In contrast, inhibition of polyamine synthesis by the ODC inhibitor DFMO attenuates the invasive characteristics of cancer cells [53, 55, 75], and supplementation with polyamine reverses the DFMO-induced decrease in invasive qualities [75]. The close correlation between increased LGX818 ic50 polyamine synthesis and increased MMP synthesis has also been shown using DFMO, which caused decreases in cancer cell expression and concentrations of MMPs, such as matrilysin, meprin, and MMP-7 [76, 77]. As mentioned above, increased polyamine synthesis is also accompanied by angiogenesis that is stimulated by cellular production of several factors, including

vascular endothelial growth factor, which allow tumor tissues to grow and survive by obtaining sufficient blood supplies [78]. DFMO has been shown to exert its anti-tumor activity by inhibiting the proliferation of endothelial cells [79]. 5-c. Possible role of polyamines on cell rooting and colonization at secondary tumor sites Cancer cells that invade blood vessels and escape from immune

system detection in circulation anchor to endothelial vasculature to establish new sites of growth. Upon vessel entry, cancer cells have access to abundant oxygen supplies that could enable cancer cells to restore their original activities such as increased gene expression that translates to enhanced enzymatic activities for polyamine synthesis, proteinase, and angiogenesis

factors. HSP assay Considering the results of our study, the expression of CD44 of normoxic cancer cells is higher than that of hypoxic cells [66], suggesting that the circulating cancer cells possibly recover their original adhesion characteristics. Once cancer cells anchor to the vessel wall of tissues and organs at secondary growth sites, they invade and rapidly grow because of their increased capacity to synthesize polyamines indispensable for cell growth and proteins that degrade the tissue matrix and create new vessels. 5-d. Polyamines help cancer cells escape immune system detection Immune suppression, often observed in cancer patients, Cyclin-dependent kinase 3 accelerates cancer spread. Various defects in cellular functions indicative of immune Tucidinostat chemical structure suppression have been reported, including attenuated adhesion properties of peripheral blood mononuclear cells (PBMCs) [80–82], impaired production of tumoricidal cytokines and chemokines [83–85], and decreased cytotoxic activity of killer cells, especially lymphokine activated killer (LAK) cells [86–89]. Several investigators have suggested that circulating factors that inhibit host immune activities are present in cancer patients [89–91]. The suppression of immune function in cancer patients can be restored following tumor eradication, further suggesting the presence of increased immunosuppressive substance(s) in cancer patients [83, 84, 89, 91].