USP9X-mediated KDM4C deubiquitination promotes lung cancer radioresistance by epigenetically inducing TGF-\u03b22 transcription

Xiaohua Jie,Rui Zhou,Tao Zhang,Gang Wu,Ye Zhao,Kunyu Yang,Shuangbing Xu,William Pat Fong,Yingchao Zhao,Rui Meng,Sheng Zhang,Xiaorong Dong

doi:10.1038/s41418-021-00740-z

Xiaohua Jie, Rui Zhou + Show 10 more

Open Access

https://doi.org/10.1038/s41418-021-00740-z

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Abstract

Radioresistance is regarded as the main barrier to effective radiotherapy in lung cancer. However, the underlying mechanisms of radioresistance remain elusive. Here, we show that lysine-specific demethylase 4C (KDM4C) is overexpressed and correlated with poor prognosis in lung cancer patients. We provide evidence that genetical or pharmacological inhibition of KDM4C impairs tumorigenesis and radioresistance in lung cancer in vitro and in vivo. Moreover, we uncover that KDM4C upregulates TGF-β2 expression by directly reducing H3K9me3 level at the TGF-β2 promoter and then activates Smad/ATM/Chk2 signaling to confer radioresistance in lung cancer. Using tandem affinity purification technology, we further identify deubiquitinase USP9X as a critical binding partner that deubiquitinates and stabilizes KDM4C. More importantly, depletion of USP9X impairs TGF-β2/Smad signaling and radioresistance by destabilizing KDM4C in lung cancer cells. Thus, our findings demonstrate that USP9X-mediated KDM4C deubiquitination activates TGF-β2/Smad signaling to promote radioresistance, suggesting that targeting KDM4C may be a promising radiosensitization strategy in the treatment of lung cancer.

Highlights

Cancer is as much a genetic disease as it is an epigenetic disease, and epigenetic alterations including histone modifications and DNA methylation are involved in tumor development and progression [1]
Using immunohistochemistry (IHC) analysis, we quantified KDM4C protein levels in a human lung cancer tissue microarray consisting of 86 fresh lung adenocarcinoma tissues matched with their adjacent nontumor tissues (NTs) and demonstrated that KDM4C localized to the nucleus and cytoplasm of cancer cells and its protein levels were considerably higher in lung cancer tissues than in adjacent NTs (Fig. 1c, d)
We provide substantial evidence that supports the novel role of KDM4C in promoting radioresistance in lung cancer

Summary

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Cancer is as much a genetic disease as it is an epigenetic disease, and epigenetic alterations including histone modifications and DNA methylation are involved in tumor development and progression [1]. Preclinical studies using LY2109761, a novel TGF-β receptor type I/II dual inhibitor, reported direct radiosensitizing effects in glioblastoma and breast cancer [18, 19]. All these studies strongly support that activation of TGF-β/Smad signaling is closely associated with cancer radioresistance. We present evidence that genetical or pharmacological inhibition of KDM4C overcomes radioresistance in lung cancer by inactivating the TGF-β2/Smad/ ATM signaling pathway. We are the first to report that the deubiquitinase USP9X is responsible for the upregulation of KDM4C in lung cancer. The reagents used were as follows: SD70 (Xcess Biosciences, M60194-b), recombinant human TGF-β2 (Abcam, ab84070), LY2109761 (Selleck, HY -12075), MG132 (Calbiochem, 474790) and cycloheximide (SigmaAldrich, A8244)

Materials and methods

Results

Discussion

Compliance with ethical standards