Hypoxia-induced exosomes contribute to a more aggressive and chemoresistant ovarian cancer phenotype: a novel mechanism linking STAT3/Rab proteins

Oncogene. 2018 Jul;37(28):3806-3821. doi: 10.1038/s41388-018-0189-0. Epub 2018 Apr 11.

Abstract

Hypoxia-mediated tumor progression, metastasis, and drug resistance are major clinical challenges in ovarian cancer. Exosomes released in the hypoxic tumor microenvironment may contribute to these challenges by transferring signaling proteins between cancer cells and normal cells. We observed that ovarian cancer cells exposed to hypoxia significantly increased their exosome release by upregulating Rab27a, downregulating Rab7, LAMP1/2, NEU-1, and also by promoting a more secretory lysosomal phenotype. STAT3 knockdown in ovarian cancer cells reduced exosome release by altering the Rab family proteins Rab7 and Rab27a under hypoxic conditions. We also found that exosomes from patient-derived ascites ovarian cancer cell lines cultured under hypoxic conditions carried more potent oncogenic proteins-STAT3 and FAS that are capable of significantly increasing cell migration/invasion and chemo-resistance in vitro and tumor progression/metastasis in vivo. Hypoxic ovarian cancer cells derived exosomes (HEx) are proficient in re-programming the immortalized fallopian tube secretory epithelial cells (FT) to become pro-tumorigenic in mouse fallopian tubes. In addition, cisplatin efflux via exosomes was significantly increased in ovarian cancer cells under hypoxic conditions. Co-culture of HEx with tumor cells led to significantly decreased dsDNA damage and increased cell survival in response to cisplatin treatment. Blocking exosome release by known inhibitor Amiloride or STAT3 inhibitor and treating with cisplatin resulted in a significant increase in apoptosis, decreased colony formation, and proliferation. Our results demonstrate that HEx are more potent in augmenting metastasis/chemotherapy resistance in ovarian cancer and may serve as a novel mechanism for tumor metastasis, chemo-resistance, and a point of intervention for improving clinical outcomes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Movement / physiology
  • Cell Proliferation / drug effects
  • Cell Proliferation / physiology
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Cisplatin / pharmacology
  • Disease Progression
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / physiology*
  • Exosomes / drug effects
  • Exosomes / metabolism*
  • Exosomes / pathology
  • Female
  • Humans
  • Hypoxia / drug therapy
  • Hypoxia / metabolism*
  • Hypoxia / pathology
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Neoplasm Metastasis / pathology
  • Ovarian Neoplasms / metabolism*
  • Ovarian Neoplasms / pathology
  • Phenotype
  • STAT3 Transcription Factor / metabolism*
  • rab GTP-Binding Proteins / metabolism*

Substances

  • STAT3 Transcription Factor
  • STAT3 protein, human
  • rab GTP-Binding Proteins
  • Cisplatin