Combination Treatment with the BRAFV600E Inhibitor Vemurafenib and the BH3 Mimetic Navitoclax for BRAF-Mutant Thyroid Carcinoma.

Abstract

BACKGROUND:

Vemurafenib is a selective BRAF inhibitor (BRAFi) that has shown promising activity in BRAFV600E-positive papillary thyroid cancer (PTC). However, adverse events and resistance to a single-agent BRAFi often require discontinuation of the targeted therapy in BRAFV600E-positive PTC. Thus, this study investigated the expression of anti-apoptotic B-cell lymphoma 2 (BCL-2) family members, which are frequently overexpressed in many human cancers to inhibit apoptosis, in PTC harboring the BRAFV600E mutation after BRAFi treatment, and then evaluated the cytotoxic effects of a homology 3 domain (BH3)-mimetic in combination with a BRAFi.

METHODS:

K1 cells (BRAFV600E-positive human PTC) were treated with various concentrations of vemurafenib to investigate the effect of the BRAFi. In addition, the study analyzed the protein expression profiles of phosphorylated ERK1/2 (p-ERK 1/2) and anti-apoptotic BCL-2 family after vemurafenib treatment and selected the target anti-apoptotic protein. Antitumor effects were measured by cell counting, and effects on apoptosis were determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and Western blot analysis.

RESULTS:

At a concentration of 10 μM, vemurafenib inhibited the growth of K1 cells by 49.4%. Western blot analysis following exposure to 10 μM vemurafenib revealed that p-ERK1/2 gradually decreased over 24 hours, but the expression of B-cell lymphoma-extralarge (BCL-XL) and BCL-2 increased after 12 hours of treatment. Based on this result, the K1 cells were treated with navitoclax (BCL-2/BCL-XL inhibitor) for 24 hours up to a concentration of 4 μM, which resulted in negligible effects on cell survival. However, a combination treatment of 0.5 μM navitoclax with 1 μM vemurafenib resulted in significantly enhanced cell growth inhibition and increased apoptosis.

CONCLUSIONS:

The results of the present study show that vemurafenib increased the expression of anti-apoptotic proteins of the BCL-2 family. Thus, the combination of vemurafenib with navitoclax may be effective in BRAFV600E-positive PTC treatment.

• Authors: Ju Hye Jeong, Ji Min Oh, Shin Young Jeong, Sang-Woo Lee, Jaetae Lee, Byeong-Cheol Ahn
• Journal: Thyroid : official journal of the American Thyroid Association (Thyroid) Vol. 29 Issue 4 Pg. 540-548 (04 2019) ISSN: 1557-9077 [Electronic] United States
• PMID: 30869573 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Aniline Compounds
• Apoptosis Regulatory Proteins
• Biomarkers, Tumor
• MAS1 protein, human
• Proto-Oncogene Mas
• Sulfonamides
• Vemurafenib
• BRAF protein, human
• Proto-Oncogene Proteins B-raf
• navitoclax

Topics

• Aniline Compounds (pharmacology)
• Antineoplastic Combined Chemotherapy Protocols (pharmacology)
• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins (metabolism)
• Biomarkers, Tumor (antagonists & inhibitors, genetics)
• Carcinoma (drug therapy, enzymology, genetics, pathology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Drug Synergism
• Genetic Predisposition to Disease
• Humans
• Mutation
• Proto-Oncogene Mas
• Proto-Oncogene Proteins B-raf (antagonists & inhibitors, genetics)
• Signal Transduction
• Sulfonamides (pharmacology)
• Thyroid Neoplasms (drug therapy, enzymology, genetics, pathology)
• Vemurafenib (pharmacology)