A BET family protein degrader provokes senolysis by targeting NHEJ and autophagy in senescent cells

Masahiro Wakita,Eiji Hara,Yoshinori Imai,Tatsuyuki Matsudaira,Naoko Ohtani,Hidehisa Iwata,Akiko Takahashi,Tze Mun Loo,Shimpei Kawamoto,Tamotsu Yoshimori,Osamu Sano,Megumi Narukawa

doi:10.1038/s41467-020-15719-6

Abstract

Although cellular senescence acts primarily as a tumour suppression mechanism, the accumulation of senescent cells in vivo eventually exerts deleterious side effects through inflammatory/tumour-promoting factor secretion. Thus, the development of new drugs that cause the specific elimination of senescent cells, termed senolysis, is anticipated. Here, by an unbiased high-throughput screening of chemical compounds and a bio-functional analysis, we identify BET family protein degrader (BETd) as a promising senolytic drug. BETd provokes senolysis through two independent but integrated pathways; the attenuation of non-homologous end joining (NHEJ), and the up-regulation of autophagic gene expression. BETd treatment eliminates senescent hepatic stellate cells in obese mouse livers, accompanied by the reduction of liver cancer development. Furthermore, the elimination of chemotherapy-induced senescent cells by BETd increases the efficacy of chemotherapy against xenograft tumours in immunocompromised mice. These results reveal the vulnerability of senescent cells and open up possibilities for its control.

Highlights

Cellular senescence acts primarily as a tumour suppression mechanism, the accumulation of senescent cells in vivo eventually exerts deleterious side effects through inflammatory/tumour-promoting factor secretion
A cell viability analysis based on measurements of the ATP levels and Caspase3/7 activity revealed that 15 small molecules preferentially induce cell death in Ras-induced senescent cells, as compared to the control nonsenescent cells
All of the tested drugs certainly showed some senolytic activity, ARV825 had the strongest senolytic activity and killed senescent human diploid fibroblasts (HDFs) at a five to ten nanomolar concentration, regardless of the manner of cellular senescence induction (Fig. 1b to e, and Supplementary Fig. 1). This is consistent with the observation that the levels of the BRD3 and BRD4 bromodomain and extra-terminal domain (BET) family proteins were significantly reduced by the 10 nM ARV825 concentration treatment in senescent cells (Fig. 1c and e)

Summary

Introduction

Cellular senescence acts primarily as a tumour suppression mechanism, the accumulation of senescent cells in vivo eventually exerts deleterious side effects through inflammatory/tumour-promoting factor secretion. The elimination of chemotherapyinduced senescent cells by BETd increases the efficacy of chemotherapy against xenograft tumours in immunocompromised mice These results reveal the vulnerability of senescent cells and open up possibilities for its control. Cellular senescence primarily acts as a tumour suppression mechanism, the accumulation of senescent cells in aged tissues may eventually promote the age-related decline of organ function and/or associated diseases, such as cancer[2,3]. The blockade of BRD4, a BET family protein, by chemical inhibitors or RNA interference robustly provokes senolysis This is due, at least in part, to the combined effects of the attenuation of non-homologous end joining (NHEJ) repair and the activation of autophagic pathway in senescent cells. These results reveal the cellular vulnerability of senescent cells, and provide valuable insights into the resistance of senescent cells to death and possibilities for its control

Methods

Results

Conclusion