KEAP1/CUL3/RBX1 E3-ligase protein complex. (A) KEAP1/CUL3/RBX1 E3-ligase protein complex exert different functions under physiological and oxidative conditions. In the absence of oxidative stress (left path), NRF2 protein level and activity is maintained at low levels through interaction with the KEAP1/CUL3/RBX1 E3-ubiquitin ligase complex. When NRF2 interacts with KEAP1, it is targeted for ubiquitination and proteasomal degradation. Under oxidative conditions (middle path), KEAP1 undergoes conformational changes, which impedes interaction with NRF2, resulting in its accumulation and translocation to the nucleus. When the KEAP1/CUL3/RBX1 E3-ubiquitin ligase complex is disrupted by absence or alteration of any of its components (right path), NRF2 is stabilized, accumulated and translocate to the nucleus. In the nucleus, NRF2 can induce expression of genes containing NRF2-regulatory sequence motifs (e.g., antioxidant response elements, AREs). Constitutive activation of NRF2, as a result of complex disruption, has been linked to tumor promotion. (B) On the left: expression levels of NFE2L2 gene in normal thyroid (grey) and tumors (black). Levels of NFE2L2 were significantly higher (p < 0.0001, Mann Whitney test) in tumors compared with normal tissue. On the right: Comparison of mRNA expression levels between samples carrying BRAF V600E mutation (red) versus those without alteration (black) (C) Different types of DNA level alterations affecting each individual complex. Figure shows the patterns and frequency of DNA copy number losses (black), hypermethylation (grey), and mutation (red) affecting each complex component (D) Status of individual complex components across a panel of 310 PTC tumors. Each row represents an individual complex component affected by any disrupting mechanisms: CUL3 (green), KEAP1 (purple), and/or RBX1 (blue). Presence of any alteration on an individual complex component is showed in red.