KRAS and neoplasm: However, PDAC cells can survive in this microenvironment due to some adaptive mutations, such as mutations in TP53 and KRAS. The acidic anaerobic microenvironment is a selective pressure that allows most malignant tumor cells to survive in competition for finite substrates and living areas with normal cells, as well as to migrate, invade and metastasize more easily [19, 28, 40, 98].