In addition, erlotinib combined with HDAC inhibitor showed a strong synergy in the suppression of cell growth by blocking the cell cycle and triggering cell apoptosis in EGFR-tyrosine kinase inhibitor (TKI)-resistant NSCLC cells, and this combined treatment led to a significant decrease in tumor growth and tumor weight compared with single agents alone [8]. This evidence concerns the gene HDAC9 and neoplasm.