BRAF Inhibitors Induce Feedback Activation of RAS Pathway in Thyroid Cancer Cells.

Elisa Bonaldi,Maria Grazia Rizzetti,Arianna Micali,Loris De Cecco,Chiara Gargiuli,Maria Grazia Borrello,Angela Greco,Emanuela Minna

doi:10.3390/ijms22115744

Elisa Bonaldi, Maria Grazia Rizzetti + Show 6 more

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https://doi.org/10.3390/ijms22115744

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Abstract

BRAFV600E is the most frequent oncogenic mutation identified in papillary thyroid cancer (PTC). In PTC patients who do not respond to standard treatment, BRAF inhibitors are currently tested as alternative strategies. However, as observed for other targeted therapies, patients eventually develop drug resistance. The mechanisms of BRAF inhibitors response are still poorly understood in a thyroid cancer (TC) context. In this study, we investigated in BRAFV600E mutated TC cell lines the effects of Vemurafenib and Dabrafenib, two BRAF inhibitors currently used in a clinical setting. We assessed cell proliferation, and the expression and activity of the thyroid function related transporter NIS following the treatment with BRAF inhibitors. In addition, we investigated the global gene expression by microarray, the relevant modulated biological processes by gene set enrichment analysis (GSEA), and TC specific gene signatures related to MAPK pathway activation, thyroid differentiation, and transcriptional profile associated with BRAFV600E or RAS mutation. We found that both inhibitors induce antiproliferative and redifferentiative effects on TC cells, as well as a rewiring of the MAPK pathway related to RAS signaling. Our results suggest a possible mechanism of drug response to the BRAF inhibitors Vemurafenib or Dabrafenib, supporting very recent findings in TC patients treated with targeted therapies.

Highlights

We profiled a panel of thyroid cancer cell lines for the presence of BRAFV600E mutation, including 13 TC cell lines derived from different thyroid tumor histotypes, and Nthy-ori 3–1 cell line (Nthy) control cells derived from non-neoplastic thyroid (NT) (Table S1)
In agreement with previous reports (Table S1), the presence of BRAFV600E was confirmed in a high fraction of the tested TC cells (67%), both in homo and in heterozygosis (Figure 1A), while as expected, it was absent (BRAF wt) in the control cells Nthy
BRAFV600E distribution in human TC tissues, BRAFV600E was found in TC cells derived from papillary thyroid cancer (PTC) and anaplastic thyroid carcinoma (ATC) tissues, while it was absent in the FTC derived cell lines

Summary

Introduction

Thyroid cancer (TC) is the most common neoplasia of the endocrine system and comprises various histological types including, among others, the well differentiated papillary and follicular thyroid carcinoma (PTC and FTC, respectively) and the undifferentiated anaplastic thyroid carcinoma (ATC), which collectively account for more than 90% of all thyroid tumors [1]. BRAFV600E is the most frequently detected mutation, followed by RAS mutations, and chromosomal rearrangements of tyrosine kinase receptors (such as RET, NTRK, and ALK) [2]. A significant association among different driver mutations and histological types of thyroid carcinomas has been identified; BRAFV600E , for instance, is detected at high frequency in PTC (60–74%, [3,4])

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