Selective Pharmacologic Inhibition of c-Jun NH2-Terminal Kinase Radiosensitizes Thyroid Anaplastic Cancer Cell Lines via Induction of Terminal Growth Arrest

Abstract

The high radioresistance of anaplastic thyroid cancer (ATC) and cultured ATC cells stipulates for the means of increasing their radiosensitivity. It has been shown that c-Jun NH(2)-terminal kinase (JNK) activation is one of the manifestations of radiation response in ATC cells. Assessment of the effect of selective JNK inhibition on ATC cell radiosensitivity and clarification of the associated mechanisms. The JNK inhibitor markedly suppressed ATC cell growth in a reversible cytostatic manner. The combination treatment with JNK inhibitor plus ionizing radiation induced a significant decrease in clonogenic survival of irradiated cells as compared with either singular treatment. The effect was not due to apoptosis of exposed cells but to a profound senescence-like terminal growth arrest occurring irrespectively of cells' p53 mutational status. Postradiational DNA damage repair was also significantly compromised in the presence of SP600125. JNK signaling is an essential component of ATC cell proliferation and survival after radiation therapy. Hence, pharmacological interference with JNK pathway in combination with radiotherapy may be a promising treatment of ATC.