Value of M2BP in predicting in‐stent restenosis in patients after coronary drug‐eluting stent implantation

Abstract Objective We evaluated the association between plasma levels of mac‐2 binding protein (M2BP) with the risk of in‐stent restenosis (ISR) after percutaneous coronary intervention (PCI). Methods Plasma M2BP levels were compared between 258 patients who experienced ISR at 12‐months post‐PCI and 258 patients, matched for age and sex, without angiographic evidence of ISR. Results The plasma M2BP level was significantly higher in the ISR than in the non‐ISR group. On multivariate analysis, adjusted for potential clinical, biochemical, and angiography characteristics, M2BP remained as an independent significant predictor of ISR. Conclusions M2BP may be an important predictive biomarker of ISR and may be useful in identifying at‐risk patients.

Mac-2 binding protein (M2BP) is a secreted glycoprotein belonging to the macrophage scavenger receptor cysteine-rich domain superfamily. 8 M2BP is widely expressed in human tissues, including the lungs, stomach, and colon, and has also been identified in human fluid, including urine, tears, saliva, breast milk, and plasma. 9 An elevated baseline level of M2BP expression is associated with poor survival among patients with various types of cancer. 9 Previous studies also revealed a pivotal role of elevated M2BP in inflammatory diseases, including hepatic fibrosis, chronic pancreatitis, bronchial asthma, and venous thrombosis. [10][11][12] The pro-inflammatory characteristics of M2BP were further revealed by an in vitro study which revealed the stimulation role of M2BP in increasing interleukin (IL)-2 production in peripheral blood mononuclear cells and IL-6 expression by bone marrow stroma cells. 13 Furthermore, a recent study showed that M2BP was expressed in pro-inflammatory M1 macrophage invitro and colocalized with human plaque macrophages in vivo. 14 More recent studies described the clinical relationship between M2BP and coronary artery disease (CAD). Observational research revealed that the plasma M2BP level was independently associated with long-term mortality among patients with CAD, where CAD was confirmed by coronary computed tomography angiography. 15 In addition, our newly published study showed that the plasma M2BP level might be a predictor of vulnerable plaque, as well as being an independent predictive factor of poor cardiovascular outcomes among patients with acute coronary syndrome (ACS). 16 These results infer a possible role of M2BP in atherosclerosis development and plaque instability.
Given the pro-inflammatory role of M2BP and mounting evidence implying its potential correlation with atherosclerosis, we speculated that M2BP might be potentially involved in the process of ISR. To test this hypothesis, we compared the plasma M2BP level in consecutive patients with angiographically documented ISR to those of patients who did not develop ISR after DES-based PCI. Provincial Hospital, which is affiliated to Shandong First Medical University, Jinan, Shandong, China. The following patients were excluded: lost to follow-up (n = 182); unwilling to undergo followup angiography (n = 225); and confirmed death (n = 50). This left 2642 patients with follow-up data at 12 months post-PCI. Of these, 673 underwent a planned follow-up CAG or CAG, at 3-12 months after the PCI procedure, due to recurrent symptoms or abnormal noninvasive test results for angina, either treadmill exercise tests or myocardial perfusion scintigraphy. After exclusion of cases of in-stent thrombosis (n = 3), ISR was identified in 308 cases. ISR was defined as recurrence of luminal diameter stenosis >50% within the stent or within adjacent segments, 5-mm proximal or distal to the stent, observed on follow-up angiography. 16 Of the 308 patients who were diagnosed with ISR, those who had concomitant valvular disease (n = 8), systematic inflammatory disease (n = 16), malignant tumor (n = 10), severe liver disease (n = 6), or moderate-severe chronic renal insufficiency (eGRF < 60 ml/min/1.73 m 2 , n = 10) were excluded.

| Study population
The remaining 258 patients with ISR formed our study cohort.
We also randomly selected another 258 age-and sex-matched patients who had no ISR on follow-up CAG, within the same study period as the control group.
All patients provided written informed consent. The protocol followed the principles of the Declaration of Helsinki and was approved by our institutional review board.

| Coronary angiography and analysis
Coronary angiography was performed according to the standard Judkins technique. Quantitative evaluation of coronary angiography was performed, before the procedure and at the 12-month follow-up, by two cardiologists who were blinded to the study protocol and to patient information. Using the outer diameter of the contrast-filled catheter as a reference, the single "worst" view, among multiple projections, was recorded as the minimal lumen diameter (MLD).
Lesion length was quantified, proximal and distal to the point of MLD, on the projection with the least amount of foreshortening. An MLD value of 0 mm was regarded as a total occlusion at baseline.
Stents were implanted via a normal-to-normal technique, using normal segment, 5-mm in length, proximal and distal to the target lesion. The late loss was defined as the difference between the MLD measured immediately after the procedure and the MLD quantified on follow-up angiography. In patients with multiple coronary lesions, the lesion with the greatest late loss was entered in the analysis.

| Statistical analysis
The normality of the distribution of data was assessed using the Kolmogorov-Smirnov test. Continuous variables were reported as the mean ± standard deviation (SD), with between-group differences evaluated using an unpaired Students' t-test. Categorical variables were reported as counts and percentages, with between-group differences evaluated using a χ 2 test. Patients with ISR were categorized into three groups according to the tertile distribution of plasma M2BP level (µg/ml). Multivariable logistic regression models were constructed to detect the relationship between ISR and plasma concentration of M2BP. Factors that were statistically significant (p < .1) on univariate analysis and those known to be clinically relevant were included in the final multivariate logistic model to identify independent predictors of ISR, as described in our previous study. 16 All tests were two-tailed, with a p-value <.05 considered significant. All analyses were performed using SPSS (version 18.0 for Windows; SPSS).

| RESULTS
The baseline clinical, laboratory and angiographic data for the study cohort are detailed in Table 1. Compared with the control group, the ISR group had a higher proportion of patients with a family history of CAD, as well as a higher proportion of cigarette smoking, the incidence of dyslipidemia, hypertension, and diabetes mellitus. Moreover, patients with ISR tended to have worse renal function, higher fasting glucose, and higher total and LDL cholesterol but lower HDL cholesterol levels than those without ISR. At the 12-month follow-up, there were no significant differences between the ISR and non-ISR groups with regard to age, sex, ejection fraction, and medical treatments.
Although the degree of coronary stenosis before PCI, the occurrence of left main coronary artery (LM) stenosis, and type of DES implanted were similar between the ISR and non-ISR group, complicated coronary lesions, such as coronary chronic total occlusions (CTO) (p < .005) and bifurcation lesions (p < .001), were more frequent in the ISR than the non-ISR group. Moreover, patients with ISR tended to have a greater number of stents implanted and a greater total length of stenting, but smaller stent diameter, than the non-ISR group (Table 1).
Nomograms provided an individualized 12-month probability risk of ISR, assuming the patient did not die of other causes within this 12-month period ( Figure 3).

| DISCUSSION
Importantly, our study shows that an elevated plasma level of M2BP at baseline is associated with an increased risk for restenosis at 12 months after coronary stent placement.
Since the introduction of percutaneous transluminal coronary angioplasty (PTCA) in 1977, restenosis, which has an occurrence rate of 32%-40% at 6 months after PTCA, has hampered the long-term efficacy of PTCA. 2,17 Use of drug-eluting stents (DES), which are coated with antiproliferative drugs, such as sirolimus or paclitaxel, has dramatically reduced the occurrence rate of ISR. 18 However, despite the use of dual antiplatelet and intensive statins therapy, the incidence of ISR after PCI remains high. 19 Although many drugs and devices have been evaluated to lower the rate of restenosis in M2BP, which circulates abundantly in plasma, exerts pathogenic effects on arteries when its level is significantly increased, as shown in our study and previous research. 11 As a member of the macrophage scavenger receptor cysteine-rich domain superfamily, M2BP was originally identified as a tumor-associated glycoprotein associated with tumor progression and metastasis. 9 An elevated expression of M2BP was also identified in inflammation-related diseases, such as venous thrombosis, asthma, and chronic pancreatitis. [10][11][12] Recently, the pro-inflammatory effect of M2BP was further described by in vitro studies, showing its capacity to induce production of IL-2 via peripheral mononuclear cells and IL-6 by bone marrow stromal cells. 13

| CONCLUSION
An elevated plasma level of M2BP at baseline appears to be asso-

CONFLICT OF INTERESTS
The authors declare that there are no conflicts of interest. We certify that none of the authors have any financial and/or nonfinancial relationships with an organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript.

AUTHOR CONTRIBUTIONS
Liming

PATIENT CONSENT STATEMENT
For investigations involving human subjects, informed consent has been obtained from the participants involved.

DATA AVAILABILITY STATEMENT
All data included in this study are available upon request by contact with the corresponding author.