PRKAA1 and neoplasm: Moreover, Ampk+/+ Mct4−/− MEF showed slowed tumourigenicity but not tumour growth as Ampk+/+ Mct4−/− MEFs exhibited a tumour volume of 200mm3 to 1000mm3 in 33 days (±6) and 40 days (±6), respectively (Figure 5a).