ATP7B (WND) protein

Copper-transporting P-type adenosine triphosphatase (ATP7B) as a cisplatin based chemoresistance marker in ovarian carcinoma: comparative analysis with expression of MDR1, MRP1, MRP2, LRP and BCRP

Intrinsic or acquired resistance to chemotherapy is the major obstacle to overcome in the treatment of patients with solid carcinoma. Cisplatin is one of the most effective chemotherapeutic agents for treating ovarian carcinoma. Recently, copper-transporting P-type adenosine triphosphatase (ATP7B) has been demonstrated as one of the genes responsible for cisplatin resistance in vitro. We hypothesized that the expression of ATP7B gene increases resistance to cisplatin in ovarian carcinoma and a priori knowledge of its expression is important for the choice of therapy. The aim of our study was to assess the role of ATP7B gene in ovarian carcinoma and compare its expression with those of multidrug resistance-related transporters such as MDR1, MRP1, MRP2, LRP and BCRP genes. The transporters' gene expression profiles from 82 patients treated with cisplatin-based chemotherapy after surgery were assessed by RT-PCR. We did not observe any significant correlation between ATP7B gene expression and those of MDR1, MRP1, MRP2, LRP or BCRP. The expression level of ATP7B gene was significantly increased (p < 0.05) in patients with moderately-/poorly-differentiated ovarian carcinomas treated with cisplatin-based chemotherapy, thus ATP7B may serve as an independent prognostic factor in these patients. In contrast, the expression level of MDR1, MRP1, MRP2, LRP and BCRP genes were not prognostic indicators of disease. These findings suggest that ATP7B gene may be considered as a novel chemoresistance marker and that inhibitor(s) of ATP7B might be useful, in patients with ovarian carcinoma treated with cisplatin-based chemotherapy.

Diagnosis and treatment of Wilson's disease

Wilson's disease (WD) has moved on from being a recognized syndrome that was uniformly fatal to a curative disease for which the genetic basis has been discovered. Most pediatric patients present with hepatic manifestations, but some may have neurologic or psychiatric features. Clinical and biochemical screening, including liver biopsy for hepatic copper analysis, remain the standard for diagnosis, but haplotype analysis for siblings is now available and should be considered for family screening when possible. Lifelong medical therapy remains the mainstay of treatment, but treatment preferences are changing from penicillamine to alternative agents such as trientine and zinc. OLT remains lifesaving for those with fulminant WD and those in whom initial medical therapy fails. The future will probably see the application of rapid and accurate molecular diagnostic testing for this disorder and new therapeutic modalities such as hepatocyte transplantation, gene replacement therapy, and gene modification.

Copper-transporting P-type adenosine triphosphatase (ATP7B) is expressed in human breast carcinoma

This is the first report to show that a copper-transporting P-type adenosine triphosphatase, ATP7B, is expressed in certain breast carcinomas, and a priori knowledge of its expression is important for the choice of therapy. We investigated the hypothesis that ATP7B, which was shown to be associated with cisplatin resistance in vitro, is expressed in certain breast carcinomas. To test this hypothesis, ATP7B expression and protein level were examined in 41 breast carcinomas using RT-PCR and immunohistochemistry. ATP7B gene / protein could be detected in 22.0% (9 / 41) of breast carcinomas and ATP7B gene expression was correlated well with the protein expression. In nine ATP7B-positive tumors, adjacent normal breast tissue was similarly analyzed, revealing that ATP7B is upregulated in breast carcinoma. ATP7B gene expression in poorly differentiated carcinoma was significantly higher than that in well- / moderately differentiated carcinoma (P = 0.012). Furthermore, we found no association between the ATP7B gene / protein expression and that of MDR1, MRP1, LRP and BCRP. These findings suggested that ATP7B gene expression might be a chemoresistance marker for cisplatin in patients with poorly differentiated breast carcinoma.

Copper transportion of WD protein in hepatocytes from Wilson disease patients in vitro

AIM

To study the effect of copper transporting P-type ATPase in copper metabolism of hepatocyte and pathogenesis of Wilson disease (WD).

