MAP3K14 and central nervous system cancer: Next, we investigated the effects of NIK knockdown using CRISPR/Cas9/small-guide (sg)RNA-mediated deletion of NIK. For these experiments, we took advantage of the highly invasive BT25 glioma line.3 NIK protein was no longer detectable in both untreated and TWEAK-treated BT25-sgNIK cells, indicating efficient sgRNA-mediated deletion of NIK (Figure 1d).