FOXM1 regulates platelet-induced anoikis resistance in pancreatic cancer cells

BACKGROUND: Resistance to anoikis, a form of programmed cell death that occurs after detachment from the surrounding extracellular matrix, is a prerequisite for the survival of circulating tumor cells (CTCs) in the bloodstream. Platelets can interact with these CTCs and protect them from cytokine- and immune cell-mediated cell death. Whether platelets can regulate anoikis resistance by controlling intrinsic gene expression changes in tumor cells that contribute to metastasis has not been studied in detail in pancreatic cancer cells. METHODS: Pancreatic cancer cells were cultured under attached or low-attachment conditions to induce and mimic anoikis. The detached cells were co-cultured with platelets and subsequent gene expression analyses were performed to identify deregulated pathways responsible for survival under detached conditions that are mediated by platelets. RESULTS: We observed a cell line-dependent sensitivity of pancreatic cancer cells to anoikis and that anoikis resistance was greatly enhanced by platelet interaction. RNA sequencing and transcriptome analyses identified FOXM1 as a differentially regulated gene between attached and detached cells, and its expression was modulated by platelets via an activated AKT signaling pathway. Manipulating FOXM1 protein expression via gain- and loss-of-function approaches or by inhibiting its activity using small-molecule inhibitors significantly impacts platelet-influenced death rates. Intriguingly, single-cell RNA sequencing and immunohistochemical analyses revealed higher FOXM1 expression in pancreatic cancer metastases than in primary tumors. CONCLUSION: Overall, these findings suggest that targeting FOXM1 may be a promising therapeutic strategy to interfere with the metastatic progression of pancreatic cancer, which might particularly benefit patients with high blood platelet counts.