Antiandrogen Therapy Radiosensitizes Androgen Receptor-Positive Cancers to 18F-FDG

J Nucl Med. 2022 Aug;63(8):1177-1183. doi: 10.2967/jnumed.121.262958. Epub 2021 Nov 12.

Abstract

A subset (35%) of triple-negative breast cancers (TNBCs) expresses androgen receptor (AR) activity. However, clinical trials with antiandrogen drugs have shown limited efficacy, with about a 19% clinical benefit rate. We investigated the therapeutic enhancement of antiandrogens as radiosensitizers in combination with 18F-FDG in TNBC. Methods: We screened 5 candidate drugs to evaluate shared toxicity when combined with either 18F-FDG, x-rays, or ultraviolet radiation, at doses below their respective half-maximal inhibitory concentrations. Cytotoxic enhancement of antiandrogen in combination with 18F-FDG was evaluated using cell proliferation and DNA damage assays. Finally, the therapeutic efficacy of the combination treatment was evaluated in mouse tumor models of TNBC and prostate cancer. Results: Bicalutamide, an antiandrogen drug, was found to share similar toxicity in combination with either 18F-FDG or x-rays, indicating its sensitivity as a radiosensitizer to 18F-FDG. Cell proliferation assays demonstrated selective toxicity of combination bicalutamide-18F-FDG in AR-positive 22RV1 and MDA-MB-231 cells in comparison to AR-negative PC3 cells. Quantitative DNA damage and cell cycle arrest assays further confirmed radiation-induced damage to cells, suggesting the role of bicalutamide as a radiosensitizer to 18F-FDG-mediated radiation damage. Animal studies in MDA-MB-231, 22RV1, and PC3 mouse tumor models demonstrated significant attenuation of tumor growth through combination of bicalutamide and 18F-FDG in the AR-positive model in comparison to the AR-negative model. Histopathologic examination corroborated the in vitro and in vivo data and confirmed the absence of off-target toxicity to vital organs. Conclusion: These data provide evidence that 18F-FDG in conjunction with antiandrogens serving as radiosensitizers has utility as a radiotherapeutic agent in the ablation of AR-positive cancers.

Keywords: 18F-FDG; antiandrogen therapy; bicalutamide; radiosensitization.

MeSH terms

  • Androgen Antagonists* / pharmacology
  • Androgen Antagonists* / therapeutic use
  • Animals
  • Cell Line, Tumor
  • Fluorodeoxyglucose F18 / therapeutic use
  • Humans
  • Mice
  • Nitriles
  • Radiation-Sensitizing Agents* / pharmacology
  • Radiation-Sensitizing Agents* / therapeutic use
  • Receptors, Androgen / metabolism
  • Triple Negative Breast Neoplasms* / drug therapy
  • Triple Negative Breast Neoplasms* / radiotherapy
  • Ultraviolet Rays

Substances

  • Androgen Antagonists
  • Nitriles
  • Radiation-Sensitizing Agents
  • Receptors, Androgen
  • Fluorodeoxyglucose F18