Enhanced delivery of cisplatin to intraperitoneal ovarian carcinomas mediated by the effects of bortezomib on the human copper transporter 1.
OBJECTIVE
The copper transporter 1 (CTR1) is a major influx transporter for platinum drugs. However, the accumulation of cisplatin in human ovarian carcinoma cells is limited by the fact that cisplatin triggers the down-regulation and proteasomal degradation of CTR1, thereby limiting its own uptake. We sought to determine whether proteasome inhibition using bortezomib would prevent human CTR1 (hCTR1) degradation and increase platinum accumulation in ovarian cancer cells.


METHODS
The effects of bortezomib on human hCTR1 expression and cisplatin accumulation were measured by Western blot, flow cytometric, and confocal digital imaging analyses. Platinum accumulation was measured by inductively coupled plasma mass spectrometry and bortezomib concentrations by liquid chromatography/mass spectrometry.


RESULTS
Bortezomib blocked the cisplatin-induced down-regulation of hCTR1 in a concentration-dependent manner and increased cisplatin uptake 1.6- to 2.4-fold. Median effect analysis showed a combination index of 0.37 at 50% cell kill, indicating a high level of synergy. The effect of bortezomib was muted in cells lacking both alleles of CTR1, showing that bortezomib was working primarily through its effect on blocking hCTR1 degradation. I.p. administration of bortezomib produced a peritoneal/plasma area under the curve ratio of 252 in a murine model. I.p. administration of bortezomib before i.p. cisplatin increased platinum accumulation in peritoneal tumors by 33% (P = 0.006).


CONCLUSIONS
Proteasomal inhibition prevented cisplatin-induced down-regulation of hCTR1 in ovarian cancer cells and enhanced drug uptake and cell killing in a synergistic manner. Bortezomib shows a large pharmacologic advantage when administered i.p. There is a strong rationale for the combined i.p. administration of bortezomib and cisplatin.
Jandial
Danielle D
DD
Department of Medicine and the Rebecca and John Moores Cancer Center, University of California, San Diego, La Jolla, California, USA.
Farshchi-Heydari
Salman
S
Larson
Christopher A
CA
Elliott
Gregory I
GI
Wrasidlo
Wolfgang J
WJ
Howell
Stephen B
SB
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D027682:Cation Transport Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D000079923:Copper Transporter 1; D016503:Drug Delivery Systems; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010051:Ovarian Neoplasms / Q000188:drug therapy*; D010534:Peritoneal Neoplasms / Q000188:drug therapy*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology*
D000970:Antineoplastic Agents; D001897:Boronic Acids; D027682:Cation Transport Proteins; D000079923:Copper Transporter 1; D011719:Pyrazines; C490079:SLC31A1 protein, human; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex; D002945:Cisplatin