Antagonistic effects of sequential administration of BL1521, a histone deacetylase inhibitor, and gemcitabine to neuroblastoma cells

Additive to synergistic induction of apoptosis has been reported as a result of sequential incubation of cancer cells with a histone deacetylase inhibitor (HDACi) and gemcitabine (dFdC), a deoxycytidine analogue with proven anti-tumour activity. This study shows that sequential treatment of two neuroblastoma cell lines with BL1521, an HDACi, and dFdC resulted in strong antagonism despite a minor increase of dFdCTP incorporation into the DNA of one cell line. Furthermore, no difference in the deoxycytidine kinase activity was observed in response to BL1521. In conclusion, cancer cells that respond to HDACi with a cell cycle arrest and differentiation may no longer be sensitive to dFdC.