METHODS

WD copper transporting properties in some organelles of the cultured hepatocytes were studied from WD patients and normal controls.These cultured hepatocytes were incubated in the media of copper 15 mg x L(-1) only, copper 15 mg x L(-1) with vincristine (agonist of P-type ATPase) 0.5mg x L(-1), or copper 15 mg x L(-1) with vanadate (antagonist of P-type ATPase) 18.39 mg x L(-1) separately. Microsome (endoplasmic reticulum and Golgi apparatus), lysosome, mitochondria, and cytosol were isolated by differential centrifugation. Copper contents in these organelles were measured with atomic absorption spectrophotometer, and the influence in copper transportion of these organelles by vanadate and vincristine were comparatively analyzed between WD patients and controls. WD copper transporting P-type ATPase was detected by SDS-PAGE in conjunction with Western blot in liver samples of WD patients and controls.

RESULTS

The specific WD proteins (M(r)155,000 lanes) were expressed in human hepatocytes, including the control and WD patients. After incubation with medium containing copper for 2 h or 24 h, the microsome copper concentration in WD patients was obviously lower than that of controls, and the addition of vanadate or vincristine would change the copper transporting of microsomes obviously. When incubated with vincristine, levels of copper in microsome were significantly increased, while incubated with vanadate, the copper concentrations in microsome were obviously decreased. The results indicated that there were WD proteins, the copper transportion P-type ATPase in the microsome of hepatocytes. WD patients possessed abnormal copper transporting function of WD protein in the microsome, and the agonist might correct the defect of copper transportion by promoting the activity of copper transportion P-type ATPase.

CONCLUSION

Copper transportion P-type ATPase plays an important role in hepatocytic copper metabolism. Dysfunction of hepatocytic WD protein copper transportion might be one of the most important factors for WD.

Copper and genomic stability in mammals

As the free ion and in the form of some complexes, there is no doubt that copper can promote damage to cellular molecules and structures through radical formation. At the same time, and perhaps as a consequence, mammals have evolved means of minimizing levels of free copper ions and destructive copper complexes that enter the organism and its cells. These means include tight binding of copper ions to protein carriers and transporters; direct exchange of copper between protein carriers, transporters, and cuproenzymes; and mobilization of secretory mechanisms and excretory pathways, as needed. As a consequence, normally, and except under certain genetic conditions, copper is likely to be benign to most mammals and not responsible for genomic instability, including fragmentation of and/or alterations to DNA, induction of mutations or apoptosis, or other toxic events. Indeed, cuproenzymes are important members of the antioxidant system of the organism.

Treatment of Wilson's disease: what are the relative roles of penicillamine, trientine, and zinc supplementation?

New options are available for the medical treatment of patients with Wilson's disease. Penicillamine is no longer the treatment of choice, as there is a growing experience with safer and more effective alternatives. Trientine may be the best choice for initial therapy in symptomatic patients requiring chelation therapy, and it may be even more effective when used in combination with zinc, which is recommended for maintenance therapy. Further studies are needed to determine the best therapy for pregnant patients with Wilson's disease, and whether combination therapy using trientine and zinc will be the next treatment of choice for all symptomatic patients with liver or neurologic disease.

Wilson's disease

During the last 90 years, Wilson's hepatolenticular degeneration has evolved from a disease presenting insurmountable challenges to the clinician's diagnostic acumen to a metabolic disorder which is diagnosable woth certainty, treatable successfully, and even preventable. It may be long before the genetic defect becomes amenable to correction and a cure of the disease becomes possible.

Biliary excretion of copper in LEC rat after introduction of copper transporting P-type ATPase, ATP7B

Wilson's disease, an autosomal recessive disorder, is characterized by the excessive accumulation of hepatic copper that results from reduced biliary copper excretion and disturbed incorporation of copper into ceruloplasmin. The ATP7B gene, responsible for the disease, encodes a copper transporting P-type ATPase. We previously demonstrated the involvement of ATP7B in hepatic copper secretion into plasma after the introduction of ATP7B into the Long-Evans Cinnamon (LEC) rat, a rodent model of Wilson's disease. In this study we found the increased copper contents of the hepatic lysosomal fractions and bile in the LEC rats after ATP7B introduction, indicating the participation of ATP7B in the biliary excretory pathway for copper.