Hyperactive ERK and Persistent mTOR Signaling Characterize Vemurafenib Resistance in Papillary Thyroid Cancer Cells

Authors

Elyse Hanly
Neha Y. Tuli
Robert B. Bednarczyk
Robert Suriano, New York Medical CollegeFollow
Jan Geliebter, New York Medical CollegeFollow
Augustine L. Moscatello, New York Medical CollegeFollow
Zbigniew Darzynkiewicz, New York Medical CollegeFollow
Raj K. Tiwari, New York Medical CollegeFollow

First Page

8676

Last Page

8687

Document Type

Article

Publication Date

2-23-2016

Department

Pathology, Microbiology and Immunology

Second Department

Otolaryngology

Third Department

Pathology, Microbiology and Immunology

Abstract

Clinical studies evaluating targeted BRAFV600E inhibitors in advanced thyroid cancer patients are currently underway. Vemurafenib (BRAFV600E inhibitor) monotherapy has shown promising results thus far, although development of resistance is a clinical challenge. The objective of this study was to characterize development of resistance to BRAFV600E inhibition and to identify targets for effective combination therapy. We created a line of BCPAP papillary thyroid cancer cells resistant to vemurafenib by treating with increasing concentrations of the drug. The resistant BCPAP line was characterized and compared to its sensitive counterpart with respect to signaling molecules thought to be directly related to resistance. Expression and phosphorylation of several critical proteins were analyzed by Western blotting and dimerization was evaluated by immunoprecipitation. Resistance to vemurafenib in BCPAP appeared to be mediated by constitutive overexpression of phospho-ERK and by resistance to inhibition of both phospho-mTOR and phospho-S6 ribosomal protein after vemurafenib treatment. Expression of potential alternative signaling molecule, CRAF, was not increased in the resistant line, although formation of CRAF dimers appeared increased. Expression of membrane receptors HER2 and HER3 was greatly amplified in the resistant cancer cells. Papillary thyroid cancer cells were capable of overcoming targeted BRAFV600E inhibition by rewiring of cell signal pathways in response to prolonged vemurafenib therapy. Our study suggests that in vitro culture of cancer cells may be useful in assessing molecular resistance pathways. Potential therapies in advanced thyroid cancer patients may combine vemurafenib with inhibitors of CRAF, HER2/HER3, ERK, and/or mTOR to delay or abort development of resistance.

Recommended Citation

Hanly, E. K., Tuli, N. Y., Bednarczyk, R. B., Suriano, R., Geliebter, J., Moscatello, A. L., et al. (2016). Hyperactive ERK and persistent mTOR signaling characterize vemurafenib resistance in papillary thyroid cancer cells. Oncotarget, 7(8), 8676-8687, doi: 10.18632/oncotarget.6779

Publisher's Statement

Originally published in Oncotarget. Licensed under CC-BY 4.0. https://doi.org/10.18632/oncotarget.6779