Inhibition of growth of human nasopharyngeal cancer xenografts in SCID mice by arsenic trioxide.

Aims and background: It is known that arsenic trioxide (As 2 O 3 ) can induce clinical remission in patients suffering from acute promyelocytic leukemia. It has been suggested that the agent might also be effective against other malignancies. This study was done to explore the efficacy of As 2 O 3 in the treatment of human nasopharyngeal cancer xenografts in SCID (severe combined immunodeficiency) mice. Methods: Human nasopharyngeal cancer cells from the CSNE-1 cell line were implanted subcutaneously into SCID mice to produce tumors. The tumor inhibitory rate in vivo was assessed after intraperitoneal administration of As 2 O 3 . Histopathological changes in the tumor tissues and the toxicity of As 2 O 3 to the liver, heart and kidneys of the host mice were also investigated. Results: At doses of 1 mg/kg and 5 mg/kg As 2 O 3 induced apoptosis in nasopharyngeal carcinoma cells. At 5 mg/kg As 2 O 3 also induced cancer cell differentiation, it reduced the PCNA expression, and inhibited tumor growth. The tumor growth inhibitory rate in this experimental group was 76.02%. No nephrotoxicity was observed histologically at these dose levels but some pathological changes in liver and cardiac tissues were found. As 2 O 3 proved lethal to the SCID mice at a dose of 10 mg/kg. Conclusion: As 2 O 3 has an inhibitory effect on human nasopharyngeal carcinoma xenografts in SCID mice. The mechanism of antitumor activity may be due, at least in part, to the induction of apoptosis and differentiation in cancer cells.