TEPP-46 activator stabilizes a PKM2 state unable to enter the nucleus. A), B) MDA-MB-231 cells, treated or untreated with TEPP-46 (10 uM, 20 hours), analyzed for PKM2pS37 or total PKM2 localization; Nuclear staining, Hoechst 33342 (blue); Scale bar, 20 μm. White arrows show indeterminate PKM2/PKM2pS37 formations in the cytoplasm. C) Immunoblot analysis of nuclear and cytoplasmic fractions of MDA-MB-231 cells upon TEPP-46 treatment. D) PKM2 oligomer state analysis in the cytoplasm of TEPP-46 treated cells. GA, glutaraldehyde crosslinking. E) Apoptosis and F) detection of ROS levels in TNBC cells treated with TEPP-46 (10 uM) for 20 hours. Bars, mean values, n = 3; error bars, SD; t test, *P < 0.05; ns, nonsignificant.