Copper-induced toxicity in macular mutant mouse: an animal model for Menkes' kinky-hair disease

Copper ions are novel therapeutic agents for uterine leiomyosarcoma

BACKGROUND

Multidrug resistance is a major concern in uterine leiomyosarcoma treatment. Development of effective chemotherapies and management of drug resistance in patients is necessary. The copper efflux transporter adenosine triphosphatase copper transporting beta is a member of the P-type adenosine triphosphatase family and is also known as a strong platinum efflux transporter. Various reports have shown the association between adenosine triphosphatase copper transporting beta and platinum resistance; however, suitable inhibitors or methods for inhibiting platinum efflux via adenosine triphosphatase copper transporting beta are not developed.

OBJECTIVE

Our study focused on platinum resistance in uterine leiomyosarcoma. The role of adenosine triphosphatase copper transporting beta in uterine leiomyosarcoma resistance to platinum drugs was investigated both in vitro and in vivo.

STUDY DESIGN

Adenosine triphosphatase copper transporting beta expression was investigated by Western blotting and the efficacy of copper sulfate pretreatment and cisplatin administration in adenosine triphosphatase copper transporting beta-expressing cells was investigated both in vitro and in vivo.

RESULTS

Western blot analysis of SK-LMS-1 cells (uterine leiomyosarcoma cell line) revealed strong adenosine triphosphatase copper transporting beta expression. A permanent SK-LMS-ATPase copper transporting beta-suppressed cell line (SK-LMS-7B cells) was generated, and cisplatin exhibited a significant antitumor effect in SK-LMS-7B cells, both in vitro (SK-LMS-1 cells, half-maximal inhibitory concentration, 17.2 μM; SK-LMS-7B cells, half-maximal inhibitory concentration, 4.2 μM, P < .01) and in xenografts compared with that in SK-LMS-1 cells (5.8% vs 62.8%, P < .01). Copper sulfate was identified as a preferential inhibitor of platinum efflux via adenosine triphosphatase copper transporting beta. In SK-LMS-1 cells pretreated with 15 μM copper sulfate for 3 hours, the cisplatin half-maximal inhibitory concentration decreased significantly compared with that in untreated cells and resulted in significantly increased intracellular platinum accumulation (1.9 pg/cell vs 8.6 pg/cell, P < .01). The combination of copper sulfate pretreatment with cisplatin administration was also effective in vivo and caused cisplatin to exhibit significantly increased antitumor effects in mice with SK-LMS-1 xenografts (3.1% vs 62.7%, P < .01).

CONCLUSION

Our study demonstrates that adenosine triphosphatase copper transporting beta is overexpressed in uterine leiomyosarcoma cells and that copper sulfate, which acts as an inhibitor of platinum efflux via adenosine triphosphatase copper transporting beta, may be a therapeutic agent in the treatment of uterine leiomyosarcoma.

Effect of age and sex on copper-induced toxicity in the macular mutant mouse. An animal model for Menkes' kinky-hair disease

It was determined if the sensitivity in macular mutant mouse to copper-induced toxicity was affected by sex or age. The sensitivity in 6-8-d-old or 3-4-wk-old macular mutant mouse to copper-induced toxicity was not affected by sex. However, 8-9-wk-old mutant females were more sensitive to copper-induced toxicity than mutant males. Furthermore, 6-8-d-old or 3-4-wk-old mutant males were more sensitive to copper-induced toxicity than 8-9-wk-old mutant males. However, age-related differences in sensitivity to copper-induced toxicity did not occur significantly in mutant females. On the other hand, in the case of normal mice, the sensitivity in 6-8-d-old or 3-4-wk-old mice to copper-induced toxicity was not also affected by sex. In contrast to mutant, however, 8-9-wk-old normal males were more sensitive to copper-induced toxicity than 8-9-wk-old normal females. Adult males were also more sensitive to copper-induced toxicity than 6-8-d-old or 3-4-wk-old males. However, age-related differences in sensitivity to copper-induced toxicity did not occur significantly in normal females. These results indicate that sex- and age-related differences in the copper-induced toxicity exist in macular mutant mice.

Intracellular distribution of hepatic copper in macular mutant mice. An animal model of Menkes' kinky-hair disease

To evaluate the role of lysosomes in copper-mediated hepatocellular injury, copper was administered, sc, to both normal and macular mutant mice at doses of 4.5, 9.0, and 18 mg Cu/kg, and the subcellular distribution of copper has been investigated in the liver of normal and mutant mice 24 h after injection. The amount of copper in all fractions of copper-treated mutant mice was markedly lower than those in copper-treated normal mice, with the exception of microsomal fraction. However, there were no distinct differences in the proportion of copper in subcellular fractions between normal and mutant mice.