a, Mammosphere assay in TNBC cells. MDA-MB-231, GILM2 and BT20 TNBC cells were cultured in ultra-low attachment plates in normal (control) or methionine-free mammosphere growth media (0% Met) with or without SAM (100 μM). Top panel, representative images showing mammospheres at day 7. Bottom panel, mammospheres were scored in ten fields from each well (mean ± SEM, n =3) *, P < 0.05, ***, P < 0.001 versus mammospheres cultured in control media without SAM. b, Flow cytometry analysis of CD44 and CD24 expression in primary mammospheres from TNBC cells grown for 6 days in control or methionine-free media with or without SAM (100 μM).