The second hypothesis seems much more likely as suggested by: i) our findings showing increased B-Raf expression in thyroid cancer cells lentivirally transduced with IRF5; ii) the protective effect of IRF5 on thyroid cells exposed to different cytotoxic drugs; iii) the reduced colony-forming potential of malignant thyrocytes displaying reduced IRF5 levels. Here, BRAF is linked to thyroid gland carcinoma.