Serum Peptidome Based Multiple Myeloma Renal Impairment Biomarker Screening

Background: Renal impairment (RI) is relatively common in patients with newly diagnosed MM (NDMM), ~20-40%, and forms one of the defining features for diagnosis of symptomatic disease. RI has a negative prognostic impact in patients with MM, with an increased risk of early death and a reduction in median survival of up to 50% compared with MM patients without RI. Identification of the early RI in MM and prompt intervention can effectively reverse the RI and prolong the survival of patients. Considering serum creatinine (SCr), blood urea nitrogen (BUN) and creatinine clearance (CrCl) are difficult to reflect early RI, cystatin C (Cys-C), as a new biomarker, has certain value for the diagnosis of early glomerular impairment in MM. However, the early stage of RI in MM was mainly renal tubular injury. Low molecular urine protein (retinol-binding protein, β-microglobulin) are effective in early renal tubular injury, but they are affected by urea PH value. This study was to screen a panel of serum peptides associated with early RI in MM.

Methods: 164 MM patients were selected from those who were newly diagnosed in the Second Affiliated Hospital of Xi'an Jiao Tong University during a given period of time (2009.1-2014.1). Their diagnoses were made according to the diagnostic criteria from the International Myeloma Working Group. The median age was 65 years old (range 36-83) and 60.4% were male. RI was defined as having a CrCl<40ml/min. Weak cation exchange magnetic bead combined with matrix assisted laser desorption/ionization time of flight mass spectrometry were used to compare and analyze serum peptidome of MM with or without RI. Correlation analysis of two variables was estimated by Spearman method. The patients were categorized into two groups according to the relative intensities of peptides (≥mean versus <mean). Overall Survival was estimated by the Kaplan-Meier method and compared using a log-rank test. The event was defined as the time from initial diagnosis to treatment-related death time. Statistical significance was defined as p<0.05.

Results: Serum peptidome of MM including 104 without RI and 50 with RI were analysed. 18 statistically different expressed peptide peaks were obtained in the molecular weight range of 700-10000Da (P<0.05), among which, 7 peptides were upregulated and 11 peptides were downregulated. Quick classifier (QC) model had optimal distinction efficiency, in the training set with a sensitivity of 93.33% and a specificity of 90%. Blind test verified that this model correctly identified 18 cases out of total 20 MM with RI and 70 cases from 74 MM without RI. Peptides with molecular weight of 3908.85Da and 3216.06Da were significant upregulated in MM patients with RI. Relative intensities of the two peptides were decreased when CrCl(38/50MM) was improved to 40ml/min after therapy. Peptide with molecular weight of 2990.08Da was significant downregulated in MM patients with RI. Its relative intensity was elevated after therapy(CrCl>40ml/min,38/50MM). Spearman correlation analysis showed that relative intensities of peptides with molecular weight of 3908.85Da, 3216.06Da and 2990.08Da were correlated with SCr(r=0.81, p<0.001; r=0.84, p<0.001; p=-0.86, p<0.001), CrCl(r=-0.79, p<0.001; r=-0.81, p<0.001; r=0.83, p<0.001), BUN(r=0.74, p<0.001; r=0.77, p<0.001; r=-0.79, p<0.001), Cys-C(r=0.81, p<0.001; r=0.84, p<0.001; r=-0.86, p<0.001). The median follow-up duration among 164 patients was 27 months (range 4-52 months). Kaplan-Meier analyses of overall survival (OS) showed that patients with higher relative intensities of peptide with 3908.85Da and 3216.06Da (≥mean relative intensity) had a significantly inferior outcome. Lower relative intensities of peptides with molecular weight of 3908.85Da and 3216.06Da (<mean relative intensity) was associated with a favorable OS (46.2±9.2% versus 16.1±6.5%, p=0.012; 41.7±9.5% versus 18.5±6.0%, P=0.021). The OS rate was higher in patients with increased relative intensity of peptides with molecular weight of 2990.08Da (≥mean relative intensity) of than in those with decreased relative intensity (<mean relative intensity)(36.1±10.5% versus 16.2±4.7%, p=0.008).

Conclusion: Peptides(3908.85Da, 3216.06Da and 2990.08Da) associated with MM RI obtained by serum peptidome technology can provide new clue for early assess and diagnose MM RI in clinical.