Oleanane triterpenoid CDDO-Me induces apoptosis in multidrug resistant osteosarcoma cells through inhibition of Stat3
Keinosuke Ryu1, Michiro Susa, Edwin Choy
1Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA 02114, USA.
Background:
The activation of signal transducer and activator of transcription 3 (Stat3) pathway correlates with tumor growth, survival, drug resistance and poor prognosis in osteosarcoma. To explore the potential therapeutic values of this pathway, we assessed both the expression and the activation of Stat3 pathway in several pairs of multidrug resistant (MDR) osteosarcoma cell lines, and tissues. To explore the potential therapeutic values of this pathway, we analyzed the ability of the synthetic oleanane triterpenoid, C-28 methyl ester of 2-cyano-3,12-dioxoolen-1,9-dien-28-oic acid (CDDO-Me), to inhibit Stat3 expression and activation as well as its effects on doxorubicin sensitivity in osteosarcoma cells.
Methods:
Expression of Stat3, phosphorylated Stat3 (pStat3) and Stat3 targeted proteins, including Bcl-XL, Survivin and MCL-1 were determined in drug sensitive and MDR osteosarcoma cell lines and tissues by Western blot analysis. The effect of CDDO-Me on osteosarcoma cell growth was evaluated by MTT and apoptosis by PARP cleavage assay and caspase-3/7 activity.
Results:
Stat3 pathway was activated in osteosarcoma tissues and in MDR cell lines. CDDO-Me inhibited growth and induced apoptosis in osteosarcoma cell lines. Treatment with CDDO-Me significantly decreased the level of nuclear translocation and phosphorylation of Stat3. The inhibition of Stat3 pathway correlated with the suppression of the anti-apoptotic Stat3 targeted genes Bcl-XL, survivin, and MCL-1. Furthermore, CDDO-Me increased the cytotoxic effects of doxorubicin in the MDR osteosarcoma cell lines.
Conclusions:
Stat3 pathway is overexpressed in MDR osteosarcoma cells. CDDO-Me significantly inhibited Stat3 phosphorylation, Stat3 nuclear translocation and induced apoptosis in osteosarcoma. This study provides the framework for the clinical evaluation of CDDO-Me, either as monotherapy or perhaps even more effectively in combination with doxorubicin to treat osteosarcoma and overcome drug resistance.
Insights
The synthetic triterpenoid CDDO-Me inhibits the Stat3 pathway, reducing osteosarcoma growth and overcoming doxorubicin resistance. This offers a new therapeutic strategy for drug-resistant osteosarcoma.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Signal transducer and activator of transcription 3 (Stat3) pathway activation is linked to osteosarcoma progression, drug resistance, and poor prognosis.
- Multidrug-resistant (MDR) osteosarcoma exhibits elevated Stat3 pathway activity.
- Assessing Stat3 pathway modulation is crucial for developing novel osteosarcoma therapies.
Purpose of the Study:
- To investigate the expression and activation of the Stat3 pathway in osteosarcoma.
- To evaluate the therapeutic potential of CDDO-Me in inhibiting Stat3 signaling.
- To determine the effect of CDDO-Me on doxorubicin sensitivity in osteosarcoma cells.
Main Methods:
- Western blot analysis to assess Stat3, phosphorylated Stat3 (pStat3), and target proteins (Bcl-XL, Survivin, MCL-1) in sensitive and MDR osteosarcoma cells and tissues.
- MTT assays to evaluate cell growth inhibition and PARP cleavage/caspase-3/7 activity assays for apoptosis.
- Analysis of CDDO-Me's impact on Stat3 phosphorylation and nuclear translocation.
Main Results:
- Stat3 pathway activation was confirmed in osteosarcoma tissues and MDR cell lines.
- CDDO-Me demonstrated significant inhibition of osteosarcoma cell growth and induced apoptosis.
- CDDO-Me treatment reduced Stat3 phosphorylation and nuclear translocation, downregulating anti-apoptotic proteins Bcl-XL, Survivin, and MCL-1.
- CDDO-Me enhanced the cytotoxic effects of doxorubicin in MDR osteosarcoma cells.
Conclusions:
- The Stat3 pathway is overexpressed in multidrug-resistant osteosarcoma.
- CDDO-Me effectively inhibits Stat3 phosphorylation and nuclear translocation, inducing apoptosis in osteosarcoma cells.
- CDDO-Me shows promise as a therapeutic agent, alone or in combination with doxorubicin, for treating osteosarcoma and overcoming drug resistance.
