Repository logo

High p16 expression and heterozygous RB1 loss are biomarkers for CDK4/6 inhibitor resistance in ER+ breast cancer.

Published version



Change log


Palafox, Marta 
Monserrat, Laia 
Bellet, Meritxell 
Villacampa, Guillermo 
Gonzalez-Perez, Abel  ORCID logo


CDK4/6 inhibitors combined with endocrine therapy have demonstrated higher antitumor activity than endocrine therapy alone for the treatment of advanced estrogen receptor-positive breast cancer. Some of these tumors are de novo resistant to CDK4/6 inhibitors and others develop acquired resistance. Here, we show that p16 overexpression is associated with reduced antitumor activity of CDK4/6 inhibitors in patient-derived xenografts (n = 37) and estrogen receptor-positive breast cancer cell lines, as well as reduced response of early and advanced breast cancer patients to CDK4/6 inhibitors (n = 89). We also identified heterozygous RB1 loss as biomarker of acquired resistance and poor clinical outcome. Combination of the CDK4/6 inhibitor ribociclib with the PI3K inhibitor alpelisib showed antitumor activity in estrogen receptor-positive non-basal-like breast cancer patient-derived xenografts, independently of PIK3CA, ESR1 or RB1 mutation, also in drug de-escalation experiments or omitting endocrine therapy. Our results offer insights into predicting primary/acquired resistance to CDK4/6 inhibitors and post-progression therapeutic strategies.



Antineoplastic Agents, Biomarkers, Breast Neoplasms, Cyclin-Dependent Kinase 4, Cyclin-Dependent Kinase 6, Drug Resistance, Neoplasm, Female, Humans, Phosphatidylinositol 3-Kinases, Protein Kinase Inhibitors, Receptors, Estrogen, Retinoblastoma Binding Proteins, Ubiquitin-Protein Ligases

Journal Title

Nat Commun

Conference Name

Journal ISSN


Volume Title



Springer Science and Business Media LLC
European Commission Horizon 2020 (H2020) Research Infrastructures (RI) (731105)