Calcium and P-glycoprotein independent synergism between schweinfurthins and verapamil

Ryan M. Sheehy, Craig H. Kuder, Zoe Bachman, Raymond J. Hohl

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Schweinfurthins are intriguing natural products with anti-cancer activities and as yet incompletely understood mechanisms of action. We investigated whether inhibitors of P-glycoprotein (Pgp), in a manner analogous to other natural products, might enhance schweinfurthins’ growth inhibitory actions by increasing intracellular schweinfurthin levels. Both the schweinfurthin-sensitive glioblastoma multiforme cell line SF-295 and relatively insensitive lung carcinoma cell line A549 were treated with 2 schweinfurthin analogs: 3-deoxyschweinfurthin B-pnitro bis-stilbene (3dSB-PNBS) and 50-methylschweinfurthin G (methyl-G). There was a synergistic enhancement of growth inhibition with the combination of the Pgp inhibitor verapamil and both analogs in SF-295 cells. Methyl-G, verapamil, and the combination did not result in alterations to intracellular calcium concentration. Verapamil increased the intracellular concentration of 3dSB-PNBS in both SF-295 and A549 cells in a Pgp-independent manner. Methyl-G, verapamil, and the combination do not result in increased ER stress. Methyl-G increased the intracellular concentration of a known Pgp substrate, Rhodamine 123 in SF-295 cells. Reduction of cellular cholesterol leads to the accumulation of Pgp substrates, as Pgp requires cholesterol for proper function. Since 3dSB enhances lovastatin-induced upregulation of the cholesterol efflux pump ABCA1, it is intriguing that cotreatment with cholesterol rescued the methyl-G-induced increase in Rhodamine 123 intracellular concentration. These studies support the hypothesis that verapamil potentiates the schweinfurthin growth inhibitory effect by increasing its intracellular concentration.

Original languageEnglish (US)
Pages (from-to)1259-1268
Number of pages10
JournalCancer Biology and Therapy
Volume16
Issue number8
DOIs
StatePublished - Jan 1 2015

Fingerprint

P-Glycoprotein
Verapamil
Calcium
Cholesterol
Rhodamine 123
Stilbenes
Biological Products
Growth
Lovastatin
Glioblastoma
Up-Regulation
Carcinoma
Cell Line
Lung
Neoplasms

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Oncology
  • Pharmacology
  • Cancer Research

Cite this

Sheehy, Ryan M. ; Kuder, Craig H. ; Bachman, Zoe ; Hohl, Raymond J. / Calcium and P-glycoprotein independent synergism between schweinfurthins and verapamil. In: Cancer Biology and Therapy. 2015 ; Vol. 16, No. 8. pp. 1259-1268.
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Calcium and P-glycoprotein independent synergism between schweinfurthins and verapamil. / Sheehy, Ryan M.; Kuder, Craig H.; Bachman, Zoe; Hohl, Raymond J.

In: Cancer Biology and Therapy, Vol. 16, No. 8, 01.01.2015, p. 1259-1268.

Research output: Contribution to journalArticle

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