GAS6 and cancer: Whereas vitamin K intake, primarily vitamin K2 (menaquinones), is mostly associated with anti-cancer effects [10], the tumour- and thrombosis-promoting properties of Gas6 raise a concern as to whether vitamin K can be safely used in patients with cancer and increased risk for thromboembolism, many of whom have signs of vitamin K deficiency with increased plasma markers for decarboxylated Gla proteins [2,10].