PRKAA1 and cancer: This paradoxical effect of vemurafenib on H1299 and Sk-mel-2 cancer cell lines was blocked by the AMPK inhibitor Compound C (Fig. 4, A–F) or the shRNA-mediated knockdowns of AMPKα1, the predominant isoform of AMPKα in H1299 cells (Fig. 4, G–I).