Polymorphic expression of decay-accelerating factor in human colorectal cancer.

Area of Science:

• Biochemistry
• Oncology
• Immunology

Background:

• Decay-accelerating factor (DAF), a complement regulatory protein, is upregulated in colorectal cancer (CRC) glands and detectable in patient stool.
• DAF's presence in stool may depend on its cell surface stability, influenced by protein glycosylation.
• Previous studies indicated enhanced DAF expression in CRC, prompting further biochemical investigation.

Purpose of the Study:

• To biochemically analyze DAF expression in colorectal cancer.
• To elucidate the mechanism of DAF release from human colorectal cancers.
• To investigate the role of glycosylation in DAF shedding.

Main Methods:

• Western and northern blotting were used to analyze DAF expression in 10 surgically resected colorectal cancer specimens.
• Glycosidase digestion was employed to analyze the glycosylation patterns of DAF protein.

Main Results:

• Northern blot analysis revealed a two- to threefold increase in DAF mRNA expression in colorectal cancer tissues compared to normal tissues.
• Western blotting showed elevated DAF protein levels in cancer tissues, with observed heterogeneity in apparent molecular weight among patients.
• Removal of O-linked sugars reduced the observed heterogeneity in DAF size.

Conclusions:

• The polymorphic expression of DAF in colorectal cancer is likely attributed to variations in O-glycosylation.
• Altered O-glycosylation may impact DAF's stability on cancer cell surfaces.
• This variability in stability could influence the amount of DAF shed into the stools of colorectal cancer patients.