LC3B: From Autophagy to Cancer

LC3B is subunit component of the LC3 autophagy biomarker associated with microtubule-associated proteins MAP1A and MAP1B and one of the best characterized markers to date. In resting state, it is cytosolic, but upon activation, is lapidated and becomes embedded in the autophagosomal membrane. The role of autophagy as an alternative cell energy source under stress (conditions such as GF deprivation, starvation, and hypoxia) is well-documented. LC3B antibody was used in confocal microscopy studies to examine a three-dimensional bovine mammary epithelial cell (MEC) culture system (1). LC3 was part of a panel of autophagic and apoptotic markers followed in the development of acinar structures in response to steroid hormones. Another morphogenesis marker study examined systemic inflammation and autophagy with a panel that included the LC3B antibody and found that cardiac patients with postoperative atrial fibrillation (POAF) after coronary artery bypass heart surgery also presented with ultrastructural atrial remodeling and impaired autophagy (2). LC3B antibody allowed researchers to adopt a multidimensional proteomics approach with immunoblot validation, which eventually enabled the identification of caspase-3 as a regulator of in human endothelial cells (HEC) in response to nutrient deficiency (3). Life has developed a quantitative and objective TR-FRET immunoassay that can be performed on a plate reader (4). This facile assay uses LC3B antibody due to its preferential affinity for the activated (membrane-bound) form of LC3B, and its high-throughput screening potential. The role of LC3B in oncology is being pursued by investigators at MD Anderson who generated LC3B antibody after their cDNA microarray analyses of autophagic glioblastoma cell lines indicated that monitoring LC3B expression would be valuable in predicting patient outcome and survival rates (5).