Effects and mechanisms of total flavonoids of Astragali Radix and calycosin on inhibiting human erythroleukemia cell line K562 Studies of apoptosis on K562 cell line induced by pseudolaric acid B in vitro Experimental study on K562 cell apoptosis induced by toosendanin extracts Effect of combined administration of Angelica polysaccharide and cytarabine on liver of human leukemia NOD/SCID mouse model