Combined targeting of epidermal growth factor receptor and MDM2 by gefitinib and antisense MDM2 cooperatively inhibit hormone-independent prostate cancer.
OBJECTIVE
The epidermal growth factor receptor (EGFR) may play a relevant role in the progression, hormone therapy resistance, and prognosis of prostate cancer patients. Also MDM2, a negative p53 regulator that interacts with retinoblastoma (Rb), E2F, p19(arf) and the ras-mitogen-activated protein kinase(MAPK) cascade plays an important role in prostate cancer progression and prognosis. On the basis of the EGFR and MDM2 role in integrating signaling pathways critical for prostate cancer progression, we investigated whether their selective combined blockade may have a cooperative antitumor effect in prostate cancer. For this purpose, we have used the EGFR tyrosine kinase inhibitor gefitinib (ZD1839, Iressa) and a second generation hybrid oligonucleotide antisense MDM2 (AS-MDM2), respectively.


METHODS
Gefitinib and AS-MDM2 were administered to hormone-refractory and hormone-dependent human prostate cancer cells in vitro and to mice bearing tumor xenografts, evaluating the effects on growth, apoptosis, and protein expression, in vitro and in vivo.


RESULTS
We demonstrated that the combination of gefitinib and AS-MDM2 synergistically inhibits the growth of hormone-independent prostate cancer cells in vitro. This effect is accompanied by the inhibition of MDM2, phosphorylated Akt (pAkt), phosphorylated MAPK (pMAPK), and vascular endothelial growth factor (VEGF) expression and by Rb hypophosphorylation. The combination of the two agents in nude mice bearing the same hormone-independent tumors caused a potent cooperative antitumor effect. Tumor samples analysis confirmed the inhibition of MDM2, pAkt, pMAPK, VEGF, and basic fibroblast growth factor expression.


CONCLUSIONS
This study shows that EGFR and MDM2 play a critical role in the growth of prostate cancer, especially hormone-dependent, and that their combined blockade by gefitinib and AS-MDM2 causes a cooperative antitumor effect, supporting the clinical development of this therapeutic strategy.
Dipartimento di Endocrinologia e Oncologia Molecolare e Clinica, Università di Napoli Federico II, Naples, Italy.
Roberto
R
Bianco
Roberta
R
Caputo
Rosa
R
Caputo
Vincenzo
V
Damiano
Sabino
S
De Placido
Corrado
C
Ficorella
Sudhir
S
Agrawal
A Raffaele
AR
Bianco
Fortunato
F
Ciardiello
Giampaolo
G
Tortora
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D066246:ErbB Receptors / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis; D000077156:Gefitinib; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology* / Q000627:therapeutic use; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D014176:Protein Biosynthesis / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051736:Proto-Oncogene Proteins c-mdm2; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D011799:Quinazolines; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D066246:ErbB Receptors; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D000077156:Gefitinib