Targeting of the E3 ubiquitin-protein ligase HUWE1 impairs DNA repair capacity and tumor growth in preclinical multiple myeloma models

Viktoria Kunz,Daniel Schwinning,Jessica Kruk,Manik Chatterjee,Kathryn S Bommert,Thorsten Stühmer,Ralf Bargou,Kurt Bommert

doi:10.1038/s41598-020-75499-3

Viktoria Kunz, Daniel Schwinning + Show 6 more

Open Access

https://doi.org/10.1038/s41598-020-75499-3

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Abstract

Experimental evidence suggests that ubiquitin-protein ligases regulate a number of cellular processes involved in tumorigenesis. We analysed the role of the E3 ubiquitin-protein ligase HUWE1 for pathobiology of multiple myeloma (MM), a still incurable blood cancer. mRNA expression analysis indicates an increase in HUWE1 expression levels correlated with advanced stages of myeloma. Pharmacologic as well as RNAi-mediated HUWE1 inhibition caused anti-proliferative effects in MM cell lines in vitro and in an MM1.S xenotransplantation mouse model. Cell cycle analysis upon HUWE1 inhibition revealed decreased S phase cell fractions. Analyses of potential HUWE1-dependent molecular functions did not show involvement in MYC-dependent gene regulation. However, HUWE1 depleted MM cells displayed increased DNA tail length by comet assay, as well as changes in the levels of DNA damage response mediators such as pBRCA1, DNA-polymerase β, γH2AX and Mcl-1. Our finding that HUWE1 might thus be involved in endogenous DNA repair is further supported by strongly enhanced apoptotic effects of the DNA-damaging agent melphalan in HUWE1 depleted cells in vitro and in vivo. These data suggest that HUWE1 might contribute to tumour growth by endogenous repair of DNA, and could therefore potentially be exploitable in future treatment developments.

Highlights

Multiple myeloma (MM) remains a largely incurable B cell cancer requiring further efforts to better understand its pathobiology
We have investigated the Homologous to E6-AP Carboxyl Terminus (HECT)-E3 ligase HUWE1, which has been implicated in a number of oncogenic processes such as MYC r egulation[6,7] and DNA damage response (DDR)[6,12,17], for its role in multiple myeloma
HUWE1 expression at either RNA- or protein level was detected in every MM cell line tested, which is in accordance with its pattern of ubiquitous expression in either normal or cancer tissue

Summary

Introduction

Multiple myeloma (MM) remains a largely incurable B cell cancer requiring further efforts to better understand its pathobiology. Dependency on the ubiquitin–proteasome system is considered to be a hallmark of this disease affecting multiple critical cellular processes including cell cycle and apoptosis regulation, DNA damage. MM PCL β-tubulin repair or development of drug resistance[13,14,15]. Some of the most successful recent therapeutic approaches are targeting this system, e.g. proteasome inhibitors and cereblon-binding IMiDs. our current knowledge about E3 ubiquitin-protein ligases, a critical but complex component of the ubiquitin–proteasome system, and their potential role for MM pathobiology, is still limited. We ask whether HUWE1 might contribute to the malignant phenotype of MM, and investigate its role for malignant growth, MYC-dependent gene regulation and the DDR

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