Interplay of protein misfolding pathway and unfolded-protein response in acute promyelocytic leukemia

Protein misfolding has traditionally been linked to the pathogenesis of various neurodegenerative diseases. However, emerging evidence from various laboratories, including ours, suggests that protein misfolding may also play a fundamental role in some malignancies, particularly those caused by fusion oncoprotein generated from chromosomal translocation. Promyelocytic leukemia (PML) fused to the retinoic acid receptor (RAR) is a fusion oncoprotein linked to the transformation of acute promyelocytic leukemia (APL), and is not only a misfolded protein itself, but also promotes misfolding of nuclear receptor corepressor (N-CoR) protein, a corepressor essential for the growth-suppressive function of several tumor-suppressor proteins. PML–RAR promotes misfolding of N-CoR by inducing aberrant post-translational modification, which destabilizes its core and promotes instability. Misfolded N-CoR, thus, contributes to differentiation arrest and survival of APL cells through loss-of-function and aberrant gain-of-fun...