CSF1R and breast cancer: (−)KU mainly binds to colony-stimulating factor 1 receptor (CSF1R) to suppress breast cancer proliferation [12], while some trans-(−)-kusunokinin and trans-(+)-isoforms could inhibit intracellular proteins, such as heat-shock protein 90 alpha (Hsp90-α) and aldo-keto reductase family 1 member B1 (AKR1B1) [13].