CREB1 and lung cancer: Since all three dephosphorylated, nuclear CRTCs can be detected in LKB1-deficient cells that are capable of co-activating CREB-mediated transcription, we would need to inactivate each gene individually or all three together to determine the contribution of the CRTC co-activation to the transcriptional program in lung cancer cells with LKB1 deficiency.