Vemurafenib potently induces endoplasmic reticulum stress-mediated apoptosis in BRAFV600E melanoma cells.

Abstract

The V600E mutation in the kinase BRAF is frequently detected in melanomas and results in constitutive activation of BRAF, which then promotes cell proliferation by the mitogen-activated protein kinase signaling pathway. Although the BRAFV600E kinase inhibitor vemurafenib has remarkable antitumor activity in patients with BRAFV600E-mutated melanoma, its effects are limited by the onset of drug resistance. We found that exposure of melanoma cell lines with the BRAFV600E mutation to vemurafenib decreased the abundance of antiapoptotic proteins and induced intrinsic mitochondrial apoptosis. Vemurafenib-treated melanoma cells showed increased cytosolic concentration of calcium, a potential trigger for endoplasmic reticulum (ER) stress, which can lead to apoptosis. Consistent with an ER stress-induced response, vemurafenib decreased the abundance of the ER chaperone protein glucose-regulated protein 78, increased the abundance of the spliced isoform of the transcription factor X-box binding protein 1 (XBP1) (which transcriptionally activates genes involved in ER stress responses), increased the phosphorylation of the translation initiation factor eIF2α (which would be expected to inhibit protein synthesis), and induced the expression of ER stress-related genes. Knockdown of the ER stress response protein activating transcription factor 4 (ATF4) significantly reduced vemurafenib-induced apoptosis. Moreover, the ER stress inducer thapsigargin prevented invasive growth of tumors formed from vemurafenib-sensitive melanoma cells in vivo. In melanoma cells with low sensitivity or resistance to vemurafenib, combination treatment with thapsigargin augmented or induced apoptosis. Thus, thapsigargin or other inducers of ER stress may be useful in combination therapies to overcome vemurafenib resistance.

• Authors: Daniela Beck, Heike Niessner, Keiran S M Smalley, Keith Flaherty, Kim H T Paraiso, Christian Busch, Tobias Sinnberg, Sophie Vasseur, Juan Lucio Iovanna, Stefan Drießen, Björn Stork, Sebastian Wesselborg, Martin Schaller, Tilo Biedermann, Jürgen Bauer, Konstantinos Lasithiotakis, Benjamin Weide, Jürgen Eberle, Birgit Schittek, Dirk Schadendorf, Claus Garbe, Dagmar Kulms, Friedegund Meier
• Journal: Science signaling (Sci Signal) Vol. 6 Issue 260 Pg. ra7 (Jan 29 2013) ISSN: 1937-9145 [Electronic] United States
• PMID: 23362240 (Publication Type: Clinical Trial, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• ATF4 protein, human
• DNA-Binding Proteins
• Indoles
• Protein Kinase Inhibitors
• Regulatory Factor X Transcription Factors
• Sulfonamides
• Transcription Factors
• X-Box Binding Protein 1
• XBP1 protein, human
• Activating Transcription Factor 4
• Vemurafenib
• BRAF protein, human
• Proto-Oncogene Proteins B-raf

Topics

• Activating Transcription Factor 4 (genetics, metabolism)
• Amino Acid Substitution
• Animals
• Apoptosis (drug effects, genetics)
• Cell Line, Tumor
• Chick Embryo
• DNA-Binding Proteins (genetics, metabolism)
• Endoplasmic Reticulum Stress (drug effects, genetics)
• Female
• Gene Knockdown Techniques
• Humans
• Indoles (pharmacology)
• Male
• Melanoma (drug therapy, genetics, metabolism, pathology)
• Mutation, Missense
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins B-raf (genetics, metabolism)
• Regulatory Factor X Transcription Factors
• Sulfonamides (pharmacology)
• Transcription Factors (genetics, metabolism)
• Vemurafenib
• X-Box Binding Protein 1