L-THP did not impair the antitumour efficacy of OXA in tumour cells nor in tumour-bearing nude mice
To explore whether L-THP might impair the antitumour efficiency of OXA, the cytotoxicity and antitumour effect of OXA were evaluated in HT29 and SW620 cells, as well as in HT29 tumour-bearing nude mice with or without L-THP. As shown in Figures 7a and 7b , co-incubation with L-THP (1-100 µM) did not reduce the cytotoxicity of OXA in the HT29 or SW620 cells. In agreement with the results in vitro , the tumour growth was markedly inhibited in the OXA-alone (8 mg/kg, single dose) group, as well as in the L-THP co-treated (10 and 20 mg/kg) groups. Meanwhile, the concentration of OXA in tumours showed no significant difference between the OXA-alone or L-THP co-administration groups.