Dominika Rittler1, Luca Hegedűs2, Tamás Garay1, József Tóvári3, Ildikó Kovács4, Balázs Döme4, Clemens Aigner2, József Tímár1, Balázs Hegedűs1,2
1 2nd Department of Pathology, Semmelweis University, Budapest
2 Department of Thoracic Surgery; Ruhrlandklinik, University Clinic Essen
3 National Institute of Oncology, Budapest
4National Koranyi Institute of TB and Pulmonology, Budapest
Introduction: BRAF mutations are one of the most common oncogenic alterations in thyroid cancer. However, mutant BRAF targeting drugs are largely ineffective. Thus, novel treatment options are needed especially against anaplastic thyroid cancer which is the most aggressive thyroid tumor with poor prognosis.
Aims: We aim to measure the therapeutic sensitivity of a novel cell line – established form the malignant pleural effusion of an anaplastic thyroid cancer patient with V600E BRAF and hTERT promoter mutations – against RAF/MEK inhibition and characterize its in vivo tumorigenicity.
Method: Cell viability, cell cycle distribution and motility was tested after treatment with BRAF- (vemurafenib, dabrafenib), panRAF- (sorafenib) and MEK-inhibitor (selumetinib) using SRB assay, image cytometry and videomicroscopy, respectively. Immunoblot assays were performed to measure Erk phosphorylation. Furthermore, a pleural carcinosis/effusion model was established by intrathoracal injection into immunocompromised mice.
Results: Higher IC50 values were measured for all inhibitors when compared to A375, a BRAF and MEK inhibition sensitive melanoma line. Of note, the activation of Erk was strongly inhibited in both following treatment. Additionally, the cell cycle showed limited response upon treatment of the anaplastic thyroid cancer line. Interestingly, the baseline proliferation was much lower in the thyroid cancer cells. In contrast, these cells migrated very fast. Importantly, combination of vemurafenib and selumetinib resulted in increased migration inhibition when compared to single treatments. In line with the high in vitro migration the thyroid cell line showed robust invasive behavior and invaded the lung, heart and muscles within two weeks after injection.
Conclusion: Patient derived tumor cell cultures might become an important tool for precision medicine. Further studies are warranted to investigate whether the in vitro impact of the BRAF/MEK combination therapy could translate to inhibition of in vivo invasion and metastasis in anaplastic thyroid cancer.
Doctoral School of Pathological Sciences