Utilizing CD44v6 and V600EBRAF-mutation for in vitro targeted combination therapy of thyroid carcinomas
Anja C. Mortensen, Juliana Imgenberg‐Kreuz, Diana Spiegelberg, Johan Botling, Marika Nestor
Abstract
Aim The aim of this study was to assess the feasibility of targeted therapy of thyroid carcinoma, first exploring potential targets BRAF, EGFR and CD44v6 in patient material through immunohostochemistry and mutation analysis. Materials and methods A patient cohort (n = 22) consisting of seven papillary (PTC), eight anaplastic (ATC) and seven follicular (FTC) thyroid carcinomas were evaluated. Additionally, eight thyroid carcinoma cells lines were analyzed for CD44v6-expression and sensitivity to the multi-kinase inhibitor sorafenib (Nexavar®), which targets numerous serine/threonine and tyrosine kinases, including the Raf family kinases. Targeted therapy using 131 I-AbN44v6, a novel anti-CD44v6 antibody, and/or sorafenib was evaluated in 3D multicellular tumor spheroids. Results Of the two cell surface proteins, EGFR and CD44v6, the latter was overexpressed >80 % of samples, while EGFR-expression levels were moderate at best in only a few samples. BRAF mutations were more common in PTC patient samples than in ATC samples, while FTC samples did not harbor BRAF mutations. CD44v6-expression levels in the thyroid carcinoma cell lines were more heterogenous compared to patient samples, while BRAF mutational status was in line with the original tumor type. Monotherapy in 3D multicellular ATC tumor spheroids with either 131 I-AbN44v6 or sorafenib resulted in delayed spheroid growth. The combination of 131 I-AbN44v6 and sorafenib was more potent and resulted in significantly impaired spheroid growth. Conclusion This "proof of concept" targeted therapy study in the in vitro ATC 3D multicellular tumor spheroids indicated applicability of utilizing CD44v6 for molecular radiotherapy both as a monotherapy and in combination with sorafenib.