Gene cluster I represents genesthat were mostly down-regulated in a subgroup of gliomas (A2b), includingHDAC11, PPARGC1B, HDAC9, HDAC5, SIRT3,SIRT5, NCOR1, HDAC8, SIRT4, and SIRT2. Insubgroup B, two genes HDAC11 and PPARGC1B were down-regulated inall tumors, suggesting that these co-factors might regulate genes commonlyinduced in tumorigenesis (e.g. anti-apoptotic and proliferation genes, or genesinvolved in oxidative metabolism). This evidence concerns the gene HDAC9 and glioma.