Cyclooxygenase-1, but not -2, is upregulated in NB4 leukemic cells and human primary promyelocytic blasts during differentiation

Abstract

Cyclooxygenase (COX)-1 or -2 and specific prostaglandin (PG) synthases catalyze the formation of various PGs. We investigated the expression and activity of COX-1 and -2 during granulocyte-oriented maturation induced by all-trans-retinoic acid (ATRA) of NB4 cells, originated from a human acute promyelocytic leukemia (APL), and in blasts from APL patients. The expression of COX isoenzymes or prostaglandin synthases was also investigated in circulating granulocytes and human bone marrow. COX-1 was expressed and enzymatically active in NB4 cells and primary blasts. COX-1 mRNA and protein were induced by ATRA. COX-1 protein increased approximately 2-3.5-fold by culture day 3 in NB4 cells and primary blasts, while basal COX-2 expression was very low and unaffected by ATRA. COX-1-dependent PGE 2 biosynthesis increased during differentiation approx. 5-fold. Indomethacin and the selective COX-1 inhibitor SC-560, but not selective COX-2 inhibition, impaired NB4 differentiation, reducing NADPH-oxidase activity, CD11b and CD11c expression. The immunohistochemistry of granulocytes and myeloid precursors in the bone marrow showed a large prevalence of COX-1 as compared to COX-2. In conclusion, COX-1 is induced during ATRA-dependent maturation and appears to contribute to myeloid differentiation both in vitro and ex vivo, and COX-1 activity may potentiate the differentiation of human APL.

Arsenic trioxide inhibits ATRA-induced prostaglandin E2 and cyclooxygenase-1 in NB4 cells, a model of acute promyelocytic leukemia

“…COX-2 protein was not detected in untreated and ATRA-treated NB4 cells, or upon treatment of As 2 O 3 for 3 or 6 days as previously described (data not shown). 19 Reverse transcription (RT)-PCR analysis revealed similar COX-1 transcript level in ATRA-and ATRA/ As 2 O 3 -treated NB-4 cells, indicating that As 2 O 3 -induced inhibition of COX-1 expression does not involve regulations at the transcriptional level.…”

“…Pretreatment of NB4 cells with 10 mM indomethacin decreased the maturation of NB4 cells in response to ATRA as previously reported. 19 Importantly, pretreatment with indomethacin dramatically blocked the differentiation of cells treated with the combination of ATRA and As 2 O 3 ( Figure 3a). These morphological data were further supported by the results of the NBT test (Figures 3b and d) and the CD11c membrane expression (Figure 3c), all showing that indomethacin dramatically blocked the differentiation of cells treated with the combination of ATRA and As 2 O 3 .…”

“…19 To assess the effect of As 2 O 3 on ATRA-dependent COX-1 expression during cell differentiation, cells were treated with 0.1 or 1 mM ATRA, and COX-1 activity was measured by the conversion of arachidonic acid into PGE 2 . Figures 1a and b (Figures 1a and b).…”

“…22 We have recently demonstrated that ATRA induces COX-1 but not COX-2 in NB4 cells and in blasts from patients with APL. 19 In the present study, we investigated the effect of co-treatment of NB4 cells with ATRA and As 2 O 3 on PG formation, COX-1 expression and cell differentiation. We found that As 2 O 3 inhibits ATRA-dependent COX-1 activity and expression in NB4 cells and that nonsteroidal antiinflammatory drugs (NSAIDs) significantly block differentiation of ATRA-and As 2 O 3 -treated NB4 cells.…”

“…COX-1 can be regulated during lymphoid maturation. [17][18][19] Retinoid isomers including ATRA and 9-cis-RA were described to induce COX-1 in human premonocytic U937 cells. 20 Retinoic acid was also described to induce COX-1 in human neuroblastoma cell lines 21 and COX-2 in synergy with platelet activating factor.…”