DPP4 and neoplasm: As many studies have shown that serum autoantibodies against tumour-associated antigens (TAAs) could serve as potential biomarkers in the detection of several types of cancer [17], the aim of this study was to analyse the relationship between DPP4 activity, sCD26 concentration, anti-CD26 isotypes, and demographic variables, using a prospective cohort of 497 individuals.