sonoactivating HMME on osteosarcoma. High‐performance liquid chromatography was used to analyze the time course of HMME in the osteosarcoma xenograft. Three hours after intravenous (IV) administration of HMME, ultrasound radiation was administered in the osteosarcoma xenograft. On day 7 after ultrasound radiation, the tumor volume and weight were measured and calculated for effect assessment, hematoxylin‐eosin staining for histopathologic examination, immunohistochemical staining for proliferating cell nuclear antigen (PCNA) expression, and terminal deoxyuridine nick end‐labeling (TUNEL) staining for apoptosis examinations. Results. The peak value of HMME in osteosarcoma tissues increased with time after IV administration of HMME and reached a plateau at 3 hours. The increasing rates of the tumor volume and weight in the control group were very fast, but the increasing rates in the ultrasound‐alone group were slower, and those in the ultrasound‐HMME group were the slowest throughout the observation period. There was a significant difference between the HMME‐ultrasound, ultrasound‐alone, and control groups (P < .01). Hematoxylin‐eosin staining showed that some cells had typical cell death such as pyknosis and nuclear fragmentation after ultrasound radiation alone. More cells with pyknosis, nuclear fragmentation, and even karyolysis were found after HMME‐ultrasound treatment. Immunohistochemical staining showed that the percentage of PCNA‐positive cells decreased and that of TUNEL‐positive cells increased after ultrasound treatment alone, and the changes in the PCNA‐ and TUNEL‐positive percentages were significantly enhanced by pretreatment with HMME (20 mg/kg, IV) for 3 hours and ultrasound radiation (10.5 MHz) for 120 seconds at an intensity of 0.8 W/cm2 (P < .05). Conclusions. Hematoporphyrin monomethyl ether pretreatment could substantially enhance the growth inhibition of ultrasound on osteosarcoma, which suggests that HMME is an efficient sonosensitizer, and ultrasound radiation with HMME could be developed as a new modality for treating osteosarcoma.