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

Chromosome 17p deletions are one of the most frequent chromosomal alterations in human cancers and also lymphoma. Although it has been assumed to be equal to p53 loss for a long time, there are emerging evidence suggesting that there would be additional p53–independent mechanisms. Our previous work identified ALOX15B, an arachidonate lipoxygenase, as a 17p tumor suppressor in lymphoma. Interestingly, five of the six ALOX genes locate on this region and frequently co-deleted with TP53. Among them, ALOX15B, ALOX12B and ALOXE3 are adjacent to one another and proximal to the centromere relative to TP53, while ALOX12 and ALOX15 are distal to the centromere relative to TP53. Herein, we show that each of the five 17p ALOX genes repress Myc-driven lymphomagenesis in mice. Mechanistically, deficiency of the ALOX arachidonate metabolism pathway activates the paralleling COX-PGE2 pathway, resulting in increasing PTGS2 expression and PGE2 level. PGE2 prevents apoptosis of pre-B cells and Ptgs2 knockdown extends the latency of Myc;shAlox15b lymphoma in vivo. Further, shAlox15b lymphoma cells are more sensitive to COX-2 inhibitor celecoxib than control lymphoma cells. Importantly, the ALOX-COX metabolism unbalance is also observed in human cancers with del(17p). Taken together, our studies reveal the tumor suppression functions of all of the five ALOX genes on chromosome 17p in lymphoma and an unprecedented arachidonate metabolism unbalance between the ALOX and COX pathways underlying human cancers with 17p deletions. Bulk RNA sequencing in Alox15b and Alox12b knock down Pre-B cells.