Valproic Acid Increases CD133 Positive Cells that Show Low Sensitivity to Cytostatics in Neuroblastoma

Area of Science:

• Oncology
• Epigenetics
• Molecular Biology

Background:

• Valproic acid (VPA), an antiepileptic drug, shows antitumor properties via histone deacetylase inhibition.
• CD133 is a cancer stem cell marker in neuroblastoma, with its transcription epigenetically regulated.
• Understanding VPA's epigenetic impact on CD133 is crucial for neuroblastoma treatment strategies.

Purpose of the Study:

• To investigate the epigenetic effects of VPA on CD133 expression in human neuroblastoma cell lines.
• To analyze the chemoresistance and cell cycle characteristics of CD133+ and CD133- neuroblastoma cells following VPA treatment.

Main Methods:

• Treatment of four human neuroblastoma cell lines with 1mM VPA.
• Assessment of CD133 promoter methylation status using bisulfite conversion and methylation-sensitive high-resolution melting analysis.
• Flow cytometry to examine chemoresistance and cell cycle distribution.
• Analysis of histone acetylation, Akt phosphorylation, and pluripotency factor expression.

Main Results:

• VPA induced CD133 expression, correlated with increased histone H3/H4 acetylation.
• CD133+ cells, prevalent in S and G2/M phases, exhibited reduced caspase-3 activation and higher proliferation/neurosphere formation capacity.
• VPA failed to induce CD133 in cell lines with methylated CD133 promoters (P1/P3); demethylation agents restored expression.
• VPA-induced CD133+ cells demonstrated increased phosphorylated Akt and pluripotency factors (Nanog, Oct-4, Sox2).

Conclusions:

• CD133 expression in neuroblastoma is controllable via histone acetylation and CpG promoter methylation.
• VPA promotes CD133+ neuroblastoma cells with enhanced proliferation and chemoresistance.
• These findings highlight potential limitations of VPA in neuroblastoma therapy due to the induction of aggressive cancer stem cell phenotypes.