Cohorts of 3-6 patients receive escalating doses of valproic acid until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience DLT. The MEPD of valproic acid is then determined using established gene methylation and toxicity criteria. Treatment continues for up to 24 months in the absence of disease progression or unacceptable toxicity.