Anti-LRG1 monoclonal antibody, clone FQS23473

Leucine-rich alpha 2 glycoprotein (LRG 1), a serum protein produced by hepatocytes, has been implicated in angiogenesis and tumor promotion. Our laboratory previously reported the expression of LRG1 in murine myeloid cell lines undergoing neutrophilic granulocyte differentiation. However, the presence of LRG1 in primary human neutrophils and a role for LRG1 in regulation of hematopoiesis have not been previously described. Here we show that LRG1 is packaged into the granule compartment of human neutrophils and secreted upon neutrophil activation to modulate the microenvironment. Using immunofluorescence microscopy and direct biochemical measurements, we demonstrate that LRG1 is present in the peroxidase-negative granules of human neutrophils. Exocytosis assays indicate that LRG1 is differentially glycosylated in neutrophils, and co-released with the secondary granule protein lactoferrin. Like LRG1 purified from human serum, LRG1 secreted from activated neutrophils also binds cytochrome c. We also show that LRG1 antagonizes the inhibitory effects of TGF beta 1 on colony growth of human CD34(+) cells and myeloid progenitors. Collectively, these data invoke an additional role for neutrophils in innate immunity that has not previously been reported, and suggest a novel mechanism whereby neutrophils may modulate the microenvironment via extracellular release of LRG1.

Nephrotoxicity limits the use of cisplatin (CP) in cancer therapy; however, current clinical measures of renal health do not reflect low degrees of kidney injury. Therefore, discovering new biomarkers for CP-induced acute kidney injury (AKI) is essential for monitoring kidney health during therapy. To identify novel candidate biomarkers in urine for reduced renal function due to CP therapy, we conducted a pilot study on cancer patients eligible for CP treatment. Urine from 30 patients was collected before (baseline) and after 3d of intravenous CP infusion. Urine samples were subjected to Isobaric Tag for Relative Absolute Quantitation (iTRAQ) analysis. Biological roles and pathways for the proteins with altered urine concentrations were identified using bioinformatic tools ITRAQ analysis detected 1411 proteins, 12 of which showed significantly altered levels. Growth differentiation factor-15 (GDF15), leucine-rich alpha-2-glycoprotein 1 (LRG1), and secreted phosphoprotein 1 (SPP1/ osteopontin, OPN) were identified as potential candidate markers by proteomic analysis and were validated by ELISA in another 30 patients and in a CP-induced AKI mouse model. Therefore, GDF15, LRG1, and SPP1 may be applied as novel candidate urinary markers of kidney injury after cisplatin treatment. These findings may facilitate the development of new methods to monitor kidney function, particularly in CP-based chemotherapy. Significance: Cisplatin is pivotal for cancer treatment; however, nephrotoxicity limits its use. Clinical measures for renal health are not reflective of early signs of acute kidney injury. Thus, new indicators of the state of renal health following cisplatin treatment will have to be discovered. This study reports the use of proteomics to mine for candidate markers of kidney injury in the urine of patients undergoing treatment with cisplatin. Results were experimentally validated using patient urine and a mouse model of cisplatin-induced acute kidney injury. The novel candidate biomarkers reported in this study may be used for the non-invasive monitoring of renal health and in mitigating the side-effects of cisplatin during the course of cancer treatment.