Overexpression of LC3A autophagy protein in follicular and diffuse large B-cell lymphomas.

Background and Objectives: Autophagy is a self-degradation mechanism induced under stress conditions in all eukaryotic cells. Its activity in human lymphomas has not been studied as yet.
Methods: In this study, the autophagic activity of lymphoid cells was investigated in follicular lymphomas (FL; 48 cases), diffuse large B-cell lymphomas (DLBCL; 78 cases), and in reactive follicular hyperplasias (41 cases), using the light chain 3A (LC3A) antibody and a standard immunohistochemical technique.
Results: In all cases, the pattern of LC3A reactivity was uniformly diffuse cytoplasmic, but expressed more frequently in FLs (68.8%) than in DLBCLs (41%) (p=0.02), and much more commonly in DLBCLs than in reactive lymph nodes (24.3%) (p<0.006). Interestingly, FLs expressing LC3A in >10% of lymphoid cells (high reactivity) were associated with the hypoxia-related protein HIF1α and the enzyme of anaerobic metabolism lactate dehydrogenase LDH5 (p=0.004 and p=0.003, respectively). Such associations, however, were not a feature in DLBCLs of increased LC3A activity.
Conclusions: LC3A expression in FLs is hypoxia-induced, whereas its expression in DLBCLs may be regulated by other molecular mechanisms. The current study provides a tool for further assessment of autophagic activity in translational and autophagy targeting therapy studies.
(Copyright © 2013 King Faisal Specialist Hospital & Research Centre. Published by Elsevier B.V. All rights reserved.)