ENPP1 is an innate immune checkpoint of the anticancer cGAMP-STING pathway
ENPP1 expression correlates with poor prognosis in many cancers, and we previously discovered that ENPP1 is the dominant hydrolase of extracellular cGAMP: a cancer-cell-produced immunotransmitter that activates the anticancer STING pathway. However, ENPP1 has other catalytic activities and the molecular and cellular mechanisms contributing to its tumorigenic effects remain unclear. Here, using single cell RNA-seq (scRNA-seq), we show that ENPP1 overexpression drives primary tumor growth and metastasis by synergistically dampening extracellular cGAMP-STING mediated antitumoral immunity and activating immunosuppressive extracellular adenosine (eADO) signaling. In addition to cancer cells, stromal and immune cells in the tumor microenvironment (TME) also express ENPP1 which functions as a gate keeper to block cGAMP sensing in these cells. Enpp1 knockout in both cancer cells and normal tissues slowed primary tumor growth and prevented metastasis in an extracellular cGAMP- and STING-dependent manner. Lastly, an ENPP1 knock-in mutation that selectively abolishes ENPP1's cGAMP hydrolysis activity phenocopied total ENPP1 knockout, demonstrating that restoration of paracrine cGAMP-STING signaling is the dominant anti-cancer mechanism of ENPP1 inhibition. In summary, selectively blocking ENPP1's cGAMP hydrolysis activity is a promising therapeutic approach for treating cancer.