Evidence for the deficiency of low-density lipoprotein receptors on human colonic carcinoma cells
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Abstract
Studies were done to determine if human colon tumor cells use low-density lipoprotein (LDL) as a source of cholesterol. Cells from six human colonic adenocarcinoma lines (CaCo-2, HT29, LS174T, SW480, SW403 and SW1417) were assayed in vitro for their ability to use LDL. The growth of the tumor cells was not diminished in lipoproteindeficient serum, implying that the presence of LDL in the culture medium was not critical for cell growth. When cell growth was inhibited with mevinolin, a drug that inhibits cholesterol synthesis, the addition of LDL to the medium had no effect on the growth of cells from five of the six lines. CaCo-2 cells showed a slight increase in growth. These results suggested that the majority of the cell lines tested were unable to use LDL. A monoclonal antibody to the human LDL receptor was used in an enzyme linked immunosorbent assay (ELISA) to determine if these cells lacked receptors for LDL. The ELISA measured binding of the monoclonal antibody to cell monolayers. Of the six cell lines tested, only CaCo-2 cells consistently demonstrated the presence of LDL receptors. The same monoclonal antibody was used to assay frozen tissue sections from four human colonic adenocarcinomas for the presence of LDL receptors. Immunohistochemical staining experiments revealed the absence of detectable LDL receptors on these tumors. Adjacent non-neoplastic mucosa showed variable staining. Cells of the surface epithelium were positively stained, while cells toward the base of the crypts were unstained. Thus, data from both cell culture and human tissue studies indicate that human colon tumor cells are often deficient in LDL receptors.
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Dissertation (Ph.D.)--Boston University
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