Interestingly, although lactate production diminished, intracellular accumulation of this metabolite was increased (Fig 4B), a result consistent with the reduced expression of MCT-1 (SLC16A1, proton coupled monocarboxylate transporter 1) in Doxy-treated mammospheres (Fig 4D), the major lactate transporter in tumor cells [42]. Here, SLC16A1 is linked to neoplasm.