Related Experiment Video
Updated: Aug 16, 2026
Ex vivo Expansion of Tumor-reactive T Cells by Means of Bryostatin 1/Ionomycin and the Common Gamma Chain Cytokines Formulation
Published on: January 14, 2011
Dexamethasone plus retinoids decrease IL-6/IL-6 receptor and induce apoptosis in myeloma cells
1Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Abstract:
Interleukin 6 (IL-6) is the most important known growth factor for multiple myeloma, and IL-6 signalling pathways are potential targets for therapy. We hypothesized that interfering with the IL-6 signalling pathway at more than one level would be more effective than a single block in inhibiting proliferation of myeloma cells. Accumulating data support the concept that glucocorticoids down-regulate IL-6, whereas retinoic acid derivatives (RA) down-regulate IL-6R in myeloma. We found that all-trans RA (ATRA), 13-cis-RA and 9-cis-RA each similarly inhibited growth of RPMI 8226 myeloma cells and that addition of dexamethasone (DEX) added to RA growth inhibition. The major effects of retinoids were to reduce the proliferative fraction and induce apoptosis whereas DEX increased the apoptotic fraction. When combined, apoptosis was enhanced. Effects of RA + DEX were also least able to be overcome by exogenous IL-6. RA decreased IL-6R levels and addition of DEX to RA delayed recovery of IL-6R levels compared with RA alone. Since RPMI 8226 cells have undetectable IL-6, we investigated U266B1 cells and found that RA and DEX decreased both IL-6 secretion and IL-6 RNA levels. Mechanistically, IL-6R down-regulation by RA was enhanced by DEX, whereas IL-6 protein and RNA levels were reduced by DEX and by RA. In summary, combinations of RA + DEX were not only more effective in inhibiting myeloma cells growth by the dual mechanisms of decreasing proliferative fraction and increasing apoptotic fraction, but were also less able to be overcome by IL-6.
Insights
Combining retinoic acid (RA) derivatives and dexamethasone (DEX) effectively inhibits multiple myeloma cell growth by reducing proliferation and increasing apoptosis. This dual-action therapy is more potent and less susceptible to resistance from Interleukin 6 (IL-6).
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Interleukin 6 (IL-6) is a critical growth factor for multiple myeloma.
- Targeting IL-6 signaling pathways offers therapeutic potential for multiple myeloma.
- Glucocorticoids and retinoic acid (RA) derivatives have shown promise in down-regulating IL-6 and IL-6 receptor (IL-6R) respectively.
Purpose of the Study:
- To investigate the combined efficacy of RA derivatives and dexamethasone (DEX) in inhibiting multiple myeloma cell proliferation.
- To explore the synergistic effects of RA and DEX on myeloma cell growth, apoptosis, and IL-6 signaling.
- To determine if combined therapy is less susceptible to exogenous IL-6 compared to single agents.
Main Methods:
- Treatment of myeloma cell lines (RPMI 8226 and U266B1) with various RA derivatives (ATRA, 13-cis-RA, 9-cis-RA) and DEX.
- Assessment of cell proliferation, apoptosis induction, and IL-6 receptor (IL-6R) levels.
- Measurement of IL-6 secretion and RNA levels in U266B1 cells.
- Evaluation of the impact of exogenous IL-6 on the efficacy of combined RA + DEX treatment.
Main Results:
- All tested RA derivatives inhibited RPMI 8226 myeloma cell growth, an effect enhanced by DEX.
- RA primarily reduced the proliferative fraction and induced apoptosis, while DEX increased apoptosis.
- Combined RA + DEX treatment showed enhanced apoptosis and reduced myeloma cell growth.
- The combination therapy was least overcome by exogenous IL-6.
- RA decreased IL-6R levels, and DEX addition delayed IL-6R recovery.
- In U266B1 cells, RA and DEX reduced IL-6 secretion and RNA levels.
- DEX enhanced RA-mediated IL-6R down-regulation, while both reduced IL-6 protein and RNA.
Conclusions:
- Combined RA and DEX therapy demonstrates superior efficacy in inhibiting multiple myeloma cell growth compared to single agents.
- The dual mechanism of action involves decreasing the proliferative fraction and increasing apoptosis.
- This combination therapy exhibits enhanced resistance to exogenous IL-6, suggesting a more robust therapeutic strategy.
- The synergistic effects of RA and DEX on IL-6 signaling pathways warrant further investigation for multiple myeloma treatment.
More Related Videos
09:57Real Time Detection of In Vitro Tumor Cell Apoptosis Induced by CD8+ T Cells to Study Immune Suppressive Functions of Tumor-infiltrating Myeloid Cells
Published on: January 29, 2019
08:49Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries
Published on: January 22, 2019