Enhanced growth inhibition by combination differentiation therapy with ligands of peroxisome proliferator-activated receptor-gamma and inhibitors of histone deacetylase in adenocarcinoma of the lung.

Histone deacetylase (HDAC) inhibitors and ligands of the peroxisome proliferator-activated receptor gamma (PPARgamma) have been shown previously to induce growth arrest and differentiation in a variety of cancer cell lines. The purpose of this study was to determine whether HDAC inhibitors function similarly in non-small cell lung cancer (NSCLC) and whether combination treatment with HDAC inhibitors and PPARgamma ligands is more efficacious than either agent alone.Nanomolar concentrations of trichostatin A induced growth arrest in five of seven NSCLC cell lines, whereas sodium phenylbutyrate (PB) was markedly less potent. In adenocarcinomas, trichostatin A up-regulated general differentiation markers (gelsolin, Mad, and p21/WAF1) and down-regulated markers of the type II pneumocyte progenitor cell lineage (MUC1 and SP-A), indicative of a more mature phenotype. PB had a similar effect. Simultaneous treatment with a PPARgamma ligand and PB enhanced the growth inhibition in adenocarcinomas but not in nonadenocarcinomas. Growth arrest was accompanied by markedly decreased cyclin D1 expression but not enhanced differentiation.The present study demonstrates potent growth-inhibitory and differentiation-inducing activity of HDAC inhibitors in NSCLC and suggests that combination differentiation therapy should be explored further for the treatment of lung adenocarcinomas.