ODC affects numerous processes in carcinogenesis through its regulation of the intracellular polyamine pool. Studies focusing on transgenic mouse models have shown an essential role of polyamines in the early promotion of tumorigenesis. One group26 reported that elevated ODC activity is sufficient to promote skin tumor formation in the carcinogen-exposed skin of K6/ODC transgenic mice, without the addition of tumor-promoting agents. Conversely, suppression of ODC expression is associated with decreased cell proliferation, increased apoptosis and decreased expression of genes affecting tumor invasion and metastasis.27, 28 Our data showed that when ODC expression in ESCC cells was knocked down, both proliferation and anchorage-independent growth of ESCC cells were significantly suppressed (Fig. 2c, d).