Interestingly, the inhibition of CDK4/CDK6 in combination with genetic (siRNA Beclin1 or siRNA ATG5) or pharmacological (HCQ, spautin-1 or bafilomycin A1) autophagy targeting induces a synergistic anti-proliferative effect in vitro and diminishes growth of patient-derived xenografts isolated from retinoblastoma-associated protein positive (Rb+) and low-molecular-weight isoforms of cyclin E (LMWE) cytoplasmic negative (LMWE cyt−) breast cancer [146]. Here, CDK4 is linked to breast cancer.