title: C4.4A as a candidate marker in the diagnosis of colorectal cancer.
abstract: C4.4A is a member of the Ly-6 family with restricted expression in non-transformed tissues. C4.4A expression in human cancer has rarely been evaluated. Thus, it became important to explore C4.4A protein expression in human tumour tissue to obtain an estimate on the frequency of expression and the correlation with tumour progression, the study focusing on colorectal cancer. The analysis of C4.4A in human tumour lines by western blot and immunoprecipitation using polyclonal rabbit antibodies that recognize different C4.4A epitopes revealed C4.4A oligomer and heavily glycosylated C4.4A isoform expression that, in some instances, inhibited antibody binding and interaction with the C4.4A ligand galectin-3. In addition, tumour cell lines released C4.4A by vesicle shedding and proteolytic cleavage. C4.4A was expressed in over 80% of primary colorectal cancer and liver metastasis with negligible expression in adjacent colonic mucosa, inflamed colonic tissue and liver. This compares well with EpCAM and CO-029 expression in over 90% of colorectal cancer. C4.4A expression was only observed in about 50% of pancreatic cancer and renal cell carcinoma. By de novo expression in colonic cancer tissue, we consider C4.4A as a candidate diagnostic marker in colorectal cancer, which possibly can be detected in body fluids.
authors.affiliation: Department of Tumour Progression and Immune Defence, German Cancer Research Centre, Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Paret
authors.forename: D
authors.initials: D
authors.lastname: Hildebrand
authors.forename: J
authors.initials: J
authors.lastname: Weitz
authors.forename: A
authors.initials: A
authors.lastname: Kopp-Schneider
authors.forename: A
authors.initials: A
authors.lastname: Kuhn
authors.forename: A
authors.initials: A
authors.lastname: Beer
authors.forename: R
authors.initials: R
authors.lastname: Hautmann
authors.forename: M
authors.initials: M
authors.lastname: Zöller
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D058851:GPI-Linked Proteins; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging
chemical_list: D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D058851:GPI-Linked Proteins; C472589:LYPD3 protein, human