AVPR2 and neoplasm: As our NDI1-HCT 116 p53−/− cells are refractory to multiple effects of metformin in vitro, we reasoned that if metformin acted directly on mitochondrial complex I within the tumor cells to reduce tumorigenesis then NDI1-HCT 116 p53−/− xenograft tumors would not be inhibited in their growth.