Inhibition of exosome release by ketotifen enhances sensitivity of cancer cells to doxorubicin

Cancer Biol Ther. 2018 Jan 2;19(1):25-33. doi: 10.1080/15384047.2017.1394544. Epub 2017 Dec 15.


Exosomes released from cancer cells support metastasis and growth of recipient cells and increase their resistance to chemotherapy. Therapeutic targeting of exosomes is a promising area in cancer research. Our aim is to test the effect of the mast cell stabilizer ketotifen on exosomes release from cancer cells and how this can modify their response to doxorubicin. Exosomes release from three cancer cell lines (MCF7, HeLa and BT549) was assessed by scan electron microscope and exosomes quantification kit. Doxorubicin export within exosomes was monitored flurometrically and cellular sensitivity to doxorubicin ± ketotifen was measured by sulphorhodamine-B and colony formation assays. The three cell lines release different amounts of exosomes with the highest quantity released from BT549 followed by MCF7 and then HeLa. Ketotifen (10 µmol L-1) reduced exosomes release in all three cell lines with different efficiency (HeLa>MCF7>BT549). Doxorubicin export via exosomes was highest in BT549, lower in HeLa and lowest in MCF7 cells. Pretreatment with ketotifen sensitized the cells to doxorubicin (HeLa>MCF7>BT549) with a sensitization factor of 27, 8 and 1.25 respectively. Increased sensitivity of cells to doxorubicin by ketotifen was proportional to its effect on exosomes release. Our data is the first report of ketotifen modulating exosomes release from cancer cells and opens the avenue for exosomes-targeting cancer therapy. The differential effects of ketotifen on doxorubicin exosomal export in the cell lines studied, suggests an opportunity of pharmacological enhancement of doxorubicin anti-tumor activity in some but not all cancer types.

Keywords: Ketotifen; chemotherapy resistance; doxorubicin; doxorubicin efflux; exosomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibiotics, Antineoplastic / pharmacology*
  • Antibiotics, Antineoplastic / therapeutic use
  • Doxorubicin / pharmacology*
  • Doxorubicin / therapeutic use
  • Drug Resistance, Neoplasm / drug effects*
  • Exosomes / drug effects*
  • Exosomes / metabolism
  • HeLa Cells
  • Humans
  • Ketotifen / pharmacology*
  • Ketotifen / therapeutic use
  • MCF-7 Cells
  • Neoplasms / drug therapy*
  • Neoplasms / pathology


  • Antibiotics, Antineoplastic
  • Doxorubicin
  • Ketotifen

Grants and funding

AlJalila Foundation Research Center. [grant number. AJF201612]