The non-steroidal anti-inflammatory drugs Sulindac sulfide and Diclofenac induce apoptosis and differentiation in human acute myeloid leukemia cells through an AP-1 dependent pathway

Acute myeloid leukemia is a heterogeneous disease with regard to the underlying genetic and molecular pathophysiology. Non-steroidal anti-inflammatory drugs (NSAIDs) exert significant anti-proliferative effects in various malignant cells in vitro and in vivo. Hence, these agents can be utilized to study potential disease specific anti-proliferative pathways. In this study, a total number of 42 bone marrow derived CD34+ cells from de novo AML patients and the AML cell lines THP-1 and HL-60 were treated with the NSAIDs Sulindac sulfide and Diclofenac. We examined viability, apoptosis, differentiation and addressed the molecular mechanisms involved. We found a consistent induction of apoptosis and to some extent myeloid differentiation in NSAID treated AML cells. Comprehensive protein and gene expression profiling of Diclofenac treated AML cells revealed transcriptional activation of GADD45 and its downstream MAPK/JNK pathway as well as increased protein levels of the Caspase-3 precursor. This points towards a role of the c-Jun NH2-terminal kinase (JNK) in NSAID mediated apoptosis. This was dependent on JNK activity as addition of a specific JNK-inhibitor abrogated apoptosis. Furthermore, the AP-1 transcription factor family members c-Jun, JunB and Fra-2 were transcriptionally activated in NSAID treated AML cells. Re-expression of these transcription factors led to activation of GADD45 with induction of apoptosis. Mechanistically, we demonstrate that NSAIDs induce apoptosis in AML through a novel pathway involving increased expression of AP-1 heterodimers, which by itself is sufficient to induce GADD45 expression with consecutive activation of JNK and induction of apoptosis.

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