Format

Send to:

Choose Destination
See comment in PubMed Commons below
Clin Cancer Res. 2009 Sep 15;15(18):5704-13. doi: 10.1158/1078-0432.CCR-09-0198. Epub 2009 Sep 8.

C-Raf is associated with disease progression and cell proliferation in a subset of melanomas.

Author information

  • 1Yale Cancer Center and Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

Abstract

PURPOSE:

Raf-kinases include three major isoforms. Although the role of B-Raf in melanoma is well established, little is known about C-Raf. We studied effects of C-Raf knockdown in vitro and assessed expression of C-Raf in a large cohort of melanomas and nevi.

EXPERIMENTAL DESIGN:

Using specific siRNAs, we knocked down C-Raf expression, and determined the effect on viability, MAP extracellular signal-regulated kinase (ERK)/ERK kinase signaling, and apoptosis in seven melanoma cell lines. We determined the IC(50) of the C-Raf inhibitors sorafenib and GW5074, and studied the effects of GW5074 on cell signaling. Using an automated method to measure in situ protein expression, we quantified C-Raf expression in 263 nevi and 523 melanomas.

RESULTS:

C-Raf was knocked down in three cell lines with detectable phospho-C-Raf, resulting in decreased viability in two of the three (YULAC and YUROB). This resulted in decreased Bcl-2 expression and phospho-Bad cleavage, without affecting phospho-MEK and phospho-ERK. Sensitivity to sorafenib and GW5074 varied. GW5074 inhibited mitogen-activated protein kinase signaling without Bcl-2 and phospho-Bad down-regulation. C-Raf was highly expressed in melanomas compared with nevi (P < 0.0001), and no nevi had high C-Raf expression. C-Raf expression was higher in metastatic than primary specimens (P = 0.0225).

CONCLUSIONS:

C-Raf siRNA knock-down results in decreased viability of YULAC (B-Raf(V600K)) and YUROB (B-Raf(WT)) melanoma cells, likely mediated by Bcl-2 inhibition rather than mitogen-activated protein kinase inhibition. Cotargeting C-Raf and parallel pathways might be an effective therapeutic approach for melanoma. C-Raf expression is up-regulated in a subset of melanomas but not in nevi, suggesting that it might be a valuable diagnostic marker and therapeutic target.

PMID:
19737955
[PubMed - indexed for MEDLINE]
PMCID:
PMC2763114
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk