In the present study, we have examined the neutral
glycolipids,
gangliosides, and
sulfoglycolipids of human rectal
adenocarcinoma (HRT-18) cells and the alterations produced by the differentiating agents,
sodium butyrate,
dimethyl sulfoxide, and
retinoic acid. Thin-layer chromatography of neutral
glycolipids showed that HRT-18 cells contained mono- and diglycosylceramides. Cells treated with differentiating agents had additional
glycolipids which comigrated with tri- and tetraglycosylceramides. Labeling of neutral
glycolipids with [3H]
galactose showed that HRT-18 cells also contain glycosylceramides larger than diglycosylceramides which also were altered by treatment with differentiating agents. In studies of acidic
glycolipids, GM3, the major
ganglioside in untreated cells, was reduced in cells treated with
retinoic acid but not in cells treated with other agents. Upon labeling with radioactive
galactose, changes were seen only in the minor
ganglioside components of treated cells. Differentiating agents also altered the patterns of sulfogalactolipids and
fucolipids in HRT-18 cells. In the case of
fucolipids, 2 new bands were observed in the cells treated with
dimethyl sulfoxide and
retinoic acid. The changes brought about by differentiating agents may identify
glycolipids involved in the process of tumorigenicity.