The Nrf2 Inhibitor Brusatol Promotes Human Osteosarcoma (MG63) Growth and Blocks EB1089-Induced Differentiation

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Metastatic osteosarcoma (OS) survival rates have stagnated for decades, necessitating novel therapeutic strategies.
• Nuclear factor erythroid 2-related factor 2 (Nrf2) is implicated in chemoradiotherapy resistance in OS.
• Brusatol (Bru) is a natural Nrf2 inhibitor with demonstrated anti-cancer effects in various tumor models.

Purpose of the Study:

• To investigate the efficacy of Brusatol (Bru) as a potential therapeutic agent for osteosarcoma (OS).
• To evaluate the effect of Nrf2 inhibition on OS cell growth and differentiation.

Main Methods:

• Utilized the human osteosarcoma cell line MG63 under normoxic and hypoxic conditions.
• Administered Brusatol (50 nM) for 3 days to assess its impact on cell proliferation.
• Investigated Brusatol's effect on MG63 differentiation when co-treated with EB1089 and lysophosphatidic acid.
• Assessed the role of Nrf2 activation using dimethyl fumarate.

Main Results:

• Brusatol significantly promoted MG63 cell growth under both normoxic (1.7-fold increase) and hypoxic (1.3-fold increase) conditions.
• Brusatol profoundly inhibited MG63 differentiation induced by EB1089 and lysophosphatidic acid (2.8-fold inhibition).
• The Nrf2 activator, dimethyl fumarate, did not reverse the observed phenotypes.

Conclusions:

• Contrary to expectations, Brusatol demonstrated pro-proliferative and anti-differentiation effects in the MG63 osteosarcoma cell line.
• These findings indicate that Brusatol may not be a suitable candidate for osteosarcoma treatment.
• Further research is needed to understand the specific mechanisms underlying Brusatol's paradoxical effects in OS.