The therapeutic effect of histone deacetylase inhibitor PCI-24781 on gallbladder carcinoma in BK5.erbB2 mice.

Background & Aims: Gallbladder carcinoma (GBCa), a type of biliary tract cancer (BTC), has proven challenging to treat, demonstrating the need for more effective therapeutic strategies. In our current study, we examined the therapeutic effects of the histone deacetylase (HDAC) inhibitor PCI-24781 against GBCa that developed in BK5.erbB2 mice.

Methods: PCI-24781 [50 mg/kg/day] and control solutions were administered to BK5.erbB2 mice for 4 weeks. The therapeutic effect of PCI-24781 was evaluated by ultrasound biomicroscopy (USBM) throughout the experiment and histological analyses at the end of the experiment. To investigate potential mechanisms underlining the therapeutic effects of PCI-24781 on GBCa in BK5.erbB2 mice, PCI-24781-treated gallbladders were subjected to Western blot and RT-PCR analysis. The inhibitory effect of PCI-24781 on the growth of BTC cells was compared to the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and gemcitabine. To study the role of miRNAs in GBCa tumorigenesis, the expression profile of 368 miRNAs in GBCas from BK5.erbB2 (both treated and untreated) and wild type mice was analyzed.

Results: Treatment of BK5.erbB2 mice with PCI-24781 for 1 month prevented 79% of GBCa cases from progression and showed a clinical effect in 47% of cases. We also confirmed a potent inhibitory effect on tumor cell growth in human BTC cell lines treated with PCI-24781. This effect was associated with downregulation of ErbB2 mRNA and ErbB2 protein/activity and upregulation of acetylated histone and acetylated tubulin. Treatment with PCI-24781 resulted in decreased expression of Muc4, an intramembrane ligand for ErbB2, in BTC cells. PCI-24781 had more effects on growth inhibition of BTC cells than SAHA. In addition, PCI-24781 effectively inhibited the growth of gemcitabine-resistant cells. miRNA profiling revealed that the expression of several miRNAs was significantly altered in GBCa in the BK5.erbB2 mouse compared to normal gallbladder, including upregulated miR21, which was downregulated by PCI-24781.

Conclusions: These results indicate that PCI-24781 potently inhibits the growth of BTC cells by decreasing ErbB2 expression and activity as well as regulating altered miRNA expression. PCI-24781 may have a potential value as a novel chemotherapeutic agent against human BTC in which ErbB2 is overexpressed.