MDM2 and cancer: On the other hand, circPCSK6—through mmu-miR-7033-5p, mmu-miR-667-5p, mmu-miR-191-3p, mmu-miR-3073a-3p, and mmu-miR-6989-3p—controls the expression of: (i) MDM2, which acts on respiratory complex I activity enhancing mitochondrial ROS production [56]; (ii) HIF-1α, involved in the prevention of oxidative stress-induced apoptosis [57]; and (iii) the ROS-induced transcription factors NFR1, which regulates ROS signaling underpinning cancer cell survival [58].