Accurate quantification of lysyl oxidase concentration in human tissue

The family of Lysyl oxidase enzymes play fundamental roles in the formation of the extracellular matrix, through catalyzing the crosslinking of collagen and elastin fibers. Lysyl oxidase (LOX) -- one of the 5 family members (LOX, LOXL1-4), is a disease biomarker, with blood concentration positively correlating with progression of fibrosis or cancer. An accurate quantification of LOX concentration can support diagnosis, monitoring of disease progression or treatment success. However, reported LOX concentrations in human blood are inconsistent. Therefore, a novel, high-throughput and sensitive digital enzyme-linked immunosorbent assay was developed using two validated and selective human anti-LOX antibodies and single molecule array technology. Both, the 56 kDa pro-form and the 32 kDa active form can be accurately measured from recombinant and native protein. The serum LOX concentration correlated with LOX activity measured in the same platform using a bio-probe. The usefulness of this technology was demonstrated in serum from bladder cancer patients wherein LOX concentration was significantly higher compared to the healthy subjects. This study demonstrates the validation and use of a sensitive and accurate method for measuring LOX concentration in human samples. This novel method may be superior than some commercially available enzyme-linked immunosorbent assay kits for accurate measurement of LOX concentrations in clinical settings.