AffinityImmuno Products

Introduction

GPNMB (glycoprotein NMB), also called osteoactivin or DC-HIL, is a type I transmembrane glycoprotein structurally related to the melanocyte protein PMEL. It participates in diverse physiological processes, including transport of melanosomes to keratinocytes, regulation of osteoblast and osteoclast activity, promotion of dendritic cell maturation, and support of autophagosome-lysosome fusion during tissue repair. GPNMB is typically confined to intracellular compartments in normal cells but relocates to the cell surface in many tumor types, where it has been implicated in inflammatory signaling within the tumor microenvironment. Sources differ on its net effect in cancer, however: early studies of melanoma cell lines found GPNMB expression associated with slower growth and reduced metastatic spread, whereas more recent reviews describe it as frequently overexpressed in cancer and contributing to tumor invasiveness and metastasis, so its overall role in tumor progression should be considered context-dependent rather than settled.

GPNMB’s relocation from intracellular compartments to the tumor cell surface, combined with its documented but still debated role in tumor invasiveness across different cancer types, makes it a candidate biomarker for tumor microenvironment research as well as its established roles in bone remodeling and dendritic cell biology.

Principle of the Assay

This kit uses a sandwich enzyme immunoassay format in which the microtiter plate wells are pre-coated with a capture antibody specific to Human GPNMB. Standards or samples are pipetted into the appropriate wells together with a biotin-conjugated detection antibody that recognizes a second epitope on Human GPNMB. Avidin conjugated to horseradish peroxidase (HRP) is then added to each well and allowed to incubate, linking the enzyme to the captured complex via the biotin label. Upon addition of TMB substrate solution, a colorimetric signal develops exclusively in wells where Human GPNMB, the biotin-conjugated antibody, and avidin-HRP are all present. The enzymatic reaction is stopped by the addition of a sulphuric acid stop solution, and absorbance is measured at 450 nm (± 10 nm). Human GPNMB concentrations in the samples are determined by comparing sample optical density values against a standard curve.