PRKAA1 and cancer: However, even if NBR2 promotes energy-induced AMPK activation through direct interaction, the interaction of NBR2 with AMPK is not influenced by phenformin, and phenformin induces AMPK activation independent of NBR2. On the other hand, NBR2 deficiency suppresses glucose uptake through the inhibition of phenformin-induced GLUT1 expression, which is the glucose transporter with the most relevance to cancer biology, as it is overexpressed in many human cancers.