Therapeutic Targeting of ATP7B in Ovarian Carcinoma.
OBJECTIVE
Resistance to platinum chemotherapy remains a significant problem in ovarian carcinoma. Here, we examined the biological mechanisms and therapeutic potential of targeting a critical platinum resistance gene, ATP7B, using both in vitro and in vivo models.


METHODS
Expression of ATP7A and ATP7B was examined in ovarian cancer cell lines by real-time reverse transcription-PCR and Western blot analysis. ATP7A and ATP7B gene silencing was achieved with targeted small interfering RNA (siRNA) and its effects on cell viability and DNA adduct formation were examined. For in vivo therapy experiments, siRNA was incorporated into the neutral nanoliposome 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC).


RESULTS
ATP7A and ATP7B genes were expressed at higher levels in platinum-resistant cells compared with sensitive cells; however, only differences in ATP7B reached statistical significance. ATP7A gene silencing had no significant effect on the sensitivity of resistant cells to cisplatin, but ATP7B silencing resulted in 2.5-fold reduction of cisplatin IC(50) levels and increased DNA adduct formation in cisplatin-resistant cells (A2780-CP20 and RMG2). Cisplatin was found to bind to the NH(2)-terminal copper-binding domain of ATP7B, which might be a contributing factor to cisplatin resistance. For in vivo therapy experiments, ATP7B siRNA was incorporated into DOPC and was highly effective in reducing tumor growth in combination with cisplatin (70-88% reduction in both models compared with controls). This reduction in tumor growth was accompanied by reduced proliferation, increased tumor cell apoptosis, and reduced angiogenesis.


CONCLUSIONS
These data provide a new understanding of cisplatin resistance in cancer cells and may have implications for therapeutic reversal of drug resistance.
Mangala
Lingegowda S
LS
Departments of Gynecologic Oncology, Experimental Therapeutics, and Cancer Biology, The University of Texas M. D. Anderson Cancer Center, USA.
Zuzel
Vesna
V
Schmandt
Rosemarie
R
Leshane
Erik S
ES
Halder
Jyotsna B
JB
Armaiz-Pena
Guillermo N
GN
Spannuth
Whitney A
WA
Tanaka
Takemi
T
Shahzad
Mian M K
MM
Lin
Yvonne G
YG
Nick
Alpa M
AM
Danes
Christopher G
CG
Lee
Jeong-Won
JW
Jennings
Nicholas B
NB
Vivas-Mejia
Pablo E
PE
Wolf
Judith K
JK
Coleman
Robert L
RL
Siddik
Zahid H
ZH
Lopez-Berestein
Gabriel
G
Lutsenko
Svetlana
S
Sood
Anil K
AK
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis; D001665:Binding Sites; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000378:metabolism / Q000494:pharmacology; D000073840:Copper-Transporting ATPases; D018736:DNA Adducts / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D010051:Ovarian Neoplasms / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D011485:Protein Binding; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D047368:Tumor Burden; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D027682:Cation Transport Proteins; D018736:DNA Adducts; D000251:Adenosine Triphosphatases; C081184:ATP7A protein, human; C000612464:ATP7B protein, human; D000073840:Copper-Transporting ATPases; D002945:Cisplatin