Abstract 4322: Kinase activity profiles distinguish papillary thyroid cancers with and without BRAF V600E mutations

Abstract

Abstract Background: Most differentiated non medullary thyroid cancers (DTC) are curatively treated by surgery and radio-active iodine ablation therapy. A subset of patients shows recurrence due to a loss of iodine transport. Two main subgroups of recurrent DTC are seen: papillary thyroid cancers (PTC) with somatic BRAF mutations (V600E) and oncocytic follicular cancer. Recurrent DTC are clinically treated by multi-kinase inhibitors such as sorafenib, with a low affinity for BRAF V600E. Vemurafenib and dabrafenib were specifically designed against this mutant. The aim of this study was twofold: - Can benign and malign DTC be classified based on kinase activity profiles? - Do sorafenib (and regorafenib) show different inhibition profiles than dabrafenib? Methods: Tissue cryosections from fresh frozen thyroid tumors were lysed. All tumor specimens were analyzed for BRAF mutations. Serine/threonine kinase (STK) activity profiles of the lysates (0.5 μg protein per array) were generated on PamChip® peptide microarrays, comprising peptide sequences from known human phosphorylation sites. The ex vivo effect of BRAF inhibitors sorafenib, regorafenib and dabrafenib on kinase activity profiles of 14 PTC's was determined as well. Data were analysed with Bionavigator software. Results: A classifier built on the STK kinase activity profiles of 57 thyroid cancer samples was able to classify malignant and benign tumors with a limited error rate. Leave One Out Cross Validation classified 26/35 of malignant and 17/22 of benign samples correctly. Kinase inhibition profiles of PTC's with sorafenib and regorafenib did not discrimate V600E mutants from wild type tumors whereas with dabrafenib 34/144 peptides were identified that potentially differentiated the groups. Conclusions: Serine/threonine kinase activity profiling appears to be able to differentiate benign and malignant thyroid tumors. Ex vivo spiking in of kinase inhibitors shows differential inhibition in tumors with a somatic BRAF mutation. Potentially, an industrial prediction platform can be envisioned for testing of novel drugs in tumor tissue. Whether individual patient responses against registered kinase inhibitors can be predicted must be investigated. Citation Format: Maria H. Hilhorst, Adrienne van den Berg, Tom van Wezel, Tim Kievits, Piet J. Boender, Rik de Wijn, Rob Ruijtenbeek, Wim Corver, Hans Morreau. Kinase activity profiles distinguish papillary thyroid cancers with and without BRAF V600E mutations. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4322. doi:10.1158/1538-7445.AM2015-4322