NFKB1 and colorectal carcinoma: We have therefore analyzed the levels of CTSD in L1-overexpressing CRC cell clones in which the signaling by NF-κB was blocked, either by expressing the IκBα super repressor (IκB-SR), or by reducing the level of the p65 NF-κB subunit using shRNA to p65 (Figure 4A).