The drug efflux pump MDR1 promotes intrinsic and acquired resistance to PROTACs in cancer cells

Alison M. Kurimchak, Carlos Herrera-Montávez, Sara Montserrat-Sangrà, Daniela Araiza-Olivera, Jianping Hu, Ryan Neumann-Domer, Mathew Kuruvilla, Alfonso Bellacosa, Joseph R. Testa, Jian Jin, James S. Duncan

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Proteolysis-targeting chimeras (PROTACs) are a promising new class of drugs that selectively degrade cellular proteins of interest. PROTACs that target oncogene products are avidly being explored for cancer therapies, and several are currently in clinical trials. Drug resistance is a substantial challenge in clinical oncology, and resistance to PROTACs has been reported in several cancer cell models. Here, using proteomic analysis, we found intrinsic and acquired resistance mechanisms to PROTACs in cancer cell lines mediated by greater abundance or production of the drug efflux pump MDR1. PROTAC-resistant cells were resensitized to PROTACs by genetic ablation of ABCB1 (which encodes MDR1) or by coadministration of MDR1 inhibitors. In MDR1-overexpressing colorectal cancer cells, degraders targeting either the kinases MEK1/2 or the oncogenic mutant GTPase KRASG12C synergized with the dual epidermal growth factor receptor (EGFR/ErbB)/MDR1 inhibitor lapatinib. Moreover, compared with single-agent therapies, combining MEK1/2 degraders with lapatinib improved growth inhibition of MDR1-overexpressing KRAS-mutant colorectal cancer xenografts in mice. Together, our findings suggest that concurrent blockade of MDR1 will likely be required with PROTACs to achieve durable protein degradation and therapeutic response in cancer.

Original languageEnglish
Article numbereabn2707
JournalScience Signaling
Issue number749
StatePublished - 30 Aug 2022


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