Successful therapy of subcutaneously growing human hepatoblastoma xenografts with topotecan*

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Abstract
Background Human hepatoblastoma is an infrequent liver tumor in children. Although many hepatoblastomas can be treated adequately with well‐defined treatment regimens, problems still persist with advanced and non‐resectable tumors; in these cases, an effective chemotherapy is necessary to improve the patients' prognosis. This underlines the need for alternative anti‐tumor agents in the treatment of human hepatoblastoma. The aim of this study was to investigate the therapeutic effects of topotecan, a water‐soluble camptothecin analog (topoisomerase‐I‐antagonist), in an in vivo model of three human hepatoblastomas xenografted subcutaneously into nude mice. Procedure Hepatoblastoma cell suspensions from three children were transplanted subcutaneously into nude mice NMRI (nu/nu). Treatment with topotecan was initiated when the tumors reached a volume between 50 and 80 mm3. A dose of 6.6 mg/kg of topotecan were given intraperitoneally every 4 days on four occasions. The tumor volume development and α‐fetoprotein alterations were measured and statistically analyzed. After the treatment, the tumors were investigated histologically and by immunhistochemistry. Results There was a significant reduction of tumor growth in all treated tumor xenografts vs. untreated control groups (mean relative volume 3.1 vs. 47.4; P = 0,0015–0,0079). Serum α‐fetoprotein levels were reduced in all three cell lines, in two of them significantly (mean 44,535 kU/l vs. 228,883 kU/l; P = 0.005–0.246). Histologically, the tumor necrosis rates were higher and immunhistochemistry showed lower proliferation activities in the treated tumor xenografts vs. the control groups. Conclusion The data show that topotecan is an effective agent in the treatment of human hepatoblastoma xenografts. From these results, treatment with topotecan appears to be a promising alternative in the pre‐ and postoperative therapy of patients suffering from human hepatoblastoma. Med Pediatr Oncol 2001;37:449–454.