NSAIDs Induce Proline Dehydrogenase/Proline Oxidase-Dependent and Independent Apoptosis in MCF7 Breast Cancer Cells

Non-steroidal anti-inflammatory drugs (NSAIDs) are considered in cancer therapy for their inhibitory effect on cyclooxygenase-2 (COX-2), which is overexpressed in most cancers. However, we found that NSAIDs as ligands of peroxisome proliferator-activated receptor-gamma (PPAR gamma)-induced apoptosis independent of the COX-2 inhibition, and the process was mediated through activation of proline dehydrogenase/proline oxidase (PRODH/POX)-dependent generation of reactive oxygen species (ROS). This mitochondrial enzyme converts proline to increment 1-pyrroline-5-carboxylate (P5C) during which ATP or ROS is generated. To confirm the role of PRODH/POX in the mechanism of NSAID-induced apoptosis we obtained an MCF7 CRISPR/Cas9 PRODH/POX knockout breast cancer cell model (MCF7(POK-KO)). Interestingly, the studied NSAIDs (indomethacin and diclofenac) in MCF7(POK-KO) cells contributed to a more pronounced pro-apoptotic phenotype of the cells than in PRODH/POX-expressing MCF7 cells. The observed effect was independent of ROS generation, but it was related to the energetic disturbances in the cells as shown by an increase in the expression of AMPK alpha (sensor of cell energy status), GLUD1/2 (proline producing enzyme from glutamate), prolidase (proline releasing enzyme), PPAR delta (growth supporting transcription factor) and a decrease in the expression of proline cycle enzymes (PYCR1, PYCRL), mammalian target of rapamycin (mTOR), and collagen biosynthesis (the main proline utilizing process). The data provide evidence that the studied NSAIDs induce PRODH/POX-dependent and independent apoptosis in MCF7 breast cancer cells.

Automated summary

This study found that non-steroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in breast cancer cells through the activation of peroxisome proliferator-activated receptor-gamma (PPAR gamma) and the generation of reactive oxygen species (ROS) via proline dehydrogenase/proline oxidase (PRODH/POX). The effect of NSAIDs on cell apoptosis is independent of cyclooxygenase-2 (COX-2) inhibition. Additionally, the study showed that the role of PRODH/POX in NSAID-induced apoptosis is more pronounced in breast cancer cells with PRODH/POX knockout. The findings suggest a potential therapeutic strategy for cancer treatment using NSAIDs.