ADP-ribosylation of serum proteins: evaluation as a potential tumor marker

Establishment of a Mass-Spectrometry-Based Method for the Identification of the In Vivo Whole Blood and Plasma ADP-Ribosylomes

Blood and plasma proteins are heavily investigated as biomarkers for different diseases. However, the post-translational modification states of these proteins are rarely analyzed since blood contains many enzymes that rapidly remove these modifications after sampling. In contrast to the well-described role of protein ADP-ribosylation in cells and organs, its role in blood remains mostly uncharacterized. Here, we discovered that plasma phosphodiesterases and/or ADP-ribosylhydrolases rapidly demodify in vitro ADP-ribosylated proteins. Thus, to identify the in vivo whole blood and plasma ADP-ribosylomes, we established a mass-spectrometry-based workflow that was applied to blood samples collected from LPS-treated pigs (Sus scrofa domesticus), which serves as a model for human systemic inflammatory response syndrome. These analyses identified 60 ADP-ribosylated proteins, 17 of which were ADP-ribosylated plasma proteins. This new protocol provides an important step forward for the rapidly developing field of ADP-ribosylation and defines the blood and plasma ADP-ribosylomes under both healthy and disease conditions.

Clinical significance of serum ADP-ribosylation and NAD glycohydrolase activity in patients with colorectal cancer

The objective of this study was to evaluate the clinical significance of serum ADP-ribosylation and NAD glycohydrolase activity in patients with colorectal cancer (CRC). A total of 108 patients with CRC who underwent curative surgery and 20 healthy volunteers were enrolled in this study. ADP-ribosylation and NAD glycohydrolase activity levels were determined. The association of ADP-ribosylation and NAD glycohydrolase with clinical and laboratory factors and their impact on overall survival (OS) and disease free survival (DFS) were shown. The preoperative ADP-ribosylation and NAD glycohydrolase activity levels were significantly higher in patients with CRC than in the control group (p<0.001). ADP-ribosylation and NAD glycohydrolase activity levels were correlated with tumor stage (p=0.05, p=0.001), stage of disease (p<0.001, p<0.001), serum CEA level (p<0.001, p<0.001), and site of lesion (p<0.001, p<0.001), respectively. Patients with high ADP-ribosylation had significantly unfavorable OS and DFS compared with those with lower levels (p<0.001, p<0.001), respectively. Moreover, the patients with high NAD glycohydrolase activity showed significantly worse OS and DFS rates, similar to ADP-ribosylation. Serum levels of ADP-ribosylation and NAD glycohydrolase activity correlate well with tumor stage, stage of disease, serum CEA level, and site of lesion. In conclusion, elevated levels of preoperative ADP-ribosylation and NAD glycohydrolase levels in serum are associated with poor prognosis in patients with CRC.

Changes in NAD/ADP-ribose metabolism in rectal cancer

The extent of ADP-ribosylation in rectal cancer was compared to that of the corresponding normal rectal tissue. Twenty rectal tissue fragments were collected during surgery from patients diagnosed as having rectal cancer on the basis of pathology results. The levels of ADP-ribosylation in rectum cancer tissue samples (95.9 +/- 22.1 nmol/ml) was significantly higher than in normal tissues (11.4 +/- 4 nmol/ml). The level of NAD+ glycohydrolase and ADP-ribosyl cyclase activities in rectal cancer and normal tissue samples were measured. Cancer tissues had significantly higher NAD+ glycohydrolase and ADP-ribosyl cyclase activities than the control tissues (43.3 +/- 9.1 vs 29.2 +/- 5.2 and 6.2 +/- 1.6 vs 1.6 +/- 0.4 nmol mg(-1) min(-1)). Approximately 75% of the NAD+ concentration was consumed as substrate in rectal cancer, with changes in NAD+/ADP-ribose metabolism being observed. When [14C]-ADP-ribosylated tissue samples were subjected to SDS-PAGE, autoradiographic analysis revealed that several proteins were ADP-ribosylated in rectum tissue. Notably, the radiolabeling of a 113-kDa protein was remarkably greater than that in control tissues. Poly(ADP)-ribosylation of the 113-kDa protein in rectum cancer tissues might be enhanced with its proliferative activity, and poly(ADP)-ribosylation of the same protein in rectum cancer patients might be an indicator of tumor diagnosis.

Induced mono-(ADP)-ribosylation of rat liver cytosolic proteins by lipid peroxidant agents

We have studied the effect of free radical generating agents on the mono-(ADP)-ribosylation of rat liver cytosolic proteins. Our results show that this post-translational modification, whose physiological significance is still unclear, is activated by lipid peroxidant agents via activation of cytoplasmatic mono-(ADP)-ribosyltransferases. The implication of free radicals in this process is demonstrated by the fact that mono-(ADP)-ribosylation can be prevented by melatonin, N-tert-butyl-alpha-phenylnitrone and dithiothreitol. On the basis of our results, we discuss the modification of proteins caused by free radicals as a possible mechanism by which they damage the cell.

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 approximately 45 and approximately 21 kDa that were immunoreactive with human CD38-specific monoclonal antibodies T16, HIT2 and OKT 10. 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.