Background: Hepatoblastoma (HB) represents the most common malignant liver tumour in childhood. For patients with high risk or recurrent HB treatment results remain still poor due to a developing multidrug resistance during chemotherapy. Therefore new therapy strategies have to be evaluated. The primary objective was to investigate the combined therapy of cytotoxic agents with sorafenib. Sorafenib has been shown to reduce tumour progression and angiogenesis. In order to investigate a treatment close to a clinical setting the effect of the combined administration of cytotoxic agents with sorafenib on HB cell lines and xenotransplanted HB tumours was determined. Methods: Cell viability of two HB cell lines (HUH6 and HepT1) was evaluated in using MTT assays after treatment with sorafenib and different cytostatic agents (cisplatin (CDDP), doxorubicin, irinotecan, topotecan). ERK signalling was investigated by Western blot analysis. NMRI mice (nu/nu) bearing subcutaneous HUH6 derived tumours were treated with Sorafenib orally (30 mg/kg, on days 4-13 and 17-24) alone or in combination with CDDP i.p. (3 mg/kg, on days 1-3 and 14-16). Tumor progression and viability were monitored by tumour volume and AFP levels. Apoptosis was assessed by TUNEL assay. Angiogenesis was determined by CD31 staining and mean vascular density (MVD) was calculated. Results: In vitro the combination of sorafenib with CDDP showed a remarkable decrease in cell viability compared to the other agents tested. However with increasing concentrations of CDDP this additive effect disappeared. CDDP alone showed an enhanced phosphorylation of ERK1/2, which is a common pathway for apoptosis induction through NOXA. CDDP in combination with sorafenib led to an overall reduced phosphorylation level of ERK1/2, which also resulted in a low HB cell viability. Since CDDP and sorafenib have an opposing effect on phosphorylation of ERK1/2, we avoid the concomitant administration of both drugs in vivo. In HB xenografts both sorafenib alone or in alternating combination with CDDP reduced tumour growth compared to the control untreated group (p < 0.05). The combination treatment showed a higher and earlier reduction of tumor volume than sorafenib alone. In addition AFP levels did not significantly change in the treatment groups. Apoptotic areas as determined by TUNEL analysis increased significantly after administration of sorafenib or sorafenib and CDDP (p < 0.08). Furthermore CD31 staining showed a significant inhibition of angiogenesis as revealed by determination of the MVD in both treatment groups (p < 0.02). Discussion: Taken together the combination therapy of Sorafenib and CDDP led to an enhanced decrease in cell viability as well as in tumour progression and angiogenesis than sorafenib alone. Therefore a combined therapy might be a promising option in the treatment of high risk or recurrent hepatoblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4337. doi:1538-7445.AM2012-4337