Experimental therapy of human prostate cancer by inhibiting MDM2 expression with novel mixed-backbone antisense oligonucleotides: in vitro and in vivo activities and mechanisms.
BACKGROUND
MDM2 oncogene is overexpressed in many human cancers including prostate cancer and MDM2 levels are associated with poor prognosis. This study was undertaken to investigate the functions of MDM2 oncogene in prostate cancer growth and the value of MDM2 as a drug target for prostate cancer therapy by inhibiting MDM2 expression.


METHODS
Antisense anti-human-MDM2 mixed-backbone oligonucleotide and its mismatch control were tested in in vitro and in vivo human prostate cancer models (LNCaP, DU 145, and PC-3) for anti-tumor activity. Targeted gene products and related proteins were analyzed and the anti-tumor activity was determined when the oligonucleotides were used alone or in combination with cancer therapeutics.


RESULTS
The antisense oligonucleotide specifically inhibited MDM2 expression in a dose- and time-dependent manner, resulting in significant anti-tumor activity in vitro and in vivo. In LNCaP cells, p53 and p21 levels were elevated. The antisense oligonucleotide also potentiated the effects of p53 activation and p21 induction by chemotherapeutic agents 10-hydroxycamptothecin, adriamycin, 5-fluorouracil, and paclitaxel. In DU145 cells, following inhibition of MDM2 expression, p21 levels were elevated although p53 levels remained unchanged. In both cell lines, the antisense oligonucleotide inhibited tumor cell growth and induced apoptosis in vitro. In a dose-dependent manner, the antisense oligonucleotide showed anti-tumor activity in nude mice bearing DU145 or PC-3 xenografts. It significantly increased therapeutic effectiveness of the chemotherapeutic agent irinotecan and slightly improved the effects of paclitaxel and Rituxan.


CONCLUSIONS
These results indicate that MDM2 has a role in prostate tumor growth through both p53-dependent and p53-independent mechanisms, indicating that MDM2 inhibitors have a broad spectrum of anti-tumor activities in human prostate cancers regardless of p53 status.
Wang
Hui
H
Department of Pharmacology and Toxicology, Division of Clinical Pharmacology, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019, USA.
Yu
Dong
D
Agrawal
Sudhir
S
Zhang
Ruiwen
R
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D003131:Combined Modality Therapy; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D005472:Fluorouracil / Q000494:pharmacology; D015316:Genetic Therapy; D006801:Humans; D066298:In Vitro Techniques; D000077146:Irinotecan; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D000964:Antimetabolites, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D000077146:Irinotecan; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D017239:Paclitaxel; D005472:Fluorouracil; D002166:Camptothecin