The Novel ATP-Competitive MEK/Aurora Kinase Inhibitor BI-847325 Overcomes Acquired BRAF Inhibitor Resistance through Suppression of Mcl-1 and MEK Expression.

Abstract

Resistance to BRAF inhibitors is a major clinical problem. Here, we evaluate BI-847325, an ATP-competitive inhibitor of MEK and Aurora kinases, in treatment-naïve and drug-resistant BRAF-mutant melanoma models. BI-847325 potently inhibited growth and survival of melanoma cell lines that were both BRAF inhibitor naïve and resistant in 2D culture, 3D cell culture conditions, and in colony formation assays. Western blot studies showed BI-847325 to reduce expression of phospho-ERK and phospho-histone 3 in multiple models of vemurafenib resistance. Mechanistically, BI-847325 decreased the expression of MEK and Mcl-1 while increasing the expression of the proapoptotic protein BIM. Strong suppression of MEK expression was observed after 48 hours of treatment, with no recovery following >72 hours of washout. siRNA-mediated knockdown of Mcl-1 enhanced the effects of BI-847325, whereas Mcl-1 overexpression reversed this in both 2D cell culture and 3D spheroid melanoma models. In vivo, once weekly BI-847325 (70 mg/kg) led to durable regression of BRAF-inhibitor naïve xenografts with no regrowth seen (>65 days of treatment). In contrast, treatment with the vemurafenib analog PLX4720 was associated with tumor relapse at >30 days. BI-847325 also suppressed the long-term growth of xenografts with acquired PLX4720 resistance. Analysis of tumor samples revealed BI-847325 to induce apoptosis associated with suppression of phospho-ERK, total MEK, phospho-Histone3, and Mcl-1 expression. Our studies indicate that BI-847325 is effective in overcoming BRAF inhibitor resistance and has long-term inhibitory effects upon BRAF-mutant melanoma in vivo, through a mechanism associated with the decreased expression of both MEK and Mcl-1.

• Authors: Manali S Phadke, Patrizia Sini, Keiran S M Smalley
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 14 Issue 6 Pg. 1354-64 (Jun 2015) ISSN: 1538-8514 [Electronic] United States
• PMID: 25873592 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: ©2015 American Association for Cancer Research.

Chemical References

• Aniline Compounds
• BI-847325
• Indoles
• MCL1 protein, human
• Myeloid Cell Leukemia Sequence 1 Protein
• Protein Kinase Inhibitors
• Adenosine Triphosphate
• Aurora Kinases
• Proto-Oncogene Proteins B-raf
• Mitogen-Activated Protein Kinase Kinases

Topics

• Adenosine Triphosphate (metabolism)
• Aniline Compounds (chemistry, pharmacology)
• Animals
• Apoptosis (drug effects, genetics)
• Aurora Kinases (antagonists & inhibitors, genetics, metabolism)
• Blotting, Western
• Cell Culture Techniques
• Cell Line, Tumor
• Drug Resistance, Neoplasm (drug effects, genetics)
• Gene Expression Regulation, Neoplastic
• Humans
• Indoles (chemistry, pharmacology)
• Melanoma (drug therapy, genetics, pathology)
• Mice, Inbred BALB C
• Mice, SCID
• Mitogen-Activated Protein Kinase Kinases (antagonists & inhibitors, genetics, metabolism)
• Molecular Structure
• Mutation
• Myeloid Cell Leukemia Sequence 1 Protein (antagonists & inhibitors, genetics, metabolism)
• Protein Kinase Inhibitors (chemistry, pharmacology)
• Proto-Oncogene Proteins B-raf (antagonists & inhibitors, genetics, metabolism)
• RNA Interference
• Reverse Transcriptase Polymerase Chain Reaction
• Xenograft Model Antitumor Assays