COX-2/PGE2 upregulation contributes to the chromosome 17p-deleted lymphoma.

Abstract

Deletions of chromosome 17p, where TP53 gene locates, are the most frequent chromosome alterations in human cancers and associated with poor outcomes in patients. Our previous work suggested that there were p53-independent mechanisms involved in chromosome 17p deletions-driven cancers. Here, we report that altered arachidonate metabolism, due to the deficiency of mouse Alox8 on chromosome 11B3 (homologous to human ALOX15B on chromosome 17p), contributes to the B cell malignancy. While the metabolites produced from lipoxygenase pathway reduced, chromosome 11B3 deletions or Alox8 loss, lead to upregulating its paralleling cyclooxygenase pathway, indicated by the increased levels of oncometabolite prostaglandin E2. Ectopic PGE2 prevented the apoptosis and differentiation of pre-B cells. Further studies revealed that Alox8 deficiency dramatically and specifically induced Cox-2(Ptgs2) gene expression. Repressing Cox-2 by its shRNAs impaired the tumorigenesis driven by Alox8 loss. And, in turn, tumor cells with Alox8 or 11B3 loss were sensitive to the COX-2 inhibitor celecoxib. This correlation between COX-2 upregulation and chromosome 17p deletions was consistent in human B-cell lymphomas. Hence, our studies reveal that the arachidonate metabolism abnormality with unbalanced ALOX and COX pathways underlies human cancers with 17p deletions and suggest new susceptibility for this disease.