Haptoglobin Polymorphisms and Fucosylation Change: Possible Influence of Variation on the Identified Lung Cancer-relevant Biomarkers

Background: Haptoglobin (Hp), an acute-phase protein, is known as a potential diagnostic biomarker in human diseases. Two alleles of Hp (Hp¹ and Hp² ) exist in humans allowing three phenotypes (Hp1-1, Hp2-1, and Hp2-2), which influence the biophysical and biological properties of Hp. Objective: This work aimed to investigate the variation of serum level and fucosylation change among Hp phenotypes in patients with lung cancer compared to healthy donors. Methods: 44 patients with lung cancer and 26 healthy blood donors who lived in the Northern-Thailand region were investigated by the glycoproteomic procedure. Results: The phenotypic distribution of the Hp (Hp1-1:Hp2-1:Hp2-2) in healthy donors was 0.04:0.38:0.58, while the patient group was 0.09:0.52:0.39. The Hp¹ allele frequency of patients with lung cancer (0.34) was higher than the healthy donor (0.23). Glycoprotein blotting technique represented that the level of serum Hp and its fucosylation were significantly higher among lung cancer patients compared to those of the healthy donors. However, a downward trend in the fucosylation level from Hp1-1 to Hp2-1, Hp2-2, was seen in the patient group, but varying in the serum Hp level. An N-linked glycan was enzymatically released from discrete Hp multimers of Hp2-1 and Hp2-2 samples. Analysis of glycan profiling by MALDI-TOF-MS showed that reduction of the fucosylated glycan was associated with the size of Hp multimers, resulting in the lower level of fucosylation in Hp2-1 and Hp2-2, respectively. Conclusion: Our finding demonstrates that the Hp phenotype is a dependent risk factor for lung cancer and should be incorporated into further clinical and biochemical investigations of diseases, including lung cancer.