scm is a rich source of growth factors and initial observations suggested that its 'epo-like ' activity could be attributed to : ( 1 ) epo , or ( 2 ) a factor which enhances the activity of small amounts of epo in the culture medium , or ( 3 ) a factor ( s ) distinct from epo which is also capable of stimulating late erythroid differentiation .
C0007634
scm
C0007589
differentiation