Graft-versus-host disease (GVHD) is a complication that can occur after a stem cell or bone marrow transplant in which the newly transplanted donor cells attack the transplant recipient’s body. Severe GVHD is a leading cause of mortality in patients receiving the transplant and can overshadow the beneficial outcomes of tumor immunotherapy. There is a need for developing diagnostic tools that can identify patients who are at higher risk of GVHD progression following allogenic stem cell transplant and predict GVHD occurrence before clinical symptoms manifest. By taking advantage of recent proteomic technologies, new disease biomarkers have been identified and validated as predictive diagnostic and prognostic tools of GVHD to facilitate timely and selective therapeutic intervention.1
The current diagnostic methods to identify GVHD employ invasive procedures, such as biopsies of target organs, and are not preferred as primary diagnostic or prognostic tests in the clinical setting. Moreover, the histological severity of the biopsy does not always correlate with the clinical outcome. On the other hand, a disease biomarker that will predict GVHD prior to clinical signs will revolutionize diagnosis of this disease and enable preemptive interventions. Additionally, it will be practical if the biomarker assay is noninvasive, such as tests in body fluids, e.g., blood, urine, and saliva.
Avant garde proteomic instruments, such as the ultra-high resolution linear ion trap Orbitrap mass spectrometer (e.g., Orbitrap Elite, Thermo Scientific), are highly efficient methods for discovery of disease biomarkers in clinical research. Bassim et al.,2 conducted proteomic analysis of patient saliva samples to identify disease biomarkers for oral chronic GVHD. Using liquid chromatography tandem mass spectrometry (LC-MS/MS) performed on a LTQ-Orbitrap Velos mass spectrometer (Thermo Scientific), they initially identified 180 proteins. Of these proteins, 102 displayed at least a 2-fold change in expression. Further, targeted label-free quantification was used to confirm 3 major proteins, namely, lactotransferrin, lactoperoxidase, and albumin. Only lactotransferrin and lactoperoxidase were found to be downregulated in oral chronic GVHD patient saliva, whereas albumin remained unaltered. Thus, targeted label-free quantification of select biomarker proteins can be successfully employed as a mass-spectrometry-based validation tool for noninvasive screening, early detection, and monitoring of chronic GVHD in a large population.
In a separate study, Schlatzer et al.3 sought to identify protein biomarkers associated with idiopathic pneumonia syndrome (IPS), a fatal complication resulting from allogenic stem cell transplant. They performed label-free proteomics assays using a LTQ-Orbitrap XL (Thermo Scientific) mass spectrometer and identified 81 IPS-associated proteins in patient plasma samples. Out of these candidate proteins, they selected the lipopolysaccaharide-binding protein (LBP) as a candidate disease biomarker for IPS and verified its increase as a function of disease using an Enzyme-linked immunosorbent assay (ELISA). The group also went on to identify a set of disease biomarkers that can potentially predict, at the time of stem cell transplant, which individuals are likely to develop IPS and also their response to corrective therapy, thus making it applicable to a wider clinical setting.
Proteomics is a rapidly advancing field that provides direct means to quantitatively detect proteins, molecules that are responsible for the pathophysiology of GVHD. Proteomics-based strategies show promise in the identification of protein biomarkers that can risk-stratify patients and enable customized treatment.
1. Paczesny, S. (2012) ‘Biomarkers for the detection of graft-versus-host disease in cancer patients after bone marrow transplantation‘, Current Biomarker Findings, 2012 (2), (pp 29-42)
2. Bassim, CW. et al., (2012) ‘Quantitative salivary proteomic differences in oral chronic graft-versus-host disease‘, Journal of Clinical Immunology, published online July 18, 2012. doi: 10.1007/s10875-012-9738-4
3. Schlatzer, D., et al, (2012) ‘Human biomarker discovery and predictive models for disease progression for idiopathic pneumonia syndrome following allogeneic stem cell transplantation‘, Molecular & Cellular Proteomics, 11, (M111.015479)