Small interfering RNA targeting bcl-2 sensitizes malignant melanoma.
Malignant melanoma is a prime example of a treatment-resistant tumor with poor prognosis. Even with innovative treatment regimens, response rates remain low, and the duration of responses is short. More than 90% of all melanomas express the antiapoptotic protein Bcl-2, shown to contribute to a chemoresistant phenotype in melanoma. We previously demonstrated that antisense-mediated inhibition of Bcl-2 sensitizes malignant melanoma to apoptosis-inducing treatment modalities. In the present study, we evaluated synthetic small interfering RNA (siRNA) compounds targeting Bcl-2 as a novel approach to downregulate Bcl-2 expression in melanoma cells. siRNA treatment led up to a 19-fold reduction of bcl-2 mRNA levels and only barely detectable Bcl-2 protein expression at low nanomolar concentrations. Silencing of Bcl-2 in melanoma cells by specific siRNA led to a moderate increase in apoptotic cell death and inhibition of cell growth. However, if siRNA compounds targeting Bcl-2 were combined with the apoptosis-inducing chemotherapeutic agent cisplatin, a massive increase in apoptotic cell death compared with controls was observed. Notably, the combination of Bcl2 siRNA and low-dose cisplatin resulted in a supra-additive effect, with nearly complete suppression of cell growth, whereas cell growth in cisplatin-only-treated cells was only moderately affected (96% vs. 25%, p < 0.001). These findings underline a key role for Bcl-2 in conferring chemoresistance to melanoma and highlight Bcl-2 siRNA strategies as novel and highly effective tools, with the potential for future targeted therapy of malignant melanoma.
Department of Clinical Pharmacology, Section of Experimental Oncology/Molecular Pharmacology, University of Vienna, Austria. Volker.Wachech@univie.ac.at
Volker
V
Wacheck
Doris
D
Losert
Patrick
P
Günsberg
Hans-Peter
HP
Vornlocher
Philipp
P
Hadwiger
Anke
A
Geick
Hubert
H
Pehamberger
Markus
M
Müller
Burkhard
B
Jansen
D017209:Apoptosis / Q000235:genetics; D001692:Biological Transport; D002455:Cell Division; D045744:Cell Line, Tumor; D020868:Gene Silencing; D006801:Humans; D007700:Kinetics; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics* / Q000493:pharmacokinetics
D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering