We previously published that inhibition of HDAC downregulates the MYC pathway in vitro.3 In the tumor samples before and after VPA treatment in the VAST trial, we examined the gene expression patterns using gene set omic analysis (GSOA) and generally applicable gene set enrichment (GAGE).34,35 By using either the C6 data sets (P = .022 by GSOA; P = 4.47 × 10−7 by GAGE) or the Hallmark pathway gene sets (P = .001 by GSOA; P = 4.42 × 10−61by GAGE) from MSigDB,36 genes regulated by MYC were downregulated in the post-treatment samples compared with the pretreatment samples. This evidence concerns the gene HDAC9 and neoplasm.