Several previously reported mouse xenograft studies using different cancer cell types reported only very small decreases in tumor size upon Tubastatin A treatment alone, even using high treatment doses, consistent with our observations that Tubastatin A incompletely inhibits KDAC6 and that even complete KDAC6 inhibition only reduces the tumor growth rate to approximately 75% [47, 48, 49]. This evidence concerns the gene HDAC6 and cancer.