FOXM1-mediated activation of phospholipase D1 promotes lipid droplet accumulation and reduces ROS to support paclitaxel resistance in metastatic cancer cells

Chemoresistance is a major challenge for the treatment of cancer with metastasis. We investigated the mechanisms of lipid metabolites involved in drug resistance. Here, metastatic cancer cells isolated from mouse models were resistant to paclitaxel treatment in vitro and in vivo when compared with parental cancer cells. FOXM1, an oncogenic transcriptional factor, was highly expressed in metastatic cancer cells, and overexpression of FOXM1 conferred parental cancer cells resistance to paclitaxel. Lipidomic analysis showed that FOXM1 increased unsaturated triglyceride (TG) and phosphatidylcholine (PC) abundance, which are the main components of lipid droplet (LD). Inhibition of LD formation sensitized cells to paclitaxel. Mechanistically, the enzyme phospholipase D1 (PLD1) was identified as a potential effector target of FOXM1. PLD1 promoted LD accumulation, which reduced the level of reactive oxygen species (ROS) and maintained endoplasmic reticulum (ER) homeostasis in resistant cells with the treatment of paclitaxel. Moreover, inhibition of PLD1 reversed FOXM1-conferred paclitaxel resistance in vitro and in vivo. This study, for the first time, reveals the role of FOXM1-mediated PLD1 in LD accumulation and paclitaxel resistance. Targeting PLD1 or LD formation may help reverse chemoresistance in metastatic cancer cells. Generally, our results identified FOXM1 as a driver of paclitaxel resistance via activation of PLD1 to promote of LD accumulation, which contributes to the maintenace of ER homeostasis when metastatic cancer cells are confronted with ROS induced by paclitaxel.