High endoplasmic reticulum activity renders multiple myeloma cells hypersensitive to mitochondrial inhibitors

Cancer Chemother Pharmacol. 2010 May;66(1):129-40. doi: 10.1007/s00280-009-1143-1. Epub 2009 Sep 25.


Multiple myeloma (MM) cells continuously secrete large amounts of immunoglobulins that are folded in the endoplasmic reticulum (ER) whose function depend on the Ca(2+) concentration inside its lumen. Recently, it was shown that the ER membrane leaks Ca(2+) that is captured and delivered back by mitochondria in order to prevent its loss. Thus, we hypothesized that the highly active and abundant ER in MM cells results in greater Ca(2+)-regulation by mitochondria which would render them sensitive to mitochondrial inhibitors. Here, we indeed find that Ca(2+) leak is greater in 3 MM, when compared to 2 B-cell leukemia cell lines. Moreover, this greater leak in MM cells is associated with hypersensitivity to various mitochondrial inhibitors, including CCCP. Consistent with our hypothesis, CCCP is more potent in inducing the unfolded protein response marker, CHOP/GADD153 in MM versus B-cell leukemia lines. Additionally, MM cells are found to be significantly more sensitive to clinically used fenofibrate and troglitazone, both of which were recently shown to have inhibitory effects on mitochondrial function. Overall, our results demonstrate that the unusually high ER activity in MM cells may be exploited for therapeutic benefit through the use of mitochondrial inhibitors including troglitazone and fenofibrate.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Calcium / metabolism
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology*
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Chromans / pharmacology
  • Endoplasmic Reticulum / metabolism*
  • Fenofibrate / pharmacology
  • Humans
  • Leukemia, B-Cell / metabolism
  • Membrane Potential, Mitochondrial / drug effects
  • Mitochondria / drug effects*
  • Mitochondria / metabolism
  • Multiple Myeloma / drug therapy*
  • Multiple Myeloma / metabolism*
  • Peroxisome Proliferator-Activated Receptors / agonists*
  • Thiazolidinediones / pharmacology
  • Transcription Factor CHOP / metabolism
  • Troglitazone
  • Uncoupling Agents / pharmacology*
  • Unfolded Protein Response / drug effects


  • Antineoplastic Agents
  • Chromans
  • Peroxisome Proliferator-Activated Receptors
  • Thiazolidinediones
  • Uncoupling Agents
  • Transcription Factor CHOP
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone
  • Troglitazone
  • Calcium
  • Fenofibrate