Targeting Squalene Epoxidase Interrupts Homologous Recombination via the ER Stress Response and Promotes Radiotherapy Efficacy

Zhipeng Hong, Tao Liu, Lingfeng Wan, Pengyan Fa, Pankaj Kumar, Yanan Cao, Chandra Bhushan Prasad, Zhaojun Qiu, Joseph Liu, Hongbing Wang, Zaibo Li, Qi En Wang, Peixuan Guo, Deliang Guo, Ayse S. Yilmaz, Lanchun Lu, Ioanna Papandreou, Naduparambil K. Jacob, Chunhong Yan, Xiaoli ZhangQing Bai She, Zhefu Ma, Junran Zhang

Research output: Contribution to journalArticlepeer-review

Abstract

Over 50% of all patients with cancer are treated with radiotherapy. However, radiotherapy is often insufficient as a monotherapy and requires a nontoxic radiosensitizer. Squalene epoxidase (SQLE) controls cholesterol biosynthesis by converting squalene to 2,3-oxidosqualene. Given that SQLE is frequently overexpressed in human cancer, this study investigated the importance of SQLE in breast cancer and non-small cell lung cancer (NSCLC), two cancers often treated with radiotherapy. SQLE-positive IHC staining was observed in 68% of breast cancer and 56% of NSCLC specimens versus 15% and 25% in normal breast and lung tissue, respectively. Importantly, SQLE expression was an independent predictor of poor prognosis, and pharmacologic inhibition of SQLE enhanced breast and lung cancer cell radiosensitivity. In addition, SQLE inhibition enhanced sensitivity to PARP inhibition. Inhibition of SQLE interrupted homologous recombination by suppressing ataxia-telangiectasia mutated (ATM) activity via the translational upregulation of wild-type p53-induced phosphatase (WIP1), regardless of the p53 status. SQLE inhibition and subsequent squalene accumulation promoted this upregulation by triggering the endoplasmic reticulum (ER) stress response. Collectively, these results identify a novel tumor-specific radiosensitizer by revealing unrecognized cross-talk between squalene metabolites, ER stress, and the DNA damage response. Although SQLE inhibitors have been used as antifungal agents in the clinic, they have not yet been used as antitumor agents. Repurposing existing SQLE-inhibiting drugs may provide new cancer treatments. Significance: Squalene epoxidase inhibitors are novel tumor-specific radiosensitizers that promote ER stress and suppress homologous recombination, providing a new potential therapeutic approach to enhance radiotherapy efficacy.

Original languageEnglish (US)
Pages (from-to)1298-1312
Number of pages15
JournalCancer Research
Volume82
Issue number7
DOIs
StatePublished - Apr 1 2022

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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