Naringenin prevents TGF-β1 secretion from breast cancer and suppresses pulmonary metastasis by inhibiting PKC activation

Breast Cancer Res. 2016 Apr 1;18(1):38. doi: 10.1186/s13058-016-0698-0.

Abstract

Background: Targeting the TGF-β1 pathway for breast cancer metastasis therapy has become an attractive strategy. We have previously demonstrated that naringenin significantly reduced TGF-β1 levels in bleomycin-induced lung fibrosis and effectively prevented pulmonary metastases of tumors. This raised the question of whether naringenin can block TGF-β1 secretion from breast cancer cells and inhibit their pulmonary metastasis.

Methods: We transduced a lentiviral vector encoding the mouse Tgf-β1 gene into mouse breast carcinoma (4T1-Luc2) cells and inoculated the transformant cells (4T1/TGF-β1) into the fourth primary fat pat of Balb/c mice. Pulmonary metastases derived from the primary tumors were monitored using bioluminescent imaging. Spleens, lungs and serum (n = 18-20 per treatment group) were analyzed for immune cell activity and TGF-β1 level. The mechanism whereby naringenin decreases TGF-β1 secretion from breast cancer cells was investigated at different levels, including Tgf-β1 transcription, mRNA stability, translation, and extracellular release.

Results: In contrast to the null-vector control (4T1/RFP) tumors, extensive pulmonary metastases derived from 4T1/TGF-β1 tumors were observed. Administration of the TGF-β1 blocking antibody 1D11 or naringenin showed an inhibition of pulmonary metastasis for both 4T1/TGF-β1 tumors and 4T1/RFP tumors, resulting in increased survival of the mice. Compared with 4T1/RFP bearing mice, systemic immunosuppression in 4T1/TGF-β1 bearing mice was observed, represented by a higher proportion of regulatory T cells and myeloid-derived suppressor cells and a lower proportion of activated T cells and INFγ expression in CD8(+) T cells. These metrics were improved by administration of 1D11 or naringenin. However, compared with 1D11, which neutralized secreted TGF-β1 but did not affect intracellular TGF-β1 levels, naringenin reduced the secretion of TGF-β1 from the cells, leading to an accumulation of intracellular TGF-β1. Further experiments revealed that naringenin had no effect on Tgf-β1 transcription, mRNA decay or protein translation, but prevented TGF-β1 transport from the trans-Golgi network by inhibiting PKC activity.

Conclusions: Naringenin blocks TGF-β1 trafficking from the trans-Golgi network by suppressing PKC activity, resulting in a reduction of TGF-β1 secretion from breast cancer cells. This finding suggests that naringenin may be an attractive therapeutic candidate for TGF-β1 related diseases.

Keywords: Breast cancer metastasis; Naringenin; PKC activation; TGF-β1 secretion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cell Line, Tumor
  • Disease Models, Animal
  • Female
  • Flavanones / administration & dosage*
  • Humans
  • Lung Neoplasms / drug therapy
  • Lung Neoplasms / pathology
  • Lung Neoplasms / secondary
  • Mammary Neoplasms, Animal / drug therapy*
  • Mammary Neoplasms, Animal / metabolism
  • Mammary Neoplasms, Animal / pathology
  • Mice
  • Neoplasm Metastasis
  • Signal Transduction / drug effects
  • Transforming Growth Factor beta1 / antagonists & inhibitors
  • Transforming Growth Factor beta1 / genetics
  • Transforming Growth Factor beta1 / metabolism*

Substances

  • Flavanones
  • Transforming Growth Factor beta1
  • naringenin