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Chitin and its derivatives—as a potential resource as well as multiple functional substrates—have generated attractive interest in various fields such as biomedical, pharmaceutical, food and environmental industries, since the first isolation of chitin in 1811. Moreover, chitosan and its chitooligosaccharides (COS) are degraded products of chitin through enzymatic and acidic hydrolysis processes; and COS, in particular, is well suited for potential biological application, due to the biocompatibility and nontoxic nature of chitosan. In this review, we investigate the current bioactivities of chitin derivatives, which are all correlated with their biomedical properties. Several new and cutting edge insights here may provide a molecular basis for the mechanism of chitin, and hence may aid its use for medical and pharmaceutical applications.

Selenium, an essential biological trace element, has been shown to reduce and prevent the incidence of cancer. Our previous studies have shown that selenite is involved in the chemoprevention of cancer and induction of apoptosis of cancer cells. In this study, we demonstrate that selenite also inhibits the invasion of tumor cells. Cancer cell invasion requires coordinated processes, such as changes in cell-cell and cell-matrix adhesion, degradation of the extracellular matrix, and cell migration. We found that selenite inhibited invasion of HT1080 human fibrosarcoma cells. Adhesion of HT1080 cells to the collagen matrix was also inhibited by treatment with selenite, but cell-cell interaction and cell motility were not affected by selenite. Moreover, selenite reduced expression of matrix metalloproteinase-2 and -9 and urokinase-type plasminogen activator, which are involved in matrix degradation, but increased a tissue inhibitor of metalloproteinase-1. This inhibitory effect of selenite on the protease expressions was mediated by the suppression of transcription factors, NF-B and AP-1. However, selenate showed no remarkable effect on all the steps of cancer cell invasion.Metastasis is the major cause of death among cancer patients. The cancer cells metastasis requires several sequential steps, such as changes in cell-ECM 1 interaction, disconnection of intercellular adhesions, and separation of single cells from solid tumor tissue, degradation of ECM, locomotion of tumor cells into the extracellular matrix, invasion of lymph and blood vessels, immunologic escape in the circulatory system, adhesion to endothelial cells, extravasation from lymph and blood vessels, proliferation of cells, and induction of angiogenesis (1).Attachment of cells to ECM molecules is mediated by the integrin family of extracellular matrix receptors. Integrins are a large family of heterodimeric proteins that transduce a variety of signals from the ECM. Through integrin and matrix interactions, many of the genes, which are critical for cell migration, survival, proliferation, differentiation (2), and ECM degradation, are activated (3, 4). In the majority of metastasizing tumors, cellular interactions with the ECM, which promote adhesion and migration, are thought to be required for primary tumor invasion, migration, and metastasis.The main groups of proteolytic enzymes involved in the tumor invasion are matrix metalloproteinases (MMPs) and serine proteases. The MMPs, a family of zinc-dependent endopeptidases, are involved in tumor invasion, metastasis, and angiogenesis in cancer (5). MMPs are important enzymes for the proteolysis of extracellular matrix proteins such as collagen, proteoglycan, elastin, laminin, and fibronectin (6). MMPs are synthesized as preproenzymes, and most of them are secreted from the cells as proenzymes. Among human MMPs reported previously, MMP-2 (gelatinase A/M r 72,000 type IV collagenase) and MMP-9 (gelatinase B/M r 92,000 type IV collagenase) are thought to be key enzymes for degrading type IV collagen, which ...

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