Inhibition of BRAF and ERK1/2 has synergistic effects on thyroid cancer growth in vitro and in vivo

Mol Carcinog. 2021 Mar;60(3):201-212. doi: 10.1002/mc.23284.

Abstract

Mutations in the BRAF gene are highly prevalent in thyroid cancer. However, the response rate of thyroid tumors to BRAF-directed therapies has been mixed. Increasingly, combination therapies inhibiting the MAPK pathway at multiple nodes have shown promise. Recently developed ERK1/2 inhibitors are of interest for use in combination therapies as they have the advantage of inhibiting the most downstream node of the MAPK pathway, therefore preventing pathway reactivation. Here, we examined the effect of combined BRAF inhibition (dabrafenib) and ERK1/2 inhibition (SCH772984) on the growth and survival of a panel of BRAF-mutant thyroid cancer cell lines using in vitro and in vivo approaches. We found that resistance due to MAPK pathway reactivation occurs quickly with single-agent BRAF inhibition, but can be prevented with combined BRAF and ERK1/2 inhibition. Combined inhibition also results in synergistic growth inhibition, decreased clonogenic survival, and enhanced induction of apoptosis in a subset of BRAF-mutant thyroid cancer cells. Finally, combined inhibition of BRAF and ERK1/2 results in enhanced inhibition of tumor growth in an anaplastic thyroid cancer in vivo model. These results provide key rationale to pursue combined BRAF and ERK1/2 inhibition as an alternative therapeutic strategy for BRAF-mutant advanced thyroid cancer patients.

Keywords: BRAF; ERK; MAPK; therapy resistance; thyroid cancer.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Apoptosis / drug effects
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / drug effects
  • Drug Synergism
  • Female
  • Humans
  • Imidazoles / administration & dosage
  • Imidazoles / pharmacology
  • Indazoles / administration & dosage
  • Indazoles / pharmacology
  • MAP Kinase Signaling System / drug effects
  • Mice
  • Mice, Nude
  • Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinase 3 / antagonists & inhibitors*
  • Mutation
  • Oximes / administration & dosage
  • Oximes / pharmacology
  • Piperazines / administration & dosage
  • Piperazines / pharmacology
  • Protein Kinase Inhibitors / pharmacology
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
  • Thyroid Neoplasms / drug therapy*
  • Thyroid Neoplasms / metabolism
  • Thyroid Neoplasms / pathology
  • Xenograft Model Antitumor Assays

Substances

  • Imidazoles
  • Indazoles
  • Oximes
  • Piperazines
  • Protein Kinase Inhibitors
  • SCH772984
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • MAPK1 protein, human
  • MAPK3 protein, human
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • dabrafenib