Abstract 1968: A novel mechanism of metastasis: Extracellular ATP promotes invasion and metastasis independent of purinergic receptor signaling

Abstract

Abstract Cancer is one of the top deadliest diseases in the US and worldwide. Metastasis, the dissemination of cancer cells from the primary tumors to distant organs, is responsible for 90% of solid tumor-related deaths. Tumor invasion and metastasis is a multistep process in which loss of cell-cell adhesion, increased proteolysis, and cell motility has been shown to be critical steps. Extracellular ATP is potentially a very important factor involved in tumor invasion and metastasis because both cell detachment and migration require energy, which is known to be mainly provided by ATP. Recent studies have indicated that the extracellular microenvironment of tumors contains much higher concentrations of ATP than normal tissues of the same cell origins. Our recent studies demonstrated that extracellular ATP is taken up by cancer cells through macropinocytosis and other endocytosis and promotes cancer cell growth, survival, and drug resistance (1-3). Based on all these, we hypothesized that extracellular ATP (eATP) plays critical roles in the regulation of tumor cell detachment, motility, invasion and tumor metastasis initiation. It was previously shown that ATP-induced purinergic receptor (PR) signaling is involved in metastasis. Our hypothesis is different in that eATP also mediates invasion and metastasis independent of PR signaling. Various bioassays were used in human non-small cell lung cancer (NSCLC) A549 cells to test our hypothesis. Our results show that eATP treatment led to a substantially increased number of floating cancer cells, and these cells were viable and formed clones in a clonogenic assay. This indicates that eATP induces cancer cell detachment. Moreover, treatment of eATP also induces cell migration in cell wounding and Transwell migration assays. In vitro invasion assay showed that eATP induced a dose-and time-dependent increase in the invasive capacities of the A549 cells. Western blot analysis indicates that eATP treatment reduced the expression of cell-cell adhesion molecule E-cadherin. PR inhibitors only slightly attenuated these effects. All these suggest novel ATP mechanisms independent of the PR signaling that are unreported before and imply novel targets for inhibiting/preventing metastasis.