Background: A hypoxic environment exists in most solid tumors because in rapidly growing tumors, the development of angiogenic vasculature is heterogenous, usually not enough to overcome the necessary oxygen supply. In an ischemic condition, cancer cells develop escape mechanisms to survive and leave the unfavorable environment. That result in the acquisition of increased potential for local invasion and evasion to distant organs. However, the escape mechanisms of cancer cells from hypoxic stress have not been fully characterized.
Materials and methods: The human colon cancer cell line LoVo was cultured in hypoxia, and the adhesive and migratory properties were analyzed. The expression of cell surface and cytoplasmic molecules was also investigated.
Results: Under hypoxic conditions, cells developed epithelial-mesenchymal transition. The expression levels of α2, α5, and β1 integrins were significantly upregulated and, as a consequence, the ability to adhere to and migrate on collagen and fibronectin was increased. On the other hand, the expression of 67-kDa laminin receptor and the abilities to adhere to and migrate on laminin were decreased. Additionally, the expression of CXCR4 was significantly increased on cells cultured in hypoxia, and the chemotactic activity to stromal cell-derived factor 1α was remarkably increased.
Conclusions: Hypoxic stress induced active epithelial-mesenchymal transition in colon cancer cells, with the typical morphologic and functional changes. These morphologic and functional changes of β1 integrins, the 67-kDa laminin receptor, and CXCR4 may be essential for the acquisition of the invasive and metastatic features in colorectal cancer.
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