4-HPR has been reported to exhibit anti-tumor effects on breast cancer cells, through suppressing NF-KB activation and inhibiting matrix metalloproteinase-9 expression [21–23], on prostate carcinoma cells, by modulating the pro-apoptotic/anti-apoptotic protein ratio, leading to an alteration of mitochondrial membrane potential and down regulating the levels of survivin [24, 25], and myeloid leukemia [28], human pancreatic cancer cells [27]. The gene discussed is MMP9; the disease is myeloid leukemia.