Comparison of haptoglobin and alpha₁-acid glycoprotein glycosylation in the sera of small cell and non-small cell lung cancer patients.

INTRODUCTION: Cancer-related carbohydrate epitopes, which are regarded as potential diagnostic and prognostic biomarkers, are carried on the main acute phase proteins. It is not clear, however, if the glycosylation profile is similar in different glycoproteins, or it is protein specific to some extent. The aim of the study was to compare fucosylation, α2,3 sialylation and expression of sialyl-Lewisx epitopes (sLe(x)) in the serum as a whole, AGP and haptoglobin of small cell (SCLC) and non-small cell lung cancer (NSCLC) patients with respect to healthy subjects as well as the cancer stage and its histological type.
MATERIAL AND METHODS: Thirty-three NSCLC, 13 SCLC patients and 20 healthy volunteers were included in the study. Carbohydrate epitopes were detected by means of their reactivity with specific lectins and monoclonal anti-sLe(x) antibodies in direct or dual-ligand ELISA tests.
RESULTS: Significantly increased fucosylation was found in total serum in both cancer groups and in NSCLC haptoglobin. No difference was observed in SCLC haptoglobin or α₁-acid glycoprotein in both cancer groups. Also α2,3 sialylation was elevated in total serum, but not in α₁-acid glycoprotein. This type of sialylation was undetectable in haptoglobin by means of MAA reactivity, in both healthy and cancer subjects. Complete sLe(x) antigens were overexpressed in total NSCLC serum and SCLC AGP, and their level was considerably lowered in cancer haptoglobin. DISCUSSION: Typical acute phase proteins, haptoglobin and AGP, exhibit different glycosylation profiles in lung cancer. Alterations observed in haptoglobin reflected the disease process better than those in AGP. Comparison of haptoglobin and AGP glycosylation to that observed in total serum suggests that some efficient carriers of disease-altered glycoproteins still remain unidentified.