CDK4 and breast cancer: This effect is evident with inhibitors directed towards cyclin-dependent kinases 4 and 6 (CDK4/6) as well as phosphoinositide 3-kinase (PI3K).831,832 Metadherin (MTDH) is frequently overexpressed in aggressive breast cancer cases where the MTDH-SND1 complex decreases the presentation of tumor antigens, hindering T cell infiltration and activation.