Vitamin C supplementation expands the therapeutic window of BETi for triple negative breast cancer

Sushmita Mustafi, Vladimir Camarena, Rehana Qureshi, Hyunho Yoon, Claude Henry Volmar, Tyler C. Huff, David W. Sant, Lihong Zheng, Shaun P. Brothers, Claes Wahlestedt, Joyce Slingerland, Gaofeng Wang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Background: Bromodomain and extra-terminal inhibitors (BETi) have shown efficacy for the treatment of aggressive triple negative breast cancer (TNBC). However, BETi are plagued by a narrow therapeutic window as manifested by severe toxicities at effective doses. Therefore, it is a limitation to their clinical implementation in patient care. Methods: The impact of vitamin C on the efficacy of small compounds including BETi was assessed by high-throughput screening. Co-treatment of TNBC by BETi especially JQ1 and vitamin C was evaluated in vitro and in vivo. Findings: High-throughput screening revealed that vitamin C improves the efficacy of a number of structurally-unrelated BETi including JQ1, I-BET762, I-BET151, and CPI-203 in treating TNBC cells. The synergy between BETi and vitamin C is due to suppressed histone acetylation (H3ac and H4ac), which is in turn caused by upregulated histone deacetylase 1 (HDAC1) expression upon vitamin C addition. Treatment with JQ1 at lower doses together with vitamin C induces apoptosis and inhibits the clonogenic ability of cultured TNBC cells. Oral vitamin C supplementation renders a sub-therapeutic dose of JQ1 able to inhibit human TNBC xenograft growth and metastasis in mice. Interpretation: Vitamin C expands the therapeutic window of BETi by sensitizing TNBC to BETi. Using vitamin C as a co-treatment, lower doses of BETi could be used to achieve an increased therapeutic index in patients, which will translate to a reduced side effect profile. Fund: University of Miami Sylvester Comprehensive Cancer Center, Bankhead Coley Cancer Research program (7BC10), Flight Attendant Medical Research Institute, and NIH R21CA191668 (to GW) and 1R56AG061911 (to CW and CHV).

Original languageEnglish (US)
Pages (from-to)201-210
Number of pages10
StatePublished - May 2019


  • BET inhibitor
  • Combination therapy
  • HDAC1
  • Histone acetylation
  • Triple negative breast cancer
  • Vitamin C

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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