Dual Inhibition of CDK4/6 and XPO1 Induces Senescence With Acquired Vulnerability to CRBN-Based PROTAC Drugs

Abstract

Background and aimsDespite the increasing number of treatment options available for liver cancer, only a small proportion of patients achieve long-term clinical benefits. Herein, we aim to develop new therapeutic approaches for liver cancer. MethodsA compound screen was conducted to identify inhibitors that could synergistically induce senescence when combined with CDK4/6 inhibitor. The combination effects of CDK4/6 inhibitor and XPO1 inhibitor on cellular senescence were investigated in a panel of human liver cancer cell lines and multiple liver cancer models. A senolytic-drug screen was performed to identify drugs that selectively killed senescent liver cancer cells. ResultsThe combination of CDK4/6 inhibitor and XPO1 inhibitor synergistically induces senescence of liver cancer cells in vitro and in vivo. The XPO1 inhibitor acts by causing accumulation of RB1 in the nucleus, leading to decreased E2F signaling and promoting senescence induction by the CDK4/6 inhibitor. Through a senolytic-drug screen, CRBN-based PROTAC ARV-825 was identified as an agent that can selectively kill senescent liver cancer cells. Upregulation of CRBN was a vulnerability of senescent liver cancer cells, making them sensitive to CRBN-based PROTAC drugs. Mechanistically, we find that USP2 directly interacts with CRBN, leading to the deubiquitination and stabilization of CRBN in senescent liver cancer cells. ConclusionOur study demonstrates a striking synergy in senescence induction of liver cancer cells through the combination of CDK4/6 inhibitor and XPO1 inhibitor. These findings also shed light on the molecular processes underlying the vulnerability of senescent liver cancer cells to CRBN-based PROTAC therapy.