The effects of bortezomib-based intermittent therapy were compared to treatment in combination with histone deacetylase (HDAC) inhibitors on drug-tolerant multiple cells [68], and demonstrated that the combination of HDAC inhibitors and high-dosage intermittent therapies, as opposed to sustained proteasome inhibitor monotherapy, can be more effective in treating this form of cancer by preventing the emergence of proteasome inhibitor tolerant cells. This evidence concerns the gene HDAC9 and cancer.