Hyaluronan (HA) is a large, negatively-charged polysaccharide that is synthesized by many types of normal and tumor cells. In many cases tumor tissue contain greater amounts of HA than the equivalent normal tissue. Previous studies by the applicant have revealed that melanoma cells with elevated levels of surface HA have a high potential for metastasis. Furthermore, the amount of cell surface HA associated with cells from a secondary tumor (SW620, lymph node metastatic cells) was much greater than that from a primary tumor (SW480, a primary human colon carcinoma from same patient), suggesting that the metastatic process selects for cells that express high levels of HA. In addition, poorly differentiated tumors that express large amounts of HA have extensive neovascularization which provides a favorable environment for both tumor growth and metastasis. Recent studies have shown that the levels of HA are significantly elevated in tumor cells present in necrotic regions of the tumor mass. These observations have led to the following working hypotheses: 1) high level of HA synthesis will promote the angiogenesis, tumor growth and metastasis; 2) inhibition of HA expression will attenuate the malignancy of tumor cells; 3) in vivo spontaneous metastatic process preferentially selects high HA expressing cells for growth in distant sites; and 4) the expression of HA is regulated by hypoxia. To test these hypotheses, the following experiments will be conducted. First, tumor cells will be transfected with cDNA for HA synthase and then examined for their malignant phenotype. Secondly, HA high expressing tumor cells will be transfected with anti-sense for HA synthase and determine if this attenuates the malignancy of tumor cells. Thirdly, difference of the expression of HA between the tumor cells in the primary tumors and the secondary metastatic will be analyzed by immunohistochemical staining. And finally, alterations in the expression of HA and HA synthase caused by hypoxia will be examined using immunohistochemical attaining and in situ hybridization. The information obtained from this study should lead to a better understanding of the role of HA in the progression of cancer and might provide a new index for diagnosis of malignancy and lead to new therapeutic approaches to slow down tumor progression.
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