Serum proteins with NAD+ glycohydrolase activity and anti-CD38 reactivity – elevated levels in serum of tumour patients

NAD+ glycohydrolase activities in serum samples from cancer patients were two- to three-fold higher than the activities in samples from healthy controls. SDS-PAGE analysis of serum samples followed by Western blotting revealed the presence of two proteins of ~45 and ~21 kDa that were immunoreactive with human CD38-specific monoclonal antibodies T16, HIT2 and OKT10. These proteins appeared to be more abundant in serum from cancer patients. NAD+ glycohydrolase activity in serum could be enriched by immunoaffinity chromatography by using T16-Sepharose 4B. The results suggest that the relative abundance of proteins immunologically related to CD38 may account for the elevated levels of glycohydrolase activities in serum of tumour patients.