Histone Deacetylase Inhibition Restores Expression of Hypoxia-Inducible Protein NDRG1 in Pancreatic Cancer

Objectives: N-myc downstream-regulated gene-1 (NDRG1) is a hypoxia-inducible and differentiation-related protein and candidate biomarker in pancreatic cancer. As NDRG1 expression is lost in high-grade tumors, the effects of the differentiating histone deacetylase inhibitor trichostatin A (TSA) were examined in human pancreatic cancer cell lines representing different tumor grades. Methods: PANC-1 (poorly differentiated) and Capan-1 (moderately to well-differentiated) cells were treated with TSA. Effects were assessed in vitro by microscopic analysis, colorimetric assays, cell counts, real-time polymerase chain reaction, and Western blotting. Results: Treatment of PANC-1 cells over 4 days with 0.5 M TSA restored cellular differentiation, inhibited proliferation, and enhanced p21(Cip1) protein expression. Trichostatin A upregulated NDRG1 mRNA and protein levels under normoxia from day 1 and by 6-fold by day 4 (P < 0.01 at all time points). After 24 hours under hypoxia, NDRG1 expression was further increased in differentiated cells (P < 0.01). Favorable changes were identified in the expression of other hypoxia-regulated genes. Conclusions: Histone deacetylase inhibitors offer a potential novel epidrug approach for pancreatic cancer by reversing the undifferentiated phenotype and allowing patients to overcome resistance and better respond to conventional cytotoxic treatments.