CSF1R and breast cancer: The work concluded that (1) W550 is the selective residue determine the kusunokinin enantiomer residence time within the CSF1R binding pocket and (2) the trans-(–) isomer was the main active component within the trans-(±)-kusunokinin racemic mixture which exhibited anticancer activities via binding and inhibition of CSF1R, while trans-(+) isomer possibly targeted additional molecules in breast cancer progression pathways